A Survey on 5G: The Next Generation of Mobile Communication
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paper_title: Visions Towards 5G: Technical Requirements and Potential Enablers

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Compared to the previous generations of mobile networks, 5G will provide a significant paradigm shift by including beyond state of the art technical solutions, like very high carrier frequencies with massive bandwidths, extreme base station and device densities, and very high number of transceiver antennas. However, unlike the previous generations, it will also be highly integrative and backward compatible: combining the novel 5G air interface and spectrum together with legacy wireless systems like LTE/LTE-A and WiFi, in order to facilitate an umbrella of high-rate coverage and a seamless user experience. In order to support this advances in the radio interface, the core network will also have to reach unprecedented levels of elasticity and intelligence. Spectrum regulation will need to be rethought and significantly improved, whereas energy and cost efficiencies will become one of the key parameters that will steer the 5G design and development. This paper elaborates on the 5G related topics, identifying the key challenges for future research and preliminary 5G standardization activities, as well as providing a comprehensive survey of the current literature.
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paper_title: 5G: The Convergence of Wireless Communications

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As the rollout of 4G mobile communication networks takes place, representatives of industry and academia have started to look into the technological developments toward the next generation (5G). Several research projects involving key international mobile network operators, infrastructure manufacturers, and academic institutions, have been launched recently to set the technological foundations of 5G. However, the architecture of future 5G systems, their performance, and mobile services to be provided have not been clearly defined. In this paper, we put forth the vision for 5G as the convergence of evolved versions of current cellular networks with other complementary radio access technologies. Therefore, 5G may not be a single radio access interface but rather a “network of networks”. Evidently, the seamless integration of a variety of air interfaces, protocols, and frequency bands, requires paradigm shifts in the way networks cooperate and complement each other to deliver data rates of several Gigabits per second with end-to-end latency of a few milliseconds. We provide an overview of the key radio technologies that will play a key role in the realization of this vision for the next generation of mobile communication networks. We also introduce some of the research challenges that need to be addressed.
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paper_title: 5G Wireless Backhaul Networks: Challenges and Research Advance

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5G networks are expected to achieve gigabit-level throughput in future cellular networks. However, it is a great challenge to treat 5G wireless backhaul traffic in an effective way. In this article, we analyze the wireless backhaul traffic in two typical network architectures adopting small cell and millimeter wave commmunication technologies. Furthermore, the energy efficiency of wireless backhaul networks is compared for different network architectures and frequency bands. Numerical comparison results provide some guidelines for deploying future 5G wireless backhaul networks in economical and highly energy-efficient ways.
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paper_title: What Will 5G Be?

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What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.
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paper_title: The requirements, challenges, and technologies for 5G of terrestrial mobile telecommunication

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In this article, we summarize the 5G mobile communication requirements and challenges. First, essential requirements for 5G are pointed out, including higher traffic volume, indoor or hotspot traffic, and spectrum, energy, and cost efficiency. Along with these changes of requirements, we present a potential step change for the evolution toward 5G, which shows that macro-local coexisting and coordinating paths will replace one macro-dominated path as in 4G and before. We hereafter discuss emerging technologies for 5G within international mobile telecommunications. Challenges and directions in hardware, including integrated circuits and passive components, are also discussed. Finally, a whole picture for the evolution to 5G is predicted and presented.
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paper_title: Cellular architecture and key technologies for 5G wireless communication networks

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The fourth generation wireless communication systems have been deployed or are soon to be deployed in many countries. However, with an explosion of wireless mobile devices and services, there are still some challenges that cannot be accommodated even by 4G, such as the spectrum crisis and high energy consumption. Wireless system designers have been facing the continuously increasing demand for high data rates and mobility required by new wireless applications and therefore have started research on fifth generation wireless systems that are expected to be deployed beyond 2020. In this article, we propose a potential cellular architecture that separates indoor and outdoor scenarios, and discuss various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications. Future challenges facing these potential technologies are also discussed.
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paper_title: Evolution Towards 5G Multi-tier Cellular Wireless Networks: An Interference Management Perspective

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The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, for example, higher data rates, excellent end-to-end performance, and user-coverage in hot-spots and crowded areas with lower latency, energy consumption, and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g. power control, cell association) in these networks with shared spectrum access (i.e. when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.
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paper_title: 5G: Personal mobile internet beyond what cellular did to telephony

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Cellular technology has dramatically changed our society and the way we communicate. First it impacted voice telephony, and then has been making inroads into data access, applications, and services. However, today potential capabilities of the Internet have not yet been fully exploited by cellular systems. With the advent of 5G we will have the opportunity to leapfrog beyond current Internet capabilities.
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paper_title: Cognitive radio in 5G: a perspective on energy-spectral efficiency trade-off

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A cognitive cellular network, which integrates conventional licensed cellular radio and cognitive radio into a holistic system, is a promising paradigm for the fifth generation mobile communication systems. Understanding the trade-off between energy efficiency, EE, and spectral efficiency, SE, in cognitive cellular networks is of fundamental importance for system design and optimization. This article presents recent research progress on the EE-SE trade-off of cognitive cellular networks. We show how EE-SE trade-off studies can be performed systematically with respect to different architectures, levels of analysis, and capacity metrics. Three representative examples are given to illustrate how EE-SE trade-off analysis can lead to important insights and useful design guidelines for future cognitive cellular networks.
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paper_title: Applications of self-interference cancellation in 5G and beyond

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Self-interference cancellation invalidates a long-held fundamental assumption in wireless network design that radios can only operate in half duplex mode on the same channel. Beyond enabling true in-band full duplex, which effectively doubles spectral efficiency, self-interference cancellation tremendously simplifies spectrum management. Not only does it render entire ecosystems like TD-LTE obsolete, it enables future networks to leverage fragmented spectrum, a pressing global issue that will continue to worsen in 5G networks. Self-interference cancellation offers the potential to complement and sustain the evolution of 5G technologies toward denser heterogeneous networks and can be utilized in wireless communication systems in multiple ways, including increased link capacity, spectrum virtualization, any-division duplexing (ADD), novel relay solutions, and enhanced interference coordination. By virtue of its fundamental nature, self-interference cancellation will have a tremendous impact on 5G networks and beyond.
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paper_title: Network function virtualization: Challenges and opportunities for innovations

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Network function virtualization was recently proposed to improve the flexibility of network service provisioning and reduce the time to market of new services. By leveraging virtualization technologies and commercial off-the-shelf programmable hardware, such as general-purpose servers, storage, and switches, NFV decouples the software implementation of network functions from the underlying hardware. As an emerging technology, NFV brings several challenges to network operators, such as the guarantee of network performance for virtual appliances, their dynamic instantiation and migration, and their efficient placement. In this article, we provide a brief overview of NFV, explain its requirements and architectural framework, present several use cases, and discuss the challenges and future directions in this burgeoning research area.
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paper_title: Macro-assisted data-only carrier for 5G green cellular systems

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As the commercial operation of 4G systems is speeding up worldwide to meet the increasingly explosive growth of mobile Internet in the 2020 era, a great many R&D efforts targeting the next generation wireless systems (5G) have been launched. With densely deployed small cells in a heterogeneous network, the excessive signaling overhead of conventional carrier design greatly degrades system performance. A new carrier designed for small cells in the next generation system will be highly beneficial toward a green communication network. In this article, we propose a macro-assisted data-only carrier for future 5G networks from a green prospective. With the help of macro base stations, control channel overhead, and cell-specific reference signals for small cells can be minimized to achieve a pure-data carrier. Under this architecture, key procedures are designed including small cell identification and access, synchronization, hand over, and small cell sleeping. Furthermore, to evaluate the potential of our proposed scheme, a complete system and link-level simulation platform according to the current 3GPP LTE standard is built. The simulation results show that our proposed systems, achieving significant performance enhancement of signaling overhead, can lead to more than 17 percent throughput improvement and 90 percent energy efficiency gain over the current LTE HetNet with on-off strategy implemented. The proposed scheme appears to be highly attractive as part of the future 5G green mobile networks.
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paper_title: Uplink contention based SCMA for 5G radio access

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Fifth generation (5G) wireless networks are expected to support very diverse applications and terminals. Massive connectivity with a large number of devices is an important requirement for 5G networks. Current LTE system is not able to efficiently support massive connectivity, especially on the uplink (UL). Among the issues that arise due to massive connectivity is the cost of signaling overhead and latency. In this paper, an uplink contention-based sparse code multiple access (SCMA) design is proposed as a solution. First, the system design aspects of the proposed multiple-access scheme are described. The SCMA parameters can be adjusted to provide different levels of overloading, thus suitable to meet the diverse traffic connectivity requirements. In addition, the system-level evaluations of a small packet application scenario are provided for contention-based UL SCMA. SCMA is compared to OFDMA in terms of connectivity and drop rate under a tight latency requirement. The simulation results demonstrate that contention-based SCMA can provide around 2.8 times gain over contention-based OFDMA in terms of supported active users. The uplink contention-based SCMA scheme can be a promising technology for 5G wireless networks for data transmission with low signaling overhead, low delay, and support of massive connectivity.
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paper_title: Cellular architecture and key technologies for 5G wireless communication networks

paper_content:

The fourth generation wireless communication systems have been deployed or are soon to be deployed in many countries. However, with an explosion of wireless mobile devices and services, there are still some challenges that cannot be accommodated even by 4G, such as the spectrum crisis and high energy consumption. Wireless system designers have been facing the continuously increasing demand for high data rates and mobility required by new wireless applications and therefore have started research on fifth generation wireless systems that are expected to be deployed beyond 2020. In this article, we propose a potential cellular architecture that separates indoor and outdoor scenarios, and discuss various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications. Future challenges facing these potential technologies are also discussed.
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paper_title: Cloud radio access network (C-RAN): a primer

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In the era of mobile Internet, mobile operators are facing pressure on ever-increasing capital expenditures and operating expenses with much less growth of income. Cloud Radio Access Network (C-RAN) is expected to be a candidate of next generation access network techniques that can solve operators' puzzle. In this article, on the basis of a general survey of C-RAN, we present a novel logical structure of C-RAN that consists of a physical plane, a control plane, and a service plane. Compared to traditional architecture, the proposed C-RAN architecture emphasizes the notion of service cloud, service-oriented resource scheduling and management, thus it facilitates the utilization of new communication and computer techniques. With the extensive computation resource offered by the cloud platform, a coordinated user scheduling algorithm and parallel optimum precoding scheme are proposed, which can achieve better performance. The proposed scheme opens another door to design new algorithms matching well with C-RAN architecture, instead of only migrating existing algorithms from traditional architecture to C-RAN.
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paper_title: Five Disruptive Technology Directions for 5G

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New research directions will lead to fundamental changes in the design of future 5th generation (5G) cellular networks. This paper describes five technologies that could lead to both architectural and component disruptive design changes: device-centric architectures, millimeter Wave, Massive-MIMO, smarter devices, and native support to machine-2-machine. The key ideas for each technology are described, along with their potential impact on 5G and the research challenges that remain.
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paper_title: Full duplex radios

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This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
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paper_title: Toward 5G: when explosive bursts meet soft cloud

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Rapid growing demand for mobile data traffic challenges capacities and service provision in the next-generation (5G) cellular networks. Real measurement data from operating cellular networks indicates that the traffic models and scenarios disobey our traditional assumptions (i.e., expressing bursty nature). As a result, current network architectures and service management may cause experience deterioration of subscribers in future networks. In this article, we propose three approaches to alleviate the influence of various traffic bursts: baseband resource pool on a cloud platform as wireless infrastructure to enhance the capacity and flexibility of networks, cloud core networks to provide dynamic extension and service flow control abilities, and software-defined bearer networks to simplify service delivery instructed by core networks. Different from conventional stovepipe-like cloud computing network architectures, our proposed architecture interconnects and shares information between entities, breaking through horizontal device barriers and vertical layers. These cloud-based approaches not only avoid the potentially negative impact of bursts, but also provide a software-controlled end-to-end service management framework for future cellular networks. In addition, by taking advantage of open interfaces of cloud-based network elements, service control algorithms and network APIs could also be implemented to realize smart and soft 5G cellular networks.
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paper_title: Dynamic Base Station Switching-On/Off Strategies for Green Cellular Networks

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In this paper, we investigate dynamic base station (BS) switching to reduce energy consumption in wireless cellular networks. Specifically, we formulate a general energy minimization problem pertaining to BS switching that is known to be a difficult combinatorial problem and requires high computational complexity as well as large signaling overhead. We propose a practically implementable switching-on/off based energy saving (SWES) algorithm that can be operated in a distributed manner with low computational complexity. A key design principle of the proposed algorithm is to turn off a BS one by one that will minimally affect the network by using a newly introduced notion of network-impact, which takes into account the additional load increments brought to its neighboring BSs. In order to further reduce the signaling and implementation overhead over the air and backhaul, we propose three other heuristic versions of SWES that use the approximate values of network-impact as their decision metrics. We describe how the proposed algorithms can be implemented in practice at the protocol-level and also estimate the amount of energy savings through a first-order analysis in a simple setting. Extensive simulations demonstrate that the SWES algorithms can significantly reduce the total energy consumption, e.g., we estimate up to 50-80% potential savings based on a real traffic profile from a metropolitan urban area.
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paper_title: Downlink and Uplink Decoupling: a Disruptive Architectural Design for 5G Networks

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Cell association in cellular networks has traditionally been based on the downlink received signal power only, despite the fact that uplink and downlink transmission powers and interference levels differed significantly. This approach was adequate in homogeneous networks with macro base stations all having similar transmission power levels. However, with the growth of heterogeneous networks where there is a big disparity in the transmit power of the different base station types, this approach is highly inefficient. In this paper, we study the notion of Downlink and Uplink Decoupling (DUDe) where the downlink cell association is based on the downlink received power while the uplink is based on the pathloss. We present the motivation and assess the gains of this 5G design approach with simulations that are based on Vodafone's LTE field trial network in a dense urban area, employing a high resolution ray-tracing pathloss prediction and realistic traffic maps based on live network measurements.
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paper_title: Full duplex techniques for 5G networks: self-interference cancellation, protocol design, and relay selection

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The wireless research community aspires to conceive full duplex operation by supporting concurrent transmission and reception in a single time/frequency channel for the sake of improving the attainable spectral efficiency by a factor of two as compared to the family of conventional half duplex wireless systems. The main challenge encountered in implementing FD wireless devices is that of finding techniques for mitigating the performance degradation imposed by self-interference. In this article, we investigate the potential FD techniques, including passive suppression, active analog cancellation, and active digital cancellation, and highlight their pros and cons. Furthermore, the troubles of FD medium access control protocol design are discussed for addressing the problems such as the resultant end-to-end delay and network congestion. Additionally, an opportunistic decode-andforward- based relay selection scheme is analyzed in underlay cognitive networks communicating over independent and identically distributed Rayleigh and Nakagami-m fading channels in the context of FD relaying. We demonstrate that the outage probability of multi-relay cooperative communication links can be substantially reduced. Finally, we discuss the challenges imposed by the aforementioned techniques and a range of critical issues associated with practical FD implementations. It is shown that numerous open challenges, such as efficient SI suppression, high-performance FD MAC-layer protocol design, low power consumption, and hybrid FD/HD designs, have to be tackled before successfully implementing FD-based systems.
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paper_title: An energy efficient and spectrum efficient wireless heterogeneous network framework for 5G systems

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In this article we explore a system framework of cooperative green heterogeneous networks for 5G wireless communication systems. We first survey the state-of-the-art on spectrum efficiency (SE), energy efficiency (EE), and quality of service (QoS) based mobile association, multi-layer interference management and power control, network wide cooperation and dynamic resource allocation for heterogeneous wireless networks. We also present the system framework of cooperative green heterogeneous networks, which aims at balancing and optimizing SE, EE, and QoS in heterogeneous wireless networks. We discuss the design principles and show some preliminary performance results on the tradeoffs among SE, EE, and QoS. Finally, we identify the technical challenges that remain in the cooperative green heterogeneous network design. The presented wireless system framework is expected to advance the understandings of the critical technical issues toward energy and spectrum efficient 5G wireless communication systems.
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paper_title: Denial of Service Prevention for 5G

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5G wireless mobile communication is expected to include a large number of advanced technologies in order to further increase bandwidth, Quality of Service (QoS), improve usability and security, decrease delays and cost of service. Software Defined Radio (SDR) will be the platform for advanced terminals. Our focus is security and especially prevention of Denial of Service (DoS) attacks which we believe will become more common in commercial networks through increasing availability of easy programmable SDRs. We propose a secret version of Adaptive Frequency Hopping, as a possible 5G technology in combination with others, with QoS estimation by means of physical layer parameters. The QoS parameter chosen is Bit Error Rate (BER) and this we use for blacklisting frequencies that we assume are under DoS attack. Our experimental results on BER estimation show this to be a promising approach.
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paper_title: Massive MIMO for Next Generation Wireless Systems

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Multi-user MIMO offers big advantages over conventional point-to-point MIMO: it works with cheap single-antenna terminals, a rich scattering environment is not required, and resource allocation is simplified because every active terminal utilizes all of the time-frequency bins. However, multi-user MIMO, as originally envisioned, with roughly equal numbers of service antennas and terminals and frequency-division duplex operation, is not a scalable technology. Massive MIMO (also known as large-scale antenna systems, very large MIMO, hyper MIMO, full-dimension MIMO, and ARGOS) makes a clean break with current practice through the use of a large excess of service antennas over active terminals and time-division duplex operation. Extra antennas help by focusing energy into ever smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include extensive use of inexpensive low-power components, reduced latency, simplification of the MAC layer, and robustness against intentional jamming. The anticipated throughput depends on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly joined terminals, the exploitation of extra degrees of freedom provided by the excess of service antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios. This article presents an overview of the massive MIMO concept and contemporary research on the topic.
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paper_title: Authentication handover and privacy protection in 5G hetnets using software-defined networking

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Recently, densified small cell deployment with overlay coverage through coexisting heterogeneous networks has emerged as a viable solution for 5G mobile networks. However, this multi-tier architecture along with stringent latency requirements in 5G brings new challenges in security provisioning due to the potential frequent handovers and authentications in 5G small cells and HetNets. In this article, we review related studies and introduce SDN into 5G as a platform to enable efficient authentication hand-over and privacy protection. Our objective is to simplify authentication handover by global management of 5G HetNets through sharing of userdependent security context information among related access points. We demonstrate that SDN-enabled security solutions are highly efficient through its centralized control capability, which is essential for delay-constrained 5G communications.
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paper_title: Handover Scheme for 5G C/U Plane Split Heterogeneous Network in High-Speed Railway

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Being a promising technology for fifth-generation (5G) communication systems, a novel railway communication system based on control/user (C/U) plane split heterogeneous networks can provide a high-quality broadband wireless service for passengers in high-speed railways with higher system capacity, better transmission reliability, and less cochannel interference. However, due to its special architecture where the C-plane and the U-plane must be split and supported by a macro Evolved Node B (eNB) and a phantom eNB, respectively, it would suffer more serious handover problem, particularly in intermacrocell handover, which directly degrades its applicability and availability in high-speed railways. Moreover, no technical specification has been released about this network architecture. Therefore, this paper focuses on redesigning and analyzing technical details and handover procedures based on Long-Term Evolution (LTE) specifications to guarantee the proposed system's practicability and generality and its analytical tractability. To resolve the handover problem, this paper proposes a handover trigger decision scheme based on GM(1, $n$) model of the grey system theory. By this scheme, the received signal quality from the $(N + hbox{1})$th measurement report can be predicted from the $N$th measurement period, and the predicted values can be then utilized to make the handover trigger decision. The simulation results show that the proposed scheme is capable of triggering handover in advance effectively and of enhancing handover success probability remarkably.
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paper_title: Device-to-device communication in 5G cellular networks: challenges, solutions, and future directions

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In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular bandwidth and all communications take place through the base stations. In this article, we envision a two-tier cellular network that involves a macrocell tier (i.e., BS-to-device communications) and a device tier (i.e., device-to-device communications). Device terminal relaying makes it possible for devices in a network to function as transmission relays for each other and realize a massive ad hoc mesh network. This is obviously a dramatic departure from the conventional cellular architecture and brings unique technical challenges. In such a two-tier cellular system, since the user data is routed through other users? devices, security must be maintained for privacy. To ensure minimal impact on the performance of existing macrocell BSs, the two-tier network needs to be designed with smart interference management strategies and appropriate resource allocation schemes. Furthermore, novel pricing models should be designed to tempt devices to participate in this type of communication. Our article provides an overview of these major challenges in two-tier networks and proposes some pricing schemes for different types of device relaying.
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paper_title: Enable device-to-device communications underlaying cellular networks: challenges and research aspects

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Device-to-device communication underlaying a cellular network is a promising technology in future wireless networks to improve network capacity and user experience. While D2D communication has great potential to improve wireless system spectral and energy efficiency due to the proximity of communication parties and higher spectrum reuse gain, tremendous work is still ongoing to turn the promising technology into a reality. This article discusses D2D technical challenges as well as standards progress and important research aspects that enable D2D communications underlaying cellular networks. The key research areas addressed include interference management, multihop D2D communications, and D2D communications in heterogeneous networks. When enabling D2D communications underlaying cellular networks, D2D communications can use either cellular downlink or cellular uplink resources. The two resource sharing modes will create different interference scenarios. The performance evaluation on D2D communications underlaying cellular networks under these two different scenarios is provided.
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paper_title: Policy-based communications for 5G mobile with customer edge switching

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Besides more capacity and faster connections, 5G is expected to provide ultra-reliable services, for example, for machine-to-machine communications. In this paper, we advocate that 5G must do its best to eliminate malicious traffic as a cause of failure of legitimate services. This paper proposes that all communications in 5G should be controlled by policy. The policies facilitate cooperation of customer networks against misbehaving actors and collecting evidence of malicious activity. Dynamic policies can react to hosts that are used in attacks. We propose a system controlled by policy that overcomes the classical weaknesses in the Internet, namely source address spoofing and denial of service attacks. We propose to improve the mobile device experience by new methods of network address translator traversal suitable for battery-powered mobile devices. We believe that 5G will be the major driver for the future Internet, which is why we relate our approach to other proposals for future Internet architecture. Our approach can be deployed one network at a time as it limits the changes to edge nodes; no compulsory changes are proposed to hosts. The paper reports the experience from experimentation and evaluates scalability and security including initial results on performance. © 2015 The Authors. Security and Communication Networks published by John Wiley & Sons, Ltd.
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paper_title: CONCERT: A Cloud-Based Architecture for Next-generation Cellular Systems

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Cellular networks are one of the cornerstones of our information-driven society. However, existing cellular systems have been seriously challenged by the explosion of mobile data traffic, the emergence of machine-type communications, and the flourishing of mobile Internet services. In this article, we propose CONCERT, a converged edge infrastructure for future cellular communications and mobile computing services. The proposed architecture is constructed based on the concept of control/data (C/D) plane decoupling. The data plane includes heterogeneous physical resources such as radio interface equipment, computational resources, and software-defined switches. The control plane jointly coordinates physical resources to present them as virtual resources, over which software-defined services including communications, computing, and management can be deployed in a flexible manner. Moreover, we introduce new designs for physical resources placement and task scheduling so that CONCERT can overcome the drawbacks of the existing baseband-up centralization approach and better facilitate innovations in next-generation cellular networks. These advantages are demonstrated with application examples on radio access networks with C/D decoupled air interface, delaysensitive machine-type communications, and realtime mobile cloud gaming. We also discuss some fundamental research issues arising with the proposed architecture to illuminate future research directions.
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paper_title: Cloud technologies for flexible 5G radio access networks

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The evolution toward 5G mobile networks will be characterized by an increasing number of wireless devices, increasing device and service complexity, and the requirement to access mobile services ubiquitously. Two key enablers will allow the realization of the vision of 5G: very dense deployments and centralized processing. This article discusses the challenges and requirements in the design of 5G mobile networks based on these two key enablers. It discusses how cloud technologies and flexible functionality assignment in radio access networks enable network densification and centralized operation of the radio access network over heterogeneous backhaul networks. The article describes the fundamental concepts, shows how to evolve the 3GPP LTE architecture, and outlines the expected benefits.
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paper_title: An Overview of Massive MIMO: Benefits and Challenges

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Massive multiple-input multiple-output (MIMO) wireless communications refers to the idea equipping cellular base stations (BSs) with a very large number of antennas, and has been shown to potentially allow for orders of magnitude improvement in spectral and energy efficiency using relatively simple (linear) processing. In this paper, we present a comprehensive overview of state-of-the-art research on the topic, which has recently attracted considerable attention. We begin with an information theoretic analysis to illustrate the conjectured advantages of massive MIMO, and then we address implementation issues related to channel estimation, detection and precoding schemes. We particularly focus on the potential impact of pilot contamination caused by the use of non-orthogonal pilot sequences by users in adjacent cells. We also analyze the energy efficiency achieved by massive MIMO systems, and demonstrate how the degrees of freedom provided by massive MIMO systems enable efficient single-carrier transmission. Finally, the challenges and opportunities associated with implementing massive MIMO in future wireless communications systems are discussed.
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paper_title: Cellular architecture and key technologies for 5G wireless communication networks

paper_content:

The fourth generation wireless communication systems have been deployed or are soon to be deployed in many countries. However, with an explosion of wireless mobile devices and services, there are still some challenges that cannot be accommodated even by 4G, such as the spectrum crisis and high energy consumption. Wireless system designers have been facing the continuously increasing demand for high data rates and mobility required by new wireless applications and therefore have started research on fifth generation wireless systems that are expected to be deployed beyond 2020. In this article, we propose a potential cellular architecture that separates indoor and outdoor scenarios, and discuss various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications. Future challenges facing these potential technologies are also discussed.
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paper_title: Quality-aware millimeter-wave device-to-device multi-hop routing for 5G cellular networks

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Millimeter-wave (mm-wave) transmission is a promising method for increasing capacity in next-generation cellular systems. However, since mm-wave signals are too weak to (i) do long-distance communication and (ii) survive in non-line-of-sight situations, multi-hop relaying is required. We thus study in this paper a multi-hop routing protocol at mm-wave (38 GHz and 28GHz) frequencies. Due to the great and steadily increasing importance of video streaming in cellular applications, we pay special attention to the maximization of video transmission quality, which makes the optimization problem different from the usual sum-rate maximization. Specifically, we develop a protocol that optimizes the “sum quality” of the transmission of different video streams, subject to constraints (minimum quality) of separate streams. We take the unique properties of mm-waves (sparse angular power spectrum, leading to low interference) into account in our method. Extensive simulation results show the superiority of our approach compared to max-min flow routing which is widely used in QoS-sensitive applications.
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paper_title: Heterogeneous statistical QoS provisioning over 5G mobile wireless networks

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As a critical step towards the next new era of mobile wireless networks, recently 5G mobile wireless networks have received significant research attention and efforts from both academia and industry. The 5G mobile wireless networks are expected to provide different delay-bounded QoS guarantees for a wide spectrum of services, applications, and users with extremely diverse requirements. Since the time-sensitive services in 5G multimedia wireless networks may vary dramatically in both a large range from milliseconds to a few seconds and diversity from uniform/ constant delay-bound to different/variable delay-bound guarantees among different wireless links, the delay-bound QoS requirements for different types of services promote the newly emerging heterogeneous statistical delay-bounded QoS provisioning over 5G mobile wireless networks, which, however, imposes many new challenging issues not encountered before in 4G wireless networks. To overcome these new challenges, in this article we propose a novel heterogeneous statistical QoS provisioning architecture for 5G mobile wireless networks. First, we develop and analyze the new heterogeneous statistical QoS system model by applying and extending the effective capacity theory. Then, through the wireless coupling channels, we apply our proposed heterogeneous statistical QoS architecture to efficiently implement the following powerful 5G-candidate wireless techniques: 1) device-to-device networks; 2) full-duplex networks; and 3) cognitive radio networks, respectively, for providing heterogeneous statistical delay-bounded QoS guarantees. Finally, using the simulation experiments we show that our proposed architecture and schemes significantly outperform the existing traditional statistical delay-bounded QoS provisioning schemes in terms of satisfying the heterogeneous delay-bounded QoS requirements while maximizing the aggregate system throughput over 5G mobile wireless networks.
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paper_title: Five Disruptive Technology Directions for 5G

paper_content:

New research directions will lead to fundamental changes in the design of future 5th generation (5G) cellular networks. This paper describes five technologies that could lead to both architectural and component disruptive design changes: device-centric architectures, millimeter Wave, Massive-MIMO, smarter devices, and native support to machine-2-machine. The key ideas for each technology are described, along with their potential impact on 5G and the research challenges that remain.
---
paper_title: Local cooperation architecture for self-healing femtocell networks

paper_content:

As the demands for mobile phone access to the data services are expanding, advantages in cellular services can be gained by offering enhanced user experience through cost-effective broadband mobile. By reducing the distance between base stations and end users, femtocells provide higher data rates and better indoor coverage. The small size of a femtocell also improves spectrum reuse, which contributes to higher spectrum efficiency. As femtocells are usually unplanned, efficient operation and maintenance are required to maximize the benefits of femtocell access. As one of the fundamental functionalities in network maintenance, a selfhealing mechanism aims to autonomously alleviate the impact of coverage or capacity loss induced by cell outage. Existing studies on the self-healing problem have focused on macrocell networks, while none of them has systematically investigated the problem in the context of femtocells networks. In this article we argue that the distinct features of the two-tier macro-femto system require dedicated architectures for self-healing femtocell networks. We present three different architectures, and further investigate their advantages and limitations. Then we call attention to the local cooperative architecture, which, with proper design, satisfies the practical requirements imposed by the salient features of femtocell networks. We further verify the benefits of the local cooperative architecture by proposing a self-healing scheme for femtocell networks.
---
paper_title: Effective RAT Selection Approach for 5G Dense Wireless Networks

paper_content:

Dense Networks (DenseNet) and Multi-Radio Access Technologies (Multi-RATs) are considered as key features of the emerging fifth generation (5G) wireless systems. A Multi- RAT DenseNet is characterized by a very dense deployment of low- power base stations (BSs) and by a multi-tier architecture consisting of heterogeneous radio access technologies. In this work, we propose an effective RAT selection algorithm that efficiently manages the RAT handover procedure by (i) choosing the most suitable RAT that guarantees high system and user performance, and (ii) reducing unnecessary handover events. In particular, the decision to trigger a handover is based on a new system parameter named Reference Base Station Efficiency (RBSE). This parameter takes into account metrics related to both the system and the user: the BS transmitted power, the BS traffic load and the users' spectral efficiency. We compare, by simulation, the proposed scheme with the standardized 3GPP policies. Results show that the proposed RAT selection scheme significantly reduces the number of handovers and the end-to- end delay while maintaining high system throughput and user spectral efficiency.
---
paper_title: Network densification: the dominant theme for wireless evolution into 5G

paper_content:

This article explores network densification as the key mechanism for wireless evolution over the next decade. Network densification includes densification over space (e.g, dense deployment of small cells) and frequency (utilizing larger portions of radio spectrum in diverse bands). Large-scale cost-effective spatial densification is facilitated by self-organizing networks and intercell interference management. Full benefits of network densification can be realized only if it is complemented by backhaul densification, and advanced receivers capable of interference cancellation.
---
paper_title: Full-dimension MIMO (FD-MIMO) for next generation cellular technology

paper_content:

This article considers a practical implementation of massive MIMO systems [1]. Although the best performance can be achieved when a large number of active antennas are placed only in the horizontal domain, BS form factor limitation often makes horizontal array placement infeasible. To cope with this limitation, this article introduces full-dimension MIMO (FD-MIMO) cellular wireless communication system, where active antennas are placed in a 2D grid at BSs. For analysis of the FD-MIMO systems, a 3D spatial channel model is introduced, on which system-level simulations are conducted. The simulation results show that the proposed FD-MIMO system with 32 antenna ports achieves 2-3.6 times cell average throughput gain and 1.5-5 times cell edge throughput gain compared to the 4G LTE system of two antenna ports at the BS.
---
paper_title: CRAHNs : Cognitive radio ad hoc networks

paper_content:

Cognitive radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrum-aware communication paradigm in wireless communications. CR networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse quality-of-service (QoS) requirements. Specifically, in cognitive radio ad hoc networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this paper, intrinsic properties and current research challenges of the CRAHNs are presented. First, novel spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. A particular emphasis is given to distributed coordination between CR users through the establishment of a common control channel. Moreover, the influence of these functions on the performance of the upper layer protocols, such as the network layer, and transport layer protocols are investigated and open research issues in these areas are also outlined. Finally, a new direction called the commons model is explained, where CRAHN users may independently regulate their own operation based on pre-decided spectrum etiquette.
---
paper_title: 5G Wireless Backhaul Networks: Challenges and Research Advance

paper_content:

5G networks are expected to achieve gigabit-level throughput in future cellular networks. However, it is a great challenge to treat 5G wireless backhaul traffic in an effective way. In this article, we analyze the wireless backhaul traffic in two typical network architectures adopting small cell and millimeter wave commmunication technologies. Furthermore, the energy efficiency of wireless backhaul networks is compared for different network architectures and frequency bands. Numerical comparison results provide some guidelines for deploying future 5G wireless backhaul networks in economical and highly energy-efficient ways.
---
paper_title: Evolution Towards 5G Multi-tier Cellular Wireless Networks: An Interference Management Perspective

paper_content:

The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, for example, higher data rates, excellent end-to-end performance, and user-coverage in hot-spots and crowded areas with lower latency, energy consumption, and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g. power control, cell association) in these networks with shared spectrum access (i.e. when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.
---
paper_title: Full duplex radios

paper_content:

This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
---
paper_title: SARA: A service-aware resource allocation scheme for device-to-device communication underlaying cellular networks

paper_content:

This paper considers the resource allocation problem for device-to-device (D2D) communication underlaying cellular networks and proposes a service-aware resource allocation (SARA) scheme for D2D communication to improve the network performance. SARA takes into account the different service requirements of D2D users. It consists of two allocation phases: on-demand resource allocation and secondary resource allocation. In the first phase, cellular user resources are allocated on demand to meet the different service requirements of D2D pairs. In the second phase, the remaining cellular user resources after the first phase are allocated to D2D users based on an objective function in order to improve the resource utilization. Simulation results show that the proposed SARA scheme can significantly improve the performance of a cellular system in terms of the satisfaction ratio of D2D pairs and the system throughput.
---
paper_title: Distributed mobility management for future 5G networks: overview and analysis of existing approaches

paper_content:

The ever-increasing demand of mobile Internet traffic is pushing operators to look for solutions to increase the available bandwidth per user and per unit of area. At the same time, they need to reduce the load in the core network at a reasonable cost in their future 5G deployments. Today’s trend points to the deployment of extremely dense networks in order to provide ubiquitous connectivity at high data rates. However, this is hard to couple with the current mobile networks’ architecture, which is heavily centralized, posing difficult challenges when coping with the foreseen explosion of mobile data. Additionally, future 5G networks will exhibit disparate types of services, posing different connectivity requirements. Distributed mobility management is emerging as a valid framework to design future mobile network architectures, taking into account the requirements for large traffic in the core and the rise of extremely dense wireless access networks. In this article, we discuss the adoption of a distributed mobility management approach for mobile networks, and analyze the operation of the main existing solutions proposed so far, including a first practical evaluation based on experiments with real Linux-based prototype implementations.
---
paper_title: Multi-hop point-to-point FDD wireless backhaul for mobile small cells

paper_content:

Point-to-point FDD microwave can be a fast-to-install and cost-effective backhaul solution for mobile small cells. However, its applications have been held back, because the state-of-the-art static backhaul deployment fails to capture drastically fluctuating small cell traffic. To address this issue we introduce a new adaptive backhaul architecture that is able to adapt to changing small cell traffic. Extended from a graph theoretic clique idea, the architecture allows changes to the overall backhaul topology, and it also allows each individual backhaul link to vary its frequency to meet traffic demand. Guard bands are adaptively reserved between some of the links to suppress adjacent-frequency interference, while being efficiently used by other links for data transmission. Our case study of 10 small cells confirms that the adaptive architecture is able to increase the small cell throughput by 75 percent compared to the static backhaul architecture. It can also reduce the backhaul bandwidth requirement by 57 percent, and enhance small cells' satisfaction by 158.4 percent with respect to their allocated bandwidths.
---
paper_title: Toward 5G: when explosive bursts meet soft cloud

paper_content:

Rapid growing demand for mobile data traffic challenges capacities and service provision in the next-generation (5G) cellular networks. Real measurement data from operating cellular networks indicates that the traffic models and scenarios disobey our traditional assumptions (i.e., expressing bursty nature). As a result, current network architectures and service management may cause experience deterioration of subscribers in future networks. In this article, we propose three approaches to alleviate the influence of various traffic bursts: baseband resource pool on a cloud platform as wireless infrastructure to enhance the capacity and flexibility of networks, cloud core networks to provide dynamic extension and service flow control abilities, and software-defined bearer networks to simplify service delivery instructed by core networks. Different from conventional stovepipe-like cloud computing network architectures, our proposed architecture interconnects and shares information between entities, breaking through horizontal device barriers and vertical layers. These cloud-based approaches not only avoid the potentially negative impact of bursts, but also provide a software-controlled end-to-end service management framework for future cellular networks. In addition, by taking advantage of open interfaces of cloud-based network elements, service control algorithms and network APIs could also be implemented to realize smart and soft 5G cellular networks.
---
paper_title: 5G: Personal mobile internet beyond what cellular did to telephony

paper_content:

Cellular technology has dramatically changed our society and the way we communicate. First it impacted voice telephony, and then has been making inroads into data access, applications, and services. However, today potential capabilities of the Internet have not yet been fully exploited by cellular systems. With the advent of 5G we will have the opportunity to leapfrog beyond current Internet capabilities.
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paper_title: Location-Aware Mobile Intrusion Detection with Enhanced Privacy in a 5G Context

paper_content:

The paper proposes a location-aware mobile Intrusion Prevention System (mIPS) architecture with enhanced privacy that is integrated in Managed Security Service (MSS). The solution is envisaged in a future fifth generation telecommunications (5G) context with increased but varying bandwidth, a virtualised execution environment and infrastructure that allows threads, processes, virtual machines and storage to be migrated to cloud computing services on demand, to dynamically scale performance and save power. 5G mobile devices will be attractive targets for malicious software, and this threat will in some cases change with location. Mobile devices will store more sensitive information and will also be used to a larger extent for sensitive transactions than they typically do today. In addition, a distributed execution environment in itself gives raise to some new security challenges. In order to handle these security challenges, we have proposed the location-aware mIPS architecture, which benefits from a distributed execution environment where processor intensive services can be outsourced to Cloud hosting providers. The mIPS supports querying location threat profiles in a privacy-preserving way, and ensures that mIPS alerts sent to the the first-line MSS are anonymised. We finally perform an analysis of potential strengths and weaknesses of the proposed approach.
---
paper_title: Cache in the air: exploiting content caching and delivery techniques for 5G systems

paper_content:

The demand for rich multimedia services over mobile networks has been soaring at a tremendous pace over recent years. However, due to the centralized architecture of current cellular networks, the wireless link capacity as well as the bandwidth of the radio access networks and the backhaul network cannot practically cope with the explosive growth in mobile traffic. Recently, we have observed the emergence of promising mobile content caching and delivery techniques, by which popular contents are cached in the intermediate servers (or middleboxes, gateways, or routers) so that demands from users for the same content can be accommodated easily without duplicate transmissions from remote servers; hence, redundant traffic can be significantly eliminated. In this article, we first study techniques related to caching in current mobile networks, and discuss potential techniques for caching in 5G mobile networks, including evolved packet core network caching and radio access network caching. A novel edge caching scheme based on the concept of content-centric networking or information-centric networking is proposed. Using trace-driven simulations, we evaluate the performance of the proposed scheme and validate the various advantages of the utilization of caching content in 5G mobile networks. Furthermore, we conclude the article by exploring new relevant opportunities and challenges.
---
paper_title: Applications of self-interference cancellation in 5G and beyond

paper_content:

Self-interference cancellation invalidates a long-held fundamental assumption in wireless network design that radios can only operate in half duplex mode on the same channel. Beyond enabling true in-band full duplex, which effectively doubles spectral efficiency, self-interference cancellation tremendously simplifies spectrum management. Not only does it render entire ecosystems like TD-LTE obsolete, it enables future networks to leverage fragmented spectrum, a pressing global issue that will continue to worsen in 5G networks. Self-interference cancellation offers the potential to complement and sustain the evolution of 5G technologies toward denser heterogeneous networks and can be utilized in wireless communication systems in multiple ways, including increased link capacity, spectrum virtualization, any-division duplexing (ADD), novel relay solutions, and enhanced interference coordination. By virtue of its fundamental nature, self-interference cancellation will have a tremendous impact on 5G networks and beyond.
---
paper_title: An energy-aware scheme for efficient spectrum utilization in a 5G mobile cognitive radio network architecture

paper_content:

This paper proposes an energy-efficient delay-aware cooperative scheme, exploited for efficient resource management and maximum energy conservation in a 5G mobile cognitive radio network architecture. The proposed scheme is based on the comparison of the queuing delays of both the secondary nodes and the Radio Access Points, when delay sensitive transmission is requested, providing optimal TV White Spaces exploitation via a spectrum broker. The spectrum broker manages the process of the energy consumption of the 5G mobile communication systems, according to the proposed delay-aware cooperative scheme and the comparative evaluation of the queuing delays. The validity of the performance of the scheme is verified through extended simulation tests, carried out under controlled experimental conditions.
---
paper_title: Secure sharing and searching for real-time video data in mobile cloud

paper_content:

In this article we propose an infrastructure that allows mobile users to securely share and search for their real-time video data. Specifically, the proposed infrastructure takes the advantages of the cloud platform and 5G technology to achieve its goals, where mobile users (connected with some external video taking device) can share their real-time video with their friends or families through the cloud while any other user with no permission cannot get any information about the video. More importantly, the infrastructure security is guaranteed even if the cloud server is hacked. In addition, our infrastructure also allows secure searching within the user's own video data. We believe our solution is practical to be deployed in the existing telecommunication platforms.
---
paper_title: Full duplex: Coming into reality in 2020?

paper_content:

Mobile traffic is projected to increase 1000 times from 2010 to 2020. This poses significant challenges on the 5th generation (5G) wireless communication system design, including network structure, air interface, key transmission schemes, multiple access, and duplexing schemes. In this paper, full duplex (FD) is discussed, aiming to highlight some insights on various issues including deployment scenarios, frame structures, reference signals (RS), interference mitigation, transceiver structures/calibration, and extension of time division duplex (TDD)/frequency division duplex (FDD) to full duplex. It is anticipated that with future standardization and deployment of FD systems, TDD and FDD will be harmoniously integrated, supporting all the existing half duplex mobile phones efficiently, and leading to a much enhanced 5G system performance.
---
paper_title: Cellular architecture and key technologies for 5G wireless communication networks

paper_content:

The fourth generation wireless communication systems have been deployed or are soon to be deployed in many countries. However, with an explosion of wireless mobile devices and services, there are still some challenges that cannot be accommodated even by 4G, such as the spectrum crisis and high energy consumption. Wireless system designers have been facing the continuously increasing demand for high data rates and mobility required by new wireless applications and therefore have started research on fifth generation wireless systems that are expected to be deployed beyond 2020. In this article, we propose a potential cellular architecture that separates indoor and outdoor scenarios, and discuss various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications. Future challenges facing these potential technologies are also discussed.
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paper_title: A heterogeneous cellular network model with inter-tier dependence

paper_content:

In heterogeneous cellular networks (HCNs), the macrocell network is usually assumed to be overlaid by multiple independent tiers of small cells. However, in reality, the locations of the base stations (BSs) belonging to different tiers are not fully independent. Accordingly, in this paper, we propose a two-tier HCN model with inter-tier dependence, where the macro-BS (MBS) and the pico-BS (PBS) deployments follow a Poisson point process (PPP) and a Poisson hole process (PHP), respectively. Under this setup, we derive bounds on the outage probabilities of both macro users and pico users, and then use a fitted Poisson cluster process to approximate the PHP, which is shown to provide a good approximation of the interference and outage. The results show that the model with inter-tier dependence appears closer to the real deployment than the two extremes with full regularity (the triangular lattice) and complete randomness (the PPP). An important conclusion is that significant gains can be obtained if PBSs are deployed smartly (away from MBSs).
---
paper_title: Network densification: the dominant theme for wireless evolution into 5G

paper_content:

This article explores network densification as the key mechanism for wireless evolution over the next decade. Network densification includes densification over space (e.g, dense deployment of small cells) and frequency (utilizing larger portions of radio spectrum in diverse bands). Large-scale cost-effective spatial densification is facilitated by self-organizing networks and intercell interference management. Full benefits of network densification can be realized only if it is complemented by backhaul densification, and advanced receivers capable of interference cancellation.
---
paper_title: 5G Wireless Backhaul Networks: Challenges and Research Advance

paper_content:

5G networks are expected to achieve gigabit-level throughput in future cellular networks. However, it is a great challenge to treat 5G wireless backhaul traffic in an effective way. In this article, we analyze the wireless backhaul traffic in two typical network architectures adopting small cell and millimeter wave commmunication technologies. Furthermore, the energy efficiency of wireless backhaul networks is compared for different network architectures and frequency bands. Numerical comparison results provide some guidelines for deploying future 5G wireless backhaul networks in economical and highly energy-efficient ways.
---
paper_title: Multi-hop point-to-point FDD wireless backhaul for mobile small cells

paper_content:

Point-to-point FDD microwave can be a fast-to-install and cost-effective backhaul solution for mobile small cells. However, its applications have been held back, because the state-of-the-art static backhaul deployment fails to capture drastically fluctuating small cell traffic. To address this issue we introduce a new adaptive backhaul architecture that is able to adapt to changing small cell traffic. Extended from a graph theoretic clique idea, the architecture allows changes to the overall backhaul topology, and it also allows each individual backhaul link to vary its frequency to meet traffic demand. Guard bands are adaptively reserved between some of the links to suppress adjacent-frequency interference, while being efficiently used by other links for data transmission. Our case study of 10 small cells confirms that the adaptive architecture is able to increase the small cell throughput by 75 percent compared to the static backhaul architecture. It can also reduce the backhaul bandwidth requirement by 57 percent, and enhance small cells' satisfaction by 158.4 percent with respect to their allocated bandwidths.
---
paper_title: Local cooperation architecture for self-healing femtocell networks

paper_content:

As the demands for mobile phone access to the data services are expanding, advantages in cellular services can be gained by offering enhanced user experience through cost-effective broadband mobile. By reducing the distance between base stations and end users, femtocells provide higher data rates and better indoor coverage. The small size of a femtocell also improves spectrum reuse, which contributes to higher spectrum efficiency. As femtocells are usually unplanned, efficient operation and maintenance are required to maximize the benefits of femtocell access. As one of the fundamental functionalities in network maintenance, a selfhealing mechanism aims to autonomously alleviate the impact of coverage or capacity loss induced by cell outage. Existing studies on the self-healing problem have focused on macrocell networks, while none of them has systematically investigated the problem in the context of femtocells networks. In this article we argue that the distinct features of the two-tier macro-femto system require dedicated architectures for self-healing femtocell networks. We present three different architectures, and further investigate their advantages and limitations. Then we call attention to the local cooperative architecture, which, with proper design, satisfies the practical requirements imposed by the salient features of femtocell networks. We further verify the benefits of the local cooperative architecture by proposing a self-healing scheme for femtocell networks.
---
paper_title: Coverage Analysis of Cognitive Femtocell Networks

paper_content:

In heterogeneous networks, interference is one of the critical issues. In this letter, we consider a two-tier downlink network composed of macrocell base stations (MBSs) and femtocell base stations (FBSs), where the locations of MBSs and FBSs are modeled by two independent Poisson point processes (PPPs). FBSs are assumed to be cognitive and become inactive when within a certain range of active MBSs. Due to the inactivation regions, the location distribution of active FBSs no longer follows PPP, complicating the calculation of coverage probability. To circumvent this, we propose an approximation to the coverage probability for both the open access and closed access policies.
---
paper_title: CRAHNs : Cognitive radio ad hoc networks

paper_content:

Cognitive radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrum-aware communication paradigm in wireless communications. CR networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse quality-of-service (QoS) requirements. Specifically, in cognitive radio ad hoc networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this paper, intrinsic properties and current research challenges of the CRAHNs are presented. First, novel spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. A particular emphasis is given to distributed coordination between CR users through the establishment of a common control channel. Moreover, the influence of these functions on the performance of the upper layer protocols, such as the network layer, and transport layer protocols are investigated and open research issues in these areas are also outlined. Finally, a new direction called the commons model is explained, where CRAHN users may independently regulate their own operation based on pre-decided spectrum etiquette.
---
paper_title: Cognitive radio in 5G: a perspective on energy-spectral efficiency trade-off

paper_content:

A cognitive cellular network, which integrates conventional licensed cellular radio and cognitive radio into a holistic system, is a promising paradigm for the fifth generation mobile communication systems. Understanding the trade-off between energy efficiency, EE, and spectral efficiency, SE, in cognitive cellular networks is of fundamental importance for system design and optimization. This article presents recent research progress on the EE-SE trade-off of cognitive cellular networks. We show how EE-SE trade-off studies can be performed systematically with respect to different architectures, levels of analysis, and capacity metrics. Three representative examples are given to illustrate how EE-SE trade-off analysis can lead to important insights and useful design guidelines for future cognitive cellular networks.
---
paper_title: An energy-aware scheme for efficient spectrum utilization in a 5G mobile cognitive radio network architecture

paper_content:

This paper proposes an energy-efficient delay-aware cooperative scheme, exploited for efficient resource management and maximum energy conservation in a 5G mobile cognitive radio network architecture. The proposed scheme is based on the comparison of the queuing delays of both the secondary nodes and the Radio Access Points, when delay sensitive transmission is requested, providing optimal TV White Spaces exploitation via a spectrum broker. The spectrum broker manages the process of the energy consumption of the 5G mobile communication systems, according to the proposed delay-aware cooperative scheme and the comparative evaluation of the queuing delays. The validity of the performance of the scheme is verified through extended simulation tests, carried out under controlled experimental conditions.
---
paper_title: On Detecting Termination in Cognitive Radio Networks

paper_content:

The cognitive radio networks are an emerging wireless communication and computing paradigm. The cognitive radio nodes execute computations on multiple heterogeneous channels in the absence of licensed users a.k.a. primary users of those bands. The termination detection is a fundamental and non-trivial problem in distributed systems. In this paper, we propose a termination detection protocol for multi-hop cognitive radio networks where the cognitive radio nodes are allowed to tune to channels that are not currently occupied by primary users and to move to different locations during the protocol execution. The proposed protocol applies a credit-distribution-and-aggregation approach and maintains a new kind of logical structure, called the virtual tree-like structure. The virtual tree-like structure helps in decreasing the latency involved in announcing termination. Unlike conventional tree structures, the virtual tree-like structure does not require a specific node to act as the root node that has to stay involved in the computation until termination announcement; hence, the root node may become idle soon after finishing its computation. Also, the protocol is able to detect the presence of licensed users and announce strong or weak termination, whichever is possible. Copyright © 2014 John Wiley & Sons, Ltd.
---
paper_title: Cognitive femtocell networks: an opportunistic spectrum access for future indoor wireless coverage

paper_content:

Femtocells have emerged as a promising solution to provide wireless broadband access coverage in cellular dead zones and indoor environments. Compared with other techniques for indoor coverage, femtocells achieve better user experience with less capital expenditure and maintenance cost. However, co-channel deployments of closed subscriber group femtocells cause coverage holes in macrocells due to co-channel interference. To address this problem, cognitive radio technology has been integrated with femtocells. CR-enabled femtocells can actively sense their environment and exploit the network side information obtained from sensing to adaptively mitigate interference. We investigate three CRenabled interference mitigation techniques, including opportunistic interference avoidance, interference cancellation, and interference alignment. Macrocell activities can be obtained without significant overhead in femtocells. In this article, we present a joint opportunistic interference avoidance scheme with Gale-Shapley spectrum sharing (GSOIA) based on the interweave paradigm to mitigate both tier interferences in macro/femto heterogeneous networks. In this scheme, cognitive femtocells opportunistically communicate over available spectrum with minimal interference to macrocells; different femtocells are assigned orthogonal spectrum resources with a one-to-one matching policy to avoid intratier interference. Our simulations show considerable performance improvement of the GSOIA scheme and validate the potential benefits of CRenabled femtocells for in-home coverage.
---
paper_title: Cognitive femtocell market: How to price?

paper_content:

Cognitive femtocell has been envisioned as a promising technology for covering indoor environment and assisting heavy-loaded macrocell network. Although lots of technical issues of it have been studied, e.g., spectrum sharing, interference mitigation, etc, the economic issues that are very important for practical femtocell deployment have not been well investigated in the literatures. In this paper, we focus on the pricing issues in cognitive femtocell network, and propose a two-tier pricing game theoretic framework with a dynamic pricing model. We first model the cognitive users' network access behavior as a 2-dimensional Markov decision process and propose a modified value iteration algorithm to find the best strategy profiles for cognitive users. Based on the analysis of users' behavior, we further design an iterative gradient descent algorithm to find the Nash equilibrium pricing strategies for both macrocell and femtocell operators. Simulation results verify our theoretic analysis and show that the proposed algorithm can quickly converge to the Nash equilibrium prices.
---
paper_title: NeXt generation/dynamic spectrum access/cognitive Radio Wireless Networks: A Survey

paper_content:

Today's wireless networks are characterized by a fixed spectrum assignment policy. However, a large portion of the assigned spectrum is used sporadically and geographical variations in the utilization of assigned spectrum ranges from 15% to 85% with a high variance in time. The limited available spectrum and the inefficiency in the spectrum usage necessitate a new communication paradigm to exploit the existing wireless spectrum opportunistically. This new networking paradigm is referred to as NeXt Generation (xG) Networks as well as Dynamic Spectrum Access (DSA) and cognitive radio networks. The term xG networks is used throughout the paper. The novel functionalities and current research challenges of the xG networks are explained in detail. More specifically, a brief overview of the cognitive radio technology is provided and the xG network architecture is introduced. Moreover, the xG network functions such as spectrum management, spectrum mobility and spectrum sharing are explained in detail. The influence of these functions on the performance of the upper layer protocols such as routing and transport are investigated and open research issues in these areas are also outlined. Finally, the cross-layer design challenges in xG networks are discussed.
---
paper_title: Cognitive radio in 5G: a perspective on energy-spectral efficiency trade-off

paper_content:

A cognitive cellular network, which integrates conventional licensed cellular radio and cognitive radio into a holistic system, is a promising paradigm for the fifth generation mobile communication systems. Understanding the trade-off between energy efficiency, EE, and spectral efficiency, SE, in cognitive cellular networks is of fundamental importance for system design and optimization. This article presents recent research progress on the EE-SE trade-off of cognitive cellular networks. We show how EE-SE trade-off studies can be performed systematically with respect to different architectures, levels of analysis, and capacity metrics. Three representative examples are given to illustrate how EE-SE trade-off analysis can lead to important insights and useful design guidelines for future cognitive cellular networks.
---
paper_title: Enable device-to-device communications underlaying cellular networks: challenges and research aspects

paper_content:

Device-to-device communication underlaying a cellular network is a promising technology in future wireless networks to improve network capacity and user experience. While D2D communication has great potential to improve wireless system spectral and energy efficiency due to the proximity of communication parties and higher spectrum reuse gain, tremendous work is still ongoing to turn the promising technology into a reality. This article discusses D2D technical challenges as well as standards progress and important research aspects that enable D2D communications underlaying cellular networks. The key research areas addressed include interference management, multihop D2D communications, and D2D communications in heterogeneous networks. When enabling D2D communications underlaying cellular networks, D2D communications can use either cellular downlink or cellular uplink resources. The two resource sharing modes will create different interference scenarios. The performance evaluation on D2D communications underlaying cellular networks under these two different scenarios is provided.
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paper_title: Resource allocation for D2D communications under proportional fairness

paper_content:

This paper deals with the dynamic spectrum sharing between underlaying device-to-device (D2D) and cellular links in a multi-carrier cellular network to maximize the weighted network sum-rate while guaranteeing the minimum individual cellular link data rates and proportional fairness among D2D links. In particular, we formulate an NP-hard non-orthogonal resource allocation problem, and develop an iterative algorithm that alternates between the sub-carrier assignment and power allocation in each iteration until convergence. It is shown that the sub-carrier assignment problem corresponds to an integer linear program while the power allocation is reformulated into a difference-between-two-concave-functions (DC) problem. We establish the important properties of the developed algorithms and prove their convergence behavior. Illustrative results indicate that the proposed non-orthogonal resource allocation algorithm significantly outperforms the orthogonal spectrum sharing counterpart.
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paper_title: Fine-grained resource allocation for cooperative device-to-device communication in cellular networks

paper_content:

Data traffic in cellular networks has dramatically surged in recent years due to the booming growth of various mobile applications. It is hence crucial to increase network capacity to accommodate new applications and services. In this article, we propose a promising concept of cooperative device-to-device communication to improve resource utilization in cellular networks. Based on a novel fine-grained resource allocation scheme, we study the problem of maximizing the minimum rate among multiple wireless links by jointly considering relay assignment, transmission scheduling, and channel allocation. Simulation results show that our proposed solutions can significantly increase resource utilization in cellular networks.
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paper_title: SARA: A service-aware resource allocation scheme for device-to-device communication underlaying cellular networks

paper_content:

This paper considers the resource allocation problem for device-to-device (D2D) communication underlaying cellular networks and proposes a service-aware resource allocation (SARA) scheme for D2D communication to improve the network performance. SARA takes into account the different service requirements of D2D users. It consists of two allocation phases: on-demand resource allocation and secondary resource allocation. In the first phase, cellular user resources are allocated on demand to meet the different service requirements of D2D pairs. In the second phase, the remaining cellular user resources after the first phase are allocated to D2D users based on an objective function in order to improve the resource utilization. Simulation results show that the proposed SARA scheme can significantly improve the performance of a cellular system in terms of the satisfaction ratio of D2D pairs and the system throughput.
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paper_title: Delay-aware cross-layer design for device-to-device communications in future cellular systems

paper_content:

Device-to-device (D2D) communications allow direct communications between nodes without transmitting data via the base stations in cellular systems, which could bring significant performance improvement. Since most applications are delay-sensitive, it is very important to consider delay performance in addition to physical layer throughput for D2D communications. To improve delay performance it is necessary to dynamically control the radio resource in a cross-layer way according to both the channel fading information and the queue length information. The former allows an observation of good transmission opportunity and the latter provides the urgency of data flows. However, the resource control with delay constraints involves stochastic optimization, which is very challenging. In this article we first summarize various approaches to solve the delay-aware resource allocation problems for D2D communications. We propose a low complexity practical solution by exploiting the interference filtering property of CSMA-like MAC protocols in the D2D system. Based on the solution structure, we further discuss the implementation issues based on LTE-Advanced systems and evaluate the associated performance and complexity. Finally we discuss the choice of MAC parameters for the overall D2D system performance.
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paper_title: Cognitive radio in 5G: a perspective on energy-spectral efficiency trade-off

paper_content:

A cognitive cellular network, which integrates conventional licensed cellular radio and cognitive radio into a holistic system, is a promising paradigm for the fifth generation mobile communication systems. Understanding the trade-off between energy efficiency, EE, and spectral efficiency, SE, in cognitive cellular networks is of fundamental importance for system design and optimization. This article presents recent research progress on the EE-SE trade-off of cognitive cellular networks. We show how EE-SE trade-off studies can be performed systematically with respect to different architectures, levels of analysis, and capacity metrics. Three representative examples are given to illustrate how EE-SE trade-off analysis can lead to important insights and useful design guidelines for future cognitive cellular networks.
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paper_title: An energy-aware scheme for efficient spectrum utilization in a 5G mobile cognitive radio network architecture

paper_content:

This paper proposes an energy-efficient delay-aware cooperative scheme, exploited for efficient resource management and maximum energy conservation in a 5G mobile cognitive radio network architecture. The proposed scheme is based on the comparison of the queuing delays of both the secondary nodes and the Radio Access Points, when delay sensitive transmission is requested, providing optimal TV White Spaces exploitation via a spectrum broker. The spectrum broker manages the process of the energy consumption of the 5G mobile communication systems, according to the proposed delay-aware cooperative scheme and the comparative evaluation of the queuing delays. The validity of the performance of the scheme is verified through extended simulation tests, carried out under controlled experimental conditions.
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paper_title: Social-aware D2D communications: qualitative insights and quantitative analysis

paper_content:

With emerging demands for local area services, device-to-device communication is conceived as a vital component for the next-generation cellular networks to improve spectral reuse, bring hop gains, and enhance system capacity. Ripening these benefits depends on efficiently solving several main technical problems, including mode selection, resource allocation, and interference management. Aiming to establish a new paradigm for solving these challenging problems in D2D communication, in this article we propose a social-aware enhanced D2D communication architecture that exploits social networking characteristics for system design. By developing a profound understanding of the interplay between social networks' properties and mobile communication problems, we qualitatively analyze how D2D communications can benefit from social features, and quantitatively assess the achievable gains in a social-aware D2D communication system.
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paper_title: Cognitive femtocell networks: an opportunistic spectrum access for future indoor wireless coverage

paper_content:

Femtocells have emerged as a promising solution to provide wireless broadband access coverage in cellular dead zones and indoor environments. Compared with other techniques for indoor coverage, femtocells achieve better user experience with less capital expenditure and maintenance cost. However, co-channel deployments of closed subscriber group femtocells cause coverage holes in macrocells due to co-channel interference. To address this problem, cognitive radio technology has been integrated with femtocells. CR-enabled femtocells can actively sense their environment and exploit the network side information obtained from sensing to adaptively mitigate interference. We investigate three CRenabled interference mitigation techniques, including opportunistic interference avoidance, interference cancellation, and interference alignment. Macrocell activities can be obtained without significant overhead in femtocells. In this article, we present a joint opportunistic interference avoidance scheme with Gale-Shapley spectrum sharing (GSOIA) based on the interweave paradigm to mitigate both tier interferences in macro/femto heterogeneous networks. In this scheme, cognitive femtocells opportunistically communicate over available spectrum with minimal interference to macrocells; different femtocells are assigned orthogonal spectrum resources with a one-to-one matching policy to avoid intratier interference. Our simulations show considerable performance improvement of the GSOIA scheme and validate the potential benefits of CRenabled femtocells for in-home coverage.
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paper_title: CONCERT: A Cloud-Based Architecture for Next-generation Cellular Systems

paper_content:

Cellular networks are one of the cornerstones of our information-driven society. However, existing cellular systems have been seriously challenged by the explosion of mobile data traffic, the emergence of machine-type communications, and the flourishing of mobile Internet services. In this article, we propose CONCERT, a converged edge infrastructure for future cellular communications and mobile computing services. The proposed architecture is constructed based on the concept of control/data (C/D) plane decoupling. The data plane includes heterogeneous physical resources such as radio interface equipment, computational resources, and software-defined switches. The control plane jointly coordinates physical resources to present them as virtual resources, over which software-defined services including communications, computing, and management can be deployed in a flexible manner. Moreover, we introduce new designs for physical resources placement and task scheduling so that CONCERT can overcome the drawbacks of the existing baseband-up centralization approach and better facilitate innovations in next-generation cellular networks. These advantages are demonstrated with application examples on radio access networks with C/D decoupled air interface, delaysensitive machine-type communications, and realtime mobile cloud gaming. We also discuss some fundamental research issues arising with the proposed architecture to illuminate future research directions.
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paper_title: Network function virtualization: Challenges and opportunities for innovations

paper_content:

Network function virtualization was recently proposed to improve the flexibility of network service provisioning and reduce the time to market of new services. By leveraging virtualization technologies and commercial off-the-shelf programmable hardware, such as general-purpose servers, storage, and switches, NFV decouples the software implementation of network functions from the underlying hardware. As an emerging technology, NFV brings several challenges to network operators, such as the guarantee of network performance for virtual appliances, their dynamic instantiation and migration, and their efficient placement. In this article, we provide a brief overview of NFV, explain its requirements and architectural framework, present several use cases, and discuss the challenges and future directions in this burgeoning research area.
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paper_title: Cloud technologies for flexible 5G radio access networks

paper_content:

The evolution toward 5G mobile networks will be characterized by an increasing number of wireless devices, increasing device and service complexity, and the requirement to access mobile services ubiquitously. Two key enablers will allow the realization of the vision of 5G: very dense deployments and centralized processing. This article discusses the challenges and requirements in the design of 5G mobile networks based on these two key enablers. It discusses how cloud technologies and flexible functionality assignment in radio access networks enable network densification and centralized operation of the radio access network over heterogeneous backhaul networks. The article describes the fundamental concepts, shows how to evolve the 3GPP LTE architecture, and outlines the expected benefits.
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paper_title: Communicating While Computing: Distributed mobile cloud computing over 5G heterogeneous networks

paper_content:

Current estimates of mobile data traffic in the years to come foresee a 1,000 increase of mobile data traffic in 2020 with respect to 2010, or, equivalently, a doubling of mobile data traffic every year. This unprecedented growth demands a significant increase of wireless network capacity. Even if the current evolution of fourth-generation (4G) systems and, in particular, the advancements of the long-term evolution (LTE) standardization process foresees a significant capacity improvement with respect to third-generation (3G) systems, the European Telecommunications Standards Institute (ETSI) has established a roadmap toward the fifth-generation (5G) system, with the aim of deploying a commercial system by the year 2020 [1]. The European Project named ?Mobile and Wireless Communications Enablers for the 2020 Information Society? (METIS), launched in 2012, represents one of the first international and large-scale research projects on fifth generation (5G) [2]. In parallel with this unparalleled growth of data traffic, our everyday life experience shows an increasing habit to run a plethora of applications specifically devised for mobile devices, (smartphones, tablets, laptops)for entertainment, health care, business, social networking, traveling, news, etc. However, the spectacular growth in wireless traffic generated by this lifestyle is not matched with a parallel improvement on mobile handsets? batteries, whose lifetime is not improving at the same pace [3]. This determines a widening gap between the energy required to run sophisticated applications and the energy available on the mobile handset. A possible way to overcome this obstacle is to enable the mobile devices, whenever possible and convenient, to offload their most energy-consuming tasks to nearby fixed servers. This strategy has been studied for a long time and is reported in the literature under different names, such as cyberforaging [4] or computation offloading [5], [6]. In recent years, a strong impulse to computation offloading has come through cloud computing (CC), which enables the users to utilize resources on demand. The resources made available by a cloud service provider are: 1) infrastructures, such as network devices, storage, servers, etc., 2) platforms, such as operating systems, offering an integrated environment for developing and testing custom applications, and 3) software, in the form of application programs. These three kinds of services are labeled, respectively, as infrastructure as a service, platform as a service, and software as a service. In particular, one of the key features of CC is virtualization, which makes it possible to run multiple operating systems and multiple applications over the same machine (or set of machines), while guaranteeing isolation and protection of the programs and their data. Through virtualization, the number of virtual machines (VMs) can scale on ?demand, thus improving the overall system computational efficiency. Mobile CC (MCC) is a specific case of CC where the user accesses the cloud services through a mobile handset [5]. The major limitations of today?s MCC are the energy consumption associated to the radio access and the latency experienced in reaching the cloud provider through a wide area network (WAN). Mobile users located at the edge of macrocellular networks are particularly disadvantaged in terms of power consumption and, furthermore, it is very difficult to control latency over a WAN. As pointed out in [7]?[9], humans are acutely sensitive to delay and jitter: as latency increases, interactive response suffers. Since the interaction times foreseen in 5G systems, in particular in the so-called tactile Internet [10], are quite small (in the order of milliseconds), a strict latency control must be somehow incorporated in near future MCC. Meeting this constraint requires a deep ?rethinking of the overall service chain, from the physical layer up to virtualization.
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paper_title: Cloud radio access network (C-RAN): a primer

paper_content:

In the era of mobile Internet, mobile operators are facing pressure on ever-increasing capital expenditures and operating expenses with much less growth of income. Cloud Radio Access Network (C-RAN) is expected to be a candidate of next generation access network techniques that can solve operators' puzzle. In this article, on the basis of a general survey of C-RAN, we present a novel logical structure of C-RAN that consists of a physical plane, a control plane, and a service plane. Compared to traditional architecture, the proposed C-RAN architecture emphasizes the notion of service cloud, service-oriented resource scheduling and management, thus it facilitates the utilization of new communication and computer techniques. With the extensive computation resource offered by the cloud platform, a coordinated user scheduling algorithm and parallel optimum precoding scheme are proposed, which can achieve better performance. The proposed scheme opens another door to design new algorithms matching well with C-RAN architecture, instead of only migrating existing algorithms from traditional architecture to C-RAN.
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paper_title: SoftAir: a software defined networking architecture for 5G wireless systems

paper_content:

Abstract One of the main building blocks and major challenges for 5G cellular systems is the design of flexible network architectures which can be realized by the software defined networking paradigm. Existing commercial cellular systems rely on closed and inflexible hardware-based architectures both at the radio frontend and in the core network. These problems significantly delay the adoption and deployment of new standards, impose significant challenges in implementing and innovation of new techniques to maximize the network capacity and accordingly the coverage, and prevent provisioning of truly- differentiated services which are able to adapt to growing and uneven and highly variable traffic patterns. In this paper, a new software-defined architecture, called SoftAir, for next generation (5G) wireless systems, is introduced. Specifically, the novel ideas of network function cloudification and network virtualization are exploited to provide a scalable, flexible and resilient network architecture. Moreover, the essential enabling technologies to support and manage the proposed architecture are discussed in details, including fine-grained base station decomposition, seamless incorporation of Openflow, mobility- aware control traffic balancing, resource-efficient network virtualization, and distributed and collaborative traffic classification. Furthermore, the major benefits of SoftAir architecture with its enabling technologies are showcased by introducing software- defined traffic engineering solutions. The challenging issues for realizing SoftAir are also discussed in details.
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paper_title: Cloud computing meets mobile wireless communications in next generation cellular networks

paper_content:

In next generation cellular networks, cloud computing will have profound impacts on mobile wireless communications. On the one hand, the integration of cloud computing into the mobile environment enables MCC systems. On the other hand, the powerful computing platforms in the cloud for radio access networks lead to a novel concept of C-RAN. In this article we study the topology configuration and rate allocation problem in C-RAN with the objective of optimizing the end-to-end performance of MCC users in next generation cellular networks. We use a decision theoretical approach to tackle the delayed channel state information problem in C-RAN. Simulation results show that the design and operation of future mobile wireless networks can be significantly affected by cloud computing, and the proposed scheme is capable of achieving substantial performance gains over existing schemes.
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paper_title: An energy efficient and spectrum efficient wireless heterogeneous network framework for 5G systems

paper_content:

In this article we explore a system framework of cooperative green heterogeneous networks for 5G wireless communication systems. We first survey the state-of-the-art on spectrum efficiency (SE), energy efficiency (EE), and quality of service (QoS) based mobile association, multi-layer interference management and power control, network wide cooperation and dynamic resource allocation for heterogeneous wireless networks. We also present the system framework of cooperative green heterogeneous networks, which aims at balancing and optimizing SE, EE, and QoS in heterogeneous wireless networks. We discuss the design principles and show some preliminary performance results on the tradeoffs among SE, EE, and QoS. Finally, we identify the technical challenges that remain in the cooperative green heterogeneous network design. The presented wireless system framework is expected to advance the understandings of the critical technical issues toward energy and spectrum efficient 5G wireless communication systems.
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paper_title: Macro-assisted data-only carrier for 5G green cellular systems

paper_content:

As the commercial operation of 4G systems is speeding up worldwide to meet the increasingly explosive growth of mobile Internet in the 2020 era, a great many R&D efforts targeting the next generation wireless systems (5G) have been launched. With densely deployed small cells in a heterogeneous network, the excessive signaling overhead of conventional carrier design greatly degrades system performance. A new carrier designed for small cells in the next generation system will be highly beneficial toward a green communication network. In this article, we propose a macro-assisted data-only carrier for future 5G networks from a green prospective. With the help of macro base stations, control channel overhead, and cell-specific reference signals for small cells can be minimized to achieve a pure-data carrier. Under this architecture, key procedures are designed including small cell identification and access, synchronization, hand over, and small cell sleeping. Furthermore, to evaluate the potential of our proposed scheme, a complete system and link-level simulation platform according to the current 3GPP LTE standard is built. The simulation results show that our proposed systems, achieving significant performance enhancement of signaling overhead, can lead to more than 17 percent throughput improvement and 90 percent energy efficiency gain over the current LTE HetNet with on-off strategy implemented. The proposed scheme appears to be highly attractive as part of the future 5G green mobile networks.
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paper_title: Integrated energy and spectrum harvesting for 5G wireless communications

paper_content:

Two important issues have arisen in 5G wireless communications: spectral efficiency and energy efficiency. The existing wireless communication architectures and technologies may not be able to address these two issues at the same time for 5G multi-tier networks where users in different tiers have different priorities for channel access. In this article, we first present the motivation for our proposal of a new paradigm of integrated spectrum and energy harvesting for 5G wireless networks, in which spectrum and energy resources are efficiently collected and intelligently managed. Then we present an integrated spectrum and energy harvesting 5G architecture for dealing with current challenges. After that, based on the proposed architecture, we provide integrated spectrum and energy control mechanisms for typical 5G networks. Finally, we propose a cooperative medium access control scheme for heterogeneous 5G networks that attracts cooperative sensing participants with heterogeneous energy harvesting capabilities. Illustrative results demonstrate significant energy and spectrum efficiency for 5G wireless networks.
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paper_title: Evolution Towards 5G Multi-tier Cellular Wireless Networks: An Interference Management Perspective

paper_content:

The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, for example, higher data rates, excellent end-to-end performance, and user-coverage in hot-spots and crowded areas with lower latency, energy consumption, and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g. power control, cell association) in these networks with shared spectrum access (i.e. when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.
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paper_title: Applications of self-interference cancellation in 5G and beyond

paper_content:

Self-interference cancellation invalidates a long-held fundamental assumption in wireless network design that radios can only operate in half duplex mode on the same channel. Beyond enabling true in-band full duplex, which effectively doubles spectral efficiency, self-interference cancellation tremendously simplifies spectrum management. Not only does it render entire ecosystems like TD-LTE obsolete, it enables future networks to leverage fragmented spectrum, a pressing global issue that will continue to worsen in 5G networks. Self-interference cancellation offers the potential to complement and sustain the evolution of 5G technologies toward denser heterogeneous networks and can be utilized in wireless communication systems in multiple ways, including increased link capacity, spectrum virtualization, any-division duplexing (ADD), novel relay solutions, and enhanced interference coordination. By virtue of its fundamental nature, self-interference cancellation will have a tremendous impact on 5G networks and beyond.
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paper_title: Authentication handover and privacy protection in 5G hetnets using software-defined networking

paper_content:

Recently, densified small cell deployment with overlay coverage through coexisting heterogeneous networks has emerged as a viable solution for 5G mobile networks. However, this multi-tier architecture along with stringent latency requirements in 5G brings new challenges in security provisioning due to the potential frequent handovers and authentications in 5G small cells and HetNets. In this article, we review related studies and introduce SDN into 5G as a platform to enable efficient authentication hand-over and privacy protection. Our objective is to simplify authentication handover by global management of 5G HetNets through sharing of userdependent security context information among related access points. We demonstrate that SDN-enabled security solutions are highly efficient through its centralized control capability, which is essential for delay-constrained 5G communications.
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paper_title: Macro-assisted data-only carrier for 5G green cellular systems

paper_content:

As the commercial operation of 4G systems is speeding up worldwide to meet the increasingly explosive growth of mobile Internet in the 2020 era, a great many R&D efforts targeting the next generation wireless systems (5G) have been launched. With densely deployed small cells in a heterogeneous network, the excessive signaling overhead of conventional carrier design greatly degrades system performance. A new carrier designed for small cells in the next generation system will be highly beneficial toward a green communication network. In this article, we propose a macro-assisted data-only carrier for future 5G networks from a green prospective. With the help of macro base stations, control channel overhead, and cell-specific reference signals for small cells can be minimized to achieve a pure-data carrier. Under this architecture, key procedures are designed including small cell identification and access, synchronization, hand over, and small cell sleeping. Furthermore, to evaluate the potential of our proposed scheme, a complete system and link-level simulation platform according to the current 3GPP LTE standard is built. The simulation results show that our proposed systems, achieving significant performance enhancement of signaling overhead, can lead to more than 17 percent throughput improvement and 90 percent energy efficiency gain over the current LTE HetNet with on-off strategy implemented. The proposed scheme appears to be highly attractive as part of the future 5G green mobile networks.
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paper_title: Handover Scheme for 5G C/U Plane Split Heterogeneous Network in High-Speed Railway

paper_content:

Being a promising technology for fifth-generation (5G) communication systems, a novel railway communication system based on control/user (C/U) plane split heterogeneous networks can provide a high-quality broadband wireless service for passengers in high-speed railways with higher system capacity, better transmission reliability, and less cochannel interference. However, due to its special architecture where the C-plane and the U-plane must be split and supported by a macro Evolved Node B (eNB) and a phantom eNB, respectively, it would suffer more serious handover problem, particularly in intermacrocell handover, which directly degrades its applicability and availability in high-speed railways. Moreover, no technical specification has been released about this network architecture. Therefore, this paper focuses on redesigning and analyzing technical details and handover procedures based on Long-Term Evolution (LTE) specifications to guarantee the proposed system's practicability and generality and its analytical tractability. To resolve the handover problem, this paper proposes a handover trigger decision scheme based on GM(1, $n$) model of the grey system theory. By this scheme, the received signal quality from the $(N + hbox{1})$th measurement report can be predicted from the $N$th measurement period, and the predicted values can be then utilized to make the handover trigger decision. The simulation results show that the proposed scheme is capable of triggering handover in advance effectively and of enhancing handover success probability remarkably.
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paper_title: Effective RAT Selection Approach for 5G Dense Wireless Networks

paper_content:

Dense Networks (DenseNet) and Multi-Radio Access Technologies (Multi-RATs) are considered as key features of the emerging fifth generation (5G) wireless systems. A Multi- RAT DenseNet is characterized by a very dense deployment of low- power base stations (BSs) and by a multi-tier architecture consisting of heterogeneous radio access technologies. In this work, we propose an effective RAT selection algorithm that efficiently manages the RAT handover procedure by (i) choosing the most suitable RAT that guarantees high system and user performance, and (ii) reducing unnecessary handover events. In particular, the decision to trigger a handover is based on a new system parameter named Reference Base Station Efficiency (RBSE). This parameter takes into account metrics related to both the system and the user: the BS transmitted power, the BS traffic load and the users' spectral efficiency. We compare, by simulation, the proposed scheme with the standardized 3GPP policies. Results show that the proposed RAT selection scheme significantly reduces the number of handovers and the end-to- end delay while maintaining high system throughput and user spectral efficiency.
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paper_title: Distributed mobility management for future 5G networks: overview and analysis of existing approaches

paper_content:

The ever-increasing demand of mobile Internet traffic is pushing operators to look for solutions to increase the available bandwidth per user and per unit of area. At the same time, they need to reduce the load in the core network at a reasonable cost in their future 5G deployments. Today’s trend points to the deployment of extremely dense networks in order to provide ubiquitous connectivity at high data rates. However, this is hard to couple with the current mobile networks’ architecture, which is heavily centralized, posing difficult challenges when coping with the foreseen explosion of mobile data. Additionally, future 5G networks will exhibit disparate types of services, posing different connectivity requirements. Distributed mobility management is emerging as a valid framework to design future mobile network architectures, taking into account the requirements for large traffic in the core and the rise of extremely dense wireless access networks. In this article, we discuss the adoption of a distributed mobility management approach for mobile networks, and analyze the operation of the main existing solutions proposed so far, including a first practical evaluation based on experiments with real Linux-based prototype implementations.
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paper_title: Analysis of Handoff Interference and Outage along Arbitrary Trajectories in Cellular Networks

paper_content:

We introduce a new system performance measure due to handoff called handoff interference, which characterizes the additional interference noise induced by the handoff process. The handoff interference experienced by a mobile unit is determined by the parameters of the handoff algorithm. We present an exact analysis of the handoff interference and the outage probability and develop a discrete-time method to efficiently and accurately compute these performance metrics along arbitrary trajectories in a cellular network. Our numerical results reveal critical tradeoffs among the critical handoff performance metrics, which should be taken into account in dimensioning the handoff parameters to optimize system performance. We discuss an example handoff design problem, which illustrates how to dimension the handoff parameters to optimize this tradeoff using the proposed handoff analysis.
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paper_title: An energy efficient and spectrum efficient wireless heterogeneous network framework for 5G systems

paper_content:

In this article we explore a system framework of cooperative green heterogeneous networks for 5G wireless communication systems. We first survey the state-of-the-art on spectrum efficiency (SE), energy efficiency (EE), and quality of service (QoS) based mobile association, multi-layer interference management and power control, network wide cooperation and dynamic resource allocation for heterogeneous wireless networks. We also present the system framework of cooperative green heterogeneous networks, which aims at balancing and optimizing SE, EE, and QoS in heterogeneous wireless networks. We discuss the design principles and show some preliminary performance results on the tradeoffs among SE, EE, and QoS. Finally, we identify the technical challenges that remain in the cooperative green heterogeneous network design. The presented wireless system framework is expected to advance the understandings of the critical technical issues toward energy and spectrum efficient 5G wireless communication systems.
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paper_title: Quality-aware millimeter-wave device-to-device multi-hop routing for 5G cellular networks

paper_content:

Millimeter-wave (mm-wave) transmission is a promising method for increasing capacity in next-generation cellular systems. However, since mm-wave signals are too weak to (i) do long-distance communication and (ii) survive in non-line-of-sight situations, multi-hop relaying is required. We thus study in this paper a multi-hop routing protocol at mm-wave (38 GHz and 28GHz) frequencies. Due to the great and steadily increasing importance of video streaming in cellular applications, we pay special attention to the maximization of video transmission quality, which makes the optimization problem different from the usual sum-rate maximization. Specifically, we develop a protocol that optimizes the “sum quality” of the transmission of different video streams, subject to constraints (minimum quality) of separate streams. We take the unique properties of mm-waves (sparse angular power spectrum, leading to low interference) into account in our method. Extensive simulation results show the superiority of our approach compared to max-min flow routing which is widely used in QoS-sensitive applications.
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paper_title: Heterogeneous statistical QoS provisioning over 5G mobile wireless networks

paper_content:

As a critical step towards the next new era of mobile wireless networks, recently 5G mobile wireless networks have received significant research attention and efforts from both academia and industry. The 5G mobile wireless networks are expected to provide different delay-bounded QoS guarantees for a wide spectrum of services, applications, and users with extremely diverse requirements. Since the time-sensitive services in 5G multimedia wireless networks may vary dramatically in both a large range from milliseconds to a few seconds and diversity from uniform/ constant delay-bound to different/variable delay-bound guarantees among different wireless links, the delay-bound QoS requirements for different types of services promote the newly emerging heterogeneous statistical delay-bounded QoS provisioning over 5G mobile wireless networks, which, however, imposes many new challenging issues not encountered before in 4G wireless networks. To overcome these new challenges, in this article we propose a novel heterogeneous statistical QoS provisioning architecture for 5G mobile wireless networks. First, we develop and analyze the new heterogeneous statistical QoS system model by applying and extending the effective capacity theory. Then, through the wireless coupling channels, we apply our proposed heterogeneous statistical QoS architecture to efficiently implement the following powerful 5G-candidate wireless techniques: 1) device-to-device networks; 2) full-duplex networks; and 3) cognitive radio networks, respectively, for providing heterogeneous statistical delay-bounded QoS guarantees. Finally, using the simulation experiments we show that our proposed architecture and schemes significantly outperform the existing traditional statistical delay-bounded QoS provisioning schemes in terms of satisfying the heterogeneous delay-bounded QoS requirements while maximizing the aggregate system throughput over 5G mobile wireless networks.
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paper_title: QoS-aware energy-efficient optimization for massive MIMO systems in 5G

paper_content:

In this paper, we consider the energy-efficient power allocation in the downlink of a large-scale multiple-input multiple-output (MIMO) system under both quality of service (QoS) constraints and maximum transmit power constraints. With these two constraints satisfied, the resource allocation strategies are proposed, which aim to maximize the energy-efficiency defined as the successfully delivered information bits per Joule energy consumed (in bits/Joule). Moreover, the power consumption consists of both transmit power and circuit power. In our work, the original problem which is nonconvex in nature is first transformed into a new convex problem. Then it is demonstrated the existence of a unique globally optimal power allocation using Lagrange multiplier method. Finally, numerical simulation results show that the number of transmit antennas plays an important role in increasing the energy efficiency, namely, we can obtain an optimal value of transmit antennas. It is revealed that the number of users and the QoS requirement have an effect on the energy efficiency.
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paper_title: Toward 5G: when explosive bursts meet soft cloud

paper_content:

Rapid growing demand for mobile data traffic challenges capacities and service provision in the next-generation (5G) cellular networks. Real measurement data from operating cellular networks indicates that the traffic models and scenarios disobey our traditional assumptions (i.e., expressing bursty nature). As a result, current network architectures and service management may cause experience deterioration of subscribers in future networks. In this article, we propose three approaches to alleviate the influence of various traffic bursts: baseband resource pool on a cloud platform as wireless infrastructure to enhance the capacity and flexibility of networks, cloud core networks to provide dynamic extension and service flow control abilities, and software-defined bearer networks to simplify service delivery instructed by core networks. Different from conventional stovepipe-like cloud computing network architectures, our proposed architecture interconnects and shares information between entities, breaking through horizontal device barriers and vertical layers. These cloud-based approaches not only avoid the potentially negative impact of bursts, but also provide a software-controlled end-to-end service management framework for future cellular networks. In addition, by taking advantage of open interfaces of cloud-based network elements, service control algorithms and network APIs could also be implemented to realize smart and soft 5G cellular networks.
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paper_title: Distributed load balancing for future 5G systems on-board high-speed trains

paper_content:

The surge of mobile broadband Internet access has nowadays reached the critical point that traffic is projected to increase dramatically in the next years and even the 4G UMTS Long term Evolution (LTE) cellular technology and its advanced version LTE-A might lack enough flexibility and system reconfiguration capability. For these reasons, the quest for the Fifth Generation (5G) of cellular technology has started. In the context of users that require high Quality of Experience (QoE) anytime and anywhere, users on-board of fast moving vehicles such as high-speed trains represent an important market segment for both telecom operators and transportation companies. In particular, people who are moving for business everyday require low latency and high throughput Internet connectivity even when moving at hundreds of kilometers per hour. In this landscape, novel algorithms can find their space in future 5G systems to cope with fast resource (re)allocation in the presence of large Doppler spread and high handover frequency. Focusing on a high-speed train (HST), in this paper we propose a simple but effective distributed load balancing algorithm to relieve service interruption caused by frequent handovers in high mobility scenarios. Our results show the effectiveness of the solution while leveraging on the concept of cell edge intelligence.
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paper_title: Resource allocation for D2D communications under proportional fairness

paper_content:

This paper deals with the dynamic spectrum sharing between underlaying device-to-device (D2D) and cellular links in a multi-carrier cellular network to maximize the weighted network sum-rate while guaranteeing the minimum individual cellular link data rates and proportional fairness among D2D links. In particular, we formulate an NP-hard non-orthogonal resource allocation problem, and develop an iterative algorithm that alternates between the sub-carrier assignment and power allocation in each iteration until convergence. It is shown that the sub-carrier assignment problem corresponds to an integer linear program while the power allocation is reformulated into a difference-between-two-concave-functions (DC) problem. We establish the important properties of the developed algorithms and prove their convergence behavior. Illustrative results indicate that the proposed non-orthogonal resource allocation algorithm significantly outperforms the orthogonal spectrum sharing counterpart.
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paper_title: Joint Resource Partitioning and Offloading in Heterogeneous Cellular Networks

paper_content:

In heterogeneous cellular networks (HCNs), it is desirable to offload mobile users to small cells, which are typically significantly less congested than the macrocells. To achieve sufficient load balancing, the offloaded users often have much lower SINR than they would on the macrocell. This SINR degradation can be partially alleviated through interference avoidance, for example time or frequency resource partitioning, whereby the macrocell turns off in some fraction of such resources. Naturally, the optimal offloading strategy is tightly coupled with resource partitioning; the optimal amount of which in turn depends on how many users have been offloaded. In this paper, we propose a general and tractable framework for modeling and analyzing joint resource partitioning and offloading in a two-tier cellular network. With it, we are able to derive the downlink rate distribution over the entire network, and an optimal strategy for joint resource partitioning and offloading. We show that load balancing, by itself, is insufficient, and resource partitioning is required in conjunction with offloading to improve the rate of cell edge users in co-channel heterogeneous networks.
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paper_title: An Overview of Load Balancing in HetNets: Old Myths and Open Problems

paper_content:

Matching the demand for resources (?load?) with the supply of resources (?capacity?) is a basic problem occurring across many fields of engineering, logistics, and economics, and has been considered extensively in both the Internet and wireless networks. The ongoing evolution of cellular communication networks into dense, organic, and irregular heterogeneous networks (HetNets) has elevated load awareness to a central problem, and introduces many new subtleties. This article explains how several long-standing assumptions about cellular networks need to be rethought in the context of a load-balanced HetNet: we highlight these as three deeply entrenched myths that we then dispel. We survey and compare the primary technical approaches to HetNet load balancing: (centralized) optimization, game theory, Markov decision processes, and the newly popular cell range expansion (a.k.a. biasing), and draw design lessons for OFDMA-based cellular systems. We also identify several open areas for future exploration.
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paper_title: Evolution Towards 5G Multi-tier Cellular Wireless Networks: An Interference Management Perspective

paper_content:

The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, for example, higher data rates, excellent end-to-end performance, and user-coverage in hot-spots and crowded areas with lower latency, energy consumption, and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g. power control, cell association) in these networks with shared spectrum access (i.e. when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.
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paper_title: SARA: A service-aware resource allocation scheme for device-to-device communication underlaying cellular networks

paper_content:

This paper considers the resource allocation problem for device-to-device (D2D) communication underlaying cellular networks and proposes a service-aware resource allocation (SARA) scheme for D2D communication to improve the network performance. SARA takes into account the different service requirements of D2D users. It consists of two allocation phases: on-demand resource allocation and secondary resource allocation. In the first phase, cellular user resources are allocated on demand to meet the different service requirements of D2D pairs. In the second phase, the remaining cellular user resources after the first phase are allocated to D2D users based on an objective function in order to improve the resource utilization. Simulation results show that the proposed SARA scheme can significantly improve the performance of a cellular system in terms of the satisfaction ratio of D2D pairs and the system throughput.
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paper_title: Social-aware D2D communications: qualitative insights and quantitative analysis

paper_content:

With emerging demands for local area services, device-to-device communication is conceived as a vital component for the next-generation cellular networks to improve spectral reuse, bring hop gains, and enhance system capacity. Ripening these benefits depends on efficiently solving several main technical problems, including mode selection, resource allocation, and interference management. Aiming to establish a new paradigm for solving these challenging problems in D2D communication, in this article we propose a social-aware enhanced D2D communication architecture that exploits social networking characteristics for system design. By developing a profound understanding of the interplay between social networks' properties and mobile communication problems, we qualitatively analyze how D2D communications can benefit from social features, and quantitatively assess the achievable gains in a social-aware D2D communication system.
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paper_title: Frame-Based Medium Access Control for 5G Wireless Networks

paper_content:

Millimeter wave (mmWave) communications is one of the key technologies for future 5th generation (5G) wireless networks. In this paper, we investigate the problem of medium access control (MAC) in mmWave networks. We develop a frame-based scheduling directional MAC protocol, termed FDMAC, to achieve the goal of leveraging collision-free concurrent transmissions to fully exploit spatial reuse in mmWave networks. The high efficiency of FDMAC is achieved by amortizing the scheduling overhead over multiple concurrent, back-to-back transmissions in a row. The core of FDMAC is a graph coloring-based scheduling algorithm, termed greedy coloring (GC) algorithm, that can compute near-optimal schedules with respect to the total transmission time with low complexity. FDMAC is analyzed and evaluated with simulations.
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paper_title: Integrated energy and spectrum harvesting for 5G wireless communications

paper_content:

Two important issues have arisen in 5G wireless communications: spectral efficiency and energy efficiency. The existing wireless communication architectures and technologies may not be able to address these two issues at the same time for 5G multi-tier networks where users in different tiers have different priorities for channel access. In this article, we first present the motivation for our proposal of a new paradigm of integrated spectrum and energy harvesting for 5G wireless networks, in which spectrum and energy resources are efficiently collected and intelligently managed. Then we present an integrated spectrum and energy harvesting 5G architecture for dealing with current challenges. After that, based on the proposed architecture, we provide integrated spectrum and energy control mechanisms for typical 5G networks. Finally, we propose a cooperative medium access control scheme for heterogeneous 5G networks that attracts cooperative sensing participants with heterogeneous energy harvesting capabilities. Illustrative results demonstrate significant energy and spectrum efficiency for 5G wireless networks.
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paper_title: SCMA for Downlink Multiple Access of 5G Wireless Networks

paper_content:

Sparse code multiple access (SCMA) is a new frequency domain non-orthogonal multiple-access technique which can improve spectral efficiency of wireless radio access. With SCMA, different incoming data streams are directly mapped to codewords of different multi-dimensional cookbooks, where each codeword represents a spread transmission layer. Multiple SCMA layers share the same time-frequency resources of OFDMA. The sparsity of codewords makes the near-optimal detection feasible through iterative message passing algorithm (MPA). Such low complexity of multi-layer detection allows excessive codeword overloading in which the dimension of multiplexed layers exceeds the dimension of codewords. Optimization of overloading factor along with modulation-coding levels of layers provides a more flexible and efficient link-adaptation mechanism. On the other hand, the signal spreading feature of SCMA can improve link-adaptation as a result of less colored interference. In this paper a technique is developed to enable multi-user SCMA (MU-SCMA) for downlink wireless access. User pairing, power sharing, rate adjustment, and scheduling algorithms are designed to improve the downlink throughput of a heavily loaded network. The advantage of SCMA spreading for lightly loaded networks is also evaluated.
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paper_title: Authentication handover and privacy protection in 5G hetnets using software-defined networking

paper_content:

Recently, densified small cell deployment with overlay coverage through coexisting heterogeneous networks has emerged as a viable solution for 5G mobile networks. However, this multi-tier architecture along with stringent latency requirements in 5G brings new challenges in security provisioning due to the potential frequent handovers and authentications in 5G small cells and HetNets. In this article, we review related studies and introduce SDN into 5G as a platform to enable efficient authentication hand-over and privacy protection. Our objective is to simplify authentication handover by global management of 5G HetNets through sharing of userdependent security context information among related access points. We demonstrate that SDN-enabled security solutions are highly efficient through its centralized control capability, which is essential for delay-constrained 5G communications.
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paper_title: Device-to-device communication in 5G cellular networks: challenges, solutions, and future directions

paper_content:

In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular bandwidth and all communications take place through the base stations. In this article, we envision a two-tier cellular network that involves a macrocell tier (i.e., BS-to-device communications) and a device tier (i.e., device-to-device communications). Device terminal relaying makes it possible for devices in a network to function as transmission relays for each other and realize a massive ad hoc mesh network. This is obviously a dramatic departure from the conventional cellular architecture and brings unique technical challenges. In such a two-tier cellular system, since the user data is routed through other users? devices, security must be maintained for privacy. To ensure minimal impact on the performance of existing macrocell BSs, the two-tier network needs to be designed with smart interference management strategies and appropriate resource allocation schemes. Furthermore, novel pricing models should be designed to tempt devices to participate in this type of communication. Our article provides an overview of these major challenges in two-tier networks and proposes some pricing schemes for different types of device relaying.
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paper_title: Policy-based communications for 5G mobile with customer edge switching

paper_content:

Besides more capacity and faster connections, 5G is expected to provide ultra-reliable services, for example, for machine-to-machine communications. In this paper, we advocate that 5G must do its best to eliminate malicious traffic as a cause of failure of legitimate services. This paper proposes that all communications in 5G should be controlled by policy. The policies facilitate cooperation of customer networks against misbehaving actors and collecting evidence of malicious activity. Dynamic policies can react to hosts that are used in attacks. We propose a system controlled by policy that overcomes the classical weaknesses in the Internet, namely source address spoofing and denial of service attacks. We propose to improve the mobile device experience by new methods of network address translator traversal suitable for battery-powered mobile devices. We believe that 5G will be the major driver for the future Internet, which is why we relate our approach to other proposals for future Internet architecture. Our approach can be deployed one network at a time as it limits the changes to edge nodes; no compulsory changes are proposed to hosts. The paper reports the experience from experimentation and evaluates scalability and security including initial results on performance. © 2015 The Authors. Security and Communication Networks published by John Wiley & Sons, Ltd.
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paper_title: Location-Aware Mobile Intrusion Detection with Enhanced Privacy in a 5G Context

paper_content:

The paper proposes a location-aware mobile Intrusion Prevention System (mIPS) architecture with enhanced privacy that is integrated in Managed Security Service (MSS). The solution is envisaged in a future fifth generation telecommunications (5G) context with increased but varying bandwidth, a virtualised execution environment and infrastructure that allows threads, processes, virtual machines and storage to be migrated to cloud computing services on demand, to dynamically scale performance and save power. 5G mobile devices will be attractive targets for malicious software, and this threat will in some cases change with location. Mobile devices will store more sensitive information and will also be used to a larger extent for sensitive transactions than they typically do today. In addition, a distributed execution environment in itself gives raise to some new security challenges. In order to handle these security challenges, we have proposed the location-aware mIPS architecture, which benefits from a distributed execution environment where processor intensive services can be outsourced to Cloud hosting providers. The mIPS supports querying location threat profiles in a privacy-preserving way, and ensures that mIPS alerts sent to the the first-line MSS are anonymised. We finally perform an analysis of potential strengths and weaknesses of the proposed approach.
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paper_title: Secure sharing and searching for real-time video data in mobile cloud

paper_content:

In this article we propose an infrastructure that allows mobile users to securely share and search for their real-time video data. Specifically, the proposed infrastructure takes the advantages of the cloud platform and 5G technology to achieve its goals, where mobile users (connected with some external video taking device) can share their real-time video with their friends or families through the cloud while any other user with no permission cannot get any information about the video. More importantly, the infrastructure security is guaranteed even if the cloud server is hacked. In addition, our infrastructure also allows secure searching within the user's own video data. We believe our solution is practical to be deployed in the existing telecommunication platforms.
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paper_title: Full duplex techniques for 5G networks: self-interference cancellation, protocol design, and relay selection

paper_content:

The wireless research community aspires to conceive full duplex operation by supporting concurrent transmission and reception in a single time/frequency channel for the sake of improving the attainable spectral efficiency by a factor of two as compared to the family of conventional half duplex wireless systems. The main challenge encountered in implementing FD wireless devices is that of finding techniques for mitigating the performance degradation imposed by self-interference. In this article, we investigate the potential FD techniques, including passive suppression, active analog cancellation, and active digital cancellation, and highlight their pros and cons. Furthermore, the troubles of FD medium access control protocol design are discussed for addressing the problems such as the resultant end-to-end delay and network congestion. Additionally, an opportunistic decode-andforward- based relay selection scheme is analyzed in underlay cognitive networks communicating over independent and identically distributed Rayleigh and Nakagami-m fading channels in the context of FD relaying. We demonstrate that the outage probability of multi-relay cooperative communication links can be substantially reduced. Finally, we discuss the challenges imposed by the aforementioned techniques and a range of critical issues associated with practical FD implementations. It is shown that numerous open challenges, such as efficient SI suppression, high-performance FD MAC-layer protocol design, low power consumption, and hybrid FD/HD designs, have to be tackled before successfully implementing FD-based systems.
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paper_title: Reliable Reporting for Massive M2M Communications With Periodic Resource Pooling

paper_content:

This letter considers a wireless M2M communication scenario with a massive number of M2M devices. Each device needs to send its reports within a given deadline and with certain reliability, e.g., 99.99%. A pool of resources available to all M2M devices is periodically available for transmission. The number of transmissions required by an M2M device within the pool is random due to two reasons-random number of arrived reports since the last reporting opportunity and requests for retransmission due to random channel errors. We show how to dimension the pool of M2M-dedicated resources in order to guarantee the desired reliability of the report delivery within the deadline. The fact that the pool of resources is used by a massive number of devices allows basing the dimensioning on the central limit theorem. The results are interpreted in the context of LTE, but they are applicable to any M2M communication system.
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paper_title: Massive MIMO for Next Generation Wireless Systems

paper_content:

Multi-user MIMO offers big advantages over conventional point-to-point MIMO: it works with cheap single-antenna terminals, a rich scattering environment is not required, and resource allocation is simplified because every active terminal utilizes all of the time-frequency bins. However, multi-user MIMO, as originally envisioned, with roughly equal numbers of service antennas and terminals and frequency-division duplex operation, is not a scalable technology. Massive MIMO (also known as large-scale antenna systems, very large MIMO, hyper MIMO, full-dimension MIMO, and ARGOS) makes a clean break with current practice through the use of a large excess of service antennas over active terminals and time-division duplex operation. Extra antennas help by focusing energy into ever smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include extensive use of inexpensive low-power components, reduced latency, simplification of the MAC layer, and robustness against intentional jamming. The anticipated throughput depends on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly joined terminals, the exploitation of extra degrees of freedom provided by the excess of service antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios. This article presents an overview of the massive MIMO concept and contemporary research on the topic.
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paper_title: Analysis of the Decoupled Access for Downlink and Uplink in Wireless Heterogeneous Networks

paper_content:

Wireless cellular networks evolve towards a heterogeneous infrastructure, featuring multiple types of Base Stations (BSs), such as Femto BSs (FBSs) and Macro BSs (MBSs). A wireless device observes multiple points (BSs) through which it can access the infrastructure and it may choose to receive the downlink (DL) traffic from one BS and send uplink (UL) traffic through another BS. Such a situation is referred to as decoupled DL/UL access . Using the framework of stochastic geometry, we derive the association probability for DL/UL. To maximize the average received power, as the relative density of FBSs initially increases, a large fraction of devices chooses decoupled access, i.e., receive from a MBS in DL and transmit through a FBS in UL. We analyze the impact that this type of association has on the average throughput in the system.
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paper_title: Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!

paper_content:

The global bandwidth shortage facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks. There is, however, little knowledge about cellular mm-wave propagation in densely populated indoor and outdoor environments. Obtaining this information is vital for the design and operation of future fifth generation cellular networks that use the mm-wave spectrum. In this paper, we present the motivation for new mm-wave cellular systems, methodology, and hardware for measurements and offer a variety of measurement results that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.
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paper_title: Network function virtualization: Challenges and opportunities for innovations

paper_content:

Network function virtualization was recently proposed to improve the flexibility of network service provisioning and reduce the time to market of new services. By leveraging virtualization technologies and commercial off-the-shelf programmable hardware, such as general-purpose servers, storage, and switches, NFV decouples the software implementation of network functions from the underlying hardware. As an emerging technology, NFV brings several challenges to network operators, such as the guarantee of network performance for virtual appliances, their dynamic instantiation and migration, and their efficient placement. In this article, we provide a brief overview of NFV, explain its requirements and architectural framework, present several use cases, and discuss the challenges and future directions in this burgeoning research area.
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paper_title: Visible light communications for 5G wireless networking systems: from fixed to mobile communications

paper_content:

Visible light communication, considered as a potential access option for 5G wireless communications, is gaining extensive attention. VLC has strengths in energy efficiency and ultra wide bandwidth, but also has weakness in transmission range and obstacles in transmission paths. This article aims to provide a conclusive investigation of the latest progress in research on VLC, which can be used as part of 5G wireless communication systems. This work highlights the strengths and weaknesses of VLC in comparison with RF-based communications, especially in spectrum, spatial reuse, security and energy efficiency. The article also investigates various lighting sources proposed for VLC systems. It summarizes the literature work on VLC networking into two categories: fixed and mobile VLC communications.
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paper_title: An Overview of Massive MIMO: Benefits and Challenges

paper_content:

Massive multiple-input multiple-output (MIMO) wireless communications refers to the idea equipping cellular base stations (BSs) with a very large number of antennas, and has been shown to potentially allow for orders of magnitude improvement in spectral and energy efficiency using relatively simple (linear) processing. In this paper, we present a comprehensive overview of state-of-the-art research on the topic, which has recently attracted considerable attention. We begin with an information theoretic analysis to illustrate the conjectured advantages of massive MIMO, and then we address implementation issues related to channel estimation, detection and precoding schemes. We particularly focus on the potential impact of pilot contamination caused by the use of non-orthogonal pilot sequences by users in adjacent cells. We also analyze the energy efficiency achieved by massive MIMO systems, and demonstrate how the degrees of freedom provided by massive MIMO systems enable efficient single-carrier transmission. Finally, the challenges and opportunities associated with implementing massive MIMO in future wireless communications systems are discussed.
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paper_title: Software defined virtual wireless network: framework and challenges

paper_content:

Due to inflexibility, design and control of existing networks are very complex. Therefore, SDN aims to separate control and data planes clearly, which is an innovative and effective approach to this problem. With SDN, a service provider can adjust the settings of a network according to various requirements dynamically and in a timely fashion. This feature is especially suitable for a wireless scenario with dynamic and unstable changing situations. Meanwhile, because various algorithms, such as traffic forwarding and quality of service, can be operated by a central controller, SDN is a natural optional technique for WNV. In this article, we illustrate the framework for combining SDN and WNV, review state-of-the-art related work, and discuss the challenges for future study.
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paper_title: M2M Communications for E-Health and Smart Grid: An Industry and Standard Perspective

paper_content:

An overview of several standardization activities for machine-to-machine (M2M) communications is presented, analyzing some of the enabling technologies and applications of M2M in industry sectors such as Smart Grid and e-Health. This summary and overview of the ongoing work in M2M from the industrial and standardization perspective complements the prevalent academic perspective of such publications to date in this field.
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paper_title: Five Disruptive Technology Directions for 5G

paper_content:

New research directions will lead to fundamental changes in the design of future 5th generation (5G) cellular networks. This paper describes five technologies that could lead to both architectural and component disruptive design changes: device-centric architectures, millimeter Wave, Massive-MIMO, smarter devices, and native support to machine-2-machine. The key ideas for each technology are described, along with their potential impact on 5G and the research challenges that remain.
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paper_title: Machine-to-Machine (M2M) Communications: Architecture, Performance and Applications

paper_content:

Part one of Machine-to-Machine (M2M) Communications covers machine-to-machine systems, architecture and components. Part two assesses performance management techniques for M2M communications. Part three looks at M2M applications, services, and standardization. Machine-to-machine communications refers to autonomous communication between devices or machines. This book serves as a key resource in M2M, which is set to grow significantly and is expected to generate a huge amount of additional data traffic and new revenue streams, underpinning key areas of the economy such as the smart grid, networked homes, healthcare and transportation. Examines the opportunities in M2M for businessesAnalyses the optimisation and development of M2M communicationsChapters cover aspects of access, scheduling, mobility and security protocols within M2M communications
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paper_title: How will NFV/SDN transform service provider opex?

paper_content:

Software defined networking and network function virtualization are widely deemed two critical pillars of the future service provider network. The expectation for significant operations cost savings from network programmability, open APIs, and operations automation is frequently mentioned as one of the primary benefits of the NFV/SDN vision. Intuitively, the flexibility and simplification values attributed to NFV/SDN lead the industry to the conclusion that operating expenses will decrease. This article provides a view into the operational costs of a typical service provider and discusses how the NFV/SDN attributes can be expected to influence the business equation. The drivers of OPEX change, the directionality of the change, and the categories of OPEX most affected based on our analysis from interactions with a number of service providers worldwide are presented in a structured analysis.
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paper_title: OpenFlow: enabling innovation in campus networks

paper_content:

This whitepaper proposes OpenFlow: a way for researchers to run experimental protocols in the networks they use every day. OpenFlow is based on an Ethernet switch, with an internal flow-table, and a standardized interface to add and remove flow entries. Our goal is to encourage networking vendors to add OpenFlow to their switch products for deployment in college campus backbones and wiring closets. We believe that OpenFlow is a pragmatic compromise: on one hand, it allows researchers to run experiments on heterogeneous switches in a uniform way at line-rate and with high port-density; while on the other hand, vendors do not need to expose the internal workings of their switches. In addition to allowing researchers to evaluate their ideas in real-world traffic settings, OpenFlow could serve as a useful campus component in proposed large-scale testbeds like GENI. Two buildings at Stanford University will soon run OpenFlow networks, using commercial Ethernet switches and routers. We will work to encourage deployment at other schools; and We encourage you to consider deploying OpenFlow in your university network too
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paper_title: Full-dimension MIMO (FD-MIMO) for next generation cellular technology

paper_content:

This article considers a practical implementation of massive MIMO systems [1]. Although the best performance can be achieved when a large number of active antennas are placed only in the horizontal domain, BS form factor limitation often makes horizontal array placement infeasible. To cope with this limitation, this article introduces full-dimension MIMO (FD-MIMO) cellular wireless communication system, where active antennas are placed in a 2D grid at BSs. For analysis of the FD-MIMO systems, a 3D spatial channel model is introduced, on which system-level simulations are conducted. The simulation results show that the proposed FD-MIMO system with 32 antenna ports achieves 2-3.6 times cell average throughput gain and 1.5-5 times cell edge throughput gain compared to the 4G LTE system of two antenna ports at the BS.
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paper_title: Challenges and conditions for wireless machine-to-machine communications in industrial environments

paper_content:

Wireless solutions are rapidly growing in machine-to-machine communications in industrial environments. These environments provide challenging conditions in terms of radio wave propagation as well as electromagnetic interference. In this article, results from the characterization of radio channel properties are summarized in order to provide some guidelines for the choice of wireless solutions in industrial environments. In conclusion, it is essential to know the sensitivity of industrial processes to time delay in data transfer. Furthermore, it is important to be aware of the radio interference environment and the manner in which different wireless technologies react upon interference. These steps will minimize the risk of unforeseen expensive disturbances in industrial processes.
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paper_title: Toward 5G densenets: architectural advances for effective machine-type communications over femtocells

paper_content:

Ubiquitous, reliable and low-latency machinetype communication, MTC, systems are considered to be value-adds of emerging 5G cellular networks. To meet the technical and economical requirements for exponentially growing MTC traffic, we advocate the use of small cells to handle the massive and dense MTC rollout. We introduce a novel 3GPP-compliant architecture that absorbs the MTC traffic via home evolved NodeBs, allowing us to significantly reduce congestion and overloading of radio access and core networks. A major design challenge has been to deal with the interference to human-type traffic and the large degree of freedom of the system, due to the unplanned deployments of small cells and the enormous amount of MTC devices. Simulation results in terms of MTC access delay, energy consumption, and delivery rate corroborate the superiority of the proposed working architecture.
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paper_title: Full duplex radios

paper_content:

This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
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paper_title: A survey of millimeter wave communications (mmWave) for 5G: opportunities and challenges

paper_content:

With the explosive growth of mobile data demand, the fifth generation (5G) mobile network would exploit the enormous amount of spectrum in the millimeter wave (mmWave) bands to greatly increase communication capacity. There are fundamental differences between mmWave communications and existing other communication systems, in terms of high propagation loss, directivity, and sensitivity to blockage. These characteristics of mmWave communications pose several challenges to fully exploit the potential of mmWave communications, including integrated circuits and system design, interference management, spatial reuse, anti-blockage, and dynamics control. To address these challenges, we carry out a survey of existing solutions and standards, and propose design guidelines in architectures and protocols for mmWave communications. We also discuss the potential applications of mmWave communications in the 5G network, including the small cell access, the cellular access, and the wireless backhaul. Finally, we discuss relevant open research issues including the new physical layer technology, software-defined network architecture, measurements of network state information, efficient control mechanisms, and heterogeneous networking, which should be further investigated to facilitate the deployment of mmWave communication systems in the future 5G networks.
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paper_title: Cache in the air: exploiting content caching and delivery techniques for 5G systems

paper_content:

The demand for rich multimedia services over mobile networks has been soaring at a tremendous pace over recent years. However, due to the centralized architecture of current cellular networks, the wireless link capacity as well as the bandwidth of the radio access networks and the backhaul network cannot practically cope with the explosive growth in mobile traffic. Recently, we have observed the emergence of promising mobile content caching and delivery techniques, by which popular contents are cached in the intermediate servers (or middleboxes, gateways, or routers) so that demands from users for the same content can be accommodated easily without duplicate transmissions from remote servers; hence, redundant traffic can be significantly eliminated. In this article, we first study techniques related to caching in current mobile networks, and discuss potential techniques for caching in 5G mobile networks, including evolved packet core network caching and radio access network caching. A novel edge caching scheme based on the concept of content-centric networking or information-centric networking is proposed. Using trace-driven simulations, we evaluate the performance of the proposed scheme and validate the various advantages of the utilization of caching content in 5G mobile networks. Furthermore, we conclude the article by exploring new relevant opportunities and challenges.
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paper_title: Applications of self-interference cancellation in 5G and beyond

paper_content:

Self-interference cancellation invalidates a long-held fundamental assumption in wireless network design that radios can only operate in half duplex mode on the same channel. Beyond enabling true in-band full duplex, which effectively doubles spectral efficiency, self-interference cancellation tremendously simplifies spectrum management. Not only does it render entire ecosystems like TD-LTE obsolete, it enables future networks to leverage fragmented spectrum, a pressing global issue that will continue to worsen in 5G networks. Self-interference cancellation offers the potential to complement and sustain the evolution of 5G technologies toward denser heterogeneous networks and can be utilized in wireless communication systems in multiple ways, including increased link capacity, spectrum virtualization, any-division duplexing (ADD), novel relay solutions, and enhanced interference coordination. By virtue of its fundamental nature, self-interference cancellation will have a tremendous impact on 5G networks and beyond.
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paper_title: Recent advancements in M2M communications in 4G networks and evolution towards 5G

paper_content:

Machine-to-Machine (M2M) communications is considered to be one of the key enablers for the provisioning of advanced applications and services such as smart cities and hospitals, as well as automated vehicular and industrial automation operation. Currently, in LTE-Advanced systems, the main focus has been on supporting massive deployment of low cost devices, with enhanced radio access network coverage. In this work, we present the recent MTC enhancements in LTE system. Detailed performance analysis based on LTE system settings is also presented. The LTE capacity evaluations performed based on devices per physical resource block indicate that significantly large number of devices can already be supported in an LTE system, based on the assumptions used, with minimal system overhead. We also present an overview of some of the key scenarios, requirements and use cases currently being considered for M2M communication in fifth generation (5G) systems. The performance requirements currently being considered for massive and ultra-reliable M2M communication are also discussed.
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paper_title: Load&Backhaul Aware Decoupled Downlink/Uplink Access in 5G Systems

paper_content:

Until the 4th Generation (4G) cellular 3GPP systems, a user equipment's (UE) cell association has been based on the downlink received power from the strongest base station. Recent work has shown that - with an increasing degree of heterogeneity in emerging 5G systems - such an approach is dramatically suboptimal, advocating for an independent association of the downlink and uplink where the downlink is served by the macro cell and the uplink by the nearest small cell. In this paper, we advance prior art by explicitly considering the cell-load as well as the available backhaul capacity during the association process. We introduce a novel association algorithm and prove its superiority w.r.t. prior art by means of simulations that are based on Vodafone's small cell trial network and employing a high resolution pathloss prediction and realistic user distributions. We also study the effect that different power control settings have on the performance of our algorithm.
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paper_title: Software-Defined Networking: A survey

paper_content:

Software-Defined Networking (SDN) is considered promising to simplify network management and enable research innovations based on the decomposition of the control and data planes. In this paper, we review SDN-related technologies. In particular, we try to cover three main parts of SDN: applications, the control plane, and the data plane anticipating that our efforts will help researchers set appropriate and meaningful directions for future SDN research.
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paper_title: Downlink and Uplink Decoupling: a Disruptive Architectural Design for 5G Networks

paper_content:

Cell association in cellular networks has traditionally been based on the downlink received signal power only, despite the fact that uplink and downlink transmission powers and interference levels differed significantly. This approach was adequate in homogeneous networks with macro base stations all having similar transmission power levels. However, with the growth of heterogeneous networks where there is a big disparity in the transmit power of the different base station types, this approach is highly inefficient. In this paper, we study the notion of Downlink and Uplink Decoupling (DUDe) where the downlink cell association is based on the downlink received power while the uplink is based on the pathloss. We present the motivation and assess the gains of this 5G design approach with simulations that are based on Vodafone's LTE field trial network in a dense urban area, employing a high resolution ray-tracing pathloss prediction and realistic traffic maps based on live network measurements.
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paper_title: Full duplex: Coming into reality in 2020?

paper_content:

Mobile traffic is projected to increase 1000 times from 2010 to 2020. This poses significant challenges on the 5th generation (5G) wireless communication system design, including network structure, air interface, key transmission schemes, multiple access, and duplexing schemes. In this paper, full duplex (FD) is discussed, aiming to highlight some insights on various issues including deployment scenarios, frame structures, reference signals (RS), interference mitigation, transceiver structures/calibration, and extension of time division duplex (TDD)/frequency division duplex (FDD) to full duplex. It is anticipated that with future standardization and deployment of FD systems, TDD and FDD will be harmoniously integrated, supporting all the existing half duplex mobile phones efficiently, and leading to a much enhanced 5G system performance.
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paper_title: Potentials and Challenges of C-RAN Supporting Multi-RATs Toward 5G Mobile Networks

paper_content:

This paper presents an overview of the cloud radio access network (C-RAN), which is a key enabler for future mobile networks in order to meet the explosive capacity demand of mobile traffic, and reduce the capital and operating expenditure burden faced by operators. We start by reviewing the requirements of future mobile networks, called 5G, followed by a discussion on emerging network concepts for 5G network architecture. Then, an overview of C-RAN and related works are presented. As a significant scenario of a 5G system, the ultra dense network deployment based on C-RAN is discussed with focuses on flexible backhauling, automated network organization, and advanced mobility management. Another import feature of a 5G system is the long-term coexistence of multiple radio access technologies (multi-RATs). Therefore, we present some directions and preliminary thoughts for future C-RAN-supporting Multi-RATs, including joint resource allocation, mobility management, as well as traffic steering and service mapping.
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paper_title: A flexible 100-antenna testbed for Massive MIMO

paper_content:

Massive multiple-input multiple-output (MIMO) is one of the main candidates to be included in the fifth generation (5G) cellular systems. For further system development it is desirable to have real-time testbeds showing possibilities and limitations of the technology. In this paper we describe the Lund University Massive MIMO testbed — LuMaMi. It is a flexible testbed where the base station operates with up to 100 coherent radio-frequency transceiver chains based on software radio technology. Orthogonal Frequency Division Multiplex (OFDM) based signaling is used for each of the 10 simultaneous users served in the 20 MHz bandwidth. Real time MIMO precoding and decoding is distributed across 50 Xilinx Kintex-7 FPGAs with PCI-Express interconnects. The unique features of this system are: (i) high throughput processing of 384 Gbps of real time baseband data in both the transmit and receive directions, (ii) low-latency architecture with channel estimate to precoder turnaround of less than 500 micro seconds, and (iii) a flexible extension up to 128 antennas. We detail the design goals of the testbed, discuss the signaling and system architecture, and show initial measured results for a uplink Massive MIMO over-the-air transmission from four single-antenna UEs to 100 BS antennas.
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paper_title: Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!

paper_content:

The global bandwidth shortage facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks. There is, however, little knowledge about cellular mm-wave propagation in densely populated indoor and outdoor environments. Obtaining this information is vital for the design and operation of future fifth generation cellular networks that use the mm-wave spectrum. In this paper, we present the motivation for new mm-wave cellular systems, methodology, and hardware for measurements and offer a variety of measurement results that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.
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paper_title: Cloud technologies for flexible 5G radio access networks

paper_content:

The evolution toward 5G mobile networks will be characterized by an increasing number of wireless devices, increasing device and service complexity, and the requirement to access mobile services ubiquitously. Two key enablers will allow the realization of the vision of 5G: very dense deployments and centralized processing. This article discusses the challenges and requirements in the design of 5G mobile networks based on these two key enablers. It discusses how cloud technologies and flexible functionality assignment in radio access networks enable network densification and centralized operation of the radio access network over heterogeneous backhaul networks. The article describes the fundamental concepts, shows how to evolve the 3GPP LTE architecture, and outlines the expected benefits.
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paper_title: Experimental Testbed for Dynamic Spectrum Access and Sensing of 5G GFDM Waveforms

paper_content:

Generalized frequency division multiplexing (GFDM) is a new candidate waveform for 5G applications. With flexible pulse shaping filtering and tail-biting cyclic prefix, GFDM has lower out of band leakage and hence is more suitable as an opportunistic cognitive radio waveform. Improved adjacent channel leakage ratio (ACLR) of GFDM makes the coexistence of secondary signals easier, with lower adjacent channel interference to legacy users. This paper details the experimental validation of the coexistence study of this 5G waveform in an LTE system. The paper also highlights the improved sensing performance of GFDM- CR waveform compared to traditional OFDM. OFDM with implicit rectangular pulse shaping has higher out of band leakage and increases the probability of false alarm; while sharper GFDM waveform demonstrates substantial spectral efficiency and produces lesser number of false alarms.
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paper_title: Cloud radio access network (C-RAN): a primer

paper_content:

In the era of mobile Internet, mobile operators are facing pressure on ever-increasing capital expenditures and operating expenses with much less growth of income. Cloud Radio Access Network (C-RAN) is expected to be a candidate of next generation access network techniques that can solve operators' puzzle. In this article, on the basis of a general survey of C-RAN, we present a novel logical structure of C-RAN that consists of a physical plane, a control plane, and a service plane. Compared to traditional architecture, the proposed C-RAN architecture emphasizes the notion of service cloud, service-oriented resource scheduling and management, thus it facilitates the utilization of new communication and computer techniques. With the extensive computation resource offered by the cloud platform, a coordinated user scheduling algorithm and parallel optimum precoding scheme are proposed, which can achieve better performance. The proposed scheme opens another door to design new algorithms matching well with C-RAN architecture, instead of only migrating existing algorithms from traditional architecture to C-RAN.
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paper_title: OpenAirInterface: A Flexible Platform for 5G Research

paper_content:

Driven by the need to cope with exponentially growing mobile data traffic and to support new traffic types from massive numbers of machine-type devices, academia and industry are thinking beyond the current generation of mobile cellular networks to chalk a path towards fifth generation (5G) mobile networks. Several new approaches and technologies are being considered as potential elements making up such a future mobile network, including cloud RANs, application of SDN principles, exploiting new and unused portions of spectrum, use of massive MIMO and full-duplex communications. Research on these technologies requires realistic and flexible experimentation platforms that offer a wide range of experimentation modes from real-world experimentation to controlled and scalable evaluations while at the same time retaining backward compatibility with current generation systems. Towards this end, we present OpenAirInterface (OAI) as a suitably flexible platform. In addition, we discuss the use of OAI in the context of several widely mentioned 5G research directions.
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paper_title: Local cooperation architecture for self-healing femtocell networks

paper_content:

As the demands for mobile phone access to the data services are expanding, advantages in cellular services can be gained by offering enhanced user experience through cost-effective broadband mobile. By reducing the distance between base stations and end users, femtocells provide higher data rates and better indoor coverage. The small size of a femtocell also improves spectrum reuse, which contributes to higher spectrum efficiency. As femtocells are usually unplanned, efficient operation and maintenance are required to maximize the benefits of femtocell access. As one of the fundamental functionalities in network maintenance, a selfhealing mechanism aims to autonomously alleviate the impact of coverage or capacity loss induced by cell outage. Existing studies on the self-healing problem have focused on macrocell networks, while none of them has systematically investigated the problem in the context of femtocells networks. In this article we argue that the distinct features of the two-tier macro-femto system require dedicated architectures for self-healing femtocell networks. We present three different architectures, and further investigate their advantages and limitations. Then we call attention to the local cooperative architecture, which, with proper design, satisfies the practical requirements imposed by the salient features of femtocell networks. We further verify the benefits of the local cooperative architecture by proposing a self-healing scheme for femtocell networks.
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paper_title: Full duplex radios

paper_content:

This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
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paper_title: Multi-hop point-to-point FDD wireless backhaul for mobile small cells

paper_content:

Point-to-point FDD microwave can be a fast-to-install and cost-effective backhaul solution for mobile small cells. However, its applications have been held back, because the state-of-the-art static backhaul deployment fails to capture drastically fluctuating small cell traffic. To address this issue we introduce a new adaptive backhaul architecture that is able to adapt to changing small cell traffic. Extended from a graph theoretic clique idea, the architecture allows changes to the overall backhaul topology, and it also allows each individual backhaul link to vary its frequency to meet traffic demand. Guard bands are adaptively reserved between some of the links to suppress adjacent-frequency interference, while being efficiently used by other links for data transmission. Our case study of 10 small cells confirms that the adaptive architecture is able to increase the small cell throughput by 75 percent compared to the static backhaul architecture. It can also reduce the backhaul bandwidth requirement by 57 percent, and enhance small cells' satisfaction by 158.4 percent with respect to their allocated bandwidths.
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paper_title: Vehicle Authentication via Monolithically Certified Public Key and Attributes

paper_content:

Vehicular networks are used to coordinate actions among vehicles in traffic by the use of wireless transceivers (pairs of transmitters and receivers). Unfortunately, the wireless communication among vehicles is vulnerable to security threats that may lead to very serious safety hazards. In this work, we propose a viable solution for coping with Man-in-the-Middle attacks. Conventionally, Public Key Infrastructure is utilized for a secure communication with the pre-certified public key. However, a secure vehicle-to-vehicle communication requires additional means of verification in order to avoid impersonation attacks. To the best of our knowledge, this is the first work that proposes to certify both the public key and out-of-band sense-able static attributes to enable mutual authentication of the communicating vehicles. Vehicle owners are bound to preprocess (periodically) a certificate for both a public key and a list of fixed unchangeable attributes of the vehicle. Furthermore, the proposed approach is shown to be adaptable with regards to the existing authentication protocols. We illustrate the security verification of the proposed protocol using a detailed proof in Spi calculus.
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Title: A Survey on 5G: The Next Generation of Mobile Communication

Section 1: Introduction
Description 1: An introduction of the paper and scope of the paper

Section 2: Desideratum of 5G Networks
Description 2: Highlight requirements of the future 5G networks including device scalability, data streaming, spectrum utilization, ubiquitous connectivity, and zero latency

Section 3: Limitations of the current cellular networks
Description 3: Detail the shortcomings of current cellular networks such as support for bursty data traffic, utilization of processing capabilities, interference issues, and user separation 

Section 4: Applications of 5G Networks
Description 4: List and describe the most prominent applications of 5G networks including personal usage, virtualized homes, smart societies, smart grids, tactile Internet, automation, healthcare, logistics, and industrial applications

Section 5: Challenges in the Development of 5G Networks
Description 5: Discuss several challenges in achieving the vision of 5G networks including data rate and capacity expansion, scalability, interference handling, energy optimization, and high reliability

Section 6: Architectures for the Future/5G Mobile Cellular Networks
Description 6: Elaborate on the existing architectures for 5G networks including multi-tier, CRN-based, D2D communication based, and cloud-based architectures 

Section 7: Implementation Issues in 5G Networks
Description 7: Review issues regarding interference, handoff, QoS, load balancing and channel access management in the context of 5G networks

Section 8: Real Demonstrations and Testbeds for 5G Networks
Description 8: Present some real demonstrations and testbeds for 5G networks 

Section 9: Concluding Remarks
Description 9: Discuss final thoughts and prominent issues, along with recommendations for future research and development in 5G networks