Licensed Spectrum Sharing Schemes for Mobile Operators: A Survey and Outlook
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paper_title: Interference Management in Femtocells

paper_content:

Increase in system capacity and data rates can be achieved efficiently in a wireless system by getting the transmitter and receiver closer to each other. Femtocells deployed in the macrocell significantly improve the indoor coverage and provide better user experience. The femtocell base station called as Femtocell Access Point (FAP) is fully user deployed and hence reduces the infrastructure, maintenance and operational cost of the operator while at the same time providing good Quality of Service (QoS) to the end user and high network capacity gains. However, the mass deployment of femtocell faces a number of challenges, among which interference management is of much importance, as the fundamental limits of capacity and achievable data rates mainly depends on the interference faced by the femtocell network. To cope with the technical challenges including interference management faced by the femtocells, researchers have suggested a variety of solutions. These solutions vary depending on the physical layer technology and the specific scenarios considered. Furthermore, the cognitive capabilities, as a functionality of femtocell have also been discussed in this survey. This article summarises the main concepts of femtocells that are covered in literature and the major challenges faced in its large scale deployment. The main challenge of interference management is discussed in detail with its types in femtocells and the solutions proposed over the years to manage interference have been summarised. In addition an overview of the current femtocell standardisation and the future research direction of femtocells have also been provided.
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paper_title: "Simple rules" for mobile network operators' strategic choices in future cognitive spectrum sharing networks

paper_content:

Spectrum sharing is becoming a necessity in future cellular networks due to the increasing traffic demand and challenges of getting exclusive spectrum. This article reviews the spectrum sharing framework that consists of regulatory, technology, and business domains. For future mobile network operators, sharing of spectrum with other operators or with other radiocommunication services - especially when using cognitive radio system technologies - is a disruptive change. Building on alternative spectrum sharing scenarios, this article discusses a set of Simple Rules for mobile network operators, both dominators and challengers, regarding spectrum sharing in future cognitive cellular networks. The Simple Rules provide a dynamic framework for both dominating and challenger mobile network operators for developing their sharing-based business models.
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paper_title: A study on the coexistence of fixed satellite service and cellular networks in a mmWave scenario

paper_content:

The use of a larger bandwith in the millimeter wave (mmWave) spectrum is one of the key components of next generation cellular networks. Currently, part of this band is allocated on a co-primary basis to a number of other applications, such as the fixed satellite services (FSSs). In this paper, we investigate the coexistence between a cellular network and FSSs in a mmWave scenario. In light of the parameters recommended by the standard and the recent results presented in the literature on the mmWave channel model, we analyze different BSs deployments and different antenna configurations at the transmitters. Finally, we show how, exploiting the features of a mmWave scenario, the coexistence between cellular and satellite services is feasible and the interference at the FSS antenna can be kept below recommended levels.
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paper_title: Modeling of interference maps for Licensed Shared Access in LTE-advanced networks supporting Carrier Aggregation

paper_content:

Cognitive Radio based Dynamic Spectrum Access (CR-DSA) has been envisaged as the foremost solution to eliminate the impending false scarcity of the radio frequency spectrum and to combat the dramatic surge in mobile data traffic. Furthermore, the revolutionary concepts - Carrier Aggregation (CA) and Licensed Shared Access (LSA) - have been conceived to support higher data rates by aggregating bandwidth from different parts of the spectrum, and to provide for a predictable Quality of Service (QoS) through spectrum sharing, respectively, so as to enhance the performance of the current generation mobile communication systems. However, an inevitable consequence of spectrum sharing is the interference induced upon the incumbent user. In this work, the prime focus of attention is on the mitigation of the interference caused by an LSA-licensed LTE-Advanced Radio Access Network (RAN) in the uplink (UL). To this end, we propose an interference management scheme based on Radio Environment Maps (REMs). Different approaches have been considered for the modeling of the requisite maps and a performance comparison between them by means of detection theory is presented. In conclusion, we prove the superior performance of the kriging spatial interpolation technique over the other approaches.
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paper_title: Performance of Mobile MIMO OFDM Systems With Application to UTRAN LTE Downlink

paper_content:

This paper analyzes the performance of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) technology through the ergodic capacity. The capacity is represented based on the mean of the effective signal-to-interference-and-noise ratio (SINR) values. The asymptotic distribution of the effective SINR in the case of independent and m-dependent quality measures, i.e., post-processed SINRs, is established analytically. The asymptotic distribution is applicable for the size of post-processed SINRs of at least 1000 samples or more and m = 10. The mean value of the effective SINR based on the moment generating function of post-processed SINR is derived. Additionally, the impact of mobility on the system performance is characterized through the ergodic capacity and a system level factor which measures user mobility. The performance of MIMO OFDM system is validated by fully dynamic 3GPP Long Term Evolution network simulations in downlink under realistic mobility scenarios with low (3 km/h), medium (30 km/h) and high (120 km/h) user speeds. The simulations verify that the derived asymptotic distributions of the effective SINR for the independent and m-dependent cases are very accurate in all mobility scenarios. The simulated ergodic capacity show clear loss in the average MIMO spectral efficiency especially in high mobility scenarios.
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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: Evaluation of spectrum access options for indoor mobile network deployment

paper_content:

The investments in indoor mobile networks are highly related to the spectrum availability and its associated authorization options. The aim of this paper is to discuss the differences in the spectrum demand taking into consideration both wide and local area network deployment requirements and the kind of actor that provides the indoor wireless access. The analysis covers different authorizations options namely licensed, unlicensed, licensed shared access (LSA) and secondary access. A quantitative approach is used to analyze the differences between macrocell and femtocell deployments focusing on deployment cost and spectrum demand. This is complemented by a qualitative study to explore and discuss the strategic business decisions of different actors in view of the available spectrum bands and spectrum authorization options. The main conclusions from this study are; spectrum has more value in macrocell deployment scenarios than in femtocell ones. More spectrum in macrocell deployment scenarios means that operators can deploy less number of new sites and exploit previous infrastructure investments. Femtocell networks are often coverage limited which allows for frequency re-use. As a consequence, the value of spectrum is not the same for mobile network operators (MNOs) and for local network operator (LNOs). MNOs are traditionally confined to macrocell deployment strategies which entail the exclusive usage of licensed bands. While, the use of licensed spectrum by LNOs may incur more cost than the cost of infrastructure deployment. This explains why the use of unlicensed bands is lucrative and viable for LNOs. Furthermore, the LSA scheme may or could soon become an enabler for LNO's business due to the prevailing technical, regulation and policies developments.
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paper_title: Using SDN as a key enabler for co-primary spectrum sharing

paper_content:

Over the past years the mobile traffic demands and the number of the connected devices have been constantly increasing thus indicating that in the near future the current spectrum usage models may fail to cover user needs. At the same time, spectrum scarcity over several Mobile Network Operators (MNOs) leads to inefficient spectrum usage. Co-primary spectrum sharing is a scheme for trading resources among MNOs, enabling flexible spectrum usage, which is arising as a possible solution to spectrum scarcity. However, up to now the schemes for co-primary shared access are hard to be implemented. The recently introduced concept of Software Defined Networking (SDN) gives the flexibility to MNOs' network configuration and, therefore, is arising as an enabler for efficiently handling spectrum trading. In this paper we present a complete functional architecture aiming at enabling co-primary spectrum sharing among MNOs. We, furthermore, propose a scheme for implementing the introduced architectural scheme, coupled with fully described information flows among the (SDN) network entities. Such solution enables the concurrent reconfiguration (when required) for both core and access network nodes, based on the spectrum trading process.
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paper_title: Decision-Theoretic Distributed Channel Selection for Opportunistic Spectrum Access: Strategies, Challenges and Solutions

paper_content:

Opportunistic spectrum access (OSA) has been regarded as the most promising approach to solve the paradox between spectrum scarcity and waste. Intelligent decision making is key to OSA and differentiates it from previous wireless technologies. In this article, a survey of decision-theoretic solutions for channel selection and access strategies for OSA system is presented. We analyze the challenges facing OSA systems globally, which mainly include interactions among multiple users, dynamic spectrum opportunity, tradeoff between sequential sensing cost and expected reward, and tradeoff between exploitation and exploration in the absence of prior statistical information. We provide comprehensive review and comparison of each kind of existing decision-theoretic solution, i.e., game models, Markovian decision process, optimal stopping problem and multi-armed bandit problem. We analyze their strengths and limitations and outline further research for both technical contents and methodologies. In particular, these solutions are critically analyzed in terms of information, cost and convergence speed, which are key concerns for practical implementation. Moreover, it is noted that each kind of existing decision-theoretic solution mainly addresses one aspect of the challenges, which implies that two or more kinds of decision-theoretic solutions should be incorporated to address more challenges simultaneously.
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paper_title: Radar, TV and Cellular Bands: Which Spectrum Access Techniques for Which Bands?

paper_content:

Opportunistic access has been considered by regulators for a number of different spectrum bands. In this paper, we discuss and qualitatively evaluate techniques used in the discovery of spectrum opportunities, also called white spaces, in the radar, TV, and cellular bands. These techniques include spectrum sensing, cooperative spectrum sensing, geolocation databases, and the use of beacons. We make the case that each of the three bands considered calls for a different set of spectrum access techniques. While TV bands are well matched to the adoption of geolocation databases, a database-assisted spectrum sensing mechanism may represent the most efficient solution to exploit the spectrum holes in radar bands. We drew this conclusion based on a multitude of factors, such as the radar antennas' constant motion, and the absence of a hidden node problems in these bands. The unpredictability of cellular systems, on the other hand, calls for a more coordinated spectrum access approach, namely beacon signaling, that could be implemented using the already established cellular infrastructure and spare bits of its logical channels.
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paper_title: Overview and comparison of recent spectrum sharing approaches in regulation and research: From opportunistic unlicensed access towards licensed shared access

paper_content:

This paper reviews recent spectrum sharing models under study in the spectrum regulation and wireless communications research domains. An overview of different spectrum regulator forums and directions is presented and their activities related to the development of spectrum sharing models are reviewed. Special emphasis is put on the recent European and US regulatory approaches for spectrum sharing. In particular, Licensed Shared Access (LSA) and Collective Use of Spectrum (CUS) models from Europe and Three-Tier Hierarchy Model from the US are analyzed in detail. A comparison is made between these approaches to identify similarities and differences in the regulatory developments. Factors for developing a successful sharing model are also discussed. For a dynamic spectrum sharing model to be adopted, it must protect the rights of entrant users without impact to the legacy systems. It must also create a reasonable straightforward opportunity for an entity that wishes to access a shared spectrum to do so in a manner that is neither overly complex nor costly to implement. The practical implementation of dynamic spectrum sharing models is likely to require different national implementations because the regulatory approaches and the incumbent spectrum uses are different in various countries.
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paper_title: Cognitive Radio for Smart Grids: Survey of Architectures, Spectrum Sensing Mechanisms, and Networking Protocols

paper_content:

Traditional power grids are currently being transformed into smart grids (SGs). SGs feature multi-way communication among energy generation, transmission, distribution, and usage facilities. The reliable, efficient, and intelligent management of complex power systems requires integration of high-speed, reliable, and secure data information and communication technology into the SGs to monitor and regulate power generation and usage. Despite several challenges, such as trade-offs between wireless coverage and capacity as well as limited spectral resources in SGs, wireless communication is a promising SG communications technology. Cognitive radio networks (CRNs) in particular are highly promising for providing timely SG wireless communications by utilizing all available spectrum resources. We provide in this paper a comprehensive survey on the CRN communication paradigm in SGs, including the system architecture, communication network compositions, applications, and CR-based communication technologies. We highlight potential applications of CR-based SG systems. We survey CR-based spectrum sensing approaches with their major classifications. We also provide a survey on CR-based routing and MAC protocols, and describe interference mitigation schemes. We furthermore present open issues and research challenges faced by CR-based SG networks along with future directions.
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paper_title: Spectrum Decision in Cognitive Radio Networks: A Survey

paper_content:

Spectrum decision is the ability of a cognitive radio (CR) to select the best available spectrum band to satisfy secondary users' (SUs') quality of service (QoS) requirements, without causing harmful interference to licensed or primary users (PUs). Each CR performs spectrum sensing to identify the available spectrum bands and the spectrum decision process selects from these available bands for opportunistic use. Spectrum decision constitutes an important topic which has not been adequately explored in CR research. Spectrum decision involves spectrum characterization, spectrum selection and CR reconfiguration functions. After the available spectrum has been identified, the first step is to characterize it based not only on the current radio environment conditions, but also on the PU activities. The second step involves spectrum selection, whereby the most appropriate spectrum band is selected to satisfy SUs' QoS requirements. Finally, the CR should be able to reconfigure its transmission parameters to allow communication on the selected band. Key to spectrum characterization is PU activity modelling, which is commonly based on historical data to provide the means for predicting future traffic patterns in a given spectrum band. This paper provides an up-to-date survey of spectrum decision in CR networks (CRNs) and addresses issues of spectrum characterization (including PU activity modelling), spectrum selection and CR reconfiguration. For each of these issues, we highlight key open research challenges. We also review practical implementations of spectrum decision in several CR platforms.
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paper_title: Radio Resource Allocation Techniques for Efficient Spectrum Access in Cognitive Radio Networks

paper_content:

This paper provides an overview of cognitive radio (CR) networks, with focus on the recent advances in resource allocation techniques and the CR networks architectural design. The contribution of this work is threefold. First, a systematic way to study the resource allocation problem is presented; various design approaches are introduced, such as signal-to-interference-and-noise ratio (SINR) or transmission power-based, and centralized or distributed methods. Second, CR optimization methods are presented, accompanied by a comprehensive study of the resource allocation problem formulations. Furthermore, quality of service criteria of the physical or/and the medium access control layers are investigated. Third, challenges in spectrum assignment are discussed, focusing on dynamic spectrum allocation, spectrum aggregation and frequency mobility. Such approaches constitute an emerging trend in efficient spectrum sharing and affect the performance of resource allocation techniques. The open issues for future research in this area are finally discussed, including adaptability-reconfigurability, dual accessibility, and energy efficiency.
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paper_title: Spectrum Assignment in Cognitive Radio Networks: A Comprehensive Survey

paper_content:

Cognitive radio (CR) has emerged as a promising technology to exploit the unused portions of spectrum in an opportunistic manner. The fixed spectrum allocation of governmental agencies results in unused portions of spectrum, which are called "spectrum holes" or "white spaces". CR technology overcomes this issue, allowing devices to sense the spectrum for unused portions and use the most suitable ones, according to some pre-defined criteria. Spectrum assignment is a key mechanism that limits the interference between CR devices and licensed users, enabling a more efficient usage of the wireless spectrum. Interference is a key factor that limits the performance in wireless networks. The scope of this work is to give an overview of the problem of spectrum assignment in cognitive radio networks, presenting the state-of-the-art proposals that have appeared in the literature, analyzing the criteria for selecting the most suitable portion of the spectrum and showing the most common approaches and techniques used to solve the spectrum assignment problem. Finally, an analysis of the techniques and approaches is presented, discussing also the open issues for future research in this area.
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paper_title: A survey of MAC issues for TV white space access

paper_content:

The opening of TV white space (TVWS) bands for cognitive access is one of the first tangible steps to solve spectrum scarcity problem in current wireless networks. However, this has also raised many new challenges to efficiently use the TVWS spectrum. One of the primary challenges is the design of efficient Medium Access Control (MAC) protocols that conform to various rules imposed to protect primary users as well as accommodate spatio-temporal variations of the TVWS spectrum. This article presents MAC-related challenges related to cognitive access to TVWS, discusses potential approaches to overcoming these challenges, and investigates open research issues. It also reviews regulatory activities in several countries and worldwide standardization efforts for TVWS access.
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paper_title: Enabling Cognitive Radios through Radio Environment Maps

paper_content:

In recent years, cognitive radios and cognitive wireless networks have been introduced as a new paradigm for enabling much higher spectrum utilization, providing more reliable and personal radio services, reducing harmful interference, and facilitating the interoperability or convergence of different wireless communication networks. Cognitive radios are goaloriented, autonomously learn from experience and adapt to changing operating conditions. Cognitive radios have the potential to drive the next generation of radio devices and wireless communication system design and to enable a variety of niche applications in demanding environments, such as spectrum-sharing networks, public safety, natural disasters, civil emergencies, and military operations. This research first introduces an innovative approach to developing cognitive radios based on the Radio Environment Map (REM). The REM can be viewed as an integrated database that provides multi-domain environmental information and prior knowledge for cognitive radios, such as the geographical features, available services and networks, spectral regulations, locations and activities of neighboring radios, policies of the users and/or service providers, and past experience. The REM, serving as a vehicle of network support to cognitive radios, can be exploited by the cognitive engine for most cognitive functionalities, such as situation awareness, reasoning, learning, planning, and decision support. This research examines the role of the REM in cognitive radio development from a network point of view, and focuses on addressing three specific issues about the REM: how to design and populate the REM; how to exploit the REM with the cognitive engine algorithms; and how to evaluate the performance of the cognitive radios. Applications of the REM to wireless local area networks (WLAN) and wireless regional area networks (WRAN) are investigated, especially from the perspectives of interference management and radio resource management, which
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paper_title: Spectrum sharing scenarios and resulting technical requirements for 5G systems

paper_content:

Cellular networks today are designed for and operate in dedicated licensed spectrum. At the same time there are other spectrum usage authorization models for wireless communication, such as unlicensed spectrum or, as widely discussed currently but not yet implemented in practice, various forms of licensed shared spectrum. Hence, cellular technology as of today can only operate in a subset of the spectrum that is in principle available. Hence, a future wireless system may benefit from the ability to access also spectrum opportunities other than dedicated licensed spectrum. It is therefore important to identify which additional ways of authorizing spectrum usage are deemed to become relevant in the future and to analyze the resulting technical requirements. The implications of sharing spectrum between different technologies are analyzed in this paper, both from efficiency and technology neutrality perspective. Different known sharing techniques are outlined and their applicability to the relevant range of future spectrum regulatory regimes is discussed. Based on an assumed range of relevant (according to the views of the authors) future spectrum sharing scenarios, a toolbox of certain spectrum sharing techniques is proposed as the basis for the design of spectrum sharing related functionality in future mobile broadband systems.
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paper_title: Spectrum pooling: an innovative strategy for the enhancement of spectrum efficiency

paper_content:

This article describes the technical challenges that have to be met when implementing the interesting new technology of spectrum pooling. This notion represents the coexistence of two mobile radio systems within the same frequency range. It enables the secondary utilization of already licensed frequency bands as aimed at by several regulatory authorities worldwide. The goal of spectrum pooling is to enhance spectral efficiency by overlaying a new mobile radio system on an existing one without requiring any changes to the actual licensed system. Several demanding tasks originate from this idea. Some of them have been solved in recent research projects. Others are subject to ongoing investigations. Here, the state of the art in spectrum pooling is presented.
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paper_title: Cellular architecture enhancement for supporting the european licensed shared access concept

paper_content:

As the demand for mobile traffic continues to grow rapidly, finding exclusive bands for mobile network operators in a harmonized manner becomes increasingly challenging. New European spectrum regulatory development aims at allowing future cellular networks to access shared spectrum bands under the licensed shared access regime as a complementary approach to current exclusive licensed and license-exempt bands. The introduction of additional spectrum by new spectrum access methods seems a necessary evolution path for cellular mobile communication networks to respond to the growing traffic in the next decade. The inclusion of the shared bands will require modifications to the existing network management as their availability and access conditions may vary locally and temporarily according to the agreed licensing conditions. Self-organizing network features will undoubtedly become an important enabler to handle the increased complexity brought by licensed shared access methods. In this article, self-organizing networking features to support the licensed shared bands are introduced. In particular, automated load balancing decisions by traffic steering are examined in detail with the purpose of matching the mobile network operators' available radio access technologies, cells, and spectrum resources to the fluctuating traffic demand.
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paper_title: Co-primary spectrum sharing for denser networks in local area

paper_content:

This work investigates co-primary spectrum sharing problem in the local area indoor dense deployment scenario. A spectrum sharing method and relevant mechanism are designed to achieve flexible spectrum usage amongst multiple operator networks. This proposed solution improves spectrum efficiency by making small cells more flexibly and efficiently utilize whole spectrum resources via intra operator spectrum allocation and inter-operator spectrum coordination. Intensive system level simulations give a detailed verification of the performance of this spectrum sharing approach.
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paper_title: Introduction of light licensing regime in Republic of Croatia

paper_content:

“Light licensing” regime is a procedure which allows easier and less time-consuming spectrum management, combining two opposite approaches: individual licensing and general authorization regime. In light licensing the role of regulator is reduced by transferring the responsibility for frequency planning and interference analysis to the license applicant. This way faster, cheaper and more efficient licensing procedure is established, thus enabling more flexible access to the RF spectrum. This rather new approach has been widely implemented over the world for frequency bands with low risk of interference, such as 60 and 80 GHz, and following the trends, this licensing regime will be implemented in Croatia in the second half of 2012. The paper gives an overview of the existing licensing procedures and provides comparative analysis of currently implemented Light Licensing regimes in different countries. Based on the case studies available the most appropriate model for the implementation of this concept in Republic of Croatia has been delivered and described in this paper in details.
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paper_title: Licensed Shared Access (LSA) — Regulatory background and view of Administrations

paper_content:

This paper reflects the view of Conference Europeenne des Postes et des Telecommunications (CEPT) Administrations on status and current work on Licensed Shared Access (LSA), related to European Communication Committee (ECC) Decisions and Reports as well as to the current regulatory framework on licensing and sharing. It explains similarities and differences between the grandfathering approach Authorized Shared Access (ASA) and LSA. The latter provides the communication basis for an enhanced future solution for more flexible sharing and is unanimously agreed within the CEPT and the Radio Spectrum Policy Group (RSPG), the high-level advisory group of European Union (EU) Member States that assists the European Commission (EC) in the development of radio spectrum policy. Reasoned by the duplicities of the approaches the paper aims to compare among the qualities and justifications of both sharing approaches, LSA and ASA. Especially the comprehensive approach provided by the framework of LSA - as amended by CEPT and EC - is highlighted, noting the relevant circumstances of both entities. Additional focus has been placed on the draft ECC Decision on “Harmonised technical and regulatory conditions for the use of the band 2.3-2.4 GHz for MFCN” [1] and its background, especially on its requested implementation via the LSA concept.
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paper_title: Spectrum sharing in the EU and the path towards standardization

paper_content:

This paper addresses the current regulatory framework, research activities and standardization efforts towards a shared use of radio spectrum in the European Union. Two main research streams are considered: The emerging concept of Licensed Shared Access that ensures a predictable Quality of Service for secondary users of spectrum and the opportunistic Device-to-Device communications that represent a recent and enormous socio-technological trend. The paper presents also research results that support the spectrum sharing standardization path in ETSI and 3GPP.
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paper_title: A techno-economic framework of spectrum combining for indoor capacity provisioning

paper_content:

Spectrum combining refers to utilizing multiple types of spectrum authorization options for a wireless network. The approach is considered as an essential ingredient of high-capacity provision in the coming years. This paper presents a techno-economic framework to analyze capacity and cost of different spectrum combining options. We focus on indoor environments where the traffic demand is expected to be extremely demanding. We describe various spectrum options such as licence-exempt, light licensing, and licensed shared access (LSA). Then, we compare various combinations of these options with increasing traffic demand over time. In terms of capacity provisioning, this framework is based on the idea that spectrum combining must be done at the right time, that is when the existing deployment can no longer satisfy capacity demand. For the cost analysis, most relevant cost drivers are included in a cost structure which becomes the backbone of this framework. The proposed framework can help network providers determine the most cost-effective spectrum acquisition strategy which can meet capacity demand in indoor environments.
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paper_title: Introduction of light licensing regime in Republic of Croatia

paper_content:

“Light licensing” regime is a procedure which allows easier and less time-consuming spectrum management, combining two opposite approaches: individual licensing and general authorization regime. In light licensing the role of regulator is reduced by transferring the responsibility for frequency planning and interference analysis to the license applicant. This way faster, cheaper and more efficient licensing procedure is established, thus enabling more flexible access to the RF spectrum. This rather new approach has been widely implemented over the world for frequency bands with low risk of interference, such as 60 and 80 GHz, and following the trends, this licensing regime will be implemented in Croatia in the second half of 2012. The paper gives an overview of the existing licensing procedures and provides comparative analysis of currently implemented Light Licensing regimes in different countries. Based on the case studies available the most appropriate model for the implementation of this concept in Republic of Croatia has been delivered and described in this paper in details.
---
paper_title: Decision-Theoretic Distributed Channel Selection for Opportunistic Spectrum Access: Strategies, Challenges and Solutions

paper_content:

Opportunistic spectrum access (OSA) has been regarded as the most promising approach to solve the paradox between spectrum scarcity and waste. Intelligent decision making is key to OSA and differentiates it from previous wireless technologies. In this article, a survey of decision-theoretic solutions for channel selection and access strategies for OSA system is presented. We analyze the challenges facing OSA systems globally, which mainly include interactions among multiple users, dynamic spectrum opportunity, tradeoff between sequential sensing cost and expected reward, and tradeoff between exploitation and exploration in the absence of prior statistical information. We provide comprehensive review and comparison of each kind of existing decision-theoretic solution, i.e., game models, Markovian decision process, optimal stopping problem and multi-armed bandit problem. We analyze their strengths and limitations and outline further research for both technical contents and methodologies. In particular, these solutions are critically analyzed in terms of information, cost and convergence speed, which are key concerns for practical implementation. Moreover, it is noted that each kind of existing decision-theoretic solution mainly addresses one aspect of the challenges, which implies that two or more kinds of decision-theoretic solutions should be incorporated to address more challenges simultaneously.
---
paper_title: A techno-economic framework of spectrum combining for indoor capacity provisioning

paper_content:

Spectrum combining refers to utilizing multiple types of spectrum authorization options for a wireless network. The approach is considered as an essential ingredient of high-capacity provision in the coming years. This paper presents a techno-economic framework to analyze capacity and cost of different spectrum combining options. We focus on indoor environments where the traffic demand is expected to be extremely demanding. We describe various spectrum options such as licence-exempt, light licensing, and licensed shared access (LSA). Then, we compare various combinations of these options with increasing traffic demand over time. In terms of capacity provisioning, this framework is based on the idea that spectrum combining must be done at the right time, that is when the existing deployment can no longer satisfy capacity demand. For the cost analysis, most relevant cost drivers are included in a cost structure which becomes the backbone of this framework. The proposed framework can help network providers determine the most cost-effective spectrum acquisition strategy which can meet capacity demand in indoor environments.
---
paper_title: Radar, TV and Cellular Bands: Which Spectrum Access Techniques for Which Bands?

paper_content:

Opportunistic access has been considered by regulators for a number of different spectrum bands. In this paper, we discuss and qualitatively evaluate techniques used in the discovery of spectrum opportunities, also called white spaces, in the radar, TV, and cellular bands. These techniques include spectrum sensing, cooperative spectrum sensing, geolocation databases, and the use of beacons. We make the case that each of the three bands considered calls for a different set of spectrum access techniques. While TV bands are well matched to the adoption of geolocation databases, a database-assisted spectrum sensing mechanism may represent the most efficient solution to exploit the spectrum holes in radar bands. We drew this conclusion based on a multitude of factors, such as the radar antennas' constant motion, and the absence of a hidden node problems in these bands. The unpredictability of cellular systems, on the other hand, calls for a more coordinated spectrum access approach, namely beacon signaling, that could be implemented using the already established cellular infrastructure and spare bits of its logical channels.
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paper_title: A survey of spectrum sensing algorithms for cognitive radio applications

paper_content:

The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.
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paper_title: Hybrid spectrum sharing in dynamic spectrum access networks

paper_content:

In this work, inefficient spectrum usage problem which will lead to spectrum scarcity in future communications has been addressed. According to Federal Communications Commission, spectrum sharing is a technique to efficiently utilize the spectrum. We analyse dynamic spectrum access concepts such as overlay spectrum sharing and underlay spectrum sharing. Our overlay and underlay analysis have been made with the use of five and eight state continuous time Markov chains respectively. We derive the steady state probability for these states and also calculate the throughput of the aforementioned spectrum sharing schemes with the use of Shannons channel capacity. In addition to that, specifically, we propose a hybrid spectrum access scheme which combines overlay and underlay spectrum sharing schemes and employ them to improve the system throughput by efficiently using the spectrum. Our approach, by using continuous time Markov chain, reduces the complexity in modelling the dynamics of primary and secondary user. We have also shown numerical results to validate the performance of the proposed scheme. Our scheme lays foundation for further works in the field, and our scheme could be enhanced in future works.
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paper_title: Overlay/Underlay Spectrum Sharing for Multi-Operator Environment in Cognitive Radio Networks

paper_content:

A new system model is introduced for spectrum sharing in a multi-operator environment. The infrastructure based cognitive radio network operates in underlay/overlay (hybrid) transmission mode sharing the spectrum of licensed users. Primary user networks (PUNs) are benefitted by the relaying capability of the cognitive radio base station so that their service degraded users due to low coverage, can enhance the performance. The cognitive radio network (CRN) also helps itself by transmitting its own data along with the primary data on the same band, while agreeing to maintain the signal to interference plus noise ratios of primary users' at a predetermined level. CRN operates in an underlay mode with an imposed interference threshold. In addition, maximizing the secondary user capacity by strategically changing the available frequencies from time slot to time slot is discussed with the introduction of two primary data relaying schemes (asynchronous / synchronous). The objective of the secondary user capacity maximization is reformulated into a linear programming problem with interference cancellation techniques. Power allocation for all the active users and the capacity of the secondary user is analyzed in both of the schemes
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paper_title: Primary radio user activity models for cognitive radio networks: A survey

paper_content:

Abstract Cognitive Radio Networks have been emerged as a promising solution for solving the problem of spectrum scarcity and improving spectrum utilization by opportunistic use of spectrum. Cognitive radio networks utilize the spectrum which is licensed to primary radio users when they are not utilizing it, i.e., when the spectrum is idle. Thus, the performance of cognitive radio networks is highly dependent upon the activity of primary radio users. Hence, it is very important to model primary radio users activity in cognitive radio networks. By keeping this in mind, several models in the literature have been proposed for modeling primary radio users activity. But there is not any source which consolidate all these models into single platform. Therefore, this paper combines all the primary radio user activity models for cognitive radio networks at a single place. The goal of this paper is to provide a single source in the form of survey paper by which a reader can get an idea about which primary radio user activity models have been used in the literature for cognitive radio networks and how the modeling is performed. Furthermore, we also discuss issues, challenges and future directions for primary radio activity models. In fact, in this paper, different primary radio user activity models have been presented along with their classification. This paper also discusses those approaches which performed real implementation for spectrum occupancy along with spectrum bands on which the implementation is performed and location where implementation is carried out. In summary, this paper provides up-to-date survey of primary radio user activity models for cognitive radio networks.
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paper_title: Spectrum Leasing in Cognitive Radio Networks: A Survey

paper_content:

Cognitive Radio (CR) is a dynamic spectrum access approach, in which unlicensed users (or secondary users, SUs) exploit the underutilized channels (or white spaces) owned by the licensed users (or primary users, PUs). Traditionally, SUs are oblivious to PUs, and therefore the acquisition of white spaces is not guaranteed. Hence, a SU must vacate its channel whenever a PU reappears on it in an unpredictable manner, which may affect the SUs’ network performance. Spectrum leasing has been proposed to tackle the aforementioned problem through negotiation between the PU and SU networks, which allows the SUs to acquire white spaces for a guaranteed period of time. Through spectrum leasing, the PUs and SUs enhance their network performances, and additionally PUs maximize their respective monetary gains. Numerous research efforts have been made to investigate the CR, whereas the research into spectrum leasing remains at its infancy. In this paper, we present a comprehensive review on spectrum leasing schemes in CR networks by highlighting some pioneering approaches and discuss the gains, functionalities, characteristics, and challenges of spectrum leasing schemes along with the performance enhancement in CR networks. Additionally, we discuss various open issues in order to spark new interests in this research area.
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paper_title: Overview and comparison of recent spectrum sharing approaches in regulation and research: From opportunistic unlicensed access towards licensed shared access

paper_content:

This paper reviews recent spectrum sharing models under study in the spectrum regulation and wireless communications research domains. An overview of different spectrum regulator forums and directions is presented and their activities related to the development of spectrum sharing models are reviewed. Special emphasis is put on the recent European and US regulatory approaches for spectrum sharing. In particular, Licensed Shared Access (LSA) and Collective Use of Spectrum (CUS) models from Europe and Three-Tier Hierarchy Model from the US are analyzed in detail. A comparison is made between these approaches to identify similarities and differences in the regulatory developments. Factors for developing a successful sharing model are also discussed. For a dynamic spectrum sharing model to be adopted, it must protect the rights of entrant users without impact to the legacy systems. It must also create a reasonable straightforward opportunity for an entity that wishes to access a shared spectrum to do so in a manner that is neither overly complex nor costly to implement. The practical implementation of dynamic spectrum sharing models is likely to require different national implementations because the regulatory approaches and the incumbent spectrum uses are different in various countries.
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paper_title: Distributed spectrum management in TV White Space Cognitive Radio Networks

paper_content:

In this paper, we investigate the spectrum management problem in TV White Space (TVWS) Cognitive Radio Networks using a game theoretical approach, accounting for adjacent-channel interference. TV Bands Devices (TVBDs) compete to access available TV channels and choose idle blocks that optimize some objective function. Specifically, the goal of each TVBD is to minimize the price paid to the Database operator and a cost function that depends on the interference between unlicensed devices. We show that the proposed TVWS management game admits a potential function under general conditions. Accordingly, we use a Best Response algorithm to converge in few iterations to the Nash Equilibrium (NE) points. We evaluate the performance of the proposed game, considering both static and dynamic TVWS scenarios and taking into account users' mobility. Our results show that at the NE, the game provides an interesting tradeoff between efficient TV spectrum use and reduction of interference between TVBDs.
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paper_title: Interference Analysis for Secondary Coexistence in TV White Space

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In this letter, the interference among mobile, heterogeneous and independently-operated secondary networks over shared TV white space is studied. Specifically, a probabilistic model for the secondary coexistence is developed, and, stemming from this, closed-form expressions of the coexistent interference probability are derived. The analytical results show that the coexistent interference is a non-linear function of the following key parameters: (i) the number of secondary networks roaming within a geographic area; (ii) the number of users belonging to each secondary network; (iii) the traffic pattern of each secondary network; (iv) the mobility pattern of each secondary network; (v) the interference range of each secondary network. The proposed analysis is crucial and preliminary for designing any coexistence protocol, since it discloses the intrinsic relationship between environmental and system parameters. Furthermore, closed-form expressions of necessary and sufficient conditions assuring that the coexistent interference is bounded by a given threshold are derived. Simulation results validate the theoretical analysis.
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paper_title: Horizontal spectrum sharing and coexistence scenarios for mutually interfering wireless systems

paper_content:

Horizontal spectrum sharing occurs when multiple users share a given band of frequencies with no central control or coordination, and all users compete for access to the available spectrum. Depending on the actual approach used to allocate transmit power over available channels, mutual interference may affect user performance. Three types of horizontal spectrum sharing scenarios will be outlined in the paper, which can be reached through different user strategies for power allocation that can be more or less greedy in terms of channel use. The impact of such strategies for power allocation on user rates and total system throughput in dense and sparse spectrum sharing scenarios will be discussed in the paper. The discussion is illustrated with numerical results obtained from simulations, which show that less greedy approaches result in a more efficient spectrum sharing scenarios than the more greedy ones.
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paper_title: A survey on mobile data offloading: technical and business perspectives

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Over the last few years, data traffic over cellular networks has seen an exponential rise, primarily due to the explosion of smartphones, tablets, and laptops. This increase in data traffic on cellular networks has caused an immediate need for offloading traffic for optimum performance of both voice and data services. As a result, different innovative solutions have emerged to manage data traffic. Some of the key technologies include Wi-Fi, femtocells, and IP flow mobility. The growth of data traffic is also creating challenges for the backhaul of cellular networks; therefore, solutions such as core network offloading and media optimization are also gaining popularity. This article aims to provide a survey of mobile data offloading technologies including insights from the business perspective as well.
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paper_title: Interference Management in Femtocells

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Increase in system capacity and data rates can be achieved efficiently in a wireless system by getting the transmitter and receiver closer to each other. Femtocells deployed in the macrocell significantly improve the indoor coverage and provide better user experience. The femtocell base station called as Femtocell Access Point (FAP) is fully user deployed and hence reduces the infrastructure, maintenance and operational cost of the operator while at the same time providing good Quality of Service (QoS) to the end user and high network capacity gains. However, the mass deployment of femtocell faces a number of challenges, among which interference management is of much importance, as the fundamental limits of capacity and achievable data rates mainly depends on the interference faced by the femtocell network. To cope with the technical challenges including interference management faced by the femtocells, researchers have suggested a variety of solutions. These solutions vary depending on the physical layer technology and the specific scenarios considered. Furthermore, the cognitive capabilities, as a functionality of femtocell have also been discussed in this survey. This article summarises the main concepts of femtocells that are covered in literature and the major challenges faced in its large scale deployment. The main challenge of interference management is discussed in detail with its types in femtocells and the solutions proposed over the years to manage interference have been summarised. In addition an overview of the current femtocell standardisation and the future research direction of femtocells have also been provided.
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paper_title: Dimensions of cooperative spectrum sharing: Rights and enforcement

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Sharing of radio spectrum requires a careful and nuanced understanding of the rights of incumbents and spectrum entrants. In addition, the dynamics of stakeholders can be understood by examining how various rights are arranged (and rearranged) among them. Importantly, understanding the rights and their distribution is the predicate to developing rational and useful enforcement approaches. In this paper, we show that spectrum sharing involves a rearrangement of the rights associated with radio spectrum among stakeholders. We show how this rearrangement of rights implies the definition of new bundles of rights, appropriate to each particular sharing scenario. We discover these rights — and their (re)arrangement — by examining several cases of spectrum use. We begin with the rights associated with exclusive use and proceed to consider rights arrangement in commons and different spectrum sharing configurations. Further, in the case of commons, we explicitly examine how governance of commons can affect the rights distribution in spectrum. In each case, the bundles of rights associated with each stakeholder changes. New bundles of rights have consequences, not only on the behavior of spectrum users but also on the enforcement process. Our examination of the bundles of rights shows that each rearrangement results in different approaches to enforcement. We demonstrate this by revisiting enforcement in the cases we examine.
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paper_title: Spectrum micro-trading for mobile operators

paper_content:

Spectrum trading is an important tool for increasing overall and local spectrum utilization, and to enable access to new and additional spectrum for mobile operators. However, the current spectrum trading regimes usually require long times to execute a trade, hence limiting the flexibility over short timescales in addition to limiting the granularity of the bandwidth and geographical units that may be traded. In this article we discuss the concept of spectrum micro-trading to enable trading of spectrum on the micro-scale in at least three dimensions: the micro-spatial, micro-temporal, and micro-frequency scales. An ecosystem for spectrum micro-trading is presented along with the most important metrics for spectrum micro-trading evaluation. Results from a simulation study for mobile operators, where spectrum is traded via auction, show that the market is viable using the proposed spectrum micro-trading model, and that spectrum utilization can be greatly improved.
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paper_title: Towards spectrum micro-trading

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Spectrum trading is an important tool to increase overall spectrum utilization and to open up opportunities for businesses to get access to desired spectrum. It has been implemented in some countries for some spectrum bands. At the same time, systems and architectures for cognitive radio technologies are being developed that are able to dynamically use spectrum bands in more flexible manners including functionalities such as dynamic bandwidth, spectrum band concatenation, sensing, channel switching and cognition. However, the current spectrum trading regimes usually require long times to execute a trade, hence limiting the flexibility over short time scales. In this paper we study spectrum micro-trading as a concept to enable trading of spectrum at the micro scale in at least three dimensions; on the micro-spatial, micro-temporal and micro-frequency scale. The ecosystem required for spectrum micro-trading and the most important metrics are defined; market viability, spectrum utilization, channel quality and social welfare. Furthermore, we propose a model for spectrum micro-trading, the Micro-trading Pixelation Model, which addresses the three dimensions on the micro scale. We then discuss the main challenges and issues that have to be solved for the realization of spectrum micro-trading with the proposed model. Finally, some initial simulation results are provided to demonstrate the performance of spectrum micro-trading.
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paper_title: Spectrum sharing improves the network efficiency for cellular operators

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The article describes the potential gain by spectrum sharing between cellular operators in terms of network efficiency. The focus of the study is on a specific resource sharing scenario: spectrum sharing between two operators in cellular downlink transmission. If frequency bands are allocated dynamically and exclusively to one operator - a case called orthogonal spectrum sharing - significant gains in terms of achievable throughput (spectrum sharing gains between 50 percent and 100 percent) and user satisfaction are reported for asymmetric scenarios at link and system level as well as from two hardware demonstrators. Additionally, if frequency bands are allocated simultaneously to two operators - a case called non-orthogonal spectrum sharing - further gains are reported. In order to achieve these, different enablers from hardware technologies and base station capabilities are required. However, we argue that all requirements are fulfilled in 3GPP and newer mobile standards. Therefore, the results and conclusions of this overview article encourage to seriously consider the inter-operator spectrum sharing technologies.
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paper_title: Capacity gains due to orthogonal spectrum sharing in multi-operator LTE cellular networks

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Static spectrum allocation leads to resource wastage and inter-operator spectrum sharing is a possible way to improve spectrum efficiency. In this work, we assume that two cellular network operators agree upon sharing part of their spectrum, which can then be dynamically accessed by either of them in a mutually exclusive way. Our goal is to numerically assess the gain, in terms of cell capacity, due to such orthogonal spectrum sharing. Hence, we propose a centralized algorithm that performs coordinated scheduling, in order to numerically evaluate an upper bound on the achievable sum capacity. The algorithm is centralized and exploits complete information on both networks to perform the optimum allocation. The simulation results illustrate the impact of the multiuser diversity and the asymmetry in the traffic load among the networks on the overall achievable gain.
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paper_title: Decision-Theoretic Distributed Channel Selection for Opportunistic Spectrum Access: Strategies, Challenges and Solutions

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Opportunistic spectrum access (OSA) has been regarded as the most promising approach to solve the paradox between spectrum scarcity and waste. Intelligent decision making is key to OSA and differentiates it from previous wireless technologies. In this article, a survey of decision-theoretic solutions for channel selection and access strategies for OSA system is presented. We analyze the challenges facing OSA systems globally, which mainly include interactions among multiple users, dynamic spectrum opportunity, tradeoff between sequential sensing cost and expected reward, and tradeoff between exploitation and exploration in the absence of prior statistical information. We provide comprehensive review and comparison of each kind of existing decision-theoretic solution, i.e., game models, Markovian decision process, optimal stopping problem and multi-armed bandit problem. We analyze their strengths and limitations and outline further research for both technical contents and methodologies. In particular, these solutions are critically analyzed in terms of information, cost and convergence speed, which are key concerns for practical implementation. Moreover, it is noted that each kind of existing decision-theoretic solution mainly addresses one aspect of the challenges, which implies that two or more kinds of decision-theoretic solutions should be incorporated to address more challenges simultaneously.
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paper_title: Spectrum sharing scenarios and resulting technical requirements for 5G systems

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Cellular networks today are designed for and operate in dedicated licensed spectrum. At the same time there are other spectrum usage authorization models for wireless communication, such as unlicensed spectrum or, as widely discussed currently but not yet implemented in practice, various forms of licensed shared spectrum. Hence, cellular technology as of today can only operate in a subset of the spectrum that is in principle available. Hence, a future wireless system may benefit from the ability to access also spectrum opportunities other than dedicated licensed spectrum. It is therefore important to identify which additional ways of authorizing spectrum usage are deemed to become relevant in the future and to analyze the resulting technical requirements. The implications of sharing spectrum between different technologies are analyzed in this paper, both from efficiency and technology neutrality perspective. Different known sharing techniques are outlined and their applicability to the relevant range of future spectrum regulatory regimes is discussed. Based on an assumed range of relevant (according to the views of the authors) future spectrum sharing scenarios, a toolbox of certain spectrum sharing techniques is proposed as the basis for the design of spectrum sharing related functionality in future mobile broadband systems.
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paper_title: Radar, TV and Cellular Bands: Which Spectrum Access Techniques for Which Bands?

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Opportunistic access has been considered by regulators for a number of different spectrum bands. In this paper, we discuss and qualitatively evaluate techniques used in the discovery of spectrum opportunities, also called white spaces, in the radar, TV, and cellular bands. These techniques include spectrum sensing, cooperative spectrum sensing, geolocation databases, and the use of beacons. We make the case that each of the three bands considered calls for a different set of spectrum access techniques. While TV bands are well matched to the adoption of geolocation databases, a database-assisted spectrum sensing mechanism may represent the most efficient solution to exploit the spectrum holes in radar bands. We drew this conclusion based on a multitude of factors, such as the radar antennas' constant motion, and the absence of a hidden node problems in these bands. The unpredictability of cellular systems, on the other hand, calls for a more coordinated spectrum access approach, namely beacon signaling, that could be implemented using the already established cellular infrastructure and spare bits of its logical channels.
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paper_title: IEEE 802.11af: a standard for TV white space spectrum sharing

paper_content:

Spectrum today is allocated in frequency blocks that serve either licensed or unlicensed services. This static spectrum allocation has limited resources to support the exponential increase in wireless devices. In this article, we present the IEEE 802.11af standard, which defines international specifications for spectrum sharing among unlicensed white space devices (WSDs) and licensed services in the TV white space band. Spectrum sharing is conducted through the regulation of unlicensed WSDs by a geolocation database (GDB), the implementation of which differs among regulatory domains. The main difference between regulatory domains is the timescale in which WSDs are controlled by the GDB, resulting in different TVWS availability and WSD operating parameters. The IEEE 802.11af standard provides a common operating architecture and mechanisms for WSDs to satisfy multiple regulatory domains. This standard opens a new approach to treat spectrum as a single entity shared seamlessly by heterogeneous services.
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paper_title: Security and Enforcement in Spectrum Sharing

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When different stakeholders share a common resource, such as the case in spectrum sharing, security and enforcement become critical considerations that affect the welfare of all stakeholders. Recent advances in radio spectrum access technologies, such as cognitive radios, have made spectrum sharing a viable option for significantly improving spectrum utilization efficiency. However, those technologies have also contributed to exacerbating the difficult problems of security and enforcement. In this paper, we review some of the critical security and privacy threats that impact spectrum sharing. We propose a taxonomy for classifying the various threats, and describe representative examples for each threat category. We also discuss threat countermeasures and enforcement techniques, which are discussed in the context of two different approaches: ex ante (preventive) and ex post (punitive) enforcement.
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paper_title: Enhancing the Capacity of Spectrum Sharing Cognitive Radio Networks

paper_content:

Spectrum sharing has attracted a lot of attention in cognitive radio recently as an effective method of alleviating the spectrum scarcity problem by allowing unlicensed users to coexist with licensed users under the condition of protecting the latter from harmful interference. In this paper, we focus on the throughput maximization of spectrum sharing cognitive radio networks and propose a novel cognitive radio system that significantly improves their achievable throughput. More specifically, we introduce a novel receiver and frame structure for spectrum sharing cognitive radio networks and study the problem of deriving the optimal power allocation strategy that maximizes the ergodic capacity of the proposed cognitive radio system under average transmit and interference power constraints. In addition, we study the outage capacity of the proposed cognitive radio system under various constraints that include average transmit and interference power constraints, and peak interference power constraints. Finally, we provide simulation results, in order to demonstrate the improved ergodic and outage throughput achieved by the proposed cognitive radio system compared to conventional spectrum sharing cognitive radio systems.
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paper_title: A survey of spectrum sensing algorithms for cognitive radio applications

paper_content:

The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.
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paper_title: Business model analysis for spectrum sharing with the spectrum broker

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This work presents the business model analysis for the spectrum sharing mechanism in the cellular network, based on the spectrum broker entity. We identify key modifications to the market and business relations, required for the spectrum sharing scenario implementation, with the focus on the network operator stimulation. Due to the fact, that the spectrum usage in the current markets is subject to various constraints coming from regulatory, standardization bodies, as well as hardware limitations point of view, various market players and their positions within described spectrum sharing scenarios are considered and analyzed. This document captures analysis of novel spectrum sharing technique on the service delivery chain, discovers new business opportunities, discuss the influence on the strategy of the current key market players. Finally, cost aspects are analyzed, where the required investments are identified for the described spectrum sharing scenario.
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paper_title: A Hierarchical Game Approach to Inter-Operator Spectrum Sharing

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In this paper, we address the problem of spectrum sharing where wireless (competitive) operators coexist in the same frequency band. First, we model this problem as a strategic non-cooperative game where operators simultaneously share the spectrum according to the Nash Equilibrium (N.E). Given a set of channel realizations, several Nash equilibria exist which render the outcome of the game unpredictable. Second, the inter-operator spectrum sharing problem is reformulated as a hierarchical power allocation game [14], where one of the operators (i.e., primary) poses as a leader and the other operator (i.e., secondary) as a follower. Using backward induction [12], the Stackelberg equilibrium (S.E) is reached where the best response of the secondary operator is taken into account upon maximizing the primary operator's payoff. It turns out that the Stackelberg approach yields better payoffs for operators compared to the classical greedy water-filling approach. Furthermore, to reach pareto-efficient boundaries, the spectrum sharing problem is formulated as a repeated game, where players interact over a longer period of time and learning from each other's strategies. Numerical results provide a comparison between the non-cooperative, hierarchical and centralized approach.
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paper_title: Inter-Operator Spectrum Sharing from a Game Theoretical Perspective

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We address the problem of spectrum sharing where competitive operators coexist in the same frequency band. First, we model this problem as a strategic non-cooperative game where operators simultaneously share the spectrum according to the Nash Equilibrium (NE). Given a set of channel realizations, several Nash equilibria exist which renders the outcome of the game unpredictable. Then, in a cognitive context with the presence of primary and secondary operators, the inter-operator spectrum sharing problem is reformulated as a Stackelberg game using hierarchy where the primary operator is the leader. The Stackelberg Equilibrium (SE) is reached where the best response of the secondary operator is taken into account upon maximizing the primary operator's utility function. Moreover, an extension to the multiple operators spectrum sharing problem is given. It is shown that the Stackelberg approach yields better payoffs for operators compared to the classical water-filling approach. Finally, we assess the goodness of the proposed distributed approach by comparing its performance to the centralized approach.
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paper_title: Cognitive Radio Techniques Under Practical Imperfections: A Survey

paper_content:

Cognitive radio (CR) has been considered as a potential candidate for addressing the spectrum scarcity problem of future wireless networks. Since its conception, several researchers, academic institutions, industries, and regulatory and standardization bodies have put their significant efforts toward the realization of CR technology. However, as this technology adapts its transmission based on the surrounding radio environment, several practical issues may need to be considered. In practice, several imperfections, such as noise uncertainty, channel/interference uncertainty, transceiver hardware imperfections, signal uncertainty, and synchronization issues, may severely deteriorate the performance of a CR system. To this end, the investigation of realistic solutions toward combating various practical imperfections is very important for the successful implementation of cognitive technology. In this direction, first, this survey paper provides an overview of the enabling techniques for CR communications. Subsequently, it discusses the main imperfections that may occur in the most widely used CR paradigms and then reviews the existing approaches toward addressing these imperfections. Finally, it provides some interesting open research issues.
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paper_title: Practical issues in spectrum sensing for multi-carrier system employing pilot tones

paper_content:

Multi-carrier techniques such as OFDM are widely adopted in the physical layer of nowadays radio communication and broadcasting systems. Therefore in cognitive radio, a robust spectrum sensing techniques for such signals is highly desired. Comparing with traditional Cyclic Prefix (CP) based method, newly reported Time-Domain Symbol Cross-correlation based spectrum sensing (TDSC) method [1][2] shows both advantages in sensing accuracy and robustness against shortness of and channel time spread pollution to CP. This sensing method is able to sense all multi-carrier signals with repeated pilot patterns. In this paper, further validations of TDSC-NP (Neyman-Pearson) and TDSC-MRC (Maximal Ratio Combining) methods are presented with practical issues taken into account, e.g. noise uncertainty, oscillator imperfection and computational complexity. The feasibility of applying TDSC for sensing Filter Bank Multi-Carrier (FBMC) signal is validated via simulation. Both simulated signal and captured DVB-T signal with real-world multi-path channel fading are analyzed and the sensing performance of captured signal agrees with that of simulated signal very well.
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paper_title: Game theory for cognitive radio networks : An overview

paper_content:

Cognitive radio technology, a revolutionary communication paradigm that can utilize the existing wireless spectrum resources more efficiently, has been receiving a growing attention in recent years. As network users need to adapt their operating parameters to the dynamic environment, who may pursue different goals, traditional spectrum sharing approaches based on a fully cooperative, static, and centralized network environment are no longer applicable. Instead, game theory has been recognized as an important tool in studying, modeling, and analyzing the cognitive interaction process. In this tutorial survey, we introduce the most fundamental concepts of game theory, and explain in detail how these concepts can be leveraged in designing spectrum sharing protocols, with an emphasis on state-of-the-art research contributions in cognitive radio networking. Research challenges and future directions in game theoretic modeling approaches are also outlined. This tutorial survey provides a comprehensive treatment of game theory with important applications in cognitive radio networks, and will aid the design of efficient, self-enforcing, and distributed spectrum sharing schemes in future wireless networks.
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paper_title: Spectrum sensing in cognitive radio networks: requirements, challenges and design trade-offs

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Opportunistic unlicensed access to the (temporarily) unused frequency bands across the licensed radio spectrum is currently being investigated as a means to increase the efficiency of spectrum usage. Such opportunistic access calls for implementation of safeguards so that ongoing licensed operations are not compromised. Among different candidates, sensing-based access, where the unlicensed users transmit if they sense the licensed band to be free, is particularly appealing due to its low deployment cost and its compatibility with the legacy licensed systems. The ability to reliably and autonomously identify unused frequency bands is envisaged as one of the main functionalities of cognitive radios. In this article we provide an overview of the regulatory requirements and major challenges associated with the practical implementation of spectrum sensing functionality in cognitive radio systems. Furthermore, we outline different design trade-offs that have to be made in order to enhance various aspects of the system's performance.
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paper_title: Using SDN as a key enabler for co-primary spectrum sharing

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Over the past years the mobile traffic demands and the number of the connected devices have been constantly increasing thus indicating that in the near future the current spectrum usage models may fail to cover user needs. At the same time, spectrum scarcity over several Mobile Network Operators (MNOs) leads to inefficient spectrum usage. Co-primary spectrum sharing is a scheme for trading resources among MNOs, enabling flexible spectrum usage, which is arising as a possible solution to spectrum scarcity. However, up to now the schemes for co-primary shared access are hard to be implemented. The recently introduced concept of Software Defined Networking (SDN) gives the flexibility to MNOs' network configuration and, therefore, is arising as an enabler for efficiently handling spectrum trading. In this paper we present a complete functional architecture aiming at enabling co-primary spectrum sharing among MNOs. We, furthermore, propose a scheme for implementing the introduced architectural scheme, coupled with fully described information flows among the (SDN) network entities. Such solution enables the concurrent reconfiguration (when required) for both core and access network nodes, based on the spectrum trading process.
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paper_title: Radio resource sharing among operators through MIMO based spatial multiplexing in 5G systems

paper_content:

Network sharing is one of the solutions for mobile operators to improve spectral efficiency and enhance coverage with smaller operational and investment costs. In this work, we propose a novel solution based on the multi-user MIMO approach for the network sharing among multiple operators. We use multiple antennas for spatial multiplexing of multiple operators on the smallest possible radio resource element. We consider three different service level agreements between the shared operators and the service provider. These agreements differ with respect to the pre-defined system utility optimization. The utilities we consider are the achievement of fairness among operators and the optimization of system spectral efficiency. We also propose new algorithms for the achievement of these utilities. The simulation results show that our algorithms perfectly achieve the service level agreements which is one of the key objectives in a shared network scenario. For the spectral efficiency we show that the resource fairness algorithm outperforms the performance results of the rate fairness algorithm.
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paper_title: Transmit beamforming for inter-operator spectrum sharing: From theory to practice

paper_content:

In this paper, four transmit beamforming (BF) techniques are selected and compared to realize inter-operator spectrum sharing, which is a promising solution for the spectrum shortage problem. The BF techniques include two game-theoretic (GT) algorithms, zero-forcing (ZF) and minimum mean square error (MMSE). After a brief description of the BF techniques in a multiple-input single-output (MISO) system, their computational complexity is analyzed. The effectiveness of these techniques in real radio frequency (RF) signal transmission is verified by implementation on a flexible hardware-in-the-loop (HIL) testbed. First, several important aspects regarding practical implementation are discussed. Afterwards, the HIL measurement results are shown, where considerable sum rate gain can be observed due to spectrum sharing. Finally, the appropriate BF technique can be chosen based on a tradeoff between complexity and performance.
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paper_title: Coordination protocol for inter-operator spectrum sharing in co-primary 5G small cell networks

paper_content:

We consider spectrum sharing between a limited set of operators having similar rights for accessing spectrum. A coordination protocol acting on the level of the RAN is designed. The protocol is non-cooperative, but assumes an agreement to a set of negotiation rules. The signaling overhead is low, and knowledge of a competitor’s channel state information is not assumed. No monetary transactions are involved; instead, spectrum sharing is based on a RAN-internal virtual currency. The protocol is applicable both in a scenario of mutual renting and when the operators form a spectrum pool. The protocol reacts to variations in interference and load of operators, and shows gains in a simulated small cell scenario.
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paper_title: Spectrum Leasing in Cognitive Radio Networks: A Survey

paper_content:

Cognitive Radio (CR) is a dynamic spectrum access approach, in which unlicensed users (or secondary users, SUs) exploit the underutilized channels (or white spaces) owned by the licensed users (or primary users, PUs). Traditionally, SUs are oblivious to PUs, and therefore the acquisition of white spaces is not guaranteed. Hence, a SU must vacate its channel whenever a PU reappears on it in an unpredictable manner, which may affect the SUs’ network performance. Spectrum leasing has been proposed to tackle the aforementioned problem through negotiation between the PU and SU networks, which allows the SUs to acquire white spaces for a guaranteed period of time. Through spectrum leasing, the PUs and SUs enhance their network performances, and additionally PUs maximize their respective monetary gains. Numerous research efforts have been made to investigate the CR, whereas the research into spectrum leasing remains at its infancy. In this paper, we present a comprehensive review on spectrum leasing schemes in CR networks by highlighting some pioneering approaches and discuss the gains, functionalities, characteristics, and challenges of spectrum leasing schemes along with the performance enhancement in CR networks. Additionally, we discuss various open issues in order to spark new interests in this research area.
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paper_title: A techno-economic framework of spectrum combining for indoor capacity provisioning

paper_content:

Spectrum combining refers to utilizing multiple types of spectrum authorization options for a wireless network. The approach is considered as an essential ingredient of high-capacity provision in the coming years. This paper presents a techno-economic framework to analyze capacity and cost of different spectrum combining options. We focus on indoor environments where the traffic demand is expected to be extremely demanding. We describe various spectrum options such as licence-exempt, light licensing, and licensed shared access (LSA). Then, we compare various combinations of these options with increasing traffic demand over time. In terms of capacity provisioning, this framework is based on the idea that spectrum combining must be done at the right time, that is when the existing deployment can no longer satisfy capacity demand. For the cost analysis, most relevant cost drivers are included in a cost structure which becomes the backbone of this framework. The proposed framework can help network providers determine the most cost-effective spectrum acquisition strategy which can meet capacity demand in indoor environments.
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paper_title: High capacity indoor and hotspot wireless systems in shared spectrum: a techno-economic analysis

paper_content:

Predictions for wireless and mobile Internet access suggest an exponential traffic increase, particularly in in-building environments. Non-traditional actors such as facility owners have a growing interest in deploying and operating their own indoor networks to fulfill the capacity demand. Such local operators will need spectrum sharing with neighboring networks because they are not likely to have their own dedicated spectrum. Management of internetwork interference then becomes a key issue for high capacity provision. Tight operator-wise cooperation provides superior performance, but at the expense of high infrastructure cost and business-related impairments. Limited coordination, on the other hand, causes harmful interference between operators, which in turn will require even denser networks. In this article, we propose a techno-economic analysis framework for investigating and comparing indoor operator strategies. We refine a traditional network cost model by introducing new inter-operator cost factors. Then we present a numerical example to demonstrate how the proposed framework can help us to compare different operator strategies. Finally, we suggest areas for future research.
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paper_title: Performance Gains of Spectrum Sharing in Multi-Operator LTE-Advanced Systems

paper_content:

In order to face the increasingly rising costs and reduce the required time to deploy and upgrade networks, network sharing is being embraced by many operators and multi-operator networks are being deployed worldwide. Despite being supported by current standards, spectrum sharing has not been widely adopted due to concerns over performance degradation under mismatched loading between systems. This paper addresses these concerns and studies the performance of spectrum sharing LTE-Advanced systems under different sharing scenarios. Advanced system level simulations are performed to measure and compare the performance of two LTE-Advanced systems under fixed spectrum allocation and spectrum sharing. Both matched and mismatched system loading are investigated under symmetric and asymmetric spectrum sharing scenarios. The performance gains are demonstrated and the bounds on spectrum sharing gains are determined.
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paper_title: A Spectrum Trading Scheme for Licensed User Incentives

paper_content:

Spectrum utility efficiency is key in designing systems that can meet the heavier demands of bandwidth and data rate of future communication technologies. Shared spectrum techniques and collaborative protocols have thus been studied to better utilize already existing spectrum resources. In this paper, we present a spectrum trading approach that allows the licensed user's (LU) resources to be efficiently shared with the secondary user (SU) network in exchange for a monetary cost. The model is based on demand and supply economics, wherein the highest bidder for spectrum resource is awarded with transmission rights over licensed spectrum. The transmission opportunities for the SU consider every state of the licensed link, in the form of dynamic spectrum access (DSA), spectrum sharing, and relaying, each of which has an optimized cost that will maximize the returns for the LU. The numerical results backed by the analytical study show that this spectrum trading scheme allows for significant improvements in data rate and spectrum transmission opportunities than previous work conducted in either DSA or the spectrum sharing fields.
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paper_title: Business models for mobile network operators in Licensed Shared Access (LSA)

paper_content:

This paper presents business models for mobile network operators (MNOs) in the new Licensed Shared Access (LSA) concept. The LSA concept allows spectrum sharing between an incumbent spectrum user and an LSA licensee under the supervision of the regulator with rules and conditions that guarantee predictable quality of service (QoS) levels to all involved spectrum users. This paper summarizes the LSA concept and its application to the mobile broadband where an MNO shares spectrum from another type of incumbent spectrum user such as military or programme making and special events (PMSE) services which corresponds to the industry driven Authorised Shared Access (ASA) concept. The paper highlights the importance of developing viable business models for the new spectrum sharing concepts as they need to provide clear benefits to the key stakeholders to be adopted in real life. The paper depicts the evolution path of business model theories and focuses on a recent action-oriented business modeling approach. This approach is applied to the mobile broadband using the LSA concept to derive business models for MNOs for accessing new LSA bands. Separate business models are derived for dominating and challenger MNOs whose market shares and amounts of exclusive spectrum license differ significantly and will face different business opportunities arising from LSA. To assess the transformation coming with the LSA concept, business models are first developed for the current situation with exclusively licensed spectrum bands. New business models are then developed for the introduction of the new shared LSA bands. The developed business models indicate that the dominating MNOs could benefit significantly from the new LSA bands which would enable dynamic traffic management to offer different service levels to different customer segments. For challenger MNOs, the LSA concept could offer the opportunity to challenge the dominating MNOs and win their customers by offering tailored services to a wider customer base using the new LSA spectrum resources. Moreover, it could significantly re-shape the business ecosystem around the mobile broadband by opening the door to non-MNO entrants.
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paper_title: Spectrum sharing improves the network efficiency for cellular operators

paper_content:

The article describes the potential gain by spectrum sharing between cellular operators in terms of network efficiency. The focus of the study is on a specific resource sharing scenario: spectrum sharing between two operators in cellular downlink transmission. If frequency bands are allocated dynamically and exclusively to one operator - a case called orthogonal spectrum sharing - significant gains in terms of achievable throughput (spectrum sharing gains between 50 percent and 100 percent) and user satisfaction are reported for asymmetric scenarios at link and system level as well as from two hardware demonstrators. Additionally, if frequency bands are allocated simultaneously to two operators - a case called non-orthogonal spectrum sharing - further gains are reported. In order to achieve these, different enablers from hardware technologies and base station capabilities are required. However, we argue that all requirements are fulfilled in 3GPP and newer mobile standards. Therefore, the results and conclusions of this overview article encourage to seriously consider the inter-operator spectrum sharing technologies.
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paper_title: Co-primary inter-operator spectrum sharing over a limited spectrum pool using repeated games

paper_content:

We consider two small cell operators deployed in the same geographical area, sharing spectrum resources from a common pool. A method is investigated to coordinate the utilization of the spectrum pool without monetary transactions and without revealing operator-specific information to other parties. For this, we construct a protocol based on asking and receiving spectrum usage favors by the operators, and keeping a book of the favors. A spectrum usage favor is exchanged between the operators if one is asking for a permission to use some of the resources from the pool on an exclusive basis, and the other is willing to accept that. As a result, the proposed method does not force an operator to take action. An operator with a high load may take spectrum usage favors from an operator that has few users to serve, and it is likely to return these favors in the future to show a cooperative spirit and maintain reciprocity. We formulate the interactions between the operators as a repeated game and determine rules to decide whether to ask or grant a favor at each stage game. We illustrate that under frequent network load variations, which are expected to be prominent in small cell deployments, both operators can attain higher user rates as compared to the case of no coordination of the resource utilization.
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paper_title: Performance Gains of Spectrum Sharing in Multi-Operator LTE-Advanced Systems

paper_content:

In order to face the increasingly rising costs and reduce the required time to deploy and upgrade networks, network sharing is being embraced by many operators and multi-operator networks are being deployed worldwide. Despite being supported by current standards, spectrum sharing has not been widely adopted due to concerns over performance degradation under mismatched loading between systems. This paper addresses these concerns and studies the performance of spectrum sharing LTE-Advanced systems under different sharing scenarios. Advanced system level simulations are performed to measure and compare the performance of two LTE-Advanced systems under fixed spectrum allocation and spectrum sharing. Both matched and mismatched system loading are investigated under symmetric and asymmetric spectrum sharing scenarios. The performance gains are demonstrated and the bounds on spectrum sharing gains are determined.
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paper_title: CellSlice: Cellular wireless resource slicing for active RAN sharing

paper_content:

We present the design and implementation of Cell-Slice, a novel system for slicing wireless resources in a cellular network for effective Radio Access Network (RAN) sharing. CellSlice is a gateway-level solution that achieves the slicing without modifying the basestations' MAC schedulers, thereby significantly reducing the barrier for its adoption. Achieving slicing with a gateway-level solution is challenging, however, since resource scheduling decisions occur at the basestations at fine timescales, and these decisions are not visible at the gateways. In the uplink direction, CellSlice overcomes the challenge by indirectly constraining the uplink scheduler's decisions using a simple feedback-based adaptation algorithm. For downlink, we build on the technique used by NVS, a native basestation virtualization solution, and show that effective downlink slicing can be easily achieved without modifying basestation schedulers. We instantiate a prototype of CellSlice on a Picochip WiMAX testbed. Through both prototype evaluation and simulations, we demonstrate that CellSlice's performance for both remote uplink and remote downlink slicing is close to that of NVS. CellSlice's design is access-technology independent, and hence can be equally applicable to LTE, LTE-Advanced and WiMAX networks.
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paper_title: Data MVNO: Cost-based pricing in Korea

paper_content:

This study defines the prepaid MVNO type that applies the 3G telecommunication facilities and Article 38, Telecommunications Business Act (Wholesale provisioning of the telecommunication service, also known as the “MVNO Act”). In addition, the cost of 3G telecommunication facilities will be separated into voice cost and data cost, before calculating the data cost. The cost-based wholesale data price will be calculated for each prepaid MVNO type, and policy implications will be presented. The Korea Communications Commission newly enacted the MVNO Act in 2010, which regulates the wholesale price of voice calls by the retail-minus method. As a result, MVNO is very limited in the diverse and innovative business model, such as convergence services, enterprises' utilization of mobile communication, and MtoM. This study will provide useful data for policy-makers preparing policies regarding data cost, wholesale price, interconnection, MVNO, mVoIP, prepay, and network neutrality, as well as for enterprises that seek to participate in various business models.
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paper_title: Business opportunities and regulatory issues of Ambient Networking

paper_content:

This paper analyzes the technological development of local access provisioning of wireless broadband through the study of commercial forces of push-pull character behind its development. The work is conducted within the Novel Access Provisioning (NAP) project that is a joint techno-economic research effort between the Royal Institute of Technology (KTH), Stockholm School of Economics (SSE) and the Swedish Telecom Agency (PTS). This paper reports the findings from a series of interviews with main representatives from actors within and outside the telecom industry confined to the Scandinavian market. The aim of the paper is to increase the understanding for the rate of diffusion of wireless broadband access solutions and to suggest innovative alternatives that may fuel its development.
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paper_title: On the performance evaluation of spectrum sharing algorithms between two UMTS operators

paper_content:

This paper proposes two new algorithms that address spectrum sharing between two Universal Mobile Telecommunication System (UMTS) operators on a pool and non-pooled basis in the UMTS extension band (2500MHz–2690MHz). The proposed pool based algorithm exploits the de-correlation in the traffic pattern based on the expected call requests. The non-pool based algorithm takes advantage of the opportunities available on the primary system during capacity limited situations on the secondary system. The simulated performance of the two Dynamic Spectrum Allocation (DSA) algorithms under peak hour loading shows improvement of 4.5% and 11% respectively over Fixed Spectrum Allocation (FSA). It is shown in the pool based algorithm that the DSA gain increases, as the traffic correlation coefficient between the two operators decrease. The results also show that the call setup delay associated with scheme depends on whether the operators share the Radio Network Controller (RNC).
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paper_title: Inter Base Station Resource Sharing and Improving the Overall Efficiency of B3G Systems

paper_content:

With the progress of technology and the fast growing demand for ubiquitous high-speed wireless services, flexible resource sharing is widely seen to be an important feature for the deployment of beyond 3G systems. Therefore, a migration from fixed allocations to a more flexible spectrum management has to be taken into account. In this context, inter-operator resource sharing in a broadband network is considered in this paper. A packet-based cellular network is developed, emphasizing the shift in the telecommunications industry towards IP-based services. We show that we can improve the overall efficiency of the system by sharing different resources in the network between several operators. Moreover, big and small operators, in addition to customers are altogether satisfied. In this paper, we use the term "resource" to not only account for spectrum sharing but also towers, base stations and time slots sharing. In our framework, we will use a physical layer cellular model with idealistic resource management, where we quantify the achievable sharing gains. We compare the performances for the non sharing case, the case where the base stations decide to share the resources as a "last resort", and also when the mobile stations always connect to the best base station, regardless of the operator. Finally, We analyze these gains in terms of quality of service, number of operators and different service classes.
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paper_title: Decentralized inter-radio access network dynamic spectrum selection scheme

paper_content:

Many radio access networks (RAN) operate in various bands, providing both common and distinct services. Currently the fixed allocation of spectrum (FSA) to various RANs creates inflexibility that leads to inefficient use of the spectrum. In this work a robust, technology neutral, decentralized, Inter-RAN dynamic spectrum selection (DSS) scheme is proposed. This work has sought to establish the basis for a generic method of DSS, wherein user equipment (UE) can obtain the most appropriate RAN for operation. Low complexity and low signaling overhead have been two important factors in designing this scheme. The impact of the proposed scheme on spectral efficiency and signaling load has been investigated. The results show an improvement in spectral efficiency with considerably low signaling overhead. Fairness in sharing, which is one of the important issues in spectrum sharing, can be easily achieved with this scheme.
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paper_title: Inter-operator spectrum sharing for cellular networks using game theory

paper_content:

In this paper, we present a game theoretical framework for DSA (Dynamic Spectrum Access) in cellular networks. We model and analyze the interaction between cellular operators with packet services, in a spectrum sharing context. We present inter-operator DSA algorithms based on game theory. A two-players non-zero sum game is formulated, where the operators are the players. We define a utility function, for the operator that takes: (1) the users throughput, (2) the spectrum price, and (3) the blocking probability into consideration. We present two system models: a) a centralized model where a DSA algorithm, for the global welfare in terms of the operators rewards, is inspired by the Pareto optimality concept. b) a distributed model, where a DSA algorithm is based on Nash equilibria concept. The convergence to NE in the distributed model is analyzed. The rewards of the operators in the centralized DSA algorithm are compared with those in the FSA (Fixed Spectrum Access) situation. The obtained rewards using the centralized DSA algorithm significantly exceed the FSA rewards. The obtained blocking probabilities are shown not to exceed the target value.
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paper_title: Spectrum sharing LTE-advanced small cell systems

paper_content:

Cellular systems are designed such that a certain amount of radio spectrum is allocated for their exclusive use to ensure that interference within these systems is tightly controlled. For competitive reasons, spectrum is divided between operators despite the resulting inefficiency in the overall spectrum utilization. For systems with relatively large cells and significant number of users per cell the loss in efficiency is modest. However, losses can become very large as cells become smaller. This paper presents a cooperative spectrum access framework that enables spectrum sharing between small cells that are being deployed by different operators. Primary spectrum owning operators broadcast their spectrum occupancy information to allow small cells of other operators to access their spectrum as secondary users. LTE-Advanced systems employing small cells are considered. Simulations show that the proposed spectrum access framework enables small cells to achieve substantial performance gains without affecting the primary spectrum owning operator even when the small cell deployment density varies significantly between operators.
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paper_title: Nonpool based spectrum sharing for two UMTS operators in the UMTS extension band

paper_content:

This paper investigates spectrum sharing (in the form of code sharing) between two Universal Mobile Telecommunication System (UMTS) operators in the UMTS extension band (2500-2690 MHz) with equal and unequal number of proprietary carriers, respectively. The paper proposes a dynamic spectrum allocation (DSA) algorithm to address the problem of spectrum sharing between two operators on a non-pool basis. It also investigates the impact of adjacent channel interference (ACI) on the spectrum sharing gain. Additionally, an architecture that enables spectrum sharing to take place between two or more UMTS operators is presented. The simulated performance of the proposed DSA algorithm shows that under peak-hour loading, up to 32% increase in capacity can be obtained when compared to currently used fixed spectrum allocation (FSA).
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paper_title: Inter-Operator Dynamic Spectrum Selection in UMTS

paper_content:

Dynamic and flexible spectrum management schemes can improve spectrum utilization efficiency and hence are promising approaches to satisfy the increasing demand for radio spectrum. This work investigates the possibility for competing network operators to partially cooperate without any operational information exchange and to exploit the instantaneous opportunities for sharing which appear within each network. Under the proposed two novel dynamic spectrum selection (DSS) protocols all handsets have a primitive cognitive ability in order to enable multi-operator functionalities for inter-operator DSS. The worst case scenario for voice traffic where two networks with the same radio access technology (RAT) having an entirely correlated average traffic distribution (same capacity demand) during the busy hour is investigated. It has been shown through a UMTS system level simulator that the suggested protocols can increase each operator's throughput by up to 10% compared to the conventional fixed spectrum allocation (FSA) scheme, and hence better spectrum utilization can be accomplished. Also, the effects of queuing incoming and handover calls before blocking or dropping them on DSS gains have been investigated. The results suggest an increase of up to 25% in throughput against the FSA if the DSS protocol and the queuing scheme are implemented.
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paper_title: Using SDN as a key enabler for co-primary spectrum sharing

paper_content:

Over the past years the mobile traffic demands and the number of the connected devices have been constantly increasing thus indicating that in the near future the current spectrum usage models may fail to cover user needs. At the same time, spectrum scarcity over several Mobile Network Operators (MNOs) leads to inefficient spectrum usage. Co-primary spectrum sharing is a scheme for trading resources among MNOs, enabling flexible spectrum usage, which is arising as a possible solution to spectrum scarcity. However, up to now the schemes for co-primary shared access are hard to be implemented. The recently introduced concept of Software Defined Networking (SDN) gives the flexibility to MNOs' network configuration and, therefore, is arising as an enabler for efficiently handling spectrum trading. In this paper we present a complete functional architecture aiming at enabling co-primary spectrum sharing among MNOs. We, furthermore, propose a scheme for implementing the introduced architectural scheme, coupled with fully described information flows among the (SDN) network entities. Such solution enables the concurrent reconfiguration (when required) for both core and access network nodes, based on the spectrum trading process.
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paper_title: Inter-operator spectrum sharing in future cellular systems

paper_content:

Inter-operator spectrum sharing has been proposed to exploit spectrum efficiency in future communication system. By using game theory and learning algorithm, we design a partially distributed implementation method. Such a method is proven to reach the system equilibrium which improves spectrum efficiency between operators. Furthermore, by queueing analysis and robust potential game, we show that the convergence rate can be accelerated by incorporating more asynchronous operator systems. This distributed implementation method creates a low complexity solution for operators to realize inter-operator spectrum sharing for 3GPP LTE-A systems or similar.
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paper_title: Mobile Network Resource Sharing Options: Performance Comparisons

paper_content:

Resource sharing among mobile network operators is a promising way to tackle growing data demand by increasing capacity and reducing costs of network infrastructure deployment and operation. In this work, we evaluate sharing options that range from simple approaches that are feasible in the near-term on traditional infrastructure to complex methods that require specialized/virtualized infrastructure. We build a simulation testbed supporting two geographically overlapped 4G LTE macro cellular networks and model the sharing architecture/process between the network operators. We compare Capacity Sharing (CS) and Spectrum Sharing (SS) on traditional infrastructure and Virtualized Spectrum Sharing (VSS) and Virtualized PRB Sharing (VPS) on virtualized infrastructure under light, moderate and heavy user loading scenarios in collocated and noncollocated E-UTRAN deployment topologies. We also study these sharing options in conservative and aggressive sharing participation modes. Based on simulation results, we conclude that CS, a generalization of traditional roaming, is the best performing and simplest option, SS is least effective and that VSS and VPS perform better than spectrum sharing with added complexity.
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paper_title: CellSlice: Cellular wireless resource slicing for active RAN sharing

paper_content:

We present the design and implementation of Cell-Slice, a novel system for slicing wireless resources in a cellular network for effective Radio Access Network (RAN) sharing. CellSlice is a gateway-level solution that achieves the slicing without modifying the basestations' MAC schedulers, thereby significantly reducing the barrier for its adoption. Achieving slicing with a gateway-level solution is challenging, however, since resource scheduling decisions occur at the basestations at fine timescales, and these decisions are not visible at the gateways. In the uplink direction, CellSlice overcomes the challenge by indirectly constraining the uplink scheduler's decisions using a simple feedback-based adaptation algorithm. For downlink, we build on the technique used by NVS, a native basestation virtualization solution, and show that effective downlink slicing can be easily achieved without modifying basestation schedulers. We instantiate a prototype of CellSlice on a Picochip WiMAX testbed. Through both prototype evaluation and simulations, we demonstrate that CellSlice's performance for both remote uplink and remote downlink slicing is close to that of NVS. CellSlice's design is access-technology independent, and hence can be equally applicable to LTE, LTE-Advanced and WiMAX networks.
---
paper_title: Gibbs Sampling based Spectrum Sharing for Multi-Operator Small Cell Networks

paper_content:

To tackle the challenge of providing higher data rates within limited spectral resources we consider the case of multiple operators sharing a common pool of radio resources in the downlink. The goal is to maintain a long term fairness of spectrum sharing with a no coordination among small cell base stations. It is assumed that the spectral allocations of the small cells are orthogonal to the macro network layer and thus, only the small cell traffic is modeled. We develop a decentralized control mechanism for base stations using Gibbs sampling based learning techniques. Four algorithms are compared addressing the co-primary multi-operator radio resource sharing under heterogeneous traffic in both centralized and distributed scenarios. The performance of these algorithms is assessed through extensive system-level simulations for two indoor small cell layouts. The main performance metrics are user throughput and fairness between operators. The numerical results demonstrate that the proposed Gibbs sampling based learning algorithm provides considerably high throughput while ensuring fairness between OPs.
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paper_title: Sensing for spectrum sharing in cognitive LTE-A cellular networks

paper_content:

In this work we present a case for dynamic spectrum sharing between different operators in systems with carrier aggregation (CA) which is an important feature in 3GPP LTE-A systems. Cross-carrier scheduling and sensing are identified as key enablers for such spectrum sharing in LTE-A. Sensing is classified as Type 1 sensing and Type 2 sensing and the role of each in the system operation is discussed. The more challenging Type 2 sensing which involves sensing the interfering signal in the presence of a desired signal is studied for a single-input single-output system. Energy detection and the most powerful test are formulated. The probability of false alarm and of detection are analyzed for energy detectors. Performance evaluations show that reasonable sensing performance can be achieved with the use of channel state information, making such sensing practically viable.
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paper_title: System-Level Assessment of Non-Orthogonal Spectrum Sharing via Transmit Beamforming

paper_content:

We assess the system-level performance of non-orthogonal spectrum sharing achieved via maximum sum-rate (SR), Nash bargaining (NB), and zero-forcing (ZF) transmit beamforming techniques. A look-up table based physical layer abstraction and radio resource management mechanisms (including packet scheduling) are proposed and incorporated in system-level simulations, jointly with other important aspects of network operation. In the simulated scenarios, the results show similar system-level performance of SR (or NB) as ZF in the context of spectrum sharing, when combined with maximum sum-rate (or proportional fair) packet scheduler. Further sensitivity analysis also shows similar behavior of all three beamforming techniques with regard to the impact on system-level performance of neighbor-cell activity level and feedback error. A more important observation from our results is that, under ideal conditions, the performance enhancement of non-orthogonal spectrum sharing over orthogonal spectrum sharing and fixed spectrum assignment is significant.
---
paper_title: Mobile Network Resource Sharing Options: Performance Comparisons

paper_content:

Resource sharing among mobile network operators is a promising way to tackle growing data demand by increasing capacity and reducing costs of network infrastructure deployment and operation. In this work, we evaluate sharing options that range from simple approaches that are feasible in the near-term on traditional infrastructure to complex methods that require specialized/virtualized infrastructure. We build a simulation testbed supporting two geographically overlapped 4G LTE macro cellular networks and model the sharing architecture/process between the network operators. We compare Capacity Sharing (CS) and Spectrum Sharing (SS) on traditional infrastructure and Virtualized Spectrum Sharing (VSS) and Virtualized PRB Sharing (VPS) on virtualized infrastructure under light, moderate and heavy user loading scenarios in collocated and noncollocated E-UTRAN deployment topologies. We also study these sharing options in conservative and aggressive sharing participation modes. Based on simulation results, we conclude that CS, a generalization of traditional roaming, is the best performing and simplest option, SS is least effective and that VSS and VPS perform better than spectrum sharing with added complexity.
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paper_title: A survey on game theory applications in wireless networks

paper_content:

While the Quality of Service (QoS) offered to users may be enhanced through innovative protocols and new technologies, future trends should take into account the efficiency of resource allocation and network/terminal cooperation as well. Game theory techniques have widely been applied to various engineering design problems in which the action of one component has impact on (and perhaps conflicts with) that of any other component. Therefore, game formulations are used, and a stable solution for the players is obtained through the concept of equilibrium. This survey collects applications of game theory in wireless networking and presents them in a layered perspective, emphasizing on which fields game theory could be effectively applied. To this end, several games are modeled and their key features are exposed.
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paper_title: Co-Primary Multi-Operator Resource Sharing for Small Cell Networks

paper_content:

To tackle the challenge of providing higher data rates within limited spectral resources we consider the case of multiple operators sharing a common pool of radio resources. Four algorithms are proposed to address co-primary multi-operator radio resource sharing under heterogeneous traffic in both centralized and distributed scenarios. The performance of these algorithms is assessed through extensive system-level simulations for two indoor small cell layouts. It is assumed that the spectral allocations of the small cells are orthogonal to the macro network layer and thus, only the small cell traffic is modeled. The main performance metrics are user throughput and the relative amount of shared spectral resources. The numerical results demonstrate the importance of coordination among co-primary operators for an optimal resource sharing. Also, maximizing the spectrum sharing percentage generally improves the achievable throughput gains over non-sharing.
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paper_title: Co-primary spectrum sharing for denser networks in local area

paper_content:

This work investigates co-primary spectrum sharing problem in the local area indoor dense deployment scenario. A spectrum sharing method and relevant mechanism are designed to achieve flexible spectrum usage amongst multiple operator networks. This proposed solution improves spectrum efficiency by making small cells more flexibly and efficiently utilize whole spectrum resources via intra operator spectrum allocation and inter-operator spectrum coordination. Intensive system level simulations give a detailed verification of the performance of this spectrum sharing approach.
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paper_title: Spectrum sharing LTE-advanced small cell systems

paper_content:

Cellular systems are designed such that a certain amount of radio spectrum is allocated for their exclusive use to ensure that interference within these systems is tightly controlled. For competitive reasons, spectrum is divided between operators despite the resulting inefficiency in the overall spectrum utilization. For systems with relatively large cells and significant number of users per cell the loss in efficiency is modest. However, losses can become very large as cells become smaller. This paper presents a cooperative spectrum access framework that enables spectrum sharing between small cells that are being deployed by different operators. Primary spectrum owning operators broadcast their spectrum occupancy information to allow small cells of other operators to access their spectrum as secondary users. LTE-Advanced systems employing small cells are considered. Simulations show that the proposed spectrum access framework enables small cells to achieve substantial performance gains without affecting the primary spectrum owning operator even when the small cell deployment density varies significantly between operators.
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paper_title: Adaptive co-primary shared access between co-located radio access networks

paper_content:

Inter-operator spectrum sharing is expected to play a key role in fulfilling the predicted spectrum demand for future wireless systems. In this work, we propose an adaptive co - primary shared access scheme between co-located Radio Access Networks (RANs) owned by different operators. In the literature, the main focus is on orthogonal spectrum sharing. In this work, the spectrum is adaptively partitioned into private and non-orthogonally shared frequency sub-bands with the aim of maximizing inter-RAN sum rate. The non-orthogonally shared frequency sub-band is simultaneously used by all the RANs, with inter-RAN interference minimized. A zero-forcing precoder is used to serve the users scheduled in the private frequency sub-band. With the exchange of inter-RAN channel state information, a sparse precoder is used as inter-RAN precoder to serve the users scheduled in the shared frequency sub-band. Using a heuristic algorithm based on user grouping, spectrum partitioning and user scheduling are optimized. Based on simulation results, the proposed adaptive spectrum sharing approach outperforms conventional approaches of orthogonal and full-band non-orthogonal spectrum sharing.
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paper_title: Performance Evaluation of Spectrum Sharing Algorithms in Single and Multi Operator Scenarios

paper_content:

The increasing demand of indoor broadband access encourages the diffusion of the "home base stations", known as femtocells. Their self installation nature envisages interference problems due to a possible overload of local femtocell installations in the same area. To reduce the interference among femtocells we propose and analyze the performance of a dynamic frequency selection strategy, according to which each femtocell is able to select one of the possible frequencies available from all the operators in order to experience the best Signal-to-Interference Ratio (SIR). We assume that mobile operators share their requency bands allowing femtocells subscribed to a certain operator to exploit the frequency resources of other operators. In this paper we evaluate the performance in terms of allowed number of active femtocells per operator when the channels available from operators increase. It is observed that the application of the proposed Dynamic Frequency Selection (DFS) algorithm with band sharing allows single operator to significantly improve the number of active femtocells deployed in the area with respect to the non band sharing case, i.e. a Spectrum Sharing Gain is achieved.
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paper_title: Dynamic inter-operator spectrum sharing for UMTS FDD with displaced cellular networks

paper_content:

The paper investigates the possibility for competing network operators to cooperate partially without operational information exchange and to share a block of UMTS carriers simultaneously to provide services. The performance of spectrum sharing in the worst case for sharing (equal capacity demands) is investigated for the downlink of the UMTS FDD system. This work continues from earlier work (Pereirasamy, M.K. et al., Proc. 5th World Wireless Congress, 2004; Proc. 15th IEEE Int. Symp. On Personal Indoor and Mobile Radio Commun. - PIMRC, 2004), extending the initial concept to take into account that operators would realistically deploy operating networks composed of separate network equipment and infrastructure. The possible gain that is offered through spectrum sharing compared to conventional systems, with only proprietary carriers for operators, is studied for speech type traffic. It is found that the relative displacement of cooperating networks has a negative impact on the trunking gain given by the spectrum sharing mechanism. Considering only speech service type, a maximum allowed network displacement is given for a spectrum shared environment with the cellular network parameters chosen for this investigation.
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paper_title: 4G: LTE/LTE-Advanced for Mobile Broadband

paper_content:

Based on the bestseller "3G Evolution - HSPA and LTE for mobile broadband" and reflecting the ongoing success of LTE throughout the world, this book focuses on LTE with full updates including LTE-Advanced to provide a complete picture of the LTE system. Overview and detailed explanations are given for the latest LTE standards for radio interface architecture, the physical layer, access procedures, broadcast, relaying, spectrum and RF characteristics, and system performance. Key technologies presented include multi-carrier transmission, advanced single-carrier transmission, advanced receivers, OFDM, MIMO and adaptive antenna solutions, advanced radio resource management and protocols, and different radio network architectures. Their role and use in the context of mobile broadband access in general is explained. Both a high-level overview and more detailed step-by-step explanations of the LTE/LTE-Advanced implementation are given. An overview of other related systems such as GSM/EDGE, HSPA, CDMA2000, and WIMAX is also provided. This book is a 'must-have' resource for engineers and other professionals in the telecommunications industry, working with cellular or wireless broadband technologies, giving an understanding of how to utilize the new technology in order to stay ahead of the competition. The authors of the book all work at Ericsson Research and have been deeply involved in 3G and 4G development and standardisation since the early days of 3G research. They are leading experts in the field and are today still actively contributing to the standardisation of LTE within 3GPP. Includes full details of the latest additions to the LTE Radio Access standards and technologies up to and including 3GPP Release 10Clear explanations of the role of the underlying technologies for LTE, including OFDM and MIMO Full coverage of LTE-Advanced, including LTE carrier aggregation, extended multi-antenna transmission, relaying functionality and heterogeneous deploymentsLTE radio interface architecture, physical layer, access procedures, MBMS, RF characteristics and system performance covered in detail
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paper_title: Resource allocation for co-primary spectrum sharing in MIMO networks

paper_content:

We study co-primary spectrum sharing concept in two small cell multiuser network. Downlink transmission is explored with Rayleigh fading in interfering broadcast channel. Both base stations and all the users are equipped with multiple antennas. Resource allocation with joint precoder and decoder design is proposed for weighted sum rate (WSR) maximization problem. The problem becomes mixed-integer and non-convex. We factor the main objective problem into two subproblems. First subproblem is subcarrier allocation where we assume that each subcarrier can be allocated to multiple users. Gale-Shapley algorithm based on stable marriage problem and transportation method are implemented for subcarrier allocation part. For the second subproblem, a joint precoder and decoder design is proposed to obtain the optimal solution for WSR maximization. Monte Carlo simulation is employed to obtain the numerical results to compare the two methods.
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paper_title: Using SDN as a key enabler for co-primary spectrum sharing

paper_content:

Over the past years the mobile traffic demands and the number of the connected devices have been constantly increasing thus indicating that in the near future the current spectrum usage models may fail to cover user needs. At the same time, spectrum scarcity over several Mobile Network Operators (MNOs) leads to inefficient spectrum usage. Co-primary spectrum sharing is a scheme for trading resources among MNOs, enabling flexible spectrum usage, which is arising as a possible solution to spectrum scarcity. However, up to now the schemes for co-primary shared access are hard to be implemented. The recently introduced concept of Software Defined Networking (SDN) gives the flexibility to MNOs' network configuration and, therefore, is arising as an enabler for efficiently handling spectrum trading. In this paper we present a complete functional architecture aiming at enabling co-primary spectrum sharing among MNOs. We, furthermore, propose a scheme for implementing the introduced architectural scheme, coupled with fully described information flows among the (SDN) network entities. Such solution enables the concurrent reconfiguration (when required) for both core and access network nodes, based on the spectrum trading process.
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paper_title: A Secure Radio Environment Map Database to Share Spectrum

paper_content:

A robust and secure database for spectrum sharing in cognitive radio networks that is obscured from the viewpoint of secondary users is presented. The database allocations secure features of white space resource usage from being learned. The design of non-inferable database is based on two cases. In the first case, the primary or spectrum lender has no knowledge of secondary users or potential jammers among them. In this case, the problem is modeled as a Markov decision process. In the second case, the primary system has some knowledge about spectrum borrowers and the problem is modeled as a Bayesian Stackelberg game. Mutual information interpretation of the Bayesian Stackelberg game is also presented. The solutions facilitate releasing more bandwidth as required by US National Broadband Plan. Applications of this scheme are manifold. This design can be used for securing spectrum resources, for example radar white spaces, while being shared with LTE and commercial communication systems. Further, it provides jammer-proof spectrum sharing among various communication, detection, and navigation systems. Simulation results verify this scheme improves system throughput while maintaining desired obfuscation level or entropy.
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paper_title: Does non-orthogonal spectrum sharing in the same cell improve the sum-rate of wireless operators?

paper_content:

We study non-orthogonal spectrum sharing to determine under what circumstances operators can gain by such sharing. To model the spectrum sharing, we use the multiple-input single-output (MISO) interference channel (IC) assuming that the operators transmit in the same band. For the baseline scenario of no sharing, we use the MISO broadcast channel (BC) assuming that the operators transmit in disjunct bands. For both the IC and BC, we give achievable (lower) and upper bounds on the maximum sum-rate. While these bounds are well-known we also propose a new fast algorithm for finding a lower bound on the sum-rate of the BC using linear beamforming. We use the bounds to numerically evaluate the potential gain of non-orthogonal spectrum sharing. In this study we assume that the operators efficiently utilize all their spatial degrees of freedom. We will see that the gains from spectrum sharing under these circumstances are limited.
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paper_title: Spectrum sharing across multiple service providers via cognitive radio nodes

paper_content:

The rapid growth of wireless industry and continuous emergence of new applications increase the demand for wireless spectrum. However, currently the spectrum assigned to different organisations is not utilised efficiently. Particularly, when an infrastructure of a service provider is overloaded and cannot accommodate more users because of the channel scarcity, the infrastructures of other service providers operating in the same area might be in under-loaded status. However, without a proper spectrum sharing scheme, the overloaded infrastructure cannot use the channels licensed to other service providers. This leads to low spectrum utilisation efficiency and higher call blocking rate of service providers. Significant research has been conducted to study sharing channels between cells within one service provider; however, sharing spectrum across different service providers is still under investigation. This paper proposes deploying a network of fixed cognitive radio (CR) nodes to maintain spectrum sharing across multiple service providers operating in the same geographical area. These CR nodes estimate the spectrum utilisation in a given area, and cooperate to provide the spectrum usage information for the overloaded infrastructures of service providers. This work discusses the implementation of the proposed CR-based spectrum sharing technique, and studies the impact of spectrum sharing on the service provider's performance. It is shown that the proposed technique reduces the call blocking rate and improves the spectrum utilisation efficiency. This technique removes the need of sensing spectrum in each user. Thus, it reduces the cost, complexity and battery power consumption of user devices.
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paper_title: Mobile Network Resource Sharing Options: Performance Comparisons

paper_content:

Resource sharing among mobile network operators is a promising way to tackle growing data demand by increasing capacity and reducing costs of network infrastructure deployment and operation. In this work, we evaluate sharing options that range from simple approaches that are feasible in the near-term on traditional infrastructure to complex methods that require specialized/virtualized infrastructure. We build a simulation testbed supporting two geographically overlapped 4G LTE macro cellular networks and model the sharing architecture/process between the network operators. We compare Capacity Sharing (CS) and Spectrum Sharing (SS) on traditional infrastructure and Virtualized Spectrum Sharing (VSS) and Virtualized PRB Sharing (VPS) on virtualized infrastructure under light, moderate and heavy user loading scenarios in collocated and noncollocated E-UTRAN deployment topologies. We also study these sharing options in conservative and aggressive sharing participation modes. Based on simulation results, we conclude that CS, a generalization of traditional roaming, is the best performing and simplest option, SS is least effective and that VSS and VPS perform better than spectrum sharing with added complexity.
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paper_title: Overview and comparison of recent spectrum sharing approaches in regulation and research: From opportunistic unlicensed access towards licensed shared access

paper_content:

This paper reviews recent spectrum sharing models under study in the spectrum regulation and wireless communications research domains. An overview of different spectrum regulator forums and directions is presented and their activities related to the development of spectrum sharing models are reviewed. Special emphasis is put on the recent European and US regulatory approaches for spectrum sharing. In particular, Licensed Shared Access (LSA) and Collective Use of Spectrum (CUS) models from Europe and Three-Tier Hierarchy Model from the US are analyzed in detail. A comparison is made between these approaches to identify similarities and differences in the regulatory developments. Factors for developing a successful sharing model are also discussed. For a dynamic spectrum sharing model to be adopted, it must protect the rights of entrant users without impact to the legacy systems. It must also create a reasonable straightforward opportunity for an entity that wishes to access a shared spectrum to do so in a manner that is neither overly complex nor costly to implement. The practical implementation of dynamic spectrum sharing models is likely to require different national implementations because the regulatory approaches and the incumbent spectrum uses are different in various countries.
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paper_title: A Survey of Measurement-Based Spectrum Occupancy Modeling for Cognitive Radios

paper_content:

Spectrum occupancy models are very useful in cognitive radio designs. They can be used to increase spectrum sensing accuracy for more reliable operation, to remove spectrum sensing for higher resource usage efficiency, or to select channels for better opportunistic access, among other applications. In this survey, various spectrum occupancy models from measurement campaigns taken around the world are investigated. These models extract different statistical properties of the spectrum occupancy from the measured data. In addition to these models, spectrum occupancy prediction is also discussed, where autoregressive and/or moving-average models are used to predict the channel status at future time instants. After comparing these different methods and models, several challenges are also summarized based on this survey.
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paper_title: "Simple rules" for mobile network operators' strategic choices in future cognitive spectrum sharing networks

paper_content:

Spectrum sharing is becoming a necessity in future cellular networks due to the increasing traffic demand and challenges of getting exclusive spectrum. This article reviews the spectrum sharing framework that consists of regulatory, technology, and business domains. For future mobile network operators, sharing of spectrum with other operators or with other radiocommunication services - especially when using cognitive radio system technologies - is a disruptive change. Building on alternative spectrum sharing scenarios, this article discusses a set of Simple Rules for mobile network operators, both dominators and challengers, regarding spectrum sharing in future cognitive cellular networks. The Simple Rules provide a dynamic framework for both dominating and challenger mobile network operators for developing their sharing-based business models.
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paper_title: Primary radio user activity models for cognitive radio networks: A survey

paper_content:

Abstract Cognitive Radio Networks have been emerged as a promising solution for solving the problem of spectrum scarcity and improving spectrum utilization by opportunistic use of spectrum. Cognitive radio networks utilize the spectrum which is licensed to primary radio users when they are not utilizing it, i.e., when the spectrum is idle. Thus, the performance of cognitive radio networks is highly dependent upon the activity of primary radio users. Hence, it is very important to model primary radio users activity in cognitive radio networks. By keeping this in mind, several models in the literature have been proposed for modeling primary radio users activity. But there is not any source which consolidate all these models into single platform. Therefore, this paper combines all the primary radio user activity models for cognitive radio networks at a single place. The goal of this paper is to provide a single source in the form of survey paper by which a reader can get an idea about which primary radio user activity models have been used in the literature for cognitive radio networks and how the modeling is performed. Furthermore, we also discuss issues, challenges and future directions for primary radio activity models. In fact, in this paper, different primary radio user activity models have been presented along with their classification. This paper also discusses those approaches which performed real implementation for spectrum occupancy along with spectrum bands on which the implementation is performed and location where implementation is carried out. In summary, this paper provides up-to-date survey of primary radio user activity models for cognitive radio networks.
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paper_title: Cellular architecture enhancement for supporting the european licensed shared access concept

paper_content:

As the demand for mobile traffic continues to grow rapidly, finding exclusive bands for mobile network operators in a harmonized manner becomes increasingly challenging. New European spectrum regulatory development aims at allowing future cellular networks to access shared spectrum bands under the licensed shared access regime as a complementary approach to current exclusive licensed and license-exempt bands. The introduction of additional spectrum by new spectrum access methods seems a necessary evolution path for cellular mobile communication networks to respond to the growing traffic in the next decade. The inclusion of the shared bands will require modifications to the existing network management as their availability and access conditions may vary locally and temporarily according to the agreed licensing conditions. Self-organizing network features will undoubtedly become an important enabler to handle the increased complexity brought by licensed shared access methods. In this article, self-organizing networking features to support the licensed shared bands are introduced. In particular, automated load balancing decisions by traffic steering are examined in detail with the purpose of matching the mobile network operators' available radio access technologies, cells, and spectrum resources to the fluctuating traffic demand.
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paper_title: Business scenarios for incumbent spectrum users in Licensed Shared Access (LSA)

paper_content:

This paper presents business scenarios for incumbent spectrum users in the new Licensed Shared Access (LSA) concept. The LSA concept aims at improving spectrum usage efficiency by introducing additional licensed spectrum users on spectrum bands whose incumbent use would permit it, while guaranteeing certain quality of service (QoS) for all users. The LSA concept could help mobile network operators (MNOs) to gain access to new spectrum bands on a shared basis in a timely manner. As the LSA concept is based on voluntariness, it needs to provide incentives for the incumbent spectrum users for the introduction of sharing. Using a foresight approach called integral scenario methodology, we propose a set of scenarios for incumbent spectrum users in LSA based on their business focus (defensive vs. aggressive) and mode of change (open vs. closed). The created scenarios are described and analyzed from regulation, business and technology perspectives, highlighting the business potential created by the introduction of LSA. The evaluation of the developed business scenarios indicates that a defensive approach for the business focus for incumbents might be preferred to focus narrowly on traditional business models. However, an aggressive approach to pursue new business opportunities with LSA might open up new opportunities which, today, cannot yet be foreseen.
---
paper_title: Optimization of Authorised/Licensed Shared Access resources

paper_content:

The expected increase of the traffic volume in mobile broadband networks and the upcoming spectrum scarcity, require an optimization of the usage of the spectrum. One of the solutions is Authorised/Licensed Shared Access (ASA/LSA) 1 , a new regulatory concept that allows license holders (incumbents) to share spectrum with other service providers, under well-defined conditions, unlocking additional bands which are used only partially in time and/or location. This paper shows the benefits of ASA, considering different methods to optimize the resources, by simulating an LTE network where a Mobile Network Operator (MNO) is allowed to use the 2300 MHz band as an ASA licensee.
---
paper_title: Cellular architecture enhancement for supporting the european licensed shared access concept

paper_content:

As the demand for mobile traffic continues to grow rapidly, finding exclusive bands for mobile network operators in a harmonized manner becomes increasingly challenging. New European spectrum regulatory development aims at allowing future cellular networks to access shared spectrum bands under the licensed shared access regime as a complementary approach to current exclusive licensed and license-exempt bands. The introduction of additional spectrum by new spectrum access methods seems a necessary evolution path for cellular mobile communication networks to respond to the growing traffic in the next decade. The inclusion of the shared bands will require modifications to the existing network management as their availability and access conditions may vary locally and temporarily according to the agreed licensing conditions. Self-organizing network features will undoubtedly become an important enabler to handle the increased complexity brought by licensed shared access methods. In this article, self-organizing networking features to support the licensed shared bands are introduced. In particular, automated load balancing decisions by traffic steering are examined in detail with the purpose of matching the mobile network operators' available radio access technologies, cells, and spectrum resources to the fluctuating traffic demand.
---
paper_title: Live field trial of Licensed Shared Access (LSA) concept using LTE network in 2.3 GHz band

paper_content:

This paper presents the results from a live field trial of the new Licensed Shared Access (LSA) concept using a TD-LTE network in the 2.3 GHz spectrum band in Finland. In the trial a live LTE network shares the spectrum from incumbent programme making and special events (PMSE) service including cordless cameras without causing harmful interference. The trial implements the new LSA concept and the required new building blocks including LSA Repository for spectrum availability information and LSA Controller for commanding the mobile communication network in the band. The trial uses a real TD-LTE base station, real network management system, and real core network. Incumbent spectrum usage data is collected to the LSA Repository and used by the LSA Controller to retrieve available spectrum bands. LSA Controller uses the network management system to configure the base station according to the spectrum availability information. Incumbent spectrum users' rights are protected by evacuating the LSA band and handing users over from the LTE network to other networks when requested by the incumbent spectrum user. Numerical results are presented to quantify the duration of the LSA band evacuation process. The demonstration shows that the new LSA concept can be implemented with existing network elements and a minimum amount of new components. The first performance results on the LSA band evacuation times indicate that the LSA band can be evacuated and released in good time and the incumbents' rights can be protected.
---
paper_title: Analysis of requirements from standardization for Licensed Shared Access (LSA) system implementation

paper_content:

Licensed Shared Access (LSA) is a novel flexible regulatory framework, which introduces a shared licensed use of a spectrum band to complement the existing exclusively licensed and license-exempt use. LSA as a general concept was first introduced by the European Commission already in 2011 and it has gained growing interest in standardization and regulatory forums in Europe since. To highlight its potential, European regulators have recently recognized LSA as a promising approach to provide mobile network operators (MNOs) access to the 2.3–2.4 GHz band. In this case, the protection of incumbent users introduces new requirements for information exchange between the incumbents and the mobile network. European Telecommunications Standards Institute's (ETSI) Reconfigurable Radio Systems (RRS) group has defined the requirements, which the LSA system needs to fulfil in order to enable mobile access to the 2.3–2.4 GHz band. This paper places LSA in the regulation and standardization landscape and presents a comprehensive overview of the activities in all relevant forums including their interrelations, to demonstrate the development of the concept. It specifically focuses on the standardization requirements on the LSA system, analyzes and maps the requirements from the ETSI RRS into the different functional blocks of the LSA architecture, and envisions how these can be taken into account in the system implementation. While the incumbent protection places a large number of new requirements on the mobile system design, the LSA system implementation is seen to be feasible by utilizing the existing LTE and LTE-Advanced features, and by developing the required new functionalities according to the standardization requirements.
---
paper_title: Cellular architecture enhancement for supporting the european licensed shared access concept

paper_content:

As the demand for mobile traffic continues to grow rapidly, finding exclusive bands for mobile network operators in a harmonized manner becomes increasingly challenging. New European spectrum regulatory development aims at allowing future cellular networks to access shared spectrum bands under the licensed shared access regime as a complementary approach to current exclusive licensed and license-exempt bands. The introduction of additional spectrum by new spectrum access methods seems a necessary evolution path for cellular mobile communication networks to respond to the growing traffic in the next decade. The inclusion of the shared bands will require modifications to the existing network management as their availability and access conditions may vary locally and temporarily according to the agreed licensing conditions. Self-organizing network features will undoubtedly become an important enabler to handle the increased complexity brought by licensed shared access methods. In this article, self-organizing networking features to support the licensed shared bands are introduced. In particular, automated load balancing decisions by traffic steering are examined in detail with the purpose of matching the mobile network operators' available radio access technologies, cells, and spectrum resources to the fluctuating traffic demand.
---
paper_title: System level performance of cellular networks utilizing ASA/LSA mechanisms

paper_content:

Flexible and efficient spectrum usage in cellular communication systems is a key to meet the service demand of forthcoming 4G and 5G networks by 2020. Recent wide-band power measurements in an urban environment show that spectrum below 6 GHz is still under-utilized. Licensed shared access (LSA) is one technique which can be deployed to make use of these valuable resources. In this paper we highlight cell-planning aspects for the implementation of licensed shared access (LSA) in LTE cellular networks. Different cellular deployments are evaluated by means of system-level simulations. Numerical results show that transmit power, antenna type and orientation, as well as antenna downtilt should be carefully evaluated during the planning of spectrum sharing deployments using LSA in cellular wireless.
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paper_title: Multi-carrier waveform based flexible inter-operator spectrum sharing for 5G systems

paper_content:

This paper presents a multi-carrier waveform based inter-operator spectrum sharing concept for 5G mobile and wireless communication systems. The proposed concept considers the flexible air-interface being developed for 5G and can support coordinated inter-operator spectrum sharing in various scenarios, including mutual renting, spectrum spot market, co-primary sharing, licensed shared access (LSA), secondary horizontal sharing etc. Compared to state-of-the-arts, the proposed concept has much broader applicability and less restrictions on infrastructure conditions, including radio access network (RAN) sharing, inter-operator synchronization and fast inter-operator signaling. Furthermore, the proposed concept allows high flexibility both in spectrum allocation and adaptation of the transmission signals to support the large variety of devices expected in 5G scenarios. The key elements of the proposed concept includes the determination of a common subcarrier grid, a two-stage allocation procedure, fragmented spectrum usage, usage of “out-of-fragment radiation masks”, and adaptation of multi-carrier waveforms. Preliminary results have shown that the proposed concept allows efficient and flexible fragmented spectrum usage, with robustness against inter-operator synchronization mismatch.
---
paper_title: Optimization of Authorised/Licensed Shared Access resources

paper_content:

The expected increase of the traffic volume in mobile broadband networks and the upcoming spectrum scarcity, require an optimization of the usage of the spectrum. One of the solutions is Authorised/Licensed Shared Access (ASA/LSA) 1 , a new regulatory concept that allows license holders (incumbents) to share spectrum with other service providers, under well-defined conditions, unlocking additional bands which are used only partially in time and/or location. This paper shows the benefits of ASA, considering different methods to optimize the resources, by simulating an LTE network where a Mobile Network Operator (MNO) is allowed to use the 2300 MHz band as an ASA licensee.
---
paper_title: Dynamic LSA for 5G networks the ADEL perspective

paper_content:

Exploiting additional radio spectrum is key to respond to the unprecedented capacity demands of mobile broadband communication systems in recent years. In fact, most of the frequency bands suitable for mobile communications are already in use by other radio services, and spectrum refarming is usually not possible or constitutes a highly time-consuming procedure. At the same time, several field measurement campaigns have shown that the occupied spectrum below 6GHz is severely underutilized, i.e. there exist “spectrum holes” in the time, frequency, and space dimensions, pointing to the possibility of using spectrum sharing as a mean to better exploit additional spectral resources. Licensed shared access (LSA) is a recent spectrum licensing paradigm that allows licensees to share the licensed spectrum of incumbents without causing harmful interference and ensuring a certain quality-of-service (QoS) for both types of players. The EU-funded project ADEL aims to enhance the current LSA paradigm by introducing 1) dynamic radio resource management (RRM), 2) sensing reasoning, based on database-assisted collaborative sensor networking, and 3) an extension to the LSA architecture that allows a more effective RRM, increasing QoS satisfaction and policy enforcement for all players, finally leading to an overall improved spectrum utilization. The key features of ADEL's enhanced LSA paradigm are outlined throughout the remainder of this paper.
---
paper_title: Business models for mobile network operators in Licensed Shared Access (LSA)

paper_content:

This paper presents business models for mobile network operators (MNOs) in the new Licensed Shared Access (LSA) concept. The LSA concept allows spectrum sharing between an incumbent spectrum user and an LSA licensee under the supervision of the regulator with rules and conditions that guarantee predictable quality of service (QoS) levels to all involved spectrum users. This paper summarizes the LSA concept and its application to the mobile broadband where an MNO shares spectrum from another type of incumbent spectrum user such as military or programme making and special events (PMSE) services which corresponds to the industry driven Authorised Shared Access (ASA) concept. The paper highlights the importance of developing viable business models for the new spectrum sharing concepts as they need to provide clear benefits to the key stakeholders to be adopted in real life. The paper depicts the evolution path of business model theories and focuses on a recent action-oriented business modeling approach. This approach is applied to the mobile broadband using the LSA concept to derive business models for MNOs for accessing new LSA bands. Separate business models are derived for dominating and challenger MNOs whose market shares and amounts of exclusive spectrum license differ significantly and will face different business opportunities arising from LSA. To assess the transformation coming with the LSA concept, business models are first developed for the current situation with exclusively licensed spectrum bands. New business models are then developed for the introduction of the new shared LSA bands. The developed business models indicate that the dominating MNOs could benefit significantly from the new LSA bands which would enable dynamic traffic management to offer different service levels to different customer segments. For challenger MNOs, the LSA concept could offer the opportunity to challenge the dominating MNOs and win their customers by offering tailored services to a wider customer base using the new LSA spectrum resources. Moreover, it could significantly re-shape the business ecosystem around the mobile broadband by opening the door to non-MNO entrants.
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paper_title: Business scenarios for incumbent spectrum users in Licensed Shared Access (LSA)

paper_content:

This paper presents business scenarios for incumbent spectrum users in the new Licensed Shared Access (LSA) concept. The LSA concept aims at improving spectrum usage efficiency by introducing additional licensed spectrum users on spectrum bands whose incumbent use would permit it, while guaranteeing certain quality of service (QoS) for all users. The LSA concept could help mobile network operators (MNOs) to gain access to new spectrum bands on a shared basis in a timely manner. As the LSA concept is based on voluntariness, it needs to provide incentives for the incumbent spectrum users for the introduction of sharing. Using a foresight approach called integral scenario methodology, we propose a set of scenarios for incumbent spectrum users in LSA based on their business focus (defensive vs. aggressive) and mode of change (open vs. closed). The created scenarios are described and analyzed from regulation, business and technology perspectives, highlighting the business potential created by the introduction of LSA. The evaluation of the developed business scenarios indicates that a defensive approach for the business focus for incumbents might be preferred to focus narrowly on traditional business models. However, an aggressive approach to pursue new business opportunities with LSA might open up new opportunities which, today, cannot yet be foreseen.
---
paper_title: Spectrum sharing in the EU and the path towards standardization

paper_content:

This paper addresses the current regulatory framework, research activities and standardization efforts towards a shared use of radio spectrum in the European Union. Two main research streams are considered: The emerging concept of Licensed Shared Access that ensures a predictable Quality of Service for secondary users of spectrum and the opportunistic Device-to-Device communications that represent a recent and enormous socio-technological trend. The paper presents also research results that support the spectrum sharing standardization path in ETSI and 3GPP.
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paper_title: Live field trial of Licensed Shared Access (LSA) concept using LTE network in 2.3 GHz band

paper_content:

This paper presents the results from a live field trial of the new Licensed Shared Access (LSA) concept using a TD-LTE network in the 2.3 GHz spectrum band in Finland. In the trial a live LTE network shares the spectrum from incumbent programme making and special events (PMSE) service including cordless cameras without causing harmful interference. The trial implements the new LSA concept and the required new building blocks including LSA Repository for spectrum availability information and LSA Controller for commanding the mobile communication network in the band. The trial uses a real TD-LTE base station, real network management system, and real core network. Incumbent spectrum usage data is collected to the LSA Repository and used by the LSA Controller to retrieve available spectrum bands. LSA Controller uses the network management system to configure the base station according to the spectrum availability information. Incumbent spectrum users' rights are protected by evacuating the LSA band and handing users over from the LTE network to other networks when requested by the incumbent spectrum user. Numerical results are presented to quantify the duration of the LSA band evacuation process. The demonstration shows that the new LSA concept can be implemented with existing network elements and a minimum amount of new components. The first performance results on the LSA band evacuation times indicate that the LSA band can be evacuated and released in good time and the incumbents' rights can be protected.
---
paper_title: Dynamic REM towards flexible spectrum management

paper_content:

Radio Environment Maps (REM) are lately emerging as a technical enabler and facilitator of dynamic spectrum access and cognitive radio scenarios. Their usage fosters many operational wireless network procedures such as spectrum access, spectrum sharing, resource usage optimization etc. Additionally, REMs are foreseen as a supplementary tool for regulation of spectrum usage. This paper covers both theoretical and practical aspects of efficient REM system design and REM construction in general. It showcases the synergy between spectrum sensing techniques and geolocation database approaches towards accurate and up-to-date radio field estimation. Furthermore, the paper provides details on recent research advances in the area of REM construction, Radio Interference Fields (RIF) derivation, source localization and propagation modelling. Finally, it analyzes several use-cases of practical implementation of REMs proving its capabilities to serve as an enabler for flexible spectrum management in future wireless networks.
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paper_title: Enabling Cognitive Radios through Radio Environment Maps

paper_content:

In recent years, cognitive radios and cognitive wireless networks have been introduced as a new paradigm for enabling much higher spectrum utilization, providing more reliable and personal radio services, reducing harmful interference, and facilitating the interoperability or convergence of different wireless communication networks. Cognitive radios are goaloriented, autonomously learn from experience and adapt to changing operating conditions. Cognitive radios have the potential to drive the next generation of radio devices and wireless communication system design and to enable a variety of niche applications in demanding environments, such as spectrum-sharing networks, public safety, natural disasters, civil emergencies, and military operations. This research first introduces an innovative approach to developing cognitive radios based on the Radio Environment Map (REM). The REM can be viewed as an integrated database that provides multi-domain environmental information and prior knowledge for cognitive radios, such as the geographical features, available services and networks, spectral regulations, locations and activities of neighboring radios, policies of the users and/or service providers, and past experience. The REM, serving as a vehicle of network support to cognitive radios, can be exploited by the cognitive engine for most cognitive functionalities, such as situation awareness, reasoning, learning, planning, and decision support. This research examines the role of the REM in cognitive radio development from a network point of view, and focuses on addressing three specific issues about the REM: how to design and populate the REM; how to exploit the REM with the cognitive engine algorithms; and how to evaluate the performance of the cognitive radios. Applications of the REM to wireless local area networks (WLAN) and wireless regional area networks (WRAN) are investigated, especially from the perspectives of interference management and radio resource management, which
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paper_title: Active antenna system enhancement for supporting Licensed Shared Access (LSA) concept

paper_content:

Mobile and wireless communication networks will need to cope with the tremendous increase in data traffic anticipated over the next decade. Beyond the levers of increased network densification and enhanced spectral efficiency more radio spectrum is clearly needed for mobile networks to fulfill capacity and coverage demands. Finding spectrum without existing incumbent usage in a harmonized manner becomes increasingly challenging. Spectrum sharing techniques can be used to optimize spectrum utilization across multiple services to share the same frequency band in a controlled manner. Another emerging technique to enhance cellular network capacity is smart antennas that can flexibly control radiation patterns. These new spectrum efficiency enhancements should be deployed in a way that requires minimum changes to the features and the architecture of the systems involved. In this paper, we concentrate on the Licensed Shared Access (LSA) concept which in recent years has received considerable interest in both European and USA regulation and standardization. We discuss how smart antennas technologies and Active Antenna System (AAS) in particular could be used to enhance LSA systems. Finally, we propose a system architecture and implementation scenarios for LSA that provides spectrum exclusion zone reduction and interference detection by using Active Antenna System.
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paper_title: Licensed Shared Access (LSA) trial demonstration using real LTE network

paper_content:

This paper presents a demonstration of the new Licensed Shared Access (LSA) concept using a TD-LTE access network in the 2.3 GHz spectrum band in Finland. In the demonstrated trial, the TD-LTE network shares the spectrum of an incumbent spectrum user, who is focused on programme making and special events (PMSE) services. The demonstrator implements the new LSA concept and the required new building blocks including LSA Repository for spectrum protection information and LSA Controller for controlling the mobile communication network in the same band. The trial uses commercial network components like multiband-terminals, TD-L TE base stations, network management system, and core network. Spectrum usage data of incumbents is collected to LSA Repository using two incumbent user tools and is actively updated to LSA Controller for radio network planning to protect the incumbent's activity in the area. LSA Controller uses the information from the base stations and incumbents to protect incumbent spectrum users' rights. This is demonstrated by providing different algorithms, which analyze base stations and sectors that need to be reconfigured to prevent interference from LTE to incumbent (and vice versa). The demonstration shows that the new LSA concept can be implemented with existing network elements and a minimum amount of new components.
---
paper_title: System level performance of cellular networks utilizing ASA/LSA mechanisms

paper_content:

Flexible and efficient spectrum usage in cellular communication systems is a key to meet the service demand of forthcoming 4G and 5G networks by 2020. Recent wide-band power measurements in an urban environment show that spectrum below 6 GHz is still under-utilized. Licensed shared access (LSA) is one technique which can be deployed to make use of these valuable resources. In this paper we highlight cell-planning aspects for the implementation of licensed shared access (LSA) in LTE cellular networks. Different cellular deployments are evaluated by means of system-level simulations. Numerical results show that transmit power, antenna type and orientation, as well as antenna downtilt should be carefully evaluated during the planning of spectrum sharing deployments using LSA in cellular wireless.
---
paper_title: Modeling of interference maps for Licensed Shared Access in LTE-advanced networks supporting Carrier Aggregation

paper_content:

Cognitive Radio based Dynamic Spectrum Access (CR-DSA) has been envisaged as the foremost solution to eliminate the impending false scarcity of the radio frequency spectrum and to combat the dramatic surge in mobile data traffic. Furthermore, the revolutionary concepts - Carrier Aggregation (CA) and Licensed Shared Access (LSA) - have been conceived to support higher data rates by aggregating bandwidth from different parts of the spectrum, and to provide for a predictable Quality of Service (QoS) through spectrum sharing, respectively, so as to enhance the performance of the current generation mobile communication systems. However, an inevitable consequence of spectrum sharing is the interference induced upon the incumbent user. In this work, the prime focus of attention is on the mitigation of the interference caused by an LSA-licensed LTE-Advanced Radio Access Network (RAN) in the uplink (UL). To this end, we propose an interference management scheme based on Radio Environment Maps (REMs). Different approaches have been considered for the modeling of the requisite maps and a performance comparison between them by means of detection theory is presented. In conclusion, we prove the superior performance of the kriging spatial interpolation technique over the other approaches.
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paper_title: Field trial of Licensed Shared Access (LSA) with enhanced LTE resource optimization and incumbent protection

paper_content:

We present an end-to-end ecosystem trial of the Licensed Shared Access (LSA) concept using a live LTE network sharing the 2.3 GHz band with incumbent wireless cameras. The entire LSA concept is implemented introducing LTE network as an additional licensed user in the band with the aid of an LSA Repository for spectrum availability information from wireless cameras and an LSA Controller for managing the LTE network. The trial goes beyond previous LSA demos by presenting enhanced LSA resource optimization with LSA Controller that is integrated into a real network management system to coordinate a heterogeneous network of macro and small cells. Enhanced incumbent protection is provided with algorithms for tracking a moving incumbent and considering aggregate interference from the LTE network to incumbent. Trial gives a unique opportunity to see live how a commercial LTE network adapts transmissions on the fly according to the location of the incumbent. Small cells are shown to improve the LSA resource use as the enhanced incumbent protection algorithm can allow small cells to continue operations in situation where macro cells need to close down.
---
paper_title: Optimization of Authorised/Licensed Shared Access resources

paper_content:

The expected increase of the traffic volume in mobile broadband networks and the upcoming spectrum scarcity, require an optimization of the usage of the spectrum. One of the solutions is Authorised/Licensed Shared Access (ASA/LSA) 1 , a new regulatory concept that allows license holders (incumbents) to share spectrum with other service providers, under well-defined conditions, unlocking additional bands which are used only partially in time and/or location. This paper shows the benefits of ASA, considering different methods to optimize the resources, by simulating an LTE network where a Mobile Network Operator (MNO) is allowed to use the 2300 MHz band as an ASA licensee.
---
paper_title: Dynamic LSA for 5G networks the ADEL perspective

paper_content:

Exploiting additional radio spectrum is key to respond to the unprecedented capacity demands of mobile broadband communication systems in recent years. In fact, most of the frequency bands suitable for mobile communications are already in use by other radio services, and spectrum refarming is usually not possible or constitutes a highly time-consuming procedure. At the same time, several field measurement campaigns have shown that the occupied spectrum below 6GHz is severely underutilized, i.e. there exist “spectrum holes” in the time, frequency, and space dimensions, pointing to the possibility of using spectrum sharing as a mean to better exploit additional spectral resources. Licensed shared access (LSA) is a recent spectrum licensing paradigm that allows licensees to share the licensed spectrum of incumbents without causing harmful interference and ensuring a certain quality-of-service (QoS) for both types of players. The EU-funded project ADEL aims to enhance the current LSA paradigm by introducing 1) dynamic radio resource management (RRM), 2) sensing reasoning, based on database-assisted collaborative sensor networking, and 3) an extension to the LSA architecture that allows a more effective RRM, increasing QoS satisfaction and policy enforcement for all players, finally leading to an overall improved spectrum utilization. The key features of ADEL's enhanced LSA paradigm are outlined throughout the remainder of this paper.
---
paper_title: Performance evaluation of spectrum sharing technologies

paper_content:

We present a description of contemporary performance evaluation approaches for spectrum sharing technologies (including dynamic spectrum access (DSA)/cognitive radios (CR)), and the perspectives of stakeholders with respect to shortcomings and resultant delayed field transition impacts. The shortcomings are examined to generate a set of desirable new attributes for more capable test and evaluation (T&E) systems and methods. Ongoing research and development (R&D) using the DYnamic Spectrum Environment emulator (DYSE) aimed at addressing these DSA/CR T&E shortcomings is described including a radar-Long Term Evolution (LTE) network sharing example, a TV whitespace sharing example using 802.22, and a position/navigation/timing (PNT) example with shared RF sources for communications and PNT.
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paper_title: Sensing for spectrum sharing in cognitive LTE-A cellular networks

paper_content:

In this work we present a case for dynamic spectrum sharing between different operators in systems with carrier aggregation (CA) which is an important feature in 3GPP LTE-A systems. Cross-carrier scheduling and sensing are identified as key enablers for such spectrum sharing in LTE-A. Sensing is classified as Type 1 sensing and Type 2 sensing and the role of each in the system operation is discussed. The more challenging Type 2 sensing which involves sensing the interfering signal in the presence of a desired signal is studied for a single-input single-output system. Energy detection and the most powerful test are formulated. The probability of false alarm and of detection are analyzed for energy detectors. Performance evaluations show that reasonable sensing performance can be achieved with the use of channel state information, making such sensing practically viable.
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paper_title: On the expiration date of spectrum sharing in mobile cellular networks

paper_content:

Driven by a combination of flat lining revenues and an explosive growth in the mobile data traffic and hence the need for network resources, mobile operators consider infrastructure-and spectrum sharing as a means to reduce operational costs. We develop and apply an assessment approach to quantify the benefits associated with spectrum sharing in an infrastructure-shared environment, and estimate the evolution of the derived 'spectrum sharing dividend' as traffic loads, radio access technologies, spectrum availability and performance targets change over time. The obtained insights can assist operators and regulators in their assessment of the merit of spectrum sharing. Analysis shows that operators with loads that peak at different times continue to benefit significantly by sharing spectrum, despite the diminishing 'trunking gains' of spectrum sharing as individual operator loads and capacities increase over time. © 2014 IFIP.
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paper_title: Spectrum sharing across multiple service providers via cognitive radio nodes

paper_content:

The rapid growth of wireless industry and continuous emergence of new applications increase the demand for wireless spectrum. However, currently the spectrum assigned to different organisations is not utilised efficiently. Particularly, when an infrastructure of a service provider is overloaded and cannot accommodate more users because of the channel scarcity, the infrastructures of other service providers operating in the same area might be in under-loaded status. However, without a proper spectrum sharing scheme, the overloaded infrastructure cannot use the channels licensed to other service providers. This leads to low spectrum utilisation efficiency and higher call blocking rate of service providers. Significant research has been conducted to study sharing channels between cells within one service provider; however, sharing spectrum across different service providers is still under investigation. This paper proposes deploying a network of fixed cognitive radio (CR) nodes to maintain spectrum sharing across multiple service providers operating in the same geographical area. These CR nodes estimate the spectrum utilisation in a given area, and cooperate to provide the spectrum usage information for the overloaded infrastructures of service providers. This work discusses the implementation of the proposed CR-based spectrum sharing technique, and studies the impact of spectrum sharing on the service provider's performance. It is shown that the proposed technique reduces the call blocking rate and improves the spectrum utilisation efficiency. This technique removes the need of sensing spectrum in each user. Thus, it reduces the cost, complexity and battery power consumption of user devices.
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paper_title: What Will 5G Be?

paper_content:

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: Spectrum sharing improves the network efficiency for cellular operators

paper_content:

The article describes the potential gain by spectrum sharing between cellular operators in terms of network efficiency. The focus of the study is on a specific resource sharing scenario: spectrum sharing between two operators in cellular downlink transmission. If frequency bands are allocated dynamically and exclusively to one operator - a case called orthogonal spectrum sharing - significant gains in terms of achievable throughput (spectrum sharing gains between 50 percent and 100 percent) and user satisfaction are reported for asymmetric scenarios at link and system level as well as from two hardware demonstrators. Additionally, if frequency bands are allocated simultaneously to two operators - a case called non-orthogonal spectrum sharing - further gains are reported. In order to achieve these, different enablers from hardware technologies and base station capabilities are required. However, we argue that all requirements are fulfilled in 3GPP and newer mobile standards. Therefore, the results and conclusions of this overview article encourage to seriously consider the inter-operator spectrum sharing technologies.
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paper_title: System-Level Assessment of Non-Orthogonal Spectrum Sharing via Transmit Beamforming

paper_content:

We assess the system-level performance of non-orthogonal spectrum sharing achieved via maximum sum-rate (SR), Nash bargaining (NB), and zero-forcing (ZF) transmit beamforming techniques. A look-up table based physical layer abstraction and radio resource management mechanisms (including packet scheduling) are proposed and incorporated in system-level simulations, jointly with other important aspects of network operation. In the simulated scenarios, the results show similar system-level performance of SR (or NB) as ZF in the context of spectrum sharing, when combined with maximum sum-rate (or proportional fair) packet scheduler. Further sensitivity analysis also shows similar behavior of all three beamforming techniques with regard to the impact on system-level performance of neighbor-cell activity level and feedback error. A more important observation from our results is that, under ideal conditions, the performance enhancement of non-orthogonal spectrum sharing over orthogonal spectrum sharing and fixed spectrum assignment is significant.
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paper_title: Transmit beamforming for inter-operator spectrum sharing

paper_content:

In EU FP7 project SAPHYRE, we study the nonorthogonal spectrum sharing scenario, in which multiple operators are allowed to utilize the same frequency band in the same location and time. A major impairment in such a scenario is the interference that the cochannel transmissions create. Assuming that the transmitters are equipped with multiple antennas, we propose various transmit beamforming techniques to manage the interference. We show that efficient operating points can be reached, when the operators cooperatively design their beamforming vectors.
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paper_title: Dynamic REM towards flexible spectrum management

paper_content:

Radio Environment Maps (REM) are lately emerging as a technical enabler and facilitator of dynamic spectrum access and cognitive radio scenarios. Their usage fosters many operational wireless network procedures such as spectrum access, spectrum sharing, resource usage optimization etc. Additionally, REMs are foreseen as a supplementary tool for regulation of spectrum usage. This paper covers both theoretical and practical aspects of efficient REM system design and REM construction in general. It showcases the synergy between spectrum sensing techniques and geolocation database approaches towards accurate and up-to-date radio field estimation. Furthermore, the paper provides details on recent research advances in the area of REM construction, Radio Interference Fields (RIF) derivation, source localization and propagation modelling. Finally, it analyzes several use-cases of practical implementation of REMs proving its capabilities to serve as an enabler for flexible spectrum management in future wireless networks.
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paper_title: Radio access network virtualization for future mobile carrier networks

paper_content:

This article presents a survey of cellular network sharing, which is a key building block for virtualizing future mobile carrier networks in order to address the explosive capacity demand of mobile traffic, and reduce the CAPEX and OPEX burden faced by operators to handle this demand. We start by reviewing the 3GPP network sharing standardized functionality followed by a discussion on emerging business models calling for additional features. Then an overview of the RAN sharing enhancements currently being considered by the 3GPP RSE Study Item is presented. Based on the developing network sharing needs, a summary of the state of the art of mobile carrier network virtualization is provided, encompassing RAN sharing as well as a higher level of base station programmability and customization for the sharing entities. As an example of RAN virtualization techniques feasibility, a solution based on spectrum sharing is presented: the network virtualization substrate (NVS), which can be natively implemented in base stations. NVS performance is evaluated in an LTE network by means of simulation, showing that it can meet the needs of future virtualized mobile carrier networks in terms of isolation, utilization, and customization.
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Title: Licensed Spectrum Sharing Schemes for Mobile Operators: A Survey and Outlook

Section 1: INTRODUCTION
Description 1: Introduce the massive growth in mobile data traffic and the necessity for wider bandwidths, leading to investigating licensed spectrum sharing as a potential solution.

Section 2: Review of the State-of-the-Art (SOTA) Survey Articles
Description 2: Discuss the context of spectrum sharing, cognitive radio networks, and other relevant literature to establish the foundation of the survey.

Section 3: Contribution of This Article
Description 3: Outline the unique insights and focus of this survey on licensed spectrum sharing scenarios for mobile operators.

Section 4: TAXONOMY OF SPECTRUM ACCESS METHODS AND AUTHORISATION REGIMES
Description 4: Categorize different authorisation regimes, their characteristics, and their implications for spectrum sharing in mobile cellular systems.

Section 5: DEPLOYMENT OF LICENSED SPECTRUM SHARING SCHEMES IN MOBILE CELLULAR NETWORKS
Description 5: Introduce deployment scenarios, key use cases, and the benefits and challenges of implementing licensed spectrum sharing schemes in mobile networks.

Section 6: INTER-OPERATOR SPECTRUM SHARING
Description 6: Explore various inter-operator spectrum sharing scenarios, related regulatory approaches, and technical and business challenges associated with these schemes.

Section 7: LICENSED SHARED ACCESS (HETEROGENEOUS SHARING PLAYERS)
Description 7: Discuss the LSA framework, its deployment requirements, technical and business challenges, and scenarios where heterogeneous players share licensed spectrum.

Section 8: LESSONS LEARNED AND FURTHER WORK
Description 8: Summarize the practical insights gained from the survey, outline open challenges, and propose potential enhancements for future spectrum sharing schemes.

Section 9: CONCLUSION
Description 9: Provide a comprehensive summary of the survey, highlighting the importance of efficient spectrum sharing schemes for future cellular systems and suggesting further research directions.