MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey
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paper_title: Wireless mesh networks: a survey

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Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.
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paper_title: On-Demand Medium Access in Multihop Wireless Networks with Multiple Beam Smart Antennas

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The paper presents a detailed discussion of various issues involved in designing a medium access control (MAC) protocol for multihop wireless networks with nodes employing multiple beam smart antennas. Multiple beam smart antennas can form several beams simultaneously and can initiate concurrent transmissions or receptions .in them, thereby increasing the throughput of the bottleneck nodes. Traditional on-demand MAC protocols for omnidirectional and single beam directional antennas based on the IEEE 802.11 distributed coordination function (DCF) mechanism cannot take advantage of this unique capability of multiple beam antennas as they do not facilitate concurrent transmissions or receptions by a node. This paper introduces a novel protocol, hybrid MAC (HMAC), which enables concurrent packet reception (CPR) and concurrent packet transmission (CPT) at a node equipped with multiple beam antennas and is backward compatible with IEEE 802.11 DCF. Simulation results show the superior performance of HMAC in most ad hoc scenarios. Moreover, in some sample topologies, the throughput of HMAC is close to the theoretical maximum. The paper also presents a wireless mesh network architecture with heterogeneous antenna technologies and illustrates the advantages of employing multiple beam smart antennas and HMAC in such networks.
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paper_title: On the Use of Smart Antennas in Multi-Hop Wireless Networks

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Smart antennas include a broad range of antenna technologies ranging from the simple switched beam to the more sophisticated adaptive arrays and multiple input multiple output (MIMO) links. Their ability to exploit multiple degrees of freedom helps them operate in different strategies to achieve different objectives ranging from rate increase, range increase, transmission power reduction, and higher link reliability. While these antennas have been significantly researched at the PHY layer leading to results that are easily translatable to single-hop wireless networks, very little is understood about their use in multi-hop wireless ad-hoc networks. Specific unanswered questions in this context include: (i) what kind of performance improvements can the different technologies and their strategies provide? (ii) for each technology, which of the different possible strategies is the optimal strategy to employ for a given network condition? and (iii) for a given network setting, which of the different smart antenna technologies will deliver the best performance? In this paper, we systematically answer these questions by comprehensively evaluating the relative benefits of the different smart antenna technologies.
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paper_title: Location Estimation in Ad Hoc Networks with Directional Antennas

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With the development of location aware sensor applications, location determination has become an increasingly important middleware technology. Numerous current technologies for location determination of sensor nodes use the received signal strength from sensor nodes using omnidirectional antennas. However, an increasing number of sensor systems are now deploying directional antennas due to their advantages like energy conservation and better bandwidth utilization. In this paper, we present techniques for location determination in a sensor network with directional antennas under different kinds of deployment of the nodes. We show how the location estimation problem can be solved by measuring the received signal strength from just one or two anchors in a 2D plane with directional antennas. We implement our technique using Berkeley MICA2 sensor motes and show that it is up to three times more accurate than triangulation using omnidirectional antennas. We also perform Matlab simulations that show the accuracy of location determination with increasing node density
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paper_title: A Survey On MAC Protocols for Wireless Adhoc Networks with Beamforming Antennas

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The beamforming antenna technology is a promising solution to many challenges facing wireless ad hoc networks. Beamforming antennas have the ability to increase the spatial reuse, improve the transmission reliability, extend the transmission range and/or save the power consumption. If they are effectively used, they can significantly improve the network capacity, lifetime, connectivity and security. However, traditional Medium Access Control (MAC) protocols fail to exploit the potential benefits due to the unique characteristics of wireless ad hoc networks with beamforming antennas. To that end, numerous MAC protocols have been designed over the years to harness the offered potential. In this paper, we survey the literature on MAC protocols proposed for wireless ad hoc networks with beamforming antennas during the last decade. We discuss the main beamforming-related challenges facing the medium access control in ad hoc networks. We present taxonomy of the MAC protocols proposed in the literature based on their mode of operation and the mechanisms used to address the challenges. In addition, we provide a qualitative comparison of the protocols highlighting their features, benefits and requirements. Finally, we provide directions for possible future work.
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paper_title: Space-time processing for wireless communications

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Space-time processing can improve network capacity, coverage, and quality by reducing co-channel interference (CCI) while enhancing diversity and array gain. This article focuses largely on the receive (mobile-to-base station) time-division multiple access (TDMA) (nonspread modulation) application for high-mobility networks. We describe a large (macro) cell propagation channel and discuss different physical effects such as path loss, fading delay spread, angle spread, and Doppler spread. We also develop a signal model incorporating channel effects. Both forward-link (transmit) and reverse-link (receive) channels are considered and the relationship between the two is discussed. Single- and multiuser models are treated for four important space-time processing problems, and the underlying spatial and temporal structure are discussed as are different algorithmic approaches to reverse link space-time professing with blind and nonblind methods for single- and multiple-user cases. We cover forward-link space-time algorithms and we outline methods for estimation of multipath parameters. We also discuss applications of space-time processing to CDMA, applications of space-time techniques to current cellular systems, and industry trends.
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paper_title: On mitigating the broadcast storm problem with directional antennas

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Broadcast has been widely used in mobile ad hoc networks (MANETs) as a communication means to disseminate information to all reachable nodes. However, the conventional broadcast scheme that broadcast packets omnidirectionally suffers from several drawbacks: excessive amount of redundant traffic, exaggerated interference/contention between neighboring nodes, and limited coverage (as a result of contention/collision). This is termed as the broadcast storm problem in S.Y.Ni et al. [1999]. In this paper, we address this problem in MANETs with the use of directional antennas. We propose three schemes: on/off directional broadcast, relay-node-based directional broadcast and location-based directional broadcast, in the increasing order of implementation complexity. We implement the proposed schemes in qualnet and compare their performances against the conventional broadcast scheme. The simulation results indicate that the proposed schemes outperform the conventional omnidirectional scheme with respect to coverage, latency, and redundancy over a wide spectrum of network topology and node mobility.
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paper_title: Capacity Improvement of Wireless Ad Hoc Networks with Directional Antennae

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Network Capacity, which is limited by interference between simultaneous transmissions of neighboring links, is a fundamental performance metric for wireless ad hoc networks. Ref. [1] showed that the capacity of wireless ad hoc networks with omnidirectional antennae does not scale well as the node density increases. Other related work ([2], [3], [4], etc.) demonstrated that the network capacity scales better with the use of directional antennae. Most previous investigations, however, were based on simplified but unrealizable models of antenna patterns. So far, there has not been a general framework for the analysis of network capacity when directional antennae of realizable generic patterns are used. Also, few papers have derived explicitly the impact of nulls and null-width in antenna pattern on network scalability. Specifically, the scale law of network capacity with general directional antennae has not yet been investigated. This paper addresses these issues. We study arbitrary and random networks (corresponding to the best case and random case respectively), where nodes with smart antennae are assumed to be located in a planar disk without mobility. We also point out how to generalize the result to that of generic directional antenna pattern. To conserve space here, we defer detailed analysis of the impact of null-width to the full paper.
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paper_title: Capacity of Ad Hoc wireless networks

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Early simulation experience with wireless ad hoc networks suggests that their capacity can be surprisingly low, due to the requirement that nodes forward each others' packets. The achievable capacity depends on network size, traffic patterns, and detailed local radio interactions. This paper examines these factors alone and in combination, using simulation and analysis from first principles. Our results include both specific constants and general scaling relationships helpful in understanding the limitations of wireless ad hoc networks. We examine interactions of the 802.11 MAC and ad hoc forwarding and the effect on capacity for several simple configurations and traffic patterns. While 802.11 discovers reasonably good schedules, we nonetheless observe capacities markedly less than optimal for very simple chain and lattice networks with very regular traffic patterns. We validate some simulation results with experiments. We also show that the traffic pattern determines whether an ad hoc network's per node capacity will scale to large networks. In particular, we show that for total capacity to scale up with network size the average distance between source and destination nodes must remain small as the network grows. Non-local traffic-patterns in which this average distance grows with the network size result in a rapid decrease of per node capacity. Thus the question “Are large ad hoc networks feasible?” reduces to a question about the likely locality of communication in such networks.
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paper_title: On Connectivity in Ad Hoc Network under Jamming Using Directional Antennas and Mobility

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In this paper we investigate the problem of maintaining connectivity under jamming in multihop ad hoc wireless networks. Connectivity is measured using a connectivity index, which indicates the probability that there exists a path between two nodes. We first show that connectivity can be drastically reduced with a relatively small number of jammers. We show that using sectored antennas can maintain connectivity in the presence of a significantly higher number of jammers at the expense of higher average number of hops. Finally, we show that mobility allows further resiliency to jamming.
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paper_title: Asymptotic connectivity in wireless ad hoc networks using directional antennas

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Connectivity is a crucial issue in wireless ad hoc networks (WANETs). Gupta and Kumar have shown that in WANETs using omnidirectional antennas, the critical transmission range to achieve asymptotic connectivity is O(radic(log n/n)) if n nodes are uniformly and independently distributed in a disk of unit area. In this paper, we investigate the connectivity problem when directional antennas are used. We first assume that each node in the network randomly beam forms in one beam direction. We find that there also exists a critical transmission range for a WANET to achieve asymptotic connectivity, which corresponds to a critical transmission power (CTP). Since CTP is dependent on the directional antenna pattern, the number of beams, and the propagation environment, we then formulate a non-linear programming problem to minimize the CTP. We show that when directional antennas use the optimal antenna pattern, the CTP in a WANET using directional antennas at both transmitter and receiver is smaller than that when either transmitter or receiver uses directional antenna and is further smaller than that when only omnidirectional antennas are used. Moreover, we revisit the connectivity problem assuming that two neighboring nodes using directional antennas can be guaranteed to beam form to each other to carry out the transmission. A smaller critical transmission range than that in the previous case is found, which implies smaller CTP.
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paper_title: A survey, classification and comparative analysis of medium access control protocols for ad hoc networks

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Recent technological advances in wireless communications offer new opportunities and challenges for wireless ad hoc networking. In the absence of the fixed infrastructure that characterizes traditional wireless networks, control and management of wireless ad hoc networks must be distributed across the nodes, thus requiring carefully designed medium access control (MAC) layer protocols. In this article we survey, classify, and analyze 34 MAC layer protocols for wireless ad hoc networks, ranging from industry standards to research proposals. Through this analysis, six key features emerge: (1) channel separation and access; (2) topology; (3) power; (4) transmission initiation; (5) traffic load and scalability; and (6) range. These features allow us to characterize and classify the protocols, to analyze the tradeoffs produced by different design decisions, and to assess the suitability of various design combinations for ad hoc network applications. The classification and the tradeoff analysis yield design guidelines for future wireless ad hoc network MAC layer protocols.
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paper_title: MACAW: a media access protocol for wireless LAN's

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In recent years, a wide variety of mobile computing devices has emerged, including portables, palmtops, and personal digital assistants. Providing adequate network connectivity for these devices will require a new generation of wireless LAN technology. In this paper we study media access protocols for a single channel wireless LAN being developed at Xerox Corporation's Palo Alto Research Center. We start with the MACA media access protocol first proposed by Karn [9] and later refined by Biba [3] which uses an RTS-CTS-DATA packet exchange and binary exponential back-off. Using packet-level simulations, we examine various performance and design issues in such protocols. Our analysis leads to a new protocol, MACAW, which uses an RTS-CTS-DS-DATA-ACK message exchange and includes a significantly different backoff algorithm.
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paper_title: Wireless medium access control protocols

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Technological advances, coupled with the flexibility and mobility of wireless systems, are the driving force behind the Anyone, Anywhere, Anytime paradigm of networking. At the same time, we see a convergence of the telephone, cable and data networks into a unified network that supports multimedia and real-time applications like voice and video in addition to data. Medium access control protocols define rules for orderly access to the shared medium and play a crucial role in the efficient and fair sharing of scarce wireless bandwidth. The nature of the wireless channel brings new issues like location-dependent carrier sensing, time varying channel and burst errors. Low power requirements and half duplex operation of the wireless systems add to the challenge. Wireless MAC protocols have been heavily researched and a plethora of protocols have been proposed. Protocols have been devised for different types of architectures, different applications and different media. This survey discusses the challenges in the design of wireless MAC protocols, classifies them based on architecture and mode of operation, and describes their relative performance and application domains in which they are best deployed.
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paper_title: Medium Access Control protocols for ad hoc wireless networks : A survey

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Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work.
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paper_title: Enhancing the performance of medium access control for WLANs with multi-beam access point

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Wireless LANs with multi-beam directional antennas have received intensive attention lately due to the potential gain in throughput performance. However, when the multi-beam directional antennas are introduced in this system, the ever popular contention-based medium access control protocol such as IEEE 802.11 MAC is no longer effective, and many challenging problems, such as beam-synchronization problem, beam-overlapping problem, mobility and receiver blocking problem (deafness problem), need to be resolved. In this paper, we propose a novel MAC protocol to carefully address these problems. In addition to improving communication efficiency, we also consider the backward compatibility in our design, whereby an IEEE 802.11 terminal can transparently access a multi-beam access point. Furthermore, we present an analytical model to evaluate the performance of multi-beam wireless LANs. Extensive simulation studies are used to validate the analytical model and show that our scheme can significantly improve the throughput performance
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paper_title: On designing MAC protocols for wireless networks using directional antennas

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We investigate the possibility of using directional antennas for medium access control in wireless ad hoc networks. Previous research in ad hoc networks typically assumes the use of omnidirectional antennas at all nodes. With omnidirectional antennas, while two nodes are communicating using a given channel, MAC protocols such as IEEE 802.11 require all other nodes in the vicinity to remain silent. With directional antennas, two pairs of nodes located in each other's vicinity may potentially communicate simultaneously, increasing spatial reuse of the wireless channel. Range extension due to higher gain of directional antennas can also be useful in discovering fewer hop routes. However, new problems arise when using directional beams that simple modifications to 802.11 may not be able to mitigate. This paper identifies these problems and evaluates the tradeoffs associated with them. We also design a directional MAC protocol (MMAC) that uses multihop RTSs to establish links between distant nodes and then transmits CTS, DATA, and ACK over a single hop. While MMAC does not address all the problems identified with directional communication, it is an attempt to exploit the primary benefits of beamforming in the presence of some of these problems. Results show that MMAC can perform better than IEEE 802.11, although we find that the performance is dependent on the topology and flow patterns in the system.
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paper_title: Enhancing the performance of medium access control for WLANs with multi-beam access point

paper_content:

Wireless LANs with multi-beam directional antennas have received intensive attention lately due to the potential gain in throughput performance. However, when the multi-beam directional antennas are introduced in this system, the ever popular contention-based medium access control protocol such as IEEE 802.11 MAC is no longer effective, and many challenging problems, such as beam-synchronization problem, beam-overlapping problem, mobility and receiver blocking problem (deafness problem), need to be resolved. In this paper, we propose a novel MAC protocol to carefully address these problems. In addition to improving communication efficiency, we also consider the backward compatibility in our design, whereby an IEEE 802.11 terminal can transparently access a multi-beam access point. Furthermore, we present an analytical model to evaluate the performance of multi-beam wireless LANs. Extensive simulation studies are used to validate the analytical model and show that our scheme can significantly improve the throughput performance
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paper_title: A Survey On MAC Protocols for Wireless Adhoc Networks with Beamforming Antennas

paper_content:

The beamforming antenna technology is a promising solution to many challenges facing wireless ad hoc networks. Beamforming antennas have the ability to increase the spatial reuse, improve the transmission reliability, extend the transmission range and/or save the power consumption. If they are effectively used, they can significantly improve the network capacity, lifetime, connectivity and security. However, traditional Medium Access Control (MAC) protocols fail to exploit the potential benefits due to the unique characteristics of wireless ad hoc networks with beamforming antennas. To that end, numerous MAC protocols have been designed over the years to harness the offered potential. In this paper, we survey the literature on MAC protocols proposed for wireless ad hoc networks with beamforming antennas during the last decade. We discuss the main beamforming-related challenges facing the medium access control in ad hoc networks. We present taxonomy of the MAC protocols proposed in the literature based on their mode of operation and the mechanisms used to address the challenges. In addition, we provide a qualitative comparison of the protocols highlighting their features, benefits and requirements. Finally, we provide directions for possible future work.
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paper_title: MACAW: a media access protocol for wireless LAN's

paper_content:

In recent years, a wide variety of mobile computing devices has emerged, including portables, palmtops, and personal digital assistants. Providing adequate network connectivity for these devices will require a new generation of wireless LAN technology. In this paper we study media access protocols for a single channel wireless LAN being developed at Xerox Corporation's Palo Alto Research Center. We start with the MACA media access protocol first proposed by Karn [9] and later refined by Biba [3] which uses an RTS-CTS-DATA packet exchange and binary exponential back-off. Using packet-level simulations, we examine various performance and design issues in such protocols. Our analysis leads to a new protocol, MACAW, which uses an RTS-CTS-DS-DATA-ACK message exchange and includes a significantly different backoff algorithm.
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paper_title: Deafness: a MAC problem in ad hoc networks when using directional antennas

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This work addresses deafness - a problem that appears when MAC protocols are designed using directional antennas. Briefly, deafness is caused when a transmitter fails to communicate to its intended receiver, because the receiver is beamformed towards a direction away from the transmitter. Existing CSMA/CA protocols rely on the assumption that congestion is the predominant cause of communication failure, and adopt backoff schemes to handle congestion. While this may be appropriate for omnidirectional antennas, for directional antennas, both deafness and congestion can be the reason for communication failures. An appropriate directional MAC protocol needs to classify the actual cause of failure, and react accordingly. This paper quantifies the impact of deafness on directional medium access control, and proposes a tone-based mechanism as one way of addressing deafness. The tone-based mechanism, ToneDMAC, assumes congestion as the default reason for communication failures, and applies a corrective measure whenever the cause is deafness. Simulation results indicate that ToneDMAC can alleviate deafness, and perform better than existing directional MAC protocols.
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paper_title: The deafness problems and solutions in wireless ad hoc networks using directional antennas

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This paper addresses the issue of deafness in directional antennas for wireless ad hoc networks. Deafness is caused when a node X repeatedly attempts to communicate with node Y but is unsuccessful, because Y is presently tuned to some other antenna beam. In this paper, we first outline the different factors which contribute to such deafness in directional antennas and its significant impact on network performance. We then propose two schemes to overcome deafness scenarios which are transparent to the underlying directional MAC protocol in use. In addition, we also claim that IEEE 802.11 short retry limit (SRL) needs a special handling in directional environment because of the presence of deafness. We have done a detailed performance evaluation of our schemes with different directional MAC protocols running over switched beam antennas and the initial results are found to be very promising.
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paper_title: Using Directional Antennas for Medium Access Control in Ad Hoc Networks

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A composition for use in the treatment for developing seedless fleshy berry of grapes. By treating the flower bunches of a grape tree with a composition containing gibberellin and cyclic 3',5'-adenylic acid in the form of an aqueous solution, it became possible to make seedless fleshy berry from grape trees belonging to varieties other than Delaware, namely belonging to Campbell-Arley, Berry A, Niagara, Kyoho, etc., from which seedless fleshy berry cannot be made by the conventional treatment with gibberellin.
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paper_title: QoS Provisioning for Wireless LANs With Multi-Beam Access Point

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Recently, the integration of smart antenna technology into existing wireless local area networks (WLANs) has been one of the hot spots of research work. In this paper, we design an IEEE 802.11-compliant medium access control (MAC) protocol, named M-HCCA, that fully takes advantage of multi-beam smart antennas equipped at the access point (AP) to not only boost the overall capacity of a WLAN, but also support quality-of-service (QoS) and power conservation for individual mobile users. Specifically, M-HCCA has the following attractive features: (i) since being a polling-based MAC scheme, M-HCCA can innately conquer the problems induced by carrier sensing or directional signals, including beam-synchronization constraint, receiver blocking problem, and unnecessary defer problem; (ii) M-HCCA achieves high real-time throughput by adaptively adjusting the sector configuration to quickly resolve contention/collision and to increase data transmission parallelism; (iii) M-HCCA employs beam-location-aware polling scheduling to not only solve the beam-overlapping problem and back/side-lobe problem, but also let real-time stations save as much energy as possible; (iv) M-HCCA adopts the mobile-assisted admission control technique such that the AP can admit as many newly streams as possible while not violating QoS guarantees made to already-admitted streams; (v) M-HCCA offers a location updating mechanism to promptly renew the beam-location information of a non-responsive station such that the miss-hit problem can be effectively alleviated. Extensive simulation results show that, in terms of throughput, real-time throughput, and energy throughput, M-HCCA significantly outperforms existing protocols even in uneven station distribution, imperfect beam-forming, and high mobility environments.
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paper_title: An Opportunistic Directional MAC Protocol for Multihop Wireless Networks with Switched Beam Directional Antennas

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Directional antennas in multihop wireless networks offer a potential increase in the spatial reuse of the wireless channel. However, existing directional MAC protocols are not capable of fully exploiting this essential benefit. In this paper, we propose OPDMAC which is an opportunistic directional MAC protocol that is motivated by the possibility of achieving higher spatial reuse. The proposed protocol is novel in its backoff mechanism with directional antennas. If a node is forced to backoff due to a missing CTS or acknowledgement in one direction, OPDMAC explores transmission opportunity in other directions. This minimizes the idle wait time of the wireless channel and increase the channel utilization. In addition, OPDMAC is found to decrease the effect of deafness without additional control overhead. Our simulation results show that OPDMAC outperforms existing directional MAC protocols in terms of throughput, delay and fairness.
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paper_title: Smart Antenna Systems for Mobile Communications

paper_content:

Note: 110 pages Reference LEMA-REPORT-2009-001 Record created on 2009-09-11, modified on 2016-08-08
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paper_title: A Survey On MAC Protocols for Wireless Adhoc Networks with Beamforming Antennas

paper_content:

The beamforming antenna technology is a promising solution to many challenges facing wireless ad hoc networks. Beamforming antennas have the ability to increase the spatial reuse, improve the transmission reliability, extend the transmission range and/or save the power consumption. If they are effectively used, they can significantly improve the network capacity, lifetime, connectivity and security. However, traditional Medium Access Control (MAC) protocols fail to exploit the potential benefits due to the unique characteristics of wireless ad hoc networks with beamforming antennas. To that end, numerous MAC protocols have been designed over the years to harness the offered potential. In this paper, we survey the literature on MAC protocols proposed for wireless ad hoc networks with beamforming antennas during the last decade. We discuss the main beamforming-related challenges facing the medium access control in ad hoc networks. We present taxonomy of the MAC protocols proposed in the literature based on their mode of operation and the mechanisms used to address the challenges. In addition, we provide a qualitative comparison of the protocols highlighting their features, benefits and requirements. Finally, we provide directions for possible future work.
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paper_title: SYN-DMAC: a directional MAC protocol for ad hoc networks with synchronization

paper_content:

Directional antenna has received intensive research interests in recent years due to its potential to increase communication efficiency and resilience to interference and jamming. In this paper, we provide a novel directional MAC protocol termed SYN-DMAC for ad hoc networks with synchronization. We demonstrate our proposed SYN-DMAC can efficiently address the major open problems in the directional MAC design such as the deafness problem, the hidden terminal problem, the exposed terminal problem and the head-of-line (HOL) blocking problem. Preliminary simulation results show that our scheme significantly improves throughput in comparison with IEEE 802.11 MAC protocol
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paper_title: A MAC protocol based on adaptive beamforming for ad hoc networks

paper_content:

This paper presents a novel slotted MAC (medium access control) protocol for nodes equipped with adaptive antenna array in ad hoc network. The protocol relies on the ability of antenna to uses DOA (direction-of-arrival) information to beamform by placing nulls in the direction of interferers thus maximize SINR (signal to interference and noise ratio) at the receiver. We studied the performance of the protocol using joint simulation in OPNET and Matlab. We studied the impact of variable number of antenna elements, DOA algorithm, and nulling. The performance of our new protocol is compared against one of the recent directional MAC protocols [R.R.N.H.V. Romit Roy Choudhury, Xue Yang, 2002]. We observe that despite the simplicity of our protocol it achieves high throughput.
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paper_title: Adaptive rate control with chip discrimination in UWB networks

paper_content:

A fundamental concern of any ad-hoc network is the mitigation of potential near/far power disparities that can occur anytime a node is communicating with a distant node in the presence of very close interfering transmitters. In this paper, we present a technique for adjusting the number of chips/bit to maximize throughput in such poor near/far power ratio environments. The technique leverages information derived from our chip discrimination approach, and also exploits the low duty cycle nature of ultra-wideband (UWB) radio. We present this simple method for detection of near pulse interference and develop it as one component for a peer-to-peer MAC layer protocol, to effect more efficient transmission rate control using only locally derived input. We demonstrate the efficacy of the technique using simulation in bursty, pulse limited environments. The technique provides improved throughput compared to fixed parameter links and equivalent theoretical M|D|1 queues.
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paper_title: Reservation-Based Directional Medium Access Control (RDMAC) Protocol for Multi-Hop Wireless Networks with Directional Antennas

paper_content:

In this paper, we study the issues of medium access control (MAC) mechanisms for multi-hop wireless networks with directional antennas. Specifically, we explore the location-dependent carrier sensing problem and the interference problem caused by the minor lobes of antennas. Existing solutions to directional antenna MAC problems rarely account for the impact of minor lobes and typically assume that the neighboring nodes' locations are known a priori. As a result, they are not applicable to practical systems or to mobile nodes. In this paper, we propose a Reservation-based Directional MAC (RDMAC) protocol for multi-hop wireless networks with directional antenna. This mechanism operates in sessions. Each session comprises two periods, namely, a reservation period and a transmission period. The reservation period is further composed of a set of two phases, namely, a probing phase and a beam-indication phase. The mechanism is designed to reduce the interference among neighboring nodes and to increase the network throughput. The performance of the proposed mechanism is evaluated analytically and via the ns2 simulator. The results show that our mechanism outperforms existing solutions in terms of higher throughput and lower delay.
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paper_title: Medium access control in ad hoc networks with MIMO links: optimization considerations and algorithms

paper_content:

we present a medium access control (MAC) protocol for ad hoc networks with multiple input multiple output (MIMO) links. MIMO links provide extremely high spectral efficiencies in multipath channels by simultaneously transmitting multiple independent data streams in the same channel. MAC protocols have been proposed in related work for ad hoc networks with other classes of smart antennas such as switched beam antennas. However, as we substantiate in the paper, the unique characteristics of MIMO links coupled with several key optimization considerations, necessitate an entirely new MAC protocol. We identify several advantages of MIMO links, and discuss key optimization considerations that can help in realizing an effective MAC protocol for such an environment. We present a centralized algorithm called stream-controlled medium access (SCMA) that has the key optimization considerations incorporated in its design. Finally, we present a distributed SCMA protocol that approximates the centralized algorithm and compare its performance against that of baseline protocols that are CSMA/CA variants.
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paper_title: A novel MAC protocol for wireless network using multi-beam directional antennas

paper_content:

The use of directional antennas in wireless networks has received growing attention because of its high spatial reuse and high antenna gains. The Medium Access Control(MAC) protocol with directional antennas is nontrivial due to the limitations in wireless environment. The existing protocols commonly assume that the nodes can operate in both directional and omni-directional modes. In this paper, we propose a new MAC protocol for multi-beam directional antennas. In the protocol, each beam-sector has its own control channel, thus the communications among different beam-sectors are independent. It uses the directional network allocation vector(DNAV) to record the establishment processes. After sensing all the sectors of the multi-beam antenna, it uses the global assignment strategy to assign the directional communication channels. Extensive simulation results show that our protocol can significantly improve the throughput of an entire wireless network at the expense of the slightly increased RTS/DRTS requests in the establishment process.
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paper_title: On-Demand Medium Access in Multihop Wireless Networks with Multiple Beam Smart Antennas

paper_content:

The paper presents a detailed discussion of various issues involved in designing a medium access control (MAC) protocol for multihop wireless networks with nodes employing multiple beam smart antennas. Multiple beam smart antennas can form several beams simultaneously and can initiate concurrent transmissions or receptions .in them, thereby increasing the throughput of the bottleneck nodes. Traditional on-demand MAC protocols for omnidirectional and single beam directional antennas based on the IEEE 802.11 distributed coordination function (DCF) mechanism cannot take advantage of this unique capability of multiple beam antennas as they do not facilitate concurrent transmissions or receptions by a node. This paper introduces a novel protocol, hybrid MAC (HMAC), which enables concurrent packet reception (CPR) and concurrent packet transmission (CPT) at a node equipped with multiple beam antennas and is backward compatible with IEEE 802.11 DCF. Simulation results show the superior performance of HMAC in most ad hoc scenarios. Moreover, in some sample topologies, the throughput of HMAC is close to the theoretical maximum. The paper also presents a wireless mesh network architecture with heterogeneous antenna technologies and illustrates the advantages of employing multiple beam smart antennas and HMAC in such networks.
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paper_title: QoS Provisioning for Wireless LANs With Multi-Beam Access Point

paper_content:

Recently, the integration of smart antenna technology into existing wireless local area networks (WLANs) has been one of the hot spots of research work. In this paper, we design an IEEE 802.11-compliant medium access control (MAC) protocol, named M-HCCA, that fully takes advantage of multi-beam smart antennas equipped at the access point (AP) to not only boost the overall capacity of a WLAN, but also support quality-of-service (QoS) and power conservation for individual mobile users. Specifically, M-HCCA has the following attractive features: (i) since being a polling-based MAC scheme, M-HCCA can innately conquer the problems induced by carrier sensing or directional signals, including beam-synchronization constraint, receiver blocking problem, and unnecessary defer problem; (ii) M-HCCA achieves high real-time throughput by adaptively adjusting the sector configuration to quickly resolve contention/collision and to increase data transmission parallelism; (iii) M-HCCA employs beam-location-aware polling scheduling to not only solve the beam-overlapping problem and back/side-lobe problem, but also let real-time stations save as much energy as possible; (iv) M-HCCA adopts the mobile-assisted admission control technique such that the AP can admit as many newly streams as possible while not violating QoS guarantees made to already-admitted streams; (v) M-HCCA offers a location updating mechanism to promptly renew the beam-location information of a non-responsive station such that the miss-hit problem can be effectively alleviated. Extensive simulation results show that, in terms of throughput, real-time throughput, and energy throughput, M-HCCA significantly outperforms existing protocols even in uneven station distribution, imperfect beam-forming, and high mobility environments.
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paper_title: Enhancing the performance of medium access control for WLANs with multi-beam access point

paper_content:

Wireless LANs with multi-beam directional antennas have received intensive attention lately due to the potential gain in throughput performance. However, when the multi-beam directional antennas are introduced in this system, the ever popular contention-based medium access control protocol such as IEEE 802.11 MAC is no longer effective, and many challenging problems, such as beam-synchronization problem, beam-overlapping problem, mobility and receiver blocking problem (deafness problem), need to be resolved. In this paper, we propose a novel MAC protocol to carefully address these problems. In addition to improving communication efficiency, we also consider the backward compatibility in our design, whereby an IEEE 802.11 terminal can transparently access a multi-beam access point. Furthermore, we present an analytical model to evaluate the performance of multi-beam wireless LANs. Extensive simulation studies are used to validate the analytical model and show that our scheme can significantly improve the throughput performance
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paper_title: On the Design of MAC Protocols for Multi-Packet Communication in IEEE 802.11 Heterogeneous Networks Using Adaptive Antenna Arrays

paper_content:

This paper discusses the design requirements for enabling multiple simultaneous peer-to-peer communications in IEEE 802.11 asynchronous networks in the presence of adaptive antenna arrays, and proposes two novel access schemes to realize multi-packet communication (MPC). Both presented solutions, which rely on the information acquired by each node during the monitoring of the network activity, are suitable for distributed and heterogeneous scenarios, where nodes equipped with different antenna systems can coexist. The first designed scheme, called threshold access MPC (TAMPC), is based on a threshold on the load sustainable by the single-node, while the second protocol, called signal-to-interference ratio (SIR) access MPC (SAMPC), is based on an accurate estimation of the SIR and on the adoption of low density parity check codes. Both protocols, which are designed to be backward compatible with the 802.11 standard, are numerically tested in realistic scenarios. Furthermore, the performance of the two schemes is compared to the theoretical one and to that of the 802.11n extension in a mobile environment.
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paper_title: Exploiting Multiple Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks.

paper_content:

Multi-Beam Antennas (MBAs) have two main characteristics: the Multi-Packet Transmission (MPT) capability and the Multi-Packet Reception (MPR) capability whereby a node can transmit/receive multiple packets at the same time. In this paper, we provide an analysis of how this MPT/MPR capability can be used to reduce the end-to-end delay in ad hoc networks. We formulate the delay reduction issue as an optimization problem. Simulations show that in order to exploit the full potential of MBAs for delay reduction, the scheduling of links has to promote the formation of star nodes and keep the formation of bridges to a minimum; which leads to the selection of routes that very often are not the shortest. We also show that using only the shortest routes has a negative impact on the delay.
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paper_title: Topology control in aerial multi-beam directional networks

paper_content:

In multi-beam directional networks, nodes are able to simultaneously transmit to all neighbors or receive from all neighbors. This spatial reuse allows for high throughputs, but in dense networks can cause significant interference. Topology control (i.e., selecting a subset of neighbors to communicate with) is vital to reduce the interference. Good topology control balances the number of links utilized to achieve fewer collisions while maintaining robust network connectivity. In this work, we discuss the underlying challenges to topology control in multi-beam direction networks. Two topology control algorithms are developed: a centralized algorithm that retains robust connectivity at the cost of reduced throughput, and a distributed algorithm that offers higher throughput but with fewer links in the network. The performance of these algorithms is demonstrated by simulation using real beam patterns from a seven-element uniform linear array.
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paper_title: Exploiting Multi-Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks

paper_content:

A Multi-Beam Antenna (MBA) can be defined as a set of directional radio transceivers. These transceivers are facing different directions to prevent signal interference with each other. MBA nodes have two main characteristics: the Multi-Packet Transmission (MPT) capability and the Multi-Packet Reception (MPR) capability whereby a node can transmit/receive multiple packets at the same time. In this paper, we provide an analysis of how this MPT/MPR capability can be used to reduce the end-to-end delay for delivered packets in ad hoc networks. Taking beam considerations (determination of the beam in which neighbors are located) into account, we formulate the delay reduction issue as an optimization problem that we solve. Our results show that to maximally exploit the full potential of MBAs for delay reduction, the scheduling of links has to promote the formation of star nodes and keep the formation of bridges to a minimum; all of which leads to the selection of routes that very often are not the shortest. In fact, using only the shortest routes has a negative impact on the delay. However, the optimal link scheduling comes at the expense of a higher overhead in terms of the total number of packet transmissions. Furthermore, the beamwidth has a direct and significant impact on the end-to-end delay and the computation time.
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paper_title: Uncoordinated MAC for Adaptive Multi-Beam Directional Networks: Analysis and Evaluation

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In this paper, we consider medium access control (MAC) policies for emerging systems that are equipped with fully digital antenna arrays which are capable of adaptive multi-beam directional communications. With this technology, a user can form multiple simultaneous transmit or receive beams, allowing for greater spatial reuse and higher network throughput. The enabling technology that we consider is the ability to use digital post-processing to form multiple receive beams in real-time without a priori knowledge of the time and angle-of-arrival of the transmission. We present a novel unslotted, uncoordinated ALOHA-like random access MAC policy for multi-beam directional systems that asymptotically achieves the capacity of the network. Such an approach is particularly useful for systems where propagation delay makes the overhead associated with any sort of coordination prohibitive. We also consider the impact of numerous practical considerations including power constraints, latency, and beamwidth on the performance of our MAC policy.
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paper_title: Complementary beamforming: new approaches

paper_content:

Smart antenna technology can greatly improve the coverage radius of wireless systems by focusing the transmitted signal (beam) toward desired users. However, beamforming has an important side effect as it creates a region, herein referred to as the complementary region, where some users in the network cannot sense the directional signals (beams). We have referred to this as the hidden beam problem in Tarokh et al.. From a physical layer perspective, beamforming reduces cochannel interference (CCI). However, in systems that use medium access-control techniques such as the carrier-sense multiple access (CSMA) protocol in wireless local area networks, during a busy period of the channel, the users in the complementary region may wrongly decide that the medium is idle and transmit packets. This may cause CCI, unnecessary retransmissions, subsequent backoff, and increased network latency. We introduced the concept of complementary beamforming (CBF) to address this issue in Tarokh et al.. In this paper, we propose two new methods, called "subspace complementary beamforming " (SCBF) and "complementary superposition beamforming" (CSBF). The SCBF uses dummy data to ensure a controlled level of received energy in all directions of eigenvectors unused by downlink beamforming. The technique works in multipath fading channels. The approach achieves similar results to those reported in Tarokh et al.. However, it enables the second technique (CSBF) which can also send data content in the complementary beam. This allows passive nodes in the network to receive "broadcast" information, while the active nodes are engaged in the exchange of user-specific data. It is shown that CBF effects can be achieved simply by increasing the transmit power of only one of antenna elements when space-division multiple access is not applied. Simulations are provided in order to quantify overall network performance improvements when using CBF, confirming significant throughput and delay performance enhancements.
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paper_title: A novel MAC layer protocol for space division multiple access in wireless ad hoc networks

paper_content:

Recently, MAC protocols using directional antennas for wireless ad hoc networks that are based on and similar to IEEE 802.11 type WLAN have been proposed. These protocols, however, are unable to attain substantial performance improvements because they do not enable the nodes to perform multiple simultaneous transmissions/receptions. In this paper, we propose a MAC layer protocol that exploits space division multiple access, thus using the property of directional reception to receive more than one packet from spatially separated transmitter nodes (equipped with smart antenna systems). Our simulation results show that drastic throughput improvements may be achieved through this scheme.
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paper_title: Transmission scheduling in ad hoc networks with directional antennas

paper_content:

Directional antennas can adaptively select radio signals of interest in specific directions, while filtering out unwanted interference from other directions. Although a couple of medium access protocols based on random access schemes have been proposed for networks with directional antennas, they suffer from high probability of collisions because of their dependence on omnidirectional mode for the transmission or reception of control packets in order to establish directional links. We propose a distributed receiver-oriented multiple access (ROMA) channel access scheduling protocol for ad hoc networks with directional antennas, each of which can form multiple beams and commence several simultaneous communication sessions. Unlike random access schemes that use on-demand handshakes or signal scanning to resolve communication targets, ROMA determines a number of links for activation in every time slot using only two-hop topology information. It is shown that significant improvements on network throughput and delay can be achieved by exploiting the multi-beam forming capability of directional antennas in both transmission and reception. The performance of ROMA is studied by simulations, and compared with a well-know static scheduling scheme that is based on global topology information.
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paper_title: Multibeam Antenna Technologies for 5G Wireless Communications

paper_content:

With the demanding system requirements for the fifth-generation (5G) wireless communications and the severe spectrum shortage at conventional cellular frequencies, multibeam antenna systems operating in the millimeter-wave frequency bands have attracted a lot of research interest and have been actively investigated. They represent the key antenna technology for supporting a high data transmission rate, an improved signal-to-interference-plus-noise ratio, an increased spectral and energy efficiency, and versatile beam shaping, thereby holding a great promise in serving as the critical infrastructure for enabling beamforming and massive multiple-input multiple-output (MIMO) that boost the 5G. This paper provides an overview of the existing multibeam antenna technologies which include the passive multibeam antennas (MBAs) based on quasi-optical components and beamforming circuits, multibeam phased-array antennas enabled by various phase-shifting methods, and digital MBAs with different system architectures. Specifically, their principles of operation, design, and implementation, as well as a number of illustrative application examples are reviewed. Finally, the suitability of these MBAs for the future 5G massive MIMO wireless systems as well as the associated challenges is discussed.
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paper_title: On-Demand Medium Access in Multihop Wireless Networks with Multiple Beam Smart Antennas

paper_content:

The paper presents a detailed discussion of various issues involved in designing a medium access control (MAC) protocol for multihop wireless networks with nodes employing multiple beam smart antennas. Multiple beam smart antennas can form several beams simultaneously and can initiate concurrent transmissions or receptions .in them, thereby increasing the throughput of the bottleneck nodes. Traditional on-demand MAC protocols for omnidirectional and single beam directional antennas based on the IEEE 802.11 distributed coordination function (DCF) mechanism cannot take advantage of this unique capability of multiple beam antennas as they do not facilitate concurrent transmissions or receptions by a node. This paper introduces a novel protocol, hybrid MAC (HMAC), which enables concurrent packet reception (CPR) and concurrent packet transmission (CPT) at a node equipped with multiple beam antennas and is backward compatible with IEEE 802.11 DCF. Simulation results show the superior performance of HMAC in most ad hoc scenarios. Moreover, in some sample topologies, the throughput of HMAC is close to the theoretical maximum. The paper also presents a wireless mesh network architecture with heterogeneous antenna technologies and illustrates the advantages of employing multiple beam smart antennas and HMAC in such networks.
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Title: MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey

Section 1: Introduction
Description 1: Provide an introduction to the topic and the purpose of the paper.

Section 2: Multi-Beam Smart Antennas
Description 2: Discuss the basics and benefits of multi-beam smart antennas in wireless mesh networks.

Section 3: Medium Access Control (MAC)
Description 3: Describe the role of MAC in wireless networks and the classification of MAC protocols.

Section 4: MAC Design Challenges for Beamforming Antennas
Description 4: Present the major challenges in designing MAC protocols for beamforming antennas.

Section 5: MAC Protocols Classification
Description 5: Classify the MAC protocols in literature for wireless mesh networks with multi-beam antennas.

Section 6: Classic MAC Protocol Designs
Description 6: Present several classic MAC protocols to address the design challenges for wireless mesh networks with multi-beam antennas.

Section 7: Discussions
Description 7: Discuss various issues relevant to the MAC protocols for wireless mesh networks using multi-beam antennas.

Section 8: Conclusion
Description 8: Summarize the findings and contributions of the paper, and suggest potential future work.