Wireless Mesh Networks (WMNs) are dynamically self-organized and self-configured, where the nodes in the network automatically establish an ad hoc network and maintain mesh connectivity. These properties make WMNs a key technology for next generation wireless networking. However, supporting Quality of Service (QoS) to enable multimedia services is still one of the major issues in next-generation WMNs. In distributed systems like WMNs, the Medium Access Control (MAC) layer is considered very important in the IEEE 802.11-based wireless networks, as it supports many crucial operational functions. Hence, QoS support in WMNs can be enhanced through the efficient cross-layer design of MAC protocols that utilizes advanced physical layer technologies viz Multiple-Input Multiple-Output (MIMO) with its multiple spatial channels that are capable of simultaneous receive or transmit streams. MIMO has become a very attractive technology in providing support for different QoS requirements. In this thesis we propose a novel QoS MIMO-aware MAC Protocol (QMMP). QMMP is a MAC protocol framework that exploits the MIMO system gains to boost QoS support. The proposed MAC framework includes the following components. The first component enables concurrent sharing of the increased MIMO bandwidth, i.e., instead of allocating all the spatial channels to one connection, connections can concurrently share the increase bandwidth via splitting the spatial channels. The second component reduces the medium access collisions problem. In distributed systems like WMNs, medium access collisions have a noticeably negative impact on resource (bandwidth) utilization as they leave the bandwidth unutilized for a long time. To address this problem, we propose a spatial channels sharing scheme during medium contention period. The third component boosts the bandwidth utilization during data transmission. We propose resource management schemes that adapt the physical data rate and the aggregation frame length according to the instantaneous channel quality. Then we propose a QoS-aware bandwidth provisioning mechanism that performs effective bandwidth distribution to further boost QoS support.

The next-generation wireless networks are expected to integrate diverse network architectures and various wireless access technologies to provide a robust solution for ubiquitous broadband wireless access, such as wireless local area networks (WLANs), Ultra-Wideband (UWB), and millimeter-wave (mmWave) based wireless personal area networks (WPANs), etc. To enhance the spectral efficiency and link reliability, smart antenna systems have been proposed as a promising candidate for future broadband access networks. To effectively exploit the increased capabilities of the emerging wireless networks, the different network characteristics and the underlying physical layer features need to be considered in the medium access control (MAC) design, which plays a critical role in providing efficient and fair resource sharing among multiple users. In this thesis, we comprehensively investigate the MAC design in both single- and multi-hop broadband wireless networks, with and without infrastructure support.

The next frontier for wireless LANs is 802.11ac, a standard that increases throughput beyond one gigabit per second. This concise guide provides in-depth information to help you plan for 802.11ac, with technical details on design, network operations, deployment, and monitoring. Author Matthew Gast—an industry expert who led the development of 802.11-2012 and security task groups at the Wi-Fi Alliance—explains how 802.11ac will not only increase the speed of your network, but its capacity as well. Whether you need to serve more clients with your current level of throughput, or serve your existing client load with higher throughput, 802.11ac is the solution. This book gets you started. Understand how the 802.11ac protocol works to improve the speed and capacity of a wireless LAN Explore how beamforming increases speed capacity by improving link margin, and lays the foundation for multi-user MIMO Learn how multi-user MIMO increases capacity by enabling an AP to send data to multiple clients simultaneously Plan when and how to upgrade your network to 802.11ac by evaluating client devices, applications, and network connections

This book constitutes the refereed proceedings of the 17th EUNICE 2011 Workshop on energy-aware communications, held in Dresden, in September 2011. The proceedings comprise 16 full papers and 7 poster papers which are presented together with the abstracts of the 3 invited talks. The topics covered are: network architectures; ad-hoc and wireless networks; system simulation; network planning, optimization, and migration; traffic engineering; quality of experience; and energy efficient architectures.

In the last two decades, the wireless arena has witnessed the emergence of an astonishing number of technologies which play a part in the definition of new wireless systems. Driven by the pressing capacity demand, the research community has developed several technological enablers. Fundamental technological building blocks that will be part of wireless systems in the near-future definitely include: Orthogonal Frequency Division Multiplexing (OFDM) modulation at the physical (PHY) layer, Multiple Input Multiple.Output (MIMO) systems, and a cross-layer (CL) stack design. While the benefits of OFDM have been recognized for several years, the real capacity improvement of MIMO antennae is still being debated today. As to the lastpoint, even if opportunities for CL have been pointed out for a long time, the impact on the actual legacy systems has not been noticeable, as investors are hesitant to implement the inherent design paradigm shift.Single and Cross-Layer MIMO Techniques for IMT-Advanced will present some advanced MIMO techniques where adaptivity, cross-layer approach, and MIMO antennae are analyzed together to show a deep impact on the sum-capacityachievable over the wireless link.The introduction presents the functional requirements for IMT-A candidate systems and the relation between IEEE802.16 and LTE wireless access networks. Then, in the first part, adaptive strategies are analyzedseparately at the PHY and Medium Access Control (MAC) layers. The second part presents an evolution of the previous approach, providing a cross-layer MIMO-ARQ protocol, where adaptive MIMO schemes, namely SpatialMultiplexing (SM) and STBC Alamouti, are used with ARQ protocol. A Multiple User (MU) network is served in DownLink (DL) with a Round Robin (RR) scheduler; the design is ready to include more advanced schedulers. The ARQstate machine at the MAC layer is aware of per-antenna ARQ. The interaction between the ARQ and the PHY layer, with a per-antenna ACK, allows resource exploitation to increase with per-antenna ACKs, shifting from MIMO Signal Processing Gain to MIMO Protocol Gain with no need for Channel State Information (CSI) feedback. The absence of CSI feedback at the PHY layer is an important characteristic of the proposedMIMO-ARQ cross-layer designs since MIMO CSI feedback (when feasible) drastically reduces the network efficiency.The added degrees of freedom offered by MIMO transmissions can make the difference if correctly exploited both at the physical and medium access layers, in particular for overcoming the problem of low MIMO channel ranks.The advantages of the paradigm shift from signal processing gain to protocol gain - together with the modifications to be applied at the classical protocol stack - are discussed in the final chapter.

A new modeling framework is introduced for the analytical study of medium access control (MAC) protocols operating in multihop wireless ad hoc networks, i.e., wireless networks characterized by the lack of any pre-existent infrastructure and where participating devices must cooperatively provide the basic functionalities that are common to any computer network. The proposed modeling framework focuses on the interactions between the physical (PHY) and MAC layers, and on the impact that each node has on the dynamics of every other node in the network. To account for the effects of both cross-layer interactions and the interference among all nodes, a novel linear model is introduced with which topology and PHY/MAC-layer aspects are naturally incorporated in what we define as interference matrices. A key feature of the model is that nodes can be modeled individually, i.e., it allows a per-node setup of many layer-specific parameters. Moreover, no spatial probability distribution or special arrangement of nodes is assumed; the model allows the computation of individual (per-node) performance metrics for any given network topology and radio channel model.