Preface

Wireless mesh networks (WMNs) have recently received a great deal of attention as a promising cost-effective solution to provide coverage and broadband wireless connectivity for mobile users to get access to different IP applications and services.

The factor that has helped WMNs become attractive is the wide application prospects from the wireless community, home and enterprise networking. Moreover, wireless mesh technologies are becoming more and more popular in the context of their integration with heterogeneous next generation networks for purposes of backhaul support, traffic offloading, load balancing, fixed-mobile convergence, etc.

However, making these WMNs operationally efficient is a challenging task. In recent years, there has been a lot of work on research issues. Nevertheless, there still exist some open research challenges related to link scheduling, channel assignment, routing and other network planning issues in multi-radio multi-channel WMNs. The main objective of this book is to highlight some recent efforts in developing novel efficient design strategies and efficient algorithms to significantly improve performance and functionality of WMNs. The results presented in this book are expected to help in taking design decisions when deploying WMNs.

Ten contributed chapters written by a group of well-known experts in wireless mesh networking are arranged in two sections.

Section 1 focuses on link scheduling schemes to select a subset of links for simultaneous transitions under interference constraints in an efficient and fair manner to guarantee a certain level of network connectivity. Besides, it describes channel assignment strategies to improve the network throughput in multi-radio multi-channel WMNs by means of an efficient channel utilization and minimization of the interference. Chapter 1 of this section describes a framework for fair link scheduling based on the application of genetic algorithms taking into account both the QoS requirements of data flows between mesh clients and underlying network characteristics affecting the overall system performance. Chapter 2 deals with the stability-based topology control mechanism using the underlying link scheduling policy of WMNs to optimize the ability of links to carry the information transported by end-to-end data flows. Chapter 3 introduces a topologycontrolled interference-aware channel assignment algorithm based on power control which intelligently assigns the available non-overlapping frequency channels to the wireless mesh routers with the objective of minimizing interference to improve network throughput. Chapter 4 discusses the optimal number of radio interfaces for wireless mesh routers depending on the topology of the mesh network (grid or random), the number of network nodes and the number of data flows in the network. Chapter 5 takes an in-depth look into recent channel assignment schemes exploiting partially overlapping channels in the context of multiple radio WMNs.

Section 2 addresses some important network planning issues related to efficient routing protocols in dynamic large-scale mesh environment, achievable capacity limit of a single wireless link between two multi-interface mesh nodes, the correctness of the mesh security architecture, fault-tolerant mesh network topology planning. Chapter 6 of the section presents an autonomous traffic balancing routing protocol based on a combination of back-pressure and geographic routing schemes. The proposed mechanism is inspired by the electrostatic potential theory and able to react adaptively to dynamic traffic environment in large-scale WMNs with a low routing overhead. Chapter 7 presents an indepth analysis of the impact of multipath and MIMO fading channels on achievable theoretical capacity limits of single links connecting mesh nodes and the impact of number of interfaces and channels per each mesh node on the end-to-end capacity limits of wireless broadband mesh networks. The capacity limits provide useful inputs towards an optimal design of cross-layer protocols. Chapter 8 examines correctness of the mesh security architecture using a protocol composition logic to prove security of the IEEE 802.11s protocol suite. Chapter 9 deals with a fault-tolerance method for guaranteeing the availability of radio coverage and connectivity of wireless mesh networks in dynamic propagation environment. It also proposes an automatic mesh router planning algorithm, which finds a minimum number of wireless mesh routers and their positions to restore the fault-tolerant network mesh topology. Chapter 10 describes a channel reservation scheme in combination with an on-demand routing protocol to establish high throughput paths in multi-radio multi-channel environments and reduce the intra/inter flow interference for the traffic going towards the mesh gateways.

Thus, this book covers a variety of issues related to link scheduling, channel assignment, routing and network planning in WMNs and provides an in-depth look into recent advances in these topics. The book can be useful for researchers, PhD students, engineers, and practitioners that are interested in wireless mesh networking.

I wish to express my deep appreciation to all Authors for their thorough work. Special thanks to Ms. Tanja Skorupan, Publishing Process manager at InTech Open Access Publisher, for her kind cooperation and patience during the preparation of this book. I wish also to thank my colleagues, Marc Portoles, José Nuñez, and Josep Mangues, for their encouragement and continuous support.

> **Andrey V. Krendzel**  Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Barcelona, Spain
