Performance Analysis of MAC Protocols for Location-Independent End-to-End Delay in Multi-Hop Wireless Mesh Networks

Abstract

Backbone wireless mesh networks (WMNs) are emerging alternatives to conventional wired backbones for metropolitan and have attracted much attention from both academic and industrial world as an infrastructure network for realizing the ubiquitous computing environment. WMN is a generalization of Wireless Ad-Hoc Networks that considers the use of heterogeneous nodes (e.g., clients and routers) and both wired and wireless connections to exchange data between these devices. The basic architecture of a WMN consists of a backbone of mesh routers (MR) and the clients that access communication services through the use of this backbone. Therefore, this backbone serves as a last mile solution that is interconnected to provide direct communication between clients (i.e., without routing the interclient traffic through any other intermediate network). This characteristic of a WMN enables it to function as an isolated autonomous network or as a last mile solution depending on the telecommunication facilities available at the place where the WMN is deployed. In a multi-hop WMN, communication between two nodes is basically carried out by forwarding packets through a number of intermediate nodes. In WMNs, nodes are comprised of mesh routers in fixed sites and mobile clients as shown in Fig.1. We call a mesh router (also called mesh node) with gateway functions a gateway node, which is equipped with wireline network interfaces to connect the internet backbone. In this chapter each mesh node operates not only as an access point (AP) for mobile clients in its own basic service set (BSS) but also as a router, forwarding packets on behalf of other nodes that may not be within direct wireless transmission range of their destinations (see Fig. 1). Mobile clients are attached to a node in their BSS. Data originating from mobile clients are relayed by intermediate relay nodes hop by hop and delivered to the gateway. One of the important problems to be solved in WMNs is the unfair bandwidth sharing problem depending on the nodes’ location. More specifically, the per node throughput may decrease and the end-to-end delay may dramatically increase with an increasing hop-count distance from the gateway. In particular, WMNs based on single radio, irrespective of its simplicity and high fault tolerance, face a significant limitation of limited network capacity. It has been shown (2) that the theoretical upper limit of the per node throughput 3