Distributed Algorithms for Joint Routing and Frame Aggregation in 802.11n Wireless Mesh Networks

Abstract

A wireless mesh network (WMN) is a special type of wireless ad-hoc network, which consists of mesh clients, mesh routers and gateways to the Internet, organized in a mesh topology. The mesh clients are often laptops, cell phones and other wireless devices. Mesh routers forward traffic between mesh clients and gateways. Despite a number of promising features provided by WMNs, such as low deployment cost, self-healing, etc., the throughput of WMNs is often limited by severe congestion and collisions, and thus cannot satisfy the increasing traffic demands of numerous applications. In this paper, we study how to maximize the throughput of IEEE 802.11n WMNs by joint routing and frame aggregation. Frame aggregation is to aggregate multiple frames into a large frame before transmission, to reduce communication overhead and alleviate collisions. We first show that previous frame aggregation strategies cannot achieve optimal network throughput. We then formulate the joint problem into a linear programming (LP) problem by considering traffic in the network as flow. As most previous algorithms for LP are centralized and difficult to deploy in large-scale WMNs, we propose a distributed algorithm to solve the formulated problem, in which each mesh router determines the amount of traffic flow for its adjacent links based on the traffic information of neighbors and interfering links. However, in realistic 802.11n WMNs, traffic is transmitted in frames instead of flow, and the traffic to different routers needs to be distinguished. Thus, we further provide an algorithm to determine the routing and frame aggregation strategy for each mesh router, using the traffic flow derived from the first algorithm. We have conducted extensive simulations to evaluate the proposed algorithms and the results demonstrate that the network throughput can be significantly improved compared with existing schemes.