Network Layer Support for Gigabit TCP Flows in Wireless Mesh Networks

Abstract

Next generation wireless networks (WMNs) are designed to provide better performance than other existing personal, local, and metropolitan wireless networks, such as Wireless Local Area Networks and WiFi. In WMNs, each link has different amount of available bandwidth, and the bandwidth fluctuates dynamically based on the wireless environment. When the available bandwidth fluctuates, Transmission Control Protocol (TCP) flows experience packet losses, packet re-ordering, and timeouts, resulting in low end-to-end throughput. To alleviate the problem of low TCP throughput, we propose a Spare-bandwidth Rate-adaptive Network Coding (SRNC) scheme. In SRNC scheme, each gateway node forwards packets after network coding. Each intermediate node also adaptively uses network coding before forwarding the packets to the outgoing links. Each mesh access node decodes the network coded packets before forwarding them to the destinations. The key feature of SRNC is that each node adapts its network coding rate based on the available bandwidth on the outgoing links, such that the access nodes can decode the packets with higher probability without significantly affecting the cross-traffic. Effectiveness of the proposed scheme is evaluated using simulation. The simulation results show that the proposed scheme uses the available bandwidth on each link efficiently and it significantly improves end-to-end throughput of TCP flows.