Throughput Optimisation in Multi-Channel Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are becoming common due to the features provided, especially the low cost and self-configuration ability. In WMNs, the data traffic is transmitted through intermediate nodes. With the nature of wireless networks, forwarding (routing) the data from the senders to the destinations and managing the network resources efficiently are challenging. There are various reasons that affect the network performance especially the throughput reduction such as signal interference, mobility and congestion. The focus of this research is to improve the throughput in the multi-channel wireless mesh networks from two perspectives. The first issue considered in this work is selecting a path with the maximum available bandwidth and low signal interference to transmit data from the source to the destination. Thus, we design two routing metrics, the Expected Transmission Time with Queueing (ETTQ) and the Delay and Interference Aware Metric (DIAM), that consider the intra-flow interference, inter-flow interference and delay. The simulation results of these routing metrics by the Network Simulator (NS2) demonstrate that the DIAM metric can estimate the intra-flow interference, inter-flow interference and delay of a link and then select the path efficiently. The second problem that has been addressed to improve the network throughput is controlling the network congestion. In this work, we address the issue of packet drops in the Interface Queue (IFQ) due to the node congestion. We solve this issue by reducing the number of dropped packets at IFQ by allocating the flow rate from the solution of a linear program (LP). The simulations using NS2 have shown that the LP-based flow rate improves the network throughput in chain networks. In addition, with the complex networks, traffic rate adjustments alone are not sufficient and we propose a simple forwarding delay scheme for the Ad Hoc On-Demand Distance Vector protocol with Forwarding delay (AODV-F) with DIAM routing metric that reduces node congestion and improves throughput. The forwarding delay scheme has also been evaluated using NS2. Moreover, the LP adjusted flow rate and the forwarding delay address the issue of maximising the flow fairness as the results have demonstrated.