Research And Optimization On Wireless Multi-hop Network Routing Based On ETX Routing Metric

To the study of wireless multi-hop networks, the metric of routing protocol is very significant and ETX, a kind of routing metric can take the problems in wireless networks into account. Such as asymmetry links, packet lost and wireless link interference. Due to the reason that the interval of sending probe packets and updating ETX is fixed and longer, the original ETX mechanism cannot find a better quality wireless link and switch to it quickly when the quality of wireless links in a wireless multi-hop network change frequently. And the performance of the original ETX mechanism will be worse.In this paper, we analyzed the disadvantages of existing ETX based routing mechanism on wireless multi-hop network. Based on original ETX rouging metric we proposed two novel optimization routing mechanisms in this paper. And the main contributions of our work are as follows:First, the disadvantage of the original ETX mechanism is proved through simulations in NS-2. Then we found factors which influence the performance of ETX based routing mechanism; To improve routing performance, an opportunistic routing mechanism (LSETX) combined with long-term and short-term routing metrics for WMN based on OLSR and ETX is introduced. This mechanism can always choose the highest throughput link to improve the performance of routing over WMN. To take real scenario of WMN into consideration, such as many client users with lower rate of data traffic in the network, the utilization of wireless bandwidth maybe lower because of the fixed probe packet sending interval. So an optimization routing mechanism with variable probe interval based on ETX is proposed (vpETX). The probe interval of ETX will be changed according to the information of data rate which is acquired from the application layer and optimize the performance of routing.The result of NS simulation shows that the opportunistic routing combined short-term and long-term metrics (LSETE) and vpETX both perform better on throughput with 20% and 17.96% incensement respectively, end-to-end delay and packet loss rate than the original ETX over different situations of WMN.