Measuring link quality based on ETX metric in multi-hop wireless networks

ETX (Expected Transmission Count) is a well-known link quality metric which has been widely used to improve the performance of ad-hoc routing protocols. However, ETX shows poor performance under high traffic load. To address this problem, this paper proposes a new link quality estimation metric called HETX (High load Expected Transmission Count) that takes into account the effects of routing control messages on the link quality under high traffic load. A reliable routing protocol using HETX is also proposed, which is called LQDV (Link Quality Distance Vector). Simulations are conducted to compare the performance of three metrics HETX, ETX and minimum hopcount. The simulation results show that HETX outperforms minimum hopcount and ETX in terms of throughput and delivery ratio under high load.