Analyzing the impact of retransmission timeout bounds in wireless mesh networks

Efficient estimation of retransmission timeout exhibits a fundamental impact on reliable transmissions of data in wireless mesh networks. Several approaches estimate retransmission timeouts for data transmissions over wired and wireless links mainly based on outcomes of already attempted data transmissions. These estimated retransmission timeouts possess significant variation over wireless links due to the unreliable nature of wireless medium. Therefore, estimation based on experience may sometime generate such retransmission timeout values that may not be feasible at any real data transmission attempt. This sort of values may result in unnecessary delay in case of unsuccessful transmission in wireless mesh networks. Therefore, to make the estimation more pragmatic, all the approaches utilize lower and upper bounds of retransmission timeouts to confine them within feasible range during the estimation. All the approaches adopt fixed values for these bounds without any significant analysis of their optimal values. However, adjusting these values may result in significant improvement in performance of wireless mesh networks. Therefore, we present a thorough analysis of the impact of variations of lower and upper bounds on wireless mesh network performance. We adopt network throughput and average energy per bit as our metrics of network performance during the analysis. We simulate wireless mesh networks in the simulator ns-2 and separately analyze the impacts of lower and upper bounds of retransmission timeouts to show that we can get optimal points for both of them.