On the Impact of Network Coding Delay for IEEE 802.11s Infrastructure Wireless Mesh Networks

The distributed coordination function (DCF) may reduce the potential of network coding in 802.11 wireless networks. Due to the randomness of DCF, the coding delay, defined as the time that a packet must wait for a coding opportunity, may increase and degrade the network performance. In this paper, we study the potential impact of the coding delay in the performance of TCP over IEEE 802.11s infrastructure wireless mesh networks. By means of simulation, we evaluate the formation of coding opportunities at the mesh access points. We find that as TCP traffic increases, the coding opportunities rise up to 70% and the coding delay increases considerably. We propose to adjust dynamically the maximum time that a packet can wait in the coding queues to reduce the coding delay. We evaluate different moving-average estimation methods for this aim. Our results show that the coding delay may be reduced with these methods using at the same time an estimation threshold. This threshold increases the estimation´s mean in order to exploit a high percentage of the coding opportunities.