The Impact of Link-Layer Retransmissions on Video Streaming in Wireless Mesh Networks (Invited Paper)

Link-layer retransmission is a feature of IEEE 802.11 standard protocol that aims to increase the reliability of data communications. However, when successive retransmissions fail, they add to the traffic congestion, raise the collision probability, and increase the end-to-end delay. Using our 4-hop wireless mesh network testbed, we evaluate the impact of link-layer retransmissions on the performance of video streaming in wireless multi-hop environment. Our experimental results show that when the traffic load is near or exceeds the network capacity, retransmissions cause erratic video quality and increase the end-to-end delay tremendously. When the best-effort traffic coexists, increasing the number of retransmissions degrades the goodput of best-effort traffic and increases the end-to-end delay of video streaming. Retransmissions add reliability and increase the video streaming quality only when the traffic volume is far below the network capacity limit.