Wireless Fountain Coding with IEEE 802.11e Block ACK for Media Streaming in Wireline-cum-WiFi Networks: A Performance Study

摘要

We develop performance models for delay-sensitive uplink media streaming over a wireline-cum-WiFi network. Since the wireless channel is normally a bottleneck for such streaming, we modify the traditional 802.11e block acknowledgment (B-ACK) scheme to work with wireless fountain coding (WFC)ȁ4;a packet-level coding scheme which codes packets in a similar manner to intrasession random network coding but delivers them in a manner similar to fountain coding. By using this modified B-ACK scheme, protocol complexity and wireless link-layer delay are potentially reduced. We analytically quantify this delay and use it to derive end-to-end packet loss/late probabilities when automatic repeat request (ARQ) and forward error correction (FEC) are jointly employed at the application-layer. We develop an integrated ns-3/EvalVid simulator to validate our models and compare them with the case when the traditional 802.11e B-ACK scheme is employed. Through simulations of video streaming, we observe that the modified B-ACK scheme does not always perform better than the traditional B-ACK scheme in terms of end-to-end packet loss/late probability and video distortion under certain conditions of the wireless channel. This observation leads us to propose a hybrid scheme that switches between the modified and traditional B-ACK strategies according to the conditions of the wireless channel and the number of packets to transmit in a block. Via simulations, we show the benefits of the hybrid scheme when compared to the traditional IEEE 802.11e B-ACK scheme under different network settings.