| Wireless local area networks exhibit substantially different characteristics from their wired counterparts: limited bandwidth, bursty packet loss, and receiver-specific loss patterns. In these environments, a network protocol should constantly adapt its algorithms and parameters in response to the changing channel conditions.; In this research, we propose and implement a reliable multicast protocol that adaptively adjusts parameters in response to channel condition changes. The relevant parameters include the proactive FEC rate, the global NACK suppression flag, and the sending rate. The protocol derives channel condition factors, such as packet loss rate and contention degree, based on feedback from receivers. The protocol is implemented at the application level and it requires no special link layer support. Analysis and simulation results show that the protocol has good overall performance in most cases, in terms of transmission throughput. The factors that degrade the performance are pointed out and discussed.; Our experience of wireless network simulation shows that an accurate channel loss model is critical to protocol performance evaluation. Based on the collected packet traces, we developed a novel channel model that takes into account the correlation of losses among multiple receivers. The model is used for evaluation of our protocol. It could be applied to other studies that involve wireless group communications. |
