Performance evaluation and enhancement of scheduled and polled block ACK multicast protocols

IEEE 802.11aa amendment introduces several protocols to increase the robustness of multimedia traffic delivery for multicast destinations. According to the recent investigations Block ACK protocol is the most efficient among them. However, it requires polling to each of the multicast group member which may cause significant overhead in the scenarios with large group size. Compared to the polling based Block ACK protocol the scheduled Block ACK protocol does not require individual polling to each group member. In this paper we compare two protocols in terms of scalability, achievable throughput, and delay in various scenarios. In addition, we introduce a frame error based RTS/CTS protection scheme which improves the performance of both schemes in hidden node scenarios. Performance evaluations show that the proposed protection scheme significantly alleviates the hidden node problem in scheduled Block ACK protocol.