Sub-Channel Assignment and Collision Resolution Enhancements for Receiver-Initiated MAC protocols

摘要

Multiple channel access interference is a major cause of throughput degradation in wireless networks because of the shared channel. IEEE 802.11 MAC protocol is a standard for medium access in wireless LANs, but suffers from contention and co-channel interference and thus performs poorly. We propose to use receiver-initiated MAC protocol, instead of the sender-oriented 802.11, to address these issues. The proposed protocol is based on carrier sensing and resolves collisions among senders based on a deterministic tree splitting algorithm to minimize the retransmissions of data packets due to hidden terminals. Further, subchannel assignment is used to exploit the parallel transmissions that are possible in multi-channel networks; thus, reducing the channel contention and improving the throughput. We also present simulation results, using ns-2 simulator, to evaluate our approach and compare it with 802.11. The simulation results indicate that collision resolution with multiple subchannel access is more effective in throughput and provides better packet delays than 802.11 MAC. We also observe that the maximum throughput is achieved when the channel is divided into three or four subchannels irrespective of the size and shape of the network and traffic load.