a bidirectional multi-channel mac protocol for improving tcp performance on multihop wireless ad hoc networks
The TCP protocol often suffers from performance problems in conventional single-channel multihop wireless ad hoc networks. The problems arise from hidden node and exposed node issues, which can lead to channel contention in the forward direction between TCP DATA packets that are part of the same TCP flow control window, as well as contention between TCP DATA and TCP ACK packets flowing in opposite directions. In this paper, we propose and evaluate a novel bidirectional multi-channel MAC protocol designed to improve TCP performance over a multihop wireless network. The protocol uses multiple transmission channels at the physical layer to reduce TCP DATA-DATA contention, and bidirectional RTS/CTS channel reservations to reduce TCP DATA-ACK collisions. With four channels, simulation results for static multihop networks show TCP throughput gains of 50\% to 180\%, compared to a conventional IEEE 802.11 MAC protocol. Fairness is also improved with our protocol, since contention is confined to a short handshake period on the control channel.
tcp performance multihop wireless ad hoc networks simulation ns-2