Design and Performance Evaluation of CAM-MAC for Ad Hoc Networks

Medium access control (MAC) protocols have been studied under different contexts for decades now. In all decentralized MAC protocols, nodes make independent decisions on when to transmit a packet and when to back-off from transmission. However the decisions often turn out to be uninformed due to deficient knowledge at individual nodes, which, in multi-channel ad hoc networks, creates a multi-channel coordination problem. In this paper, we introduce a notion of cooperation that has not been explored before to address this problem, and thereby propose a protocol called CAM-MAC. Qualitatively, CAM-MAC needs only a single transceiver per node and is fully asynchronous. Quantitatively, (i) our analysis shows that CAM-MAC has an throughput upper bound of 91% of hardware capacity, and simulations show that its average throughput achieves 96% of the upper bound, (ii) although CAM-MAC uses a control channel, both our analysis and simulations show that it can saturate 14.2 channels and typically does not suffer from the control channel bottleneck problem, (iii) in the comparison of CAMMAC with and without cooperation, we observe a throughput improvement of 281% and 173% in single-hop and multi-hop networks, respectively, which shows the value of cooperation, (iv) compared with three recent and representative multi-channel MAC protocols, MMAC [2], SSCH [3] and AMCP [4], CAMMAC substantially outperforms all of them.