Handling Triple Hidden Terminal Problems for Multi-Channel MAC in Long-Delay Underwater Sensor Networks

In this paper, we investigate the multi-channel MAC problem in underwater acoustic sensor networks. To reduce hardware cost, only one acoustic transceiver is often preferred on every node. In a single-transceiver multi-channel long-delay underwater network, new hidden terminal problems, namely multi-channel hidden terminal and long-delay hidden terminal (together with the traditional multi-hop hidden terminal problem, we refer to them as "triple hidden terminal problems"), are identified and studied in this paper. Based on our findings, we propose a new MAC protocol, called CUMAC, for long delay multi-channel underwater sensor networks. CUMAC utilizes the cooperation of neighboring nodes for collision detection, and a simple tone device is designed for distributed collision notification, providing better system efficiency while keeping overall cost low. Analytical and simulation results show that CUMAC can greatly improve the system throughput and energy efficiency via effectively solving the complicated triple hidden terminal problems.