SFM-MAC: Multichannel MAC Protocol for Underwater Sensor Networks Based on Underwater Passive Localization Mechanisms

With the continuous development of ocean research in recent years, underwater acoustic sensor networks, as the extension of terrestrial wireless sensor networks (WSNs), play an increasingly important role in ocean and coastal research. To solve the problem of spatial unfairness caused by spatiotemporal uncertainty of underwater acoustic signal propagation in underwater WSNs and improve the throughput of underwater networks, this paper proposes a slottedfloor multichannel medium access control (SFM-MAC) protocol based on a single transceiver. SFM-MAC uses an underwater passive localization algorithm to obtain location information and then transforms spatiotemporal information to avoid the synchronization of the whole network to reduce the spatiotemporal uncertainty of underwater networks; further, it uses request to send (RT)/channel announcement/channel listening/clear to send ( CTS) handshaking mechanism to avoid multichannel hidden terminal problems and achieve fair access. In addition, the paper uses the Markov chain to construct the reservation model of control channels, and theoretically analyzes and calculates the theoretical throughput of the multichannel MAC protocol under the condition of reserved collision. Simulation experiments show that the network fairness index of SFM-MAC is 15% higher than that of traditional RTS/ CTS protocols. The effective network throughput of SFM-MAC in different business scenarios is 60-70% and 12-15% higher than the single-channel underwater MAC protocol SF acquisition multiple access and the multichannel underwater MAC protocol, respectively.