BMF-MAC: A Bidirectional Multi-flow MAC Protocol for Multihop Underwater Acoustic Sensor Networks

Due to the atypical characteristics of the physical media in underwater acoustic sensor networks (UW-ASN)--mostly because of long propagation delay, low bandwidth and high error rate--several challenges arise while designing the MAC protocol. In this paper, we propose a Bidirectional Multi-flow MAC protocol (BMF-MAC) for UW-ASN, to efficiently handle multi-hop multi-flow traffic load patterns such a way that multiple streams of data transmissions concurrently proceed while adapting with varying traffic condition. BMF-MAC supports constitution of multi-hop flows by considering all pending packets in routing layer buffer and all flow setups requests from neighbors when setting up a flow, contrary to other underwater MAC protocols. The proposed MAC introduces a data transmission technique using the bidirectional multi-flow packet method for sending multiple data packets of the same flow in the reverse direction and thus improve channel utilization. The protocol is aimed to schedule more data transmission over multiple multi-hop flows, thus permitting rapid distribution of data and reduction of latency. Results show that BMF-MAC protocol outperforms existing CMRT protocol in terms of network throughput and packet delivery latency.