From NUEESS

Overview

The long propagation delay of underwater acoustic communications has made traditional handshaking-based medium access control (MAC) protocols inefficient for underwater sensor networks (UWSNs). We envision that this unique feature, although often taken as negative, can be leveraged to improve the parallelism between multiple senders, i.e., transmitting data simultaneously so as to achieve higher channel utilization. The proposed DAP-MAC is a novel delay-aware probability-based MAC protocol, which eliminates the handshaking process and utilizes concurrent transmissions to significantly improve the network throughput. Our extensive simulations demonstrate that DAP-MAC achieves better system throughput than the existing representative underwater MAC protocols.

The main features of DAP-MAC are summarized below.

• Transmission pipelining. We extract the channel access compatibility relation, characterized by the distance difference between senders and their common intended receiver, and utilize it to achieve transmision pipelining, i.e. parallel transmissions, which significantly improves the channel utilization.

• Stochastic Transmission Strategy. The optimal stochastic transmission strategy elimiates the usage of inefficient handshaking, which is yielded by a utility-optimization framework maximizing the network throughput and maintaining minimal packet collisions.

• Distributive with Low Overhead. We show theoretically that the optimal throughput can be achieved distributively with only small control overhead, which makes DAP-MAC very suitable for long-delay and power-hungry UWSNs.

• Robust under Mobility. The run-time derived compatibility relation, the dynamically updated optimal transmission strategy, and the additional guard in determining the compatibility, together enhance the adaptiveness of DAP-MAC to underwater network dynamics.

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