A Network Access Mechanism for Multihop Underwater Acoustic Local Area Networks

Multihop underwater acoustic local area networks (MUA-LANs), which can greatly improve the access ability of underwater networks, suffer from the lack of network access mechanism utilized by new nodes to join the networks. Existing network access mechanisms for terrestrial wireless LANs cannot be directly applied to MUA-LANs due to the multihop topologies of MUA-LANs and the acoustic channel features of limited bandwidth and high propagation delay. In this paper, we present a network access mechanism constituted by three phases of network discovery, relay path determining, and association for MUA-LANs. The basic idea of our network access mechanism is to let the nodes that have joined a network assist new nodes in accessing the network by multihop relay forwarding. We theoretically verify that the unbalanced energy consumption is serious in MUA-LANs. Therefore, we present a lifetime and energy efficiency-based relay path selection algorithm in relay path determining phase. This algorithm can significantly prolong the network lifetime and improve energy efficiency. In association phase, we employ a MAC address forwarding tables mechanism. By utilizing this mechanism, multihop relay forwarding can be realized easily. The simulation results have confirmed that the proposed network access mechanism can achieve excellent performance owing to the lifetime and energy efficiency-based relay path selection algorithm and the MAC address forwarding tables mechanism.