Research On MAC Layer Protocol For Underwater Acoustic Network Multicast Communication Mode

With the decline of land resources,people are paying more and more attention to the resource-rich ocean.Underwater environment is complex.Underwater acoustic channel and terrestrial radio channel are very different.Underwater acoustic channel has large transmission delay,limited bandwidth,strong time-varying spatial variation and severe fading.In order to improve the network throughput and channel utilization,this paper starts from the communication mode of the node,and designs the efficient underwater medium access control(MAC)layer protocol in the node multicast communication mode.In this paper,the development and research status of underwater acoustic communication network are introduced in detail.The structure of underwater sensor network protocol is introduced.The existing MAC protocol based on pre-allocation,MAC protocol of random competition and MAC protocol of underwater acoustic network are analyzed.The problem of underwater wireless sensor network is clarified,which lays the theoretical foundation for the following research.Firstly,the upper bounds of the underwater acoustic network throughput based on the unicast and multicast communication modes are deduced respectively.The objective modular network testbed in C++(OMNeT++)simulation verifies that the multicast communication mode can improve the network throughput and reduce the end-to-end delay of the message.The use of non-time slot limited receive strategy solves the problem that the time slot allocation multicast communication mode slot resource waste.In order to constrain the conflict of data packets,three kinds of cases of collision are deduced,the time-slot scheduling constraint is deduced,and the Bellman-Ford algorithm is used to solve the problem of differential constrained system.Secondly,a multicast mode heuristic TDMA protocol(MH-TDMA)is proposed,and the unavailability time of the nodes is obtained by the solution of the slot scheduling constraints.The conflict target graph is established by using the large transmission delay of the underwater acoustic network.The MH-TDMA protocol includes three parts: priority heuristic rule,conflict target graph generation algorithm and node's sending time selection algorithm.The network maintenance strategy is formulated to ensure the correct and complete operation of the protocol for node death and new node joining.Finally,the OMNeT ++ simulation platform is briefly introduced,and the underwater acoustic communication network is built with OMNeT++.Aiming at the multicast mode heuristic TDMA protocol proposed in this paper,five kinds of network scale are used to simulate the network performance in four topologies of ring,tree,line and grid using non-time-slotted condition.It is proved that the multicast mode heuristic TDMA protocol can improve the network throughput and reduce the average end-to-end delay of the message.