水下传感网络中免时钟同步的TDMA-MAC协议

MAC based on TDMA without clock synchronization in underwater sensor networks

水下声传感网络广泛用于海洋环境的监测。然而,声信号的低传播速度给接入通信媒介提出挑战。为此,提出基于传输时延分配的媒体接入控制(Medium Access Control,MAC)协议(Transmit Delay Allocation-MAC,TDA-MAC)。TDA-MAC协议能够在无需集中时钟同步环境下,为节点提供时分多址接入(Time Division Multiple Access,TDMA)。具体而言,网关先估计离网络内所有传感节点的传播时延,然后,网关向每个节点传递传输时延指示包(Transmit Delay Instruction,TDI),一旦接收到来自网关广播的REQ包,节点就等待TDI包内的传输时延后,再传输数据包。仿真数据表明,提出的TDMA-MAC协议的网络吞吐量逼近于基于同步策略的TDMA协议。

This paper investigates the application of underwater acoustic sensor networks for large scale monitoring of the ocean environment.The low propagation speed of acoustic signals presents a fundamental challenge in coordinating the access to the shared communication medium in such networks.Therefore,Transmit Delay Allocation-Medium Access Control(TDA-MAC)is proposed in this paper.TDA-MAC is capable of providing time division multiple access(TDMA)to sensor nodes without the need for centralized clock synchronization.Gateway node estimates the propagation delays to all sensor nodes in the network.Afterwards,a transmit delay instruction(TDI)packet is sent to every sensor node.Upon receiving the broadcast REQ packet,any node that has data to transmit,waits a particular amount of time,defined in its transmit delay instruction,and then transmits its data packet.Simulation results show that proposed protocols are capable of closely matching the throughput and packet delay performance of ideal synchronized TDMA.