延迟容忍及冲突避免的水声网络S-Aloha协议

Delay tolerant and collision avoidance S-Aloha protocol for underwater acoustic networks

在S-Aloha协议的基础上,针对水声信道传播延时高的特点,设计了一种适合于水声网络的DTCAS-Aloha协议。该协议中,发送节点首先根据传播延时调整开始发送数据包的时刻,使数据包第1个比特到达目的节点的时刻与时隙同步。同时,节点通过提取侦听到数据包的信息和传播延时获取周围邻节点的忙时间和相应的忙状态,从而判断本节点即将发送的数据包或ACK在任意节点处是否会发生碰撞,达到避免冲突和提高吞吐量的目的。仿真结果表明,与原始S-Aloha协议相比,DTCASAloha协议在集中式单跳网络和分布式多跳网络中均具有较高的吞吐量和较低的冲突率。

On the basis of S-Aloha protocol,aiming at the long propagation delay characteristic in underwater channel,a new protocol called DTCAS-Aloha is proposed,which is suitable for underwater acoustic networks.The first key point is that the DTCAS-Aloha adjusts the data frame transmission time according to the propagation delay to align the arrival time of the first bit of the data frames with the start of slots.Moreover,DTCAS-Aloha takes advantage of the propagation delay and the information extracted from overheard frames to calculate the busy duration of every neighboring node,along with the indications of whether these busy states are caused by transmitting or receiving.When a node has data to transmit,it should check whether the data frame or the ACK frame will result in a collision at any node.The DTCAS-Aloha can avoid collisions and boost the throughput.The simulation results show that the throughput of DTCAS-Aloha is higher than that of S-Aloha and the collision ratio of DTCAS-Aloha is lower than that of S-Aloha in both centralized single-hop network and distributed multi-hop network.