Research On Adaptive Underwater Wireless Sensor Network MAC Protocol Based On Contention And Contention-free Fusion

Because of its wide application in ocean exploration,oil exploitation and data acquisition,underwater wireless sensor network(UWSN)has attracted close attention.Media access control(MAC)protocol is one of the core issues in the design of underwater wireless sensor network.A reasonable and efficient MAC protocol is particularly important for the development of underwater wireless sensor network.Therefore,the MAC protocol for underwater wireless sensor network is studied in this paper.In order to solve the problems of changing network loads and the decrease of throughput caused by semi-static time slot allocation,two hybrid MAC protocols which are suitable for underwater environment are proposed.The performance analysis and simulation experiments are carried out.The main idea of this paper is as follows:(1)For the dynamic network load,a load-based time slot allocation(LBTSA)for underwater wireless sensor network hybrid MAC protocol is designed.LBTSA combines TDMA(time division multiple access)and CSMA/CA(carrier sense multiple access/collision avoidance)very well.LBTSA selects the slot allocation scheme according to the load.Then,based on the priority of the slave nodes and the optimal number of backoff stages,the host node selects the optimal access control protocol.This not only adapts well to changing network loads,but also maximizes network throughput.(2)For the decrease of throughput caused by semi-static time slot allocation,a dynamic time slot allocation(DTSA)based on queue length for underwater wireless sensor network hybrid MAC protocol is designed.DTSA combines TDMA with CSMA/CA.According to the queue length of the slave nodes,the protocol candynamically allocate time slots to the slave nodes to implement adaptive time slot allocation.This can not only avoid the problem of insufficient channel utilization,but also maximize network throughput.The LBTSA and DTSA proposed in this paper are mainly used to solve the problems of the dynamic network load and the decrease of throughput caused by semi-static time slot allocation.The simulation results show that the total throughput of LBTSA is 8% higher than that of TDMA,and 45% higher than CSMA/CA;the throughput of LBTSA is 21% higher than that of HCR(a hybrid mac protocol using channel reservation)and 115% higher than that of H-MAC(hybrid MAC).The end-to-end delay of LBTSA is 60% lower than that of HCR and 87% lower than that of H-MAC.LBTSA can achieve higher throughput and lower delay.The simulation results show that the total throughput of DTSA is 16% higher than that of HCR,and47% higher than H-MAC.Therefore,DTSA is superior to hybrid MAC protocols without time slot allocation scheme.