Research Of MAC Protocol Based On Underwater Optical-acoustic Hybrid Wireless Sensor Network

To achieve real-time or quasi-real-time fast and reliable transmission of underwater data,this paper puts forward a new type of OA-UWSN(optical-acoustic hybrid underwater wireless sensor network).The network uses acoustic and opticalchannel to achieve high-speed underwater reliable communication.At the same time,according to the characteristics of the OA-UWSN,a channel reservation MAC(media access control)layer protocol OA-Handshakebased on optical and acoustic handshake is designed for this network.Furtherly,in order to solve the conflict caused by handshake information transmission,a MAC layer protocol backoff OA-Handshake based on back-off mechanism is designed.The paper mainly completes the following aspects:First,the OA-UWSN model is designed.The network uses acoustic channelto transmit control information to ensure the reliability of data transmission;and the underwater optical communications is used toachiece high-speed data transmission;multi-hop is used to increase the communication distance.Second,a channel reservation MAC layer protocol based on optical andacoustic handshake is designed for theOA-UWSN.The protocol relies on handshaking signals to ensure the reliability of the communication and time slot reservation mechanisms to avoid data collisions.Initially,the acoustic channel is used for acoustic handshake to confirm the node that will be communicated.After optical handshake is successful,time slots are allocated to a node that will transmit optical data.If the transmission environment does not premit the optical communication,then the sound channel is used to transmit some important data and the control information.Furthermore,due to O-A Handshake protocolcouldn’t avoid the conflict when the handshake information is transmitting,so an O-A Handshake agreement based on back-off mechanism is proposed furtherly.When the network load is heavy,the protocol can effectively avoid data conflicts.Simulation results prove that the protocol will achieve higher channel utilization and network throughput.Finally,OMNET++ simulation software is used to simulate the OA-UWSN and MAC layer protocols.Simulation results show that OA-UWSN has higher communication data than traditional underwater acoustic networks and is more reliable than underwater optical networks.The OA-UWSN channel utilization of the O-A Handshake protocol is 23% higher than the T-Lohi protocol,and the network throughput is 34% higher.After the number of nodes exceeds 70,the OA-UWSN channel utilization of the backoff O-A Handshake protocol is 14% higher than the O-A Handshake protocol,and the throughput is14% higher.