Research And Design On Hybrid MAC Protocol For Underwater Acoustic Sensor Networks

Modern terrestrial and wireless communications have constituted a huge communications network,but the development of communication in the ocean is still lagging behind.The underwater acoustic sensor network plays a very important role in many fields of military and civilian military intelligence collection,marine resources exploration and development,disaster warning etc.in recent years,with the increasing development and utilization of the ocean,underwater acoustic sensor network has become a new research hotspot.Underwater acoustic sensor network is characterized by the use of underwater acoustic communication,compared with traditional radio communication,it has lower transmission bandwidth,larger transmission delay and higher transmission error rate ect.At present,underwater acoustic sensor network is mostly composed of many sensor nodes,most of these sensor nodes are long-term distribution in the interior of the ocean,thus to increase the average end of underwater acoustic sensor network data throughput and end-to-end delay in case of reducing energy consumption is a problem that needs to be solved.One of the keys to achieve high efficient data transmission is MAC(Multiple Access Control)protocol for underwater acoustic sensor networks.This paper according to the characteristics of underwater acoustic sensor and underwater acoustic communication,two kinds of MAC protocols for underwater acoustic sensor networks are designed and studied based on different network scenarios.Firstly,a load adaptive CSMA(Carrier Sense Multiple Access)hybrid protocol LA-CSMA(Load Adaptive-Carrier Sense Multiple Access)is proposed for underwater acoustic sensor networks with relatively small nodes and common channels in each node.The hybrid protocol also combines the advantages of competition and fixed distribution agreement,when the networks load is small using the CMSA competition agreement with smaller delay,when the network load is larger using higher throughput of TDMA(Time Division Multiple Address)protocol.Due to LA-CSMA protocol for the traditional CSMA protocol targeted improvements,making the whole protocol slots as interval,messages are sent and received within a time slot,at the same time back off algorithm to the competition agreement has further improved,adding competitive priority and optimal elimination rate to improve competition efficiency,meanwhile we focus on the conversion of the protocol to determine the optimal situation of the conversion value.Through the LA-CSMA protocol simulation by the simulation software,founding that it is more suitable for network load changing than CSMA and TDMA,taking into account both the performance.Then,a clustering based MACA(Multiple Access with Collision Avoidance)hybrid protocol CH-MACA(Clustering Hybrid-Multiple Access with Collision Avoidance)is proposed for large-scale centralized underwater acoustic sensor networks.The hybrid protocol clustering large scale centralized networks,intra cluster and cluster head communication adopts different data transmission protocols,the intra cluster communication takes LA-CSMA protocol,the cluster head communication adopts MACA protocol based on contention,at the same time according to the underwater acoustic signals’ transmission characteristics,the MACA protocol used in cluster head communication is improved,adding interception mechanism to effectively prevent hidden terminals,besides,adding the protection time to prevent data loss cannot be timely retransmission in data transmission.Through the CH-MACA protocol simulation by the simulation software found that when the traffic is larger,have better network throughput and average end-to-end delay than TDMA and MACA,and the energy loss is relatively small.