Research On MAC Protocols For Underwater Acoustic Networks

Along with the increasing depletion of land resources, the ocean which contains abundant resources is gradually concerned by the human. Underwater acoustic communication networks(UAN) plays an important role in the development and utilization of marine resources, for instance, Ocean sampling, Environmental monitoring, Disaster prevention, Assisted navigation, Distributed tactical surveillance, Mine reconnaissance. Underwater environment is poor, Underwater acoustic channel is different from the land-based radio channel, Limited communication bandwidth, Large propagation delay, Multi-path effect, Doppler shift, Severe fading, Strongly time-varying, Spatially variable, Random and so on.Firstly, Underwater acoustic communication network architecture and the land-based radio network architecture are very different, the energy problem of the node is more serious, and Underwater acoustic communication network architecture are also different from the traditional OSI model, the experts generally divided underwater acoustic communication networks into three layers:the network layer, the data link layer and the physical layer. The data link layer mainly play for the network layer the role of providing reliable link, which was divided into logical link layer (LLC) and media access control layer (MAC). The paper mainly studies media access control layer protocol.Then, this paper analyzes some of the MAC protocol and the problem faced by MAC protocol in the underwater acoustic communication networks, mainly foucs on the problem of the energy efficiency, Reasoning the energy efficiency issue should be considered importantly.Secondly, considering the energy efficiency issue, the paper mainly researches two typical MAC protocol:802.11 and S-MAC protocol.802.11 protocol owns two types:point coordination function (PCF) and Distributed Coordination function(DCF), the paper manily researches the DCF. S-MAC protocol is based on the IEEE 802.11 protocol, considering from the energy efficiency to improve. Which reduces the idle listening time by periodically listen/ sleep mechanism to improve the network energy efficiency. Because the fixed time rate of listen/sleep in S-MAC, which can not adapt to dynamic changes in network load, so this paper proposes a improved protocol of dynamic adjustment listen/sleep duty cycle.At last. the relevant network scenarios were constructed to study the performance of the related protocol in underwater acoustic environment by NS2 simulation environment. Considering the characteristic of underwater acoustic environment, The paper statistics and analysis four network indicators:network delay, throughput, energy consumption, packet success rate. Simulation results show that S-MAC protocol is superior in energy to 802.11DCF in the three network scenarios, mainly due to S-MAC protocol uses a periodic listen and sleep mechanism, When the network traffic is heavy,the improved protocol is better than the original S-MAC protocol on energy efficiency.