Study On MAC Protocols For Underwater Acoustic Networks

Underwater sensor networks find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation, tactical surveillance, and mine reconnaissance. Key differences between terrestrial radio wireless networks and underwater sensor networks are the large propagation delay of sound, extremely low point-to-point data rates and high raw BER. Thus it is often proposed that media access control (MAC) protocols for underwater networks be developed ground up and not directly adopt existing terrestrial protocols.The main work is to design a MAC protocol of underwater acoustic networks to ensure the data transmitted transparently between the network layer and physical layer. It is under the assumption that the physical layer is fully meet the requirements.Three widely used MAC protocols: ALOHA, basic CSMA/CA and response mode CSMA/CA are simulated under the condition of acoustic channel. The network capability is compared. The simulation results show that the basic CSMA/CA has a higher error rate compared with the response mode CSMA/CA, but the overall capabilities are superior to the other types of protocol. The basic CSMA/CA is more suitable for underwater acoustic communication network.Binary exponential backoff (BEB) algorithm is used when the data packets are in collision. The data rate of underwater acoustic communication network is usually very low, the BEB algorithm wastes a lot of backoff time and make the media access delay significantly slowed. In this paper, in order to overcome the access speed, the BEB algorithm is improved. The improved backoff algorithm could adaptive adjustment the current channel idle time slot, simulation results show that the media access delay, network utilization, etc. have been improved.