Study On Performance Of MAC Protocols For Underwater Acoustic Sensor Networks

With the increasing demand for human resources and decreasing land resources, improving underwater acoustic communication technology and sensor network technology have prompted the development of Underwater Acoustic Sensor Networks(UASN) for ocean exploration. Because of its broad application prospects in military and civilian, UASN is gradually concerned by the countries around the world. Since the underwater environment is quite different from the air, UASN can not directly use the existing protocols for the land sensor networks. In addition, underwater acoustic channel is low transmission rate, narrow bandwidth, large signal attenuation, serious multipath interference and so on, which make the protocol design of UASN more difficult.In this paper, the characteristics of UASN are studied firstly, and then the underwater acoustic communication simulation platform is added in the network simulation software NS2 according to the characteristics of the underwater acoustic channel. According to the existing competitive MAC protocols theory, the pure ALOHA, the slotted ALOHA, non-persistent CSMA and 1-persistent CSMA protocol codes are written, and they are compared with IEEE 802.11 in terms of average transmission delay, network throughput and average arrival rate of UASN. The results show that the handshake mechanism, physical carrier sensing, virtual carrier sensing, Data transmission slotted of competitive MAC protocols is in poor performance in terms of reducing the probability of data collision in propagation delay larger underwater environment, and nodes need to be in the sensing state, consume more energy, which is not suitable for the energy limited UASN.As the main consideration of the MAC protocol for UASN is to save energy, this dissertation studies the S-MAC protocol with sleep mechanism, and adds it to the underwater environment. The problems of scheduling and energy waste in underwater environment are analyzed, then from the aspect of saving energy, the broadcast scheduling mechanism is improved, the sleep mechanism is added, and E-MAC is put forward. Through the same simulation scenarios, the E-MAC and S-MAC simulation experiments are conducted to compare their network survival time, energy consumption of receiving a certain number of packets and packet arrival rate. The results show that the E-MAC protocol has less energy consumption of sending a single packet, longer network lifetime, and higher packet arrival rate.