Underwater Acoustic Sensor Network Mac Protocol Research

The underwater acoustic sensor network, a newly-emerged network technology, has been used in such wide areas as oceanographic data collection, pollution monitoring, disaster warning, offshore exploration, navigational assistant and tactical surveillance application. And those unmanned underwater machines, such as UUV,AUV, can be found in the applications of collaborative monitoring missions like marine resources exploration and data gathering. While the implementing of these applications lies in the key technology——underwater acoustic communications technology. The underwater acoustic sensor network is composed of a number of sensors and vehicles which are deployed to perform collaborative monitoring tasks over a given area.However, it will take several months, or even a year to install each sensor joint. And as the sensor joints are supported by batteries, the operating life of the underwater acoustic technology will be greatly limited due to the limited battery power. In addition, the efficiency of underwater acoustic sensor network will also be reduced as a result of narrow underwater channel bandwidth,multipath and propagation delay. Therefore, it is a critically important mission for underwater acoustic network to design an underwater acoustic communication technology which can improve the throughput and reliability of network to the greatest extent, and at the same time, energy consumption and propagation delay can also be lowered effectively.Since the net structure of underwater acoustic sensor network is particularly organized, the design target of MAC protocol is different from those in traditional land-based wireless sensor network. In underwater acoustic sensor network, the primary consideration is to save energy, and then comes the expansionary. While terrestrial wireless networks attached more importance to the throughput, delay and fairness, which are compared less important with those underwater acoustic sensor network.The paper is mainly focused on the research of MAC protocol, in which the characteristics of underwater acoustic sensor network and its effects to MAC protocol are discussed. Meanwhile, a brief description of existed underwater MAC protocol and an emulation experiment geared to some of the protocols are carried out. Finally, we propose a new mixed MAC protocol suited for underwater acoustic network, and its validity has been verified through emulation experiment.