Research Of Efficient MAC Protocol For Mobile Underwater Wireless Sensor Networks

With the deepening of human to the marine exploration, underwater wireless sensor network(UWSN) has become a new research hotspot because of the application in oceanographic data collection, environment monitoring, exploration of marine resources and national defense strategy. Sound waves become the carrier of underwater communication. In addition, the underwater acoustic channel is featured with low bandwidth, long latency and dynamic in underwater environment, which makes the existing protocols and technologies in terrestrial wireless sensor networks cannot be directly applied to UWSN.This paper studies medium access control(MAC) protocol for UWSN. Network characteristics and architecture of UWSN are presented, as well as the key issues in underwater MAC protocol design, such as hidden stations and space-time uncertainty. Furthermore, the existing typical underwater MAC protocol will be elaborated, such as R-MAC, Slotted FAMA, ALOHA, T-MAC and so on.In view of the dynamic communication environment for UWSN, a motion model of underwater sensor node is analyzed as well as the motion prediction algorithm. And a new MAC protocol of underwater mobile sensor networks based on variable-length slots: VS FAMA was proposed. In VS FAMA, the time-slot would adaptive adjust according to the distance between nodes, so that it can make better use of the time-slot resource. It is also a reservation-based protocol. The goodput performance of the proposed protocol is verified by extensive simulation.