Concerning the problem of spatial-temporal uncertainty caused by low bandwidth and high latency as well as insufficient network state observations in UnderWater Acoustic Sensor Network (UWASN), a medium access control protocol based on Partially Observable Markov Decision Process (POMDP) for UWASN was presented in this paper. Firstly, the link quality and residual energy of each node were divided into multiple discrete levels for expressing nodes' state information. After that, channel access probability was predicted by receivers through the history information of channel state observation and channel access actions, and then the optimal channel scheduling strategy for senders was acquired. Senders communicate with receivers and transmit data packets in their time slots according to the assigned sequence from the optimal channel scheduling strategy. When the communication was completed, the states of next time slot of the related nodes were predicted based on the statistics of the network transfer probabilities. Simulation results show that the proposed protocol can improve the data packet transmission rate as well as the network throughput, and decrease the energy consumption.

In order to decrease the influence caused by low bandwidth and high latency on Media Access Control (MAC) layer in Underwater Acoustic Sensor Network (UWASN), an Evolutionary Game Theory based MAC (EGT-MAC) protocol was proposed. In EGT-MAC, each sensor node adopted two strategies including spatial multiplexing and temporal multiplexing. With the replication kinetics equation, each strategy got an evolutionary stable strategy and reached stable equilibrium of evolution. In this way, it improved channel utilization rate and data transmission efficiency to achieve performance optimization for MAC protocol. The simulation results show that EGT-MAC can improve the network throughput as well as the transmission rate of data packet.