Integrated Time Synchronization and Multiple Access Protocol for Underwater Acoustic Sensor Networks

Due to the limited energy and mobility of the traditional sensor nodes, autonomous underwater glider (AUG) is widely used in underwater acoustic sensor networks to achieve long-term and large-scale marine environmental monitoring. In the communication between AUGs, time synchronization (TS) and multiple access control process (MACP) both need control frames to guarantee the data transmission. However, the independent execution of these two processes causes the control frames to be sent repeatedly, resulting in more transmission delay and energy cost. In order to communicate between AUGs more efficiently, an integrated TS with multiple access (TSMA) protocol is proposed in this paper. Within the AUG group, an AUG is selected as the beacon node to provide a standard clock to complete the intra-group TS process, while inter-group TS adopts the non-beacon synchronization method. In the TS process, the effect of the relative movement between AUGs is considered to improve the accuracy of synchronization. Besides, we create a new control frame that can fuse the message exchange of TS and MACP. Simulation results show that TSMA has a better performance in terms of the packet delivery fraction, synchronization errors, and energy efficiency.