A wave-like amendment-based time-division medium access slot allocation mechanism for underwater acoustic sensor networks

Recently, there has been a growing interest in monitoring aqueous environments using Underwater Acoustic Sensor Networks (UASNs). In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes into the acoustic channel, which is characterized by high propagation delay and low data rate, which is challenging for system synchronization, energy consumption and network output. Most researches in MAC protocol used for UASNs adopt collision avoidance mechanism with handshaking methods at present. But the long acoustic propagation delay results in low throughput and poor energy efficiency. In this paper, we propose a new amendment-based TDMA slot allocation mechanism, which is named WA-TDMA. Slot allocation starts from the node which launched as the center outward to form the wave-like proliferation and the slot allocation and amendment are continuously, which like the performance of wave. This can shorten the initialization time of the network. With the help of amendment, protocol can adjust slot usage to improve slots utilization and deal with slots reuse problem. The main function of the amendment is to avoid the slot collision, and improve the efficiency of slot using. The key characteristic of our mechanism is that it deals with holistic slot allocation problem well, and improve the slots utilization with certain protect distance at the same time.