Asymmetric Collision Phenomenon and its Impact on Underwater Acoustic Networks

Through experimental results, we reveal an asymmetric collision phenomenon in Underwater Acoustic Networks (UANs), which is caused by the different collision tolerance of preamble and data fields in acoustic communications. The asymmetric collision phenomenon can significantly affect the performance of underwater MAC protocols. In order to accurately evaluate underwater MAC, we develop an asymmetric collision model and use slotted ALOHA, a popular random access MAC in UANs, as an example to illustrate how asymmetric collision affects MAC performance under different network settings and routing strategies. Simulation results verify that the asymmetric model is superior to the traditional model in terms of collision probability, throughput and throughput-progress calculations.