Collision classification MAC protocol for underwater acoustic communication networks using directional antennas

Traditional underwater acoustic communication networks (UACNs) generally use omnidirectional transmission technology that causes a large number of data-packet collisions, thus resulting in low network throughput and high end-to-end delays. Compared with omnidirectional transmission technology, directional technology only sends and receives data packets in a specified direction. This can significantly reduce the probability of collisions and improve network performance. However, it also causes a deafness problem, which occurs when the sending node sends a data packet to the receiving node but the receiving node is unable to reply to the sender, because its antenna beam is closed. To resolve this issue, this study proposes a collision classification media access control (CC-MAC) protocol for UACNs. With this protocol, the underwater acoustic channel is divided into two subchannels, and the nodes transmit corresponding data types on them. The sending node can estimate the current status of the receiving node (i.e., no collision, normal collision, deafness) according to the type of the data packet received and the sub-channel it arrived on, and it can choose correct options to improve network efficiency. Finally, we verify the performance of CC-MAC via simulations, showing that the protocol achieved higher network throughput and lower end-to-end delays.