A TDMA based EM controlled multi-channel MAC protocol for underwater sensor networks

Successful wireless communications in underwater with high throughput possess a great challenge still today. Due to the unique environment in underwater, medium access protocols (MAC) for terrestrial networks are not suitable for such environment. High attenuation of electromagnetic (EM) wave in water makes acoustic wave a more appropriate choice for communication in underwater. However, the low available bandwidth, high propagation delays and spatial-temporal uncertainty of the nodes make the MAC protocols with acoustic channel a vast area for research. In this paper, we propose a novel multi-channel MAC protocol for underwater sensor networks (UWSNs) employing both acoustic and EM waves. The proposed MAC protocol has a single EM based control channel which is used for managing the node data transmission times and confirmation messages. On the other hand, multiple acoustic channels are used as the data communication channels. In the proposed protocol, time division multiple access (TDMA) technique is used for control channel to prevent any collision between control signals of the nodes. Because of the nature of zero collision in the control channel, the whole MAC scheme remains in a collision-less state. Extensive simulations are carried out for evaluating the performance of the proposed MAC protocol demonstrating its validity.