An efficient self-deployment methodology for maximized coverage of mobile underwater sensor networks

A well-optimized and well-performed communication network protocol is necessary to build successful underwater acoustic sensor networks (UWASNs). But for wired and wireless communication, medium access control (MAC) has a great effect on network performance and optimization. But unlike land-based MAC protocols, underwater MAC protocols come with various challenges and issues like high propagation delay, limited bandwidth for communication signals, large attenuation in network signals, and the high noise level in signals. It is very challenging to build a well-optimized underwater MAC protocol. Also, in UWASN, sensor nodes are generally divided into sub-network parts to reduce the propagation delay of data signals. But this creates the problem of non-uniform traffic load in sensor nodes. So, considering these issues, dynamic hold time MAC (DHT-MAC) protocol is proposed here. In this protocol, depending on the distance from the central node, sensor nodes are divided into two sub-network zones (parent node and child node). Depending on the traffic load and propagation delay, the child nodes can change their respective parent nodes dynamically. Advantage of the proposed method is that, if any of the parent nodes stops working, the child node will connect to the nearest parent node. When collecting the data signals, it has been observed that child nodes have a light traffic load compared to parent nodes. So dynamic cooperative transmission MAC (DCT-MAC) protocol which is a contention-based MAC protocol has been used in child nodes and as parent nodes have high traffic load, reservation-based MAC protocol has been used.