DBR Routing Protocol Improvement In Underwater Acoustic Sensor Network

Due to certain conditions of underwater environment, providing an efficient and scalable routing protocol in underwater acoustic sensor networks(UASN), has many challenges. Communication in UASNs is done through acoustic channel; therefore presenting low speed, high error bit rate, small bandwidth, variable and high propagation delay. Also, in UASNs, improving the energy efficiency is one of the most important issues since replacement or recharging of nodes batteries has a high cost. Moreover, many proposed routing protocols for UASNs, use full information about the position of the nodes, and obtaining this information is a fundamental challenge in these networks. In this thesis, a new protocol is proposed in which only the depth information of the nodes is used in the routing process. The protocol is based on Depth-based Routing protocol(DBR).The improved DBR(iDBR) does not require full-dimensional location information of sensor nodes. Instead, it needs only local depth information, which can be easily obtained with an inexpensive depth sensor that can be equipped in every underwater sensor node. A key advantage of our protocol is that it can handle network dynamics efficiently without the assistance of a localization service. The proposed protocol improves DBR by balancing the overall energy consumption and thereby increase the network lifetime. In order to reach that objective the protocol takes into account the residual energy of the nodes in the routing calculations. It also takes advantage of a novel network architecture, which has multiple surface sinks. The surface sinks communicate with each other using surface radio and form a radio network on the water surface. Such network architecture not only can bring about many benefits such as high throughput but also energy efficiency. Moreover, we took a cross-layer approach for the routing protocol implementation by using an adaptive OFDMA-based MAC protocol whose Energy Conscious operation mode offers better energy efficiency. The MAC protocol design approach exploits the multi-path characteristics of a fading acoustic channel to convert it into parallel independent acoustic sub-channels that undergo flat fading. Communication between node pairs within the network is done using subsets of these sub-channels, depending on the configurations of the active mode of operation.