Network-Coding-Based Cooperative Transmission in Wireless Sensor Networks: Diversity-Multiplexing Tradeoff and Coverage Area Extension

In Wireless Sensor Networks large number of nodes and limited energy available per node calls for designing efficient transmission protocols. Cooperative transmission is one of the protocols which helps wireless nodes to achieve spatial diversity, which translates into reduction in transmission power or increase in coverage area. Cooperative protocol can be realized with or without (called conventional afterward) network coding; and the network-coding-based (respectively the conventional) protocol can be operated in either static or adaptive manner. For an efficient operation of cooperative protocols, good quality inter-source channels are required, which in turn depend on relative location of nodes within a network. In this work, a three-node cooperative network consisting of source, relay, and destination nodes is considered. At high signalto-noise ratio values, we first approximate the outage probability result when the network-coding-based adaptive protocol is implemented. Then, based on the approximate probability result, a diversity-multiplexing tradeoff is studied; the result shows that this protocol performs similar to an amplify-and-forward protocol. Next, for the various protocols, the coverage area and relative location of the relay that minimizes the outage are studied; for that the exact outage probability results are used. Over wider geographic area, network-coding-based static and adaptive protocols perform better than their conventional counterparts, and this happens when the relaying node is positioned closer to the destination than the source. The conventional protocols perform better when the relay is positioned closer to the source. In Wireless Sensor Networks, assuming that relay nodes which are closer to both the source and destination exist, these results help as a guide in selecting with which node to cooperate (relay selection) when one cooperative scheme is implemented.