Lifetime maximization of secondary cooperative systems in underlay cognitive radio networks

In this work, we consider relay selection strategy in an amplify-and-forward cooperative cognitive ratio system in order to prolong lifetime of the energy-constrained relay network. The network lifetime considered in this work is based on the outage probability of the secondary cooperative system. Not only the channel condition of each relay, selection of best relay has to satisfy the interference constraint for primary user as well as the residual power of each relay. Here, we proposed four strategies to select the relay for prolonging the lifetime depending on the channel state information (CSI) and residual energy information (REI). From the simulation results, the minimum outage probability strategy (MOP) performs the best among four strategies.