Adaptive relay selection on individual power constraint for hybrid relay systems

Hybrid relay systems using an amplify and forward (AF) protocol and a decode and forward (DF) protocol together are introduced in cooperative networks. For this hybrid system with a power constraint, we propose an adaptive relay selection algorithm to extend the network lifetime while avoiding the degradation of the received signal to noise ratio (SNR) at the destination. In the adaptive relay selection algorithm, two relays are selected among many as the channel state information (CSI) and the residual power of each relay are considered. One is chosen to operate in the AF protocol, and the other is in the DF protocol. Simulation results show that the proposed algorithm achieves better performance than those of conventional methods.