Erasure based error analysis with M-ary PSK signaling for cooperative diversity systems

We consider a cooperative diversity system comprising of a source, a decode and forward (DF) relay and a destination. The performance of the decode and forward (DF) protocol in a cooperative diversity system depends solely on the accuracy of decoding of the symbols at the relay. In this work, we pine to improve the accuracy of the decoding process and in-turn the performance of the cooperative diversity system by introducing erasure regions in the decoding process at the relay. The erasure regions are designed in such a way that if the received signal lies in any of these regions then, the relay does not participate in the cooperation. At the destination, a modified selection combining scheme known as scaled selection combining (SSC) is employed. A theoretical expression for the end-to-end symbol error probability of an M-ary PSK modulation in a Rayleigh fading environment is derived based on the paired error approach invoking the idea of the erasure regions. Simulation results substantiated with theoretical results elucidate that the cooperative diversity system with erasure significantly outperforms the system without erasure.