Performance analysis of turbo-coded cooperative relaying in spectrum-sharing systems

This paper provides an analytical study on the bit-error rate (BER) of the turbo-coded cooperative relaying in spectrum-sharing systems subject to Rayleigh fading. It is assumed that a single relay that maximizes the received signal- to-noise ratio (SNR) is selected in a secondary multi-relay network. We consider that the transmit power conditions of the underlay system is controlled by the joint power constraint of the interference in the primary network and the maximum allowable transmission power at the secondary network. Moreover, the proposed scheme takes into account the effect of primary user (PU) interference on the neighboring secondary network. First, we derive an expression of a tight upper bound for the BER of the secondary network. Then, we investigate the cooperative diversity gain of the underlying scheme. Finally, the proposed analysis is validated by Monte-Carlo simulations.