Cognitive Incremental Relaying Networks with Spectrum Sharing and Hardware Impairments

In this paper, we investigate the outage performance of underlay cognitive amplify-and-forward incremental relaying networks with multiple relays and subject to hardware impairments. Unlike regular cooperative diversity networks, which make an inefficient use of the channel resources because relays always forward the source signal regardless the channel conditions, incremental relaying exploits limited feedback from the destination terminal, and sends a single bit to indicate success. If the destination provides a negative bit via feedback, the relay retransmits an amplified version of the source signal. The end-to-end signal-to-noise-and-distortion ratio (SNDR) of incremental relaying over independent non-identical Rayleigh fading channels is formulated for partial relay selection (PR) and opportunistic relay selection (OR) schemes, based on which the respective outage probabilities are evaluated. Our simulation results show that the incremental relaying protocol can achieve maximum diversity with a more efficient channel utilization and better performance compared to fixed cooperation.