Asymptotic outage analysis of incremental decode and forward cognitive radio relay network

In this paper, we consider a secondary incremental relaying (IR) network that operates simultaneously with multiple primary receivers in the same frequency band under spectrum sharing constraints. The IR network consists of multiple decode-and-forward (DF) relays and employs opportunistic relay selection for cooperation. We analyze the outage probability of the network where the selected relay opts to cooperate when the destination fails to decode the direct transmission from source.We derive the expression of asymptotic outage probability, diversity gain and coding gain. The diversity gain was found to be the same as that of a non-spectrum sharing system. Furthermore, we investigate the impact of number of relays and primary-to-secondary network distance on outage probability and coding gains, which is validated through numerical simulation.