Outage performance of causal cognitive radio Z-interference fading channel with cognitive relaying

In this paper, we analyze the outage performance of causal cognitive radio Z-interference fading channel where cognitive user transmits concurrently with primary transmission while ensuring no degradation in primary´s outage performance. Cognitive relay with best channel gain to primary receiver is selected from the set of qualified neighboring inactive cognitive users to relay primary´s message. Analytical and simulations results show that cognitive relaying leads to improved outage mutual information and additional diversity for primary receiver while achieving significant outage mutual information for cognitive user.