Cognitive relaying systems based on network and superposition coding in multiple access primary channels

We propose a cognitive relaying protocol using network and superposition coding in multiple access primary channels, where two licensed primary users A and B transmit to a common destination D with the assistance of an unlicensed secondary transceiver C that acts as a relay. The secondary transceiver C attains the opportunity of spectrum sharing by relaying the primary users messages. Network coding and superposition coding are utilized at C that superimposes its own message on network-coded primary signals. In this paper, the probability of outage regions is computed for multiple access channel (MAC) as well as the achievable region. Based on the probability of these regions, we analytically derive the outage probabilities for both the primary and secondary systems under the cognitive relaying protocol in multiple access primary channels.