Jointly cooperative decode-and-forward relaying for secondary spectrum access

A new transmission protocol for joint cooperation between a primary and secondary user in a cognitive radio system is proposed. If successful decoding is achieved, the primary/secondary transmitters behave as relays for the other system. With more efficient use of the communication resource, performance is enhanced. The proposed scheme builds on the work and offers improved outage probabilities for both the primary and secondary systems. The paper provides a full characterization of the Markov Chain describing the protocol behavior and a closed form expression for the stationary distribution of the chain. Furthermore, exact computation or tight approximations for the outage probabilities for all states of the chain are derived. Simulation results exhibit a performance improvement between 22 and 48 percent for primary system and an uniform decrease of outage probability for secondary system.