A cooperative spectrum sharing protocol for cognitive two-way AF relaying system

This paper investigates the performance of a cooperative spectrum sharing protocol for cognitive two-way amplify-and-forward (AF) relaying system. In the proposed framework, two primary users (PUs), PU
1
and PU
2
coexist with a secondary user (SU) in the same frequency band albeit with different priorities. Primary users by virtue of having a license to operate over the frequency band have higher priority than secondary user. When bidirectional communication between PU
1
and PU
2
is not possible due to link failure or deteriorating channel conditions, PUs seek the assistance of the secondary user. SU by acting as a two-way AF relay helps in forwarding the information from PU
1
to PU
2
and vice-versa, in exchange, it is allowed to access the PU's spectrum. Our analysis shows that two-way relaying helps in improving the spectral efficiency and reducing the outage probability of primary and secondary user. Good agreement between theoretical and simulation results validate the analytically obtained expressions.