A relay-triggered cooperative spectrum sensing in cognitive radio networks

A relay-triggered cooperative spectrum sensing scheme is proposed in this paper to detect the spectrum opportunities for cognitive radio (CR) networks. Firstly, we design a relay-triggered individual spectrum sensing scheme. Specifically, we exploit a relay signal generated by a cognitive transmitter (CT) who has relaying capability and acts as a full-duplex amplitude-and-forward relay to trigger the primary link's close-loop power control (CLPC) which has been frequently used in practical wireless communication application, resulting in primary transmitter adjusts its transmit power under CLPC, the CR receiver observes the energy of the primary signal and decides whether the primary receivers (PRs) are within or out of CT's coverage. Then, considering the fact that local spectrum sensing may be not reliable due to the fading and shadowing effects, we further develop the proposed individual spectrum sensing scheme to a new collaborative one where multiple CRs are involved in sensing and the common receiver combines the decisions received from cooperative CRs to get a final decision which will improve the sensing performance. Finally, the performances of the proposed schemes are illustrated by simulations.