Joint subcarrier and power allocation for reciprocally-benefited spectrum sharing in cognitive radio networks

Aiming at reducing the outage probability of primary users (PU) and obtaining spectrum resources for secondary users (SU), in this paper, we proposed a joint subcarrier and power allocation scheme (JSPA) for reciprocally-benefited spectrum sharing with SUs cooperating with PUs. In JSPA scheme, SUs adopt the decode-and-forward (DF) relaying protocol to help PUs in a two-stage way. Meanwhile, a fraction of unallocated licensed spectrum is allocated for the secondary transmission in every stage. However, if the two-stage cooperation still cannot satisfy PUs´ outage quality-of-service (QoS) requirement, SUs then switch to the access mode to entirely capture the licensed spectrum. Our proposal is to maximize the average transmission rate of SUs through joint allocation of subcarriers and power. The closed-form expressions about the outage probability and average transmission rate of both PUs and SUs are derived. Simulation results show that compared with the conventional cognitive cooperation schemes, the average transmission rate of SUs improves.