Energy-efficient resource allocation for OFDM-based cognitive cooperation system using adaptive relaying strategy

We consider a spectrum sharing protocol in which a secondary system can operate on the same spectrum with a primary user. In the protocol, the secondary system helps the primary system achieve its target rate by acting as a relay for the primary system. As a reward, the remaining subcarriers can be used for the secondary transmission. In order to alleviate the disadvantages of amplify-and-forward (AF) and decode-and-forward (DF) relaying techniques, an adaptive relaying scheme is proposed. In this paper, we study energy efficient resource allocation for the cognitive cooperation system. The considered problem is modeled as a non-convex optimization problem which takes into account the total transmit power of the secondary system and the minimum required data rate of the primary system. The optimal set of subcarriers used for cooperation, subcarrier power allocation and relaying technique are derived for maximization of the energy efficiency (EE) of the secondary system by using fractional programming and dual theory. Simulation results demonstrate that significant performance gains can be achieved by the devised scheme.