Energy-efficient power allocation for OFDM-based cognitive radio with timeout probability constraint of primary users

An energy efficiency (EE) maximization scheme in a spectrum overlay scenario with multiple primary users (PUs) and one cognitive radio (CR) user (secondary user, SU) co-existing side by side bands is considered, where instead of using conventional interference power constraint (IPC) to ensure normal transmission of PUs, a timeout probability constraint (TPC) transformed from the delay effect of PUs is proposed to limit the interference from SU. We formulate the resulting problem as an epigraph problem and transform the non-convex objective function to the convex one. Numerical and simulation results are provided to show the impacts of system parameters and verify the efficiency of our proposed scheme.