On optimized decode and forward relay assisted CR system design for throughput maximization

This paper proposes a joint spectral sensing and secondary data transmission scheme in a decode-and-forward (DF) relay assisted cognitive radio network (CRN). Periodic spectral sensing is done in each frame that primarily consists of two slots: sensing slot and data transmission slot. Sensing information of cognitive source (CS) and cognitive relay (CR) are cooperatively combined at CS to determine reliably the presence or absence of the primary user (PU). An optimization framework is developed to determine the sensing time, data transmission time for CS and CR along with their associated transmission power with an aim to maximize the average throughput of secondary transmission under the constraints of target detection probability, sum transmission power and interference to PU. Simulation results show that significant improvement in average throughput is achieved when the transmission power of CS and CR are jointly optimized with the sensing duration and transmission time of CS and CR. Performance improvement over amplify-and-forward (AF) relay is also reported.