User cooperation in OFDM-based cognitive radio networks with simultaneous wireless information and power transfer

In this paper, we consider user cooperation in a cognitive radio network (CRN) which is operated in orthogonal frequency division multiplexing (OFDM) scheme in the context of simultaneous wireless information and power transfer (SWIPT). In particular, the secondary transmitter (ST) cannot only relay the received primary signals to assist primary transmission and earn more opportunities to utilize the primary spectrum, but also extract energy from part of those signals to power both the relay transmission and the secondary transmission. Under such protocol, we propose two joint information and energy cooperation schemes corresponding to two practical receiver architectures at the ST, namely, time switching and power splitting. The SU's achievable rate is maximized by jointly optimizing time and power allocations in cooperative transmission while meeting the PU's Quality-of-Service requirement. Simulation results demonstrate that the proposed user cooperation schemes significantly improve the achievable throughput.