Research On Limited Feedback In Cognitive Radio Networks

In recent years, as an effective measure to improve spectrum utilization, Cognitive Radio(CR) is attracting more scholars' attention. The previous research on cognitive radio is mainly about spectrum detection, spectrum management, power control and interference temperature. This paper researches on the limited feedback in cognitive radio networks, based on the theory of feedback.MIMO technology provides the spatial resources that can be shared and allocated, which is beneficial to cognitive radio networks. But the transmitters should be with prior knowledge of channel state information, so that MIMO works well. In traditional MIMO networks, the transmitter can estimate the required CSI by exploiting channel reciprocity and feedback. In cognitive radio networks, the secondary transmitter can observe primary transmission to estimate secondary-to-primary CSI, or the primary receiver sends quantized secondary-to-primary CSI to secondary transmitter. The secondary user designs beamforming, controls transmit power to maximize capacity and avoids interference to the primary user. The capacity of feedback channel is limited, so the primary user sends the quantized channel state information to the secondary user.This paper first researches on the effect of channel state information and the interference power control of the primary user to the secondary user. It is obvious that the multiple antennas of secondary transmitter can increase capacity of secondary user. Then the paper introduces some theory about limited feedback, researching on the performance of the cognitive radio network, and introduces cooperative feedback. The last chapter focuses on the cooperative feedback of cognitive radio networks with both primary user and secondary user, designing the beamforming vector of secondary user, controlling the transmit power of secondary user based on the feedback CSI and IPC. The last is the simulation result.