Optimal cooperative beamforming design in cognitive radio networks with multiple secondary user links

Abstract

Summary In this paper, a novel beamforming method is proposed for a more realistic cognitive radio system with several secondary transmitters and receivers, a number of relays, and 1 primary transmitter and receiver. When the primary user link is idle, all secondary transmitters access temporal spectrum holes to simultaneously broadcast their information to the relays each associated with an infinite buffer. In the next stage, the relays transmit the information to the secondary receivers using a cooperative beamforming method no matter whether primary user link is silent or not. The proposed method of designing the beamforming vector enables the system to maximize the power received by the secondary users while maintaining the interference plus noise power at the primary user receiver below a predefined threshold. Results of simulations confirm validity of the method and improved performance compared to the zero‐forcing beamforming. The impact of channel quality between nodes on the performance of the system is also investigated.

Beamforming and power allocation in the downlink of MIMO cognitive radio systems based on multiobjective optimization

“…The same argument can be concluded for SINR S optimization in respect to v S . The numerator of SINR is convex, and the optimized vectors in (14)…”

“…Besides, an effective power allocation technique can remove or reduce the interference induced from SU to PU . As a result in recent years, joint power allocation and beamforming has been widely studied in the literature for CR systems …”

“…Therefore, CR and MIMO have been combined in order to benefit the capacity of multiple antennas . An efficient way to achieve spatial multiplexing and limit interference in MIMO CR systems is beamforming of transceiver antennas . Besides, an effective power allocation technique can remove or reduce the interference induced from SU to PU .…”

“…15 As a result in recent years, joint power allocation and beamforming has been widely studied in the literature for CR systems. 13,14 Beamforming and power allocation of MIMO CR studies can be categorized into two classes. In one category, some separate pair users communicate with each other in the presence of other pair users such as previous studies.…”

“…[10][11][12] An efficient way to achieve spatial multiplexing and limit interference in MIMO CR systems is beamforming of transceiver antennas. 13,14 Besides, an effective power allocation technique can remove or reduce the interference induced from SU to PU. 15 As a result in recent years, joint power allocation and beamforming has been widely studied in the literature for CR systems.…”