Relay beamforming with power minimization in cognitive radio network

This paper studies the cognitive one-way relay network which is composed of a pair of primary transmitter and receiver. A two-step one-way amplify-and-forward (AF) relaying scheme is used by the primary network who utilizes the cognitive radio (CR) terminals as its relay nodes. Simultaneously, the cognitive information is transmitted by multiple CR terminals to the CR base station. In the first phase of AF relaying, the primary signal is forwarded by transmitter to the CRs/relays. The CRs/relays multiple the cognitive signals to the received primary signal and accomplish a distributed beamforming in the second phase of relaying. The authors aim at minimizing the CRs/relays power under the different signal to interference pulse noise ratio (SINR) restraints at the primary receiver and the cognitive base station (BS). The results can be seen from the simulation that the minimum CR terminals/relays power will increase with the rising of the SINR constraints. Besides, the performance difference between CR terminals/relays beamforming and without beam-forming is affected by the minimum CR terminals transmit power and the number of relays. Furthermore, with the number of CR terminals/relays rising, the performance difference is decreasing.