Performance Analyze Of The Secondary Entwork In The Cognitive Radio Network

Due to the rapid development of wireless communications, the radio spectrum-it is believed-is becoming crowded. Cognitive radio, which would allow secondary users/networks (SUs/SNs) to share the allocated spectrum with primary users/networks (PUs/PNs) under some conditions, is a way to improve spectrum utilization. Sometimes the PN or the SN is too large to ensure reliable communication for every link. An efficient way to address this issue is to transmit signals, with the help of one or more relays, which can compensate for the effects of signal fading and shadowing. Cognitive relay network which is a cognitive radio network with the secondary network of a relay network is a potential way to improve the performance of the SUs and guarantee the quality of service (QoS) of the PUs. There is a very important practical significance to research the key technology of the cognitive relay network.The paper analyzes the performance of the SN in the cognitive relay network with the following there aspects:first, the relays which located at different places use the cooperative beamforming to maximize the SINR of the receiver in the SN with the QoS of the PN guaranteed; second, the joint relay and receive beamforming was designed to maximize the capacity of the SN when the receiver node of the SN is equipped with multi-antennas; third, the outage probability of the SN is derived with the interference from the PN to SN considered. The first two areas are research on the beamforming in the cognitive relay network, and based on the principle of the convex optimization, the iterative algorithms are proposed to get the beamforming vector; while the last part use the probability density function (PDF) of the channel gain and the basis knowledge of the probability theory to derive the closed-form expression of the outage probability. Through these studies, we get the main factors impacting the beamforming gain of the cognitive relay network and the degree of the effect from the primary network on the outage probability of the secondary network.