Abstract: In the users’multiple antenna cognitive multiple antenna cooperation feedback system,the channel direction information has quantization error,thus the existing user selection method will not be able to maximize the second user system capacity,and increase the primary user system interference．In order to eliminate the influence of the quantization error on the primary and secondary user system,this paper put forward a kind of statistical independent factor second users selection method based on the BD precoding．Analysis and simulation results show that the proposed scheme effectively enhances the second user system capacity in the primary user system interference limited conditions.

Key words: Cognitive radio,Spectrum share,MIMO,Broadcast channels