By deducing the distribution of the normalized channel covariance matrix,a novel limited feedback scheme is proposed under multiple users（MU） multiple-input multiple-output（MIMO） broadcast channel（BC） system.The proposed scheme has advantages in three aspects.First,it has no constraints on the number of users or antennas.Second,each user＇s feedback bits are independent of the number of receiving antennas.Third,the proposed scheme avoids the storage of large-size codebook on the transceivers.Simulation results show that the performance of the proposed scheme is close to the perfect channel state information（CSI） case and it just needs a small number of feedback bits.
CHENG Tie-zheng,YUAN Chao-wei School of Information and Communication Engineering,Beijing University of Posts and Telecommunications,Beijing 100876,China
In cooperative spectrum sensing, more secondary user makes more opportunity for detecting the vacant spectrums, which resulting the spectrum utilization improved, however much bandwidth would be occupied for sending the local observation results, inducing the reduced secondary throughput. In this paper, an adaptive algorithm for selecting detection threshold was proposed, where the maximized secondary throughput can always be achieved while assuring sufficient protection to primary user, regardless of the number of sensing users in cognitive radio networks. Theoretical analysis and simulation results validate the proposed scheme.
