Beamforming for MIMO cognitive radio with single primary and multiple secondary users

Linear MMSE Channel Estimation for Underlay Cognitive Radio Networks

“…Other studies have proved that different beamforming techniques may cause improvements on the spectral efficiency [4] and also SINR maximization [5]. Therefore, the following facts are enough reasons to motivate the study of channel estimation techniques and their impact on the performance of CR networks: 1) Accuracy in the CSI estimations brings huge improvements to wireless transmissions; 2) Accurate CSI estimations allow CR devices to successfully explore powerful interference cancellation techniques; 3) The imperfections of the CSI estimations are due to the miss-detection of signals; 4) Study of imperfect CSI effects brings means of analysing possible errors and extrapolation of interference thresholds; 5) Current communication protocols allow transmission periods dedicated to training and channel estimation; 6) Use of known pilot sequences allows SUs to estimate both SU's and PU's channel matrix.…”