A multiuser cognitive communication system is considered under the existence of multiple primary transmissions where the spatial multiplexing mode of operation is implemented among the nodes. Simultaneous spectrum sensing and data reception is performed on the cognitive systems. In order to efficiently decoding the secondary data streams MMSE detection is carried out at the secondary receiver. At the remaining signal we also perform spectrum sensing to detect the presence of primary activity or not. The detection performance is plotted with the means of ROC curves. The probability of unexpected interference is estimated and also is minimized when the secondary vacate the channel.

Keywords : Cognitive Radio, Detection probabilities, Spectrum Sensing, Energy Detection, MMSE.