Abstract: Spectral efficiency gain of an uplink Cognitive Radio (CR) Multi-Input-Multi-Output system in which the Secondary User (SU) is allowed to share the spectrum with the Primary User (PU) using a specific precoding scheme to communicate with a common receiver. They adopt a Successive Interference Cancellation (SIC) technique to eliminate the effect of the detected primary signal transmitted through the exploited eigen modes. We extend this process to achieve high data rate compare to existing , we modified the channel into frequency selective fading channel and applying relay based protocol (ARP) , by this mentioned modification we can achieve high SNR communication. In a cognitive radio network, the secondary users are allowed to utilize the frequency bands of primary users when these bands are not currently being used. To support this spectrum reuse functionality, the secondary users are required to sense the radio frequency environment, and once the primary users are found to be active, the secondary users are required to vacate the channel within a certain amount of time. Therefore, spectrum sensing is of significant importance in cognitive radio networks.

Keywords: Multi-Input-Multi-Output system, Secondary User (SU), Successive Interference Cancellation (SIC) technique