Cooperative spectrum sharing with multi antenna based Amplify-and-Forward and Decode-and-Forward Relay

Performance of a cooperative spectrum sharing with the help of a multi-antenna based cognitive relay (CR) employing best relay selection strategy is analyzed in presence of non-identical Rayleigh fading channel in this paper. A cognitive relay equipped with multiple antennas at the input employs selection combining (SC) on the signals received from secondary user source (S) via multiple receiving antenna at the input and forwards the received signal to secondary user destination (D) using a Amplify-and-Forward (AF) and Decode-and-Forward (DF) protocols. The outage probability performance has been evaluated, when received signals are coherently combined at both the relays with multi-antenna and destination using Selection Combining (SC) and Best Relay (BS) selection schemes respectively. The effects of number of relay antennas (L) and number of relays (K) on the system performance have also been studied. A tradeoff between relay antennas and number of relays is also indicated.