This letter presents two outage-optimal relaying schemes to improve the performance of a wireless energy harvesting system in cognitive radio networks. The performance of both schemes is then evaluated and compared by carrying out numerical simulations, and we also derive the analytic expression for the outage probability of the secondary system.

In this paper, we propose and analyze the opportunistic amplify-and-forward (AF) relaying scheme using antenna selection in conjunction with different adaptive transmission techniques over Rayleigh fading channels. In this scheme, the best antenna of a source and the best relay are selected for communication between the source and destination. Closed-form expressions for the outage probability and average symbol error rate (SER) are derived to confirm that increasing the number of antennas is the best option as compared with increasing the number of relays. We also obtain closed-form expressions for the average channel capacity under three different adaptive transmission techniques: 1) optimal power and rate adaptation; 2) constant power with optimal rate adaptation; and 3) channel inversion with a fixed rate. The channel capacity performance of the considered adaptive transmission techniques is evaluated and compared with a different number of relays and various antennas configurations for each adaptive technique. Our derived analytical results are verified through extensive Monte Carlo simulations.

In this letter, we study cooperative transmission in wireless multicast networks. An opportunistic cooperative multicast scheme based on coded cooperation (OCM-CC) is proposed and its closed-form expression of outage performance is obtained. Through numeric evaluation, we analyze its outage probability with different numbers of relays and different cooperative ratios.

In this letter, we first provide the closed-form exact outage probability of opportunistic single relay selection in decode-and-forward (DF) relaying with the direct source-destination link under arbitrarily distributed Rayleigh fading channels. The signals from the source and the selected relay are combined at the destination by using maximal ratio combining (MRC). We derive the probability density function (PDF) and the cumulative density function (CDF) of received SNR at the destination. Numerical results show that the analytic results exactly match with the simulated ones.