Cooperative Amplify-and-Forward relaying in cognitive radio networks

In this paper, we consider an underlay cognitive radio network consisting of a primary transmitter (PT), a primary receiver (PR), a secondary transmitter (ST) and a secondary receiver (SR). We propose a two time slot spectrum sharing scheme based on cooperative relay transmission in addition to a practical design of the antenna weights at the ST to achieve high performance at the primary and the secondary networks. To analyze the performance of our proposed scheme, we first derive a closed form expression for the diversity order achieved at the PR and the SR. We then show through simulations that our proposed scheme, compared to conventional systems where no cooperation occurs, results in an improved quality of service at both the primary and the secondary networks, namely, the error rate and the ergodic capacity.