Cooperative Spectrum-Sharing with Two-Way AF Relaying in the Presence of Direct Communications

Abstract

In this paper, we investigate a three-phase two-way (TW) amplify-and-forward (AF) relaying for cognitive radio networks. By utilizing the direct communications, the end user can employ diversity combining techniques, i.e., maximal ratio combining (MRC) and selection combining (SC), to achieve the full diversity. We derive the closed-form and asymptotic expressions for user and system outage probabilities which allows us to highlight the advantage of cooperative cognitive communications. The numerical results, obtained through compact forms of these outage probabilities, yield that the cognitive TW AF relaying scheme can significantly enhance the reliability of unlicensed networks in which the transmit power at secondary users is strictly governed.