Date Added: Aug 2012
Cognitive radio is an emerging and powerful technology to improve the utilization of limited wireless spectrum resources. Unlicensed secondary users are permitted to use the licensed resource so long as the Quality of Service (QoS) of primary transmission is not affected. Until recently, there have been many research efforts on dynamic spectrum sharing such as cooperation, which has great potential to be used in cognitive radio networks. In this paper, the authors have considered a secondary transmitter to act as a relay for primary transmission. A more practical cooperative spectrum-sharing scheme based on Decode-and-Forward (DF) relaying was proposed, where superposition coding has been applied by the cognitive user acts as a relay.