A cooperative communication approach for voluntary secondary users in cognitive radio networks

Cognitive radio is a new network technology that provides an opportunity for secondary users to utilize the spectrum in an opportunistic manner. With this technology, effective spectrum usage is aimed by preventing the spectrum bands remain unexploited when it is not used by primary users. Cooperative communication is a new technology that depends on cooperation of communication systems among each other. In cooperative communication technology, a couple of users make transmission diversity by transmitting signals over one another. In this work, a new approach that secondary users act as a relay of the cooperative communication when they sense the spectrum is proposed. According to proposed approach, because secondary users do not communicate while sensing, they help other users as relay in these times. The proposed relay uses amplify and forward cooperative communication protocol in order to prevent any interruption that remote users may be exposed because of signal attenuation. It is seen that this approach has better performance than cognitive radio system that do not use cooperative communication.