Ergodic and outage capacity maximization of cognitive radio networks in cooperative relay environment using optimal power allocation

Cognitive radio solves the problem of scarcity of radio spectrum to a great extent in that it allows unlicensed users to coexist with licensed users. It allows effective utilization of radio spectrum by offering radio cells the ability of radio sensing and dynamic spectrum sharing. The throughput of spectrum sharing cognitive radio can be maximized by performing data transmission and spectrum sensing at the same time. Cooperative communications and networking allow distributed terminals in a wireless network. The main problem with cognitive radio is to sense the presence of primary users over a wide range of spectrum. Cooperative spectrum sensing is used here to detect those users more reliably. It is investigated whether cooperative communication for spectrum in cognitive radio enhances the efficiency of spectrum sharing. The maximum power that can be adapted by the secondary user without causing significant interference to a primary user is investigated. An algorithm is proposed for the same. Closed-form expression for ergodic throughput is derived for the systems and is compared with the conventional cognitive radio system. An expression for the outage capacity of the system is also derived for average transmit and interference power constraints under truncated channel information with fixed rate technique.