Optimal Power Allocation for Fading Cognitive Multiple Access Channels: Individual Outage Capacity Region

This paper is concerned with a spectrum sharing cognitive radio network. In particular, the individual outage capacity region for a M-user fading cognitive multiple access network sharing the same spectrum with an existing primary network is first characterized. The primary network´s transmission is assumed to be protected by the interference power constraint. Then, under the interference power constraint and the individual transmit power constraint of each user, the individual outage capacity region is implicitly obtained by characterizing the boundary points on the individual usage probability region for a given rate vector. The optimal power allocation and decoding strategy is then derived by the Lagrange dual decomposition method. It is proved that the optimal decoding strategy is the successive decoding strategy, and the decoding order is determined by dual variables together with the channel fading gains of the primary and secondary links. Finally, several numerical examples are given to validate the proposed studies.