Adaptive transmission in multiple input multiple output cognitive radio systems

This paper proposes an adaptive power allocation scheme in cognitive radio system under MIMO fading channel. In the spectrum-sharing system, the secondary user (SU) can use the primary user´s (PU) spectrum band under some limitations. In this research, we consider that the SU´s transmission power has to be limited to ensure an acceptable effect on the primary´s receiver, meanwhile the QoS of the primary user´s should be guaranteed. Under the limitations of average and peak received-power at the side of PU´s receiver, we get the optimum power allocation scheme of SU, and the channel capacity is adopted as the metric of the system performance. Finally, we verify the theoretical results through numerical simulations.