Minimum Average BER Power Allocation for Fading Channels in Cognitive Radio Networks

This paper considers a secondary user (SU) sharing the spectrum licensed to a primary user (PU) if limited interference caused to the latter can be guaranteed. In particular, besides the interference power constraint at the PU to protect the PU, the transmit power of the SU is also considered. Under such a setup, we consider the average bit error rate (BER) as the performance metric for the SU, and then derive the optimal power allocation strategies to achieve the minimum average BER of the SU. Simulation results are presented and discussed. It is shown that the optimal power allocation strategies can achieve substantial performance gain for the SU over the water-filling method.