Minimum BER analysis and the effect of extra channel side information on BER

In this paper, we design optimal power allocation in cognitive radio in terms of spectrum sharing where secondary users concurrently transmit with primary users over the same band subject to an interference threshold constraint at primary receivers. The average bit error rate (BER) of the secondary link is minimized under either average or peak interference power constraint of secondary users at the primary´s receiver. We derive closed-form expression for evaluating the minimum average BER under Nakagami channels. Furthermore, by numerical results, we show that reducing extra channel side information (CSI) which can be provided at the secondary transmitter has a small impact on the bit error rate.