Minimum BER analysis in cognitive radio

This paper is concerned with the design of optimal power allocation strategies in opportunistic spectrum-sharing wireless channels where secondary users are allowed to coexist with the primary users as long as the interference they caused to the primary user is less than a predefined threshold level. We formulate and solve several minimization problems for the average BER experienced by a secondary transmitter-receiver pair under different average and peak interference power constraints at the primary receiver. New closed-form results for the average minimum BERs are derived over Nakagami fading channels for most cases examined. The other contribution of this work lies in reducing extra channel side information at the secondary transmitter, which has very minimal impact on the BER of the secondary link.