Efficient signal detection for cognitive radio relay networks under imperfect channel estimation

Abstract

AbstractAssuming imperfect channel knowledge at the destination, we propose an improved detector for an underlay cognitive (secondary) amplify‐and‐forward wireless relay network coexisting with a primary transmission system. At first, we adjust the amplify‐and‐forward relay amplification factors by taking into account the interference temperature constraint at the primary receiver. In a second step, for the case of coherent distributed space‐time coding at the relays and maximum a posteriori signal detection at the destination, we propose a modified detector formulation. The proposed scheme reduces the impact of channel uncertainty on the receiver performance by appropriately exploiting the statistics of the channel estimation errors. Furthermore, it takes into account the interference level limitation imposed by the primary transmission system on the relays. Through some numerical results, we show that the proposed detector reduces significantly the required power level to achieve a target performance at the destination, which is of special interest for underlay cognitive radio systems. This way, the proposed receiver allows a reduction of the required protection area around the primary transmitter, leading to the increased of flexibility of the cognitive radio network design. Copyright © 2016 John Wiley & Sons, Ltd.