Improved MAP Signal Detection for Amplify-and-Forward Relay Networks with Imperfect Channel State Information

In amplify-and-forward wireless relay networks, channel state information is required at the destination for signal detection when coherent distributed space-time coding is performed at the relays. We consider in this paper signal detection in the case of imperfect partial channel knowledge at the destination. For the case of maximum a posteriori signal detection, we propose a modified detector formulation that takes the variance of channel estimation errors into account, and reduces the impact of channel uncertainty on the receiver performance. We show that the proposed modification permits a significant performance improvement, while increasing only slightly the receiver’s complexity. It is of special interest for non-constant modulus signal constellations of relatively large size, as well as for relatively low pilot powers.