A Channel Estimation Scheme for Amplify-and-Forward OFDM Relay Networks

The channel state information (CSI) of all links should be available at all nodes for cooperative strategies design in relay networks. However, many channel estimation methods for amplify-and-forward (AF) relay networks only estimate a compound CSI of source-relay-destination (S-R-D) link. In this paper, we propose a channel estimation scheme for destination to disintegrate the CSIs of S-R and R-D links from the cascaded S-R-D link in AF relay networks. The proposed scheme estimates the CSI of R-D link firstly by utilizing some pilot signals inserted at the relay node. Then, the CSI of S-R link is estimated based on the received pilot signals and the pre-estimated CSI of R-D link. The channel estimation error of the proposed scheme is also analyzed. Especially, least square (LS) algorithm and minimum mean square error (MMSE) algorithm for the CSI estimation of S-R link are compared. We verify that the mean square error of LS estimation for S-R link is nonconvergent but that of MMSE estimation is convergent. At the end of this paper, simulation results are given to support the theoretical results.