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In order to reduce the feedback load of multi-user orthogonal frequency division multiplexing( OFDM)-based wireless systems,a practical limited bits feedback precoding algorithm is proposed with direct source-destination link based on amplify-andforward cooperative relay network under frequency selective fading channels.Using joint minimum mean square error( MMSE) filter,the receiving decoding matrix is designed for each user in the paper.Source precoding( beamforming) matrix is optimized with convex function of weight mean square error( MSE).Relay precoding matrix is obtained under MSE decomposition and convex optimization.The precoding matrix index is fed back for clustered subcarrier of OFDM with limited feedback.Then using interpolation algorithm,all precoding matrices are achieved at base station( BS)and relay nodes.Simulations indicate the effectiveness of the proposed limited feedback joint precoding and beamforming design.The proposed method can improve bit error rate( BER)performance and obtain better sum-rate performance in contrast to existing algorithms.It displays the BER performance is close to that of the unquantified precoding feedback method.
In order to reduce the feedback load of multi-user orthogonal frequency division multiplexing (OFDM) -based wireless systems, a practical limited bits feedback precoding algorithm is proposed with direct source-destination link based on amplify-and-forward cooperative relay network under frequency selective fading (MMSE) filter, the receiving decoding matrix is designed for each user in the paper. Source precoding (beamforming) matrix is optimized with convex function of weight mean square error (MSE) .Relay precoding matrix is obtained under MSE decomposition and convex optimization. The precoding matrix index is fed back for clustered subcarrier of OFDM with limited feedback. Chen using interpolation algorithm, all precoding matrices are achieved at base station (BS) and relay node. Simulations indicate the effectiveness of the proposed limited feedback joint precoding and beamforming design.The proposed method can improve bit error rate (BER) perf ormance and obtain better sum-rate performance in contrast to existing algorithms. It displays the BER performance is close to that of the unquantified precoding feedback method.