V-BLAST Receiver for MIMO Relay Networks with Imperfect CSI

Previous work demonstrated that the improvements in spectral efficiency and link reliability can be obtained in wireless relay networks employing terminals with MIMO capability. We propose to apply the non layered and layered ZF (V-BLAST) receiver to the relay and destination terminals in coherent MIMO relay networks under two-hop half-duplex relaying. Considering the channel estimation is often imperfect due to the noise and interference, this paper assumes that no perfect channel state information (CSI) is available for both backward and forward channels. The V-BLAST receiver is extended to the imperfect CSI under the assumption that the channel estimation errors are independent complex Gaussian random variables with zero mean and known second-order statistics. A robust symbol detection ordering criterion is proposed for applying ZF V-BLAST to the MIMO relay networks. This new ordering rule aims at providing, in each layer, the maximum average signal to interference- plus-noise ratio (SINR), over the random channel errors. Our simulations show that aided by the new ordering criterion, the suboptimal ZF operators, directly resulted from the imperfect CSI, is capable of alleviating the effect of CSI errors and improving the robustness of V-BLAST system.