Linear decoding of QO-STBC under imperfect channel estimation conditions

Abstract

Quasi-orthogonal space-time block-code (QO-STBC) was developed to overcome the transmission rate drawbacks of orthogonal-space-time block-code (O-STBC) for more than two transmit antennas. QO-STBC scheme achieves full transmission rate and partial diversity order, but with increase in decoding complexity. This is due to the presence of interference terms in its detection matrix. Matrix manipulation methods known as Givens rotation (GR) and Eigen value decomposition (EVD) have been applied to the channel matrix of conventional QO-STBC (C-QO-STBC) scheme to generate the interference free detection matrix. It results into simple linear decoding of the conventional QO-STBC scheme. Givens rotation and Eigen value decomposition methods result into two new QO-STBC schemes known as Givens rotation QO-STBC scheme (GR-QO-STBC) and Eigen value decomposition QO-STBC scheme (EVD-QO-STBC). Both new QO-STBC schemes have been analyzed in terms of its bit error rate performance (BER) under the condition that the receiver has perfect knowledge of channel state information (CSI). But, in realistic environment, it is not possible for channel estimator to estimate the channel without estimation error. Therefore, we analyze the performance of both new QO-STBC schemes in terms of BER under the condition of imperfect CSI at the receiver side. The Rayleigh flat fading channel is used for this analysis. Simulation results are provided to show the impact of channel estimation errors on the performance of both new QO-STBC schemes. We also analyze the performance of GR-QO-STBC scheme and EVD-QO-STBC scheme under MIMO system using 4×2 and 3×2 antenna systems along with the simulation results.