Abstract: To improve the performance of LSTA(Layered Space-Time Architecture) in downlink correlated fading MIMO (Multiple-Input Mulitple-Output) systems, a novel DSSS(Direct Sequence Spread Spectrum) based LSTA combining eigenbeamforming is proposed. The transmitter takes advantage of the eigenvectors of the SCM(Spatial Covariance Matrix) of the correlated channels to spread and weigh the signals of each layer. The spatial eigenbeams are formed to carry the signals being spread. The receiver distinguishes the signals from different beams via dispreading operations; therefore co-channel interferences are eliminated effectively. The proposed scheme has the some advantage of dispensing with designing OSS and can be applied to downlink transmission at the cost of loss in the spreading spectrum. Simulation results show that the new scheme greatly outperforms ZF-LSTA(LSTA using ZF algorithm).

Key words: correlated fading MIMO systems, DSSS based layered space-time architecture, eigenbeamforming