| Vertical Bell Lab Layered Space-Time (VBLAST) is an emerging spatial modulation technique, that provides high spectral efficiency due to its use of multiple transmit and receiver antennas. We present novel schemes; consisting of combinations of Transmit Antenna Selection (TAS) with Power Allocation (PA), to improve the error rate performance of VBLAST systems. Our schemes provide significant performance gain over VLAST because of enhanced transmit diversity introduced by transmit antenna selection. Our scheme may be used for uplink wireless system, where the total power is limited by the mobile terminal battery. The effect of limited rate feedback link is investigated by sending quantized power weights from receiver to transmitter. The simulation results show that even one-bit, codebook for power weights can achieve performance close to that of unlimited rate feedback link in low and medium SNR regions. We also present a novel PA technique alloting power in the joint space-frequency domain to reduce the error rate, and apply our scheme to frequency selective MIMO-OFDM channels. In addition, an analytical analysis of transmit correlated Successive interference Cancelling Zero Forcing (SIC-ZF) VBLAST in flat fading channels is presented. Over frequency selective channels, the performance of SIC-ZF VBLAST is assessed by computer simulation. |
