Combining Beamforming and Space-Time Coding Using Quantized Feedback

We combine space-time coding and transmit beamforming over multiple-antenna quasi-static fading channels using limited-rate channel state information at the transmitter (CSIT). The combining is performed using a class of constellation sets inspired from orthogonal designs and directional beamforming or in general, unitary preceding with quantized feedback. This constellation class is called partly orthogonal designs (PODs). The conventional way of combining coding and quantized feedback beamforming is through precoded space-time block codes (PSTBCs) that provide full-diversity order with all system configurations in terms of the number of feedback regions and the number of transmit antennas. PODs maintain the same advantage. However, they require less decoding and quantization complexity compared to PSTBCs. We develop POD structures, analyze their performance, and optimize them based on pairwise error probability analysis. PODs create a larger combining space compared to PSTBCs. We can show that with certain system configurations, PODs outperform PSTBCs. Using PODs, we also propose a combined coding, beamforming, and spatial multiplexing scheme over multiple-antenna multi-user channels that enables a low-complexity joint interference cancellation scheme.