Channel Prediction and Predictive Vector Quantization Aided Channel Impulse Response Feedback for SDMA Downlink Preprocessing

Invoking SDMA in the down-link (DL) has the potential of increasing the achievable throughput with the aid of linear transmit preprocessing, provided that the channel impulse responses (CIRs) of all users and all antenna elements are known at the DL transmitter. However, in a frequency division duplex (FDD) system, since these CIRs have to be transmitted by the mobile terminals (MTs) to the base station (BS), they are naturally out-dated. Hence, we proposed a periodical CIR update scheme employing a channel predictor at the DL transmitter for predicting the CIR taps for each future symbol transmission instant and hence to mitigate the performance degradation imposed by the associated signalling delays. Moreover, a predictive vector quantizer (PVQ) is used at the MTs for compressing the CIRs before their uplink transmission. Compared to a conventional vector quantizer (VQ), PVQ has significantly reduced the CIR feedback bit rate. Hence, with the aid of the same feedback bit rate, the new PVQ scheme can provide more accurate CIR information or support a channel having a higher Doppler frequency.