MUTP aided MIMO downlink communication system with noisy feedback: Analysis and performance results

In this letter, we study and present the performance of multi-user transmitter preprocessing (MUTP) assisted downlink (DL) communications, where the channel state information (CSI) required at the transmitter to carry out the MUTP is estimated at the receiver, and conveyed to the base station (BS) with the aid of a noisy feedback channel that undergoes fading as well. In particular, the CSI is estimated with a known channel estimation technique, and the phases and magnitudes of the CSI are vector quantized and fed back to the transmitter via a fading feedback channel. This vector quantized CSI which is also corrupted by noise is recovered with the aid of a minimum mean square error (MMSE) based hard detector. The recovered CSI is then exploited to formulate the preprocessing matrix which is based on creating an orthogonal subspace to the interfering subspace. Our simulations show that the impact of codebook size and quantization errors play a dominant role in determining the performance of the considered DL system in terms of the achievable symbol error rate (SER).