Performance of multiuser MIMO-OFDM precoding techniques with quantized channel information

It is well known that precoding techniques in multiuser multiple-input multiple-output (MU-MIMO) communication systems improve the whole data throughput since they allow for spatial multiplexing of different users. However, these techniques require a precise knowledge of the channel information at the transmitter. In most of the current systems, transmitter can not estimate the channel so feedback information has to be provided by the receiver. In this paper, we propose a new limited feedback approach where Vector Quantization (VQ) is applied over the channel frequency response. Different configurations of feedback bits per subcarrier in a multiuser MIMO-OFDM system have been simulated. Additionally, different precoding schemes based on the estimated channel information have been tested and BER performance has been evaluated. Results show that, for a similar cost of feedback information (bits/subcarrier), better channel estimates are achieved using longer vectors in the VQ codebook, whereas optimal non-linear precoding schemes perform well even for large channel estimation errors.