Quantized CDI Based Tomlinson Harashima Precoding for Broadcast Channels

For the Multiuser Multiple-Input Single-Output (MU-MISO) system in a downlink (DL) scenario, we design a non-linear precoding scheme, namely the spatial Tomlinson-Harashima precoder (S-THP) based on the total mean squared error (MSE) criterion. The channel state information (CSI) available at the transmitter for precoding is the quantized channel direction information (CDI) relayed back in a frequency division duplex (FDD) system from each receiver using B feedback bits received error-free and quasi-instantaneous. The proposed MMSE-S-THP with a suboptimum precoding order clearly outperforms the linear precoding scheme given in [1] starting from a certain Signal-to-Noise Ratio (SNR) and a number of feedback bits in terms of Bit Error Ratio (BER).