Trellis precoding for the broadcast channel

This paper considers the vector Gaussian broadcast channel where a single transmitter with multiple antennas sends independent information to multiple receivers. An achievable rate region is derived by decomposing the broadcast channel into a series of single-user channels with non-causal side information. The side information may be completely pre-subtracted using precoding techniques. A practical trellis precoding method is presented. Trellis precoding can be viewed as a generalization of the Tomlinson-Harashima(1971, 1969) precoder. By taking into account the entire non-causal side-information sequence, a trellis precoder gives an additional shaping gain up to 1.53 dB compared to a Tomlinson precoder.