Scale-Only Tomlinson-Harashima Precoding

With the introduction of a dither sequence and scaling factors, dithered Tomlinson-Harashima precoding (THP) has shown to outperform conventional spatial THP in multi-user MIMO systems. Through a careful analysis of dithered THP, this paper exhibits that it is not only possible, but also beneficial, to eliminate the dither sequence and develop efficient scale-only THP, and the key is to resolve the scaling factors. By capturing the dependency of the interference level on the scaling factors through a closed-form piece-wise function, we formulated a new method to optimize the scaling factors. We present that the new scale-only THP is not only simpler, but also performs better. As much as 1 dB of performance gain is observed at the low signal-to-noise region.