On the Performance of Tomlinson-Harashima-Precoding with Tilted Constellation in Two User Gaussian Broadcast Channels

Abstract:
Tomlinson-Harashima-precoding with tilted constellation was proposed to overcome the power loss of conventional Tomlinson-Harashima-precoding. In case of a two user broadcast transmission, this power loss of the precoded signal can not be directly transferred to the overall transmit symbol. Instead, depending on the parameter setup, even a power gain was shown in the two user case. In this work the influence of the tilted constellation to the overall transmit signal in a broadcast transmission based on QAM modulation is investigated. It is shown that still power losses and power gains are possible, but the required power has smaller maxima in the tilted case. The performance of Tomlinson-Harashima-precoding with tilted constellation as broadcast technique is investigated. It is shown that the achievable rate region of a transmission with fixed transmit power slightly outperforms the region achievable with the conventional constellation. Index Terms — Tomlinson-Harashima-precoding, broadcast channel, power loss.