A transmit-power efficient MIMO-THP design

In this paper, an improved multiple input multiple output Tomlinson-Harashima precoder (MIMO-THP) is introduced, where the transmit power loss is reduced based on optimizing the interference to be canceled. The concept behind the proposed technique builds on the fact that both the desired and interfering signals originate from the base station (BS) of the downlink system itself. Based on this observation, the proposed method influences the resulting interference, to reduce the transmission power required to cancel it, without altering the information content of the downlink message. The aim is to bring the interference closer to the replicas of the desired symbols for all users in the THP modulo-extended constellation. In this way, the power required to pre-subtract interference is decreased. Theoretical and simulation results both confirm that, by optimizing the interference to be canceled, the proposed technique offers a considerable transmit power reduction compared to conventional THP while securing an equal error rate performance.