Low-complexity frequency-domain Tomlinson-Harashima precoding for low-PAPR SC-LFDMA system

In this paper, we propose an improved frequency-domain Tomlinson-Harashima precoding (FD-THP) scheme for low-PAPR Single-Carrier Localized Frequency Division Multiple Access (SC-LFDMA) transmission. Unlike the traditional FD-decision feedback equalizer (DFE) receiver, we jointly design a low-complexity FD-THP at the transmitter and a frequency-domain equalization (FDE) at the receiver to effectively combat the severe inter-symbol interference (ISI) channel, resulting in a better BER performance without error propagation. Moreover, to maintain a good tradeoff between the BER and the transmit peak-to-average power ratio (PAPR) increase due to the use of FD-THP, we constrain the number of feedback taps in the design. A Gaussian approximation (GA) based BER analysis is employed to obtain the optimal number of THP taps for the SC-LFDMA system. Simulation results demonstrate that the proposed scheme significantly outperform the FD-DFE receiver. Besides, the FD-THP has much lower complexity than the original time-domain THP (TD-THP), and the GA-based BER analysis coincides well with the simulation curves.