Receiver Design for the Low-Cost TeraHertz Communication System with Hardware Impairment

TeraHertz (THz) communication has drawn increasing interest from both academic and industrial fields due to its capability of attaining data transmission over 100 Gb/s. To generate THz-band carriers, one promising low-cost electronic approach is the frequency-multiplier-last architecture, which however induces undesirable nonlinearity. Another substantial issue in THz communication systems is the residual hardware impairment in the mixer and power amplifier (PA), which are usually neglected under low-rate scenarios, but considered to be pronounced in the ultra-high-speed THz wireless links. With the existence of all these radio-frequency (RF) imperfections at the transmitter, conventional receiver design for lower-frequency bands is no longer applicable. In this paper, a single-carrier THz communication system utilizing the frequency-multiplier-last architecture is investigated. By jointly considering the overall RF imperfections of the mixer, the PA, and the frequency multiplier at the transmitter, a sophisticated mathematical model of the induced distortions on transmitted THz signals is provided. Based on the model, a low-complexity closed-form minimum mean Euclidean distance (MMED) channel estimator is firstly derived. Afterwards, the aggregate distortions plus thermal noise on the THz signals are approximated as a signal-dependent and spatially-colored noise term, where a closed-form quasi-maximum-likelihood (quasi-ML) detector is developed for the THz communication system. Simulation results demonstrate that our proposed receiver design is capable of significantly enhancing the performance of the THz system compared with its conventional counterparts, in terms of channel estimation accuracy and bit-error rate (BER).