Phase noise suppression scheme for OFDM system in Terahertz band based on pilot and constellation design

Terahertz (THz) communication is becoming a promising technology for 6G communication system to realize Tbps data rate to support emerging ultra-high-speed applications. Benefit from the high spectrum efficiency and anti-multipath fading capability, Orthogonal Frequency Division Multiplexing (OFDM) technique has obtained significant attention in terahertz communication system. However, one major challenge of high frequency OFDM systems is the phase noise. The general solution is to insert pilots in subcarriers to estimate and compensate for phase noise which causes a waste of spectrum resources. To tackle this challenge, we firstly propose a pilot generation method based on cyclic code shift keying (CCSK) to transmit more information while estimating the phase noise. Furthermore, a constellation diagram design method with anti-phase noise based on Archimedes spiral is proposed to greatly reduce the power of the pilot signal. Simulation results illustrate that the pilot pattern designed in this paper can improve the spectrum efficiency, and the spiral constellation shows superior symbol error rate (SER) performance even when the average pilot power is much lower than the signal average power, about 2.7dB