The Effect and Compensation of Phase Noise on Orthogonal Frequency Division Multiplexing (OFDM) System

Yubin Lin

doi:10.4236/cs.2018.97011

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) is characterized by its high data rate. However, the modulation method used in the system is subject to the influence of phase noise due to the need of time synchronization. In this paper, an algorithm based on MMSE (minimum mean square error) is developed to compensate the influence of both the common phase error (CPE) and inter carrier interference (ICI), which are two aspects of phase noise, under common Gaussian white noise. The result of noise cancellation is presented in signal-to-noise ratio (SNR) and symbol error rate (SER). Like digital signal in general, SNR can reduce SER with or without phase noise compensation. The compensation of phase noise significantly reduces the SER of the decoded signal. However, the bandwidth of phase noise still determines the signal accuracy. Under high bandwidth of phase noise, increasing SNR will only slightly increase SER, which is not efficient.

Highlights

Orthogonal Frequency Division Multiplexing (OFDM) is widely used in the telecommunication industry
An algorithm based on MMSE is developed to compensate the influence of both the common phase error (CPE) and inter carrier interference (ICI), which are two aspects of phase noise, under common Gaussian white noise
OFDM signal is generated from 64 quadrature-amplitude modulation (QAM) under inverse fast Fourier transform (IFFT)

Summary

Introduction

Orthogonal Frequency Division Multiplexing (OFDM) is widely used in the telecommunication industry. The phase noise problem is critical to the system’s efficiency because phase noise produces inter carrier interference (ICI) and the result rotation of the constellation map is called common phase error (CPE) which degrades the quality of the receiving signal [7]. Many have done research into this problem by getting a better approximation of phase noise using phase-locked-loop (PLL) [11] and other advanced estimation algorithms [12]. In this experiment, the phase noise is produced through Wiener Process—a stochastic process with random increments at non-negative time t [13]. An algorithm is used to correct the effect of phase noise, and the results of the correction are displayed as symbol error rate versus signal to noise ratio

OFDM System

Phase Noise

Common Phase Error

Inter-Carrier Interference

Results and Discussion