Improved Training Sequence Channel Estimation Scheme in 16QAM MB-OFDM UWBoF System

Changqing Xiang,Jincan Xu,Xuan Zhou,Xi Yang,Xiaojun Zhu,Qiong He,Junmin Liu

doi:10.1155/2020/6273892

Abstract

In this paper, an improved channel estimation scheme based on time-domain orthogonal gray complementary training sequence (Golay TS) is proposed to resist subcarrier mutual beat interference in 16-quadrature amplitude modulation multiband orthogonal-frequency-division-multiplexing ultrawide band over fiber (16QAM MB-OFDM UWBoF) systems. The simulation results showed that the performance of system with the improved Golay TS channel estimation scheme was improved by about 1 dB compared with the traditional Golay TS channel estimation scheme, at a bit error rate (BER) of 3.8 × 10−3 after 70 km standard single mode fiber (SSMF) transmission. At the same time, the synchronization and channel estimation performance of Golay TS and the selected frequency-domain orthogonal training sequences (TSs) were compared. The simulation results showed that the performance of system with the TSs channel estimation was improved by about 2.7 dB compared with the improved Golay TS channel estimation.

Highlights

As we all know, symbol timing synchronization is a key step that must be performed before signal demodulation at the receiving end of the signal. erefore, the symbol timing synchronization step is very important [1,2,3]
The training sequence is accompanied by many MB-OFDM UWB data symbols, and the system overhead brought by training sequence can almost be negligible. erefore, the scheme of joint synchronization and channel estimation based on a single training sequence has the advantages of low complexity and high accuracy, so it is suitable for such quasistatic channels of optical fiber systems
In terms of channel estimation, for the 16QAM MBOFDM UWBoF system, the bit error rate (BER) performance of the channel estimation based on three training sequences was simulated after 70 km standard single mode fiber (SSMF) transmission

Summary

Introduction

Symbol timing synchronization is a key step that must be performed before signal demodulation at the receiving end of the signal. erefore, the symbol timing synchronization step is very important [1,2,3]. The impact of ISMI interference only can fall on evennumbered subcarriers, and the data of odd-numbered subcarriers are not affected, so a simple and effective improvement scheme for traditional Golay TS channel estimation is used to estimate. Since the symbol modulation of BPSK is only performed on odd subcarriers, we can directly use the single-tap frequency-domain estimation scheme to obtain the corresponding channel response, whose function on its odd subcarriers can be defined as follows:. Erefore, the scheme of joint synchronization and channel estimation based on a single training sequence has the advantages of low complexity and high accuracy, so it is suitable for such quasistatic channels of optical fiber systems. BER/EVM calculate De-Interleaver Demapper Equalization Channel Est. 128-FFT Removing CP Symbol sync

LPF DC block

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