WO2015123989A1 - Procédé et système d'égalisation de canaux basés sur une estimation de canaux dans le domaine temporel - Google Patents

Procédé et système d'égalisation de canaux basés sur une estimation de canaux dans le domaine temporel Download PDF

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Publication number
WO2015123989A1
WO2015123989A1 PCT/CN2014/086212 CN2014086212W WO2015123989A1 WO 2015123989 A1 WO2015123989 A1 WO 2015123989A1 CN 2014086212 W CN2014086212 W CN 2014086212W WO 2015123989 A1 WO2015123989 A1 WO 2015123989A1
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WIPO (PCT)
Prior art keywords
sequence
filter
training sequence
signal
channel
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PCT/CN2014/086212
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English (en)
Chinese (zh)
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张帆
王丹
丁瑞
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北京大学
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Publication of WO2015123989A1 publication Critical patent/WO2015123989A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
    • H04L25/03114—Arrangements for removing intersymbol interference operating in the time domain non-adaptive, i.e. not adjustable, manually adjustable, or adjustable only during the reception of special signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/024—Channel estimation channel estimation algorithms

Definitions

  • the present invention relates to the field of coherent optical communication transmission, and relates to a channel equalization method based on time domain channel estimation, and a system for implementing the method.
  • Coherent communication based on digital signal processing technology is an important solution for long-distance optical fiber communication transmission systems. How to overcome the communication channel damage is an important issue to be solved. Communication channel impairments reduce the signal to noise ratio of the signal and introduce intersymbol interference, resulting in the generation of errors. In fiber-optic communication systems, an equalization algorithm estimates the channel and compensates for linear distortion of the channel to attenuate or eliminate inter-symbol interference.
  • TDE time domain equalization
  • FDE frequency domain equalization
  • Time Domain Equalization (TDE) algorithm performs channel impulse response estimation based on the training sequence or signal-based constellation characteristics, and compensates the signal in the time domain.
  • the channel estimation algorithm based on the training sequence is more complicated.
  • the channel estimation algorithm based on the characteristics of the signal constellation depends on the modulation format. When the modulation format is changed, the algorithm also needs to be changed, and the algorithm effect is different. Due to the dispersion in the fiber, when the dispersion is large, the equalization algorithm requires more equalizer taps, resulting in higher algorithm complexity.
  • Frequency Domain Equalization (FDE) algorithm.
  • the algorithm performs estimation of the channel transfer function based on the training sequence and compensates the signal in the frequency domain.
  • the channel estimation algorithm is simple, and when the dispersion is large, the algorithm complexity is still low. But the algorithm needs to insert a cyclic prefix/suffix to the signal, which causes a certain signal rate overhead.
  • the present invention provides an effective channel equalization method based on time domain channel estimation, and a system for implementing the method.
  • the present invention adopts the following technical solutions:
  • a channel equalization method based on time domain channel estimation includes the following steps:
  • the first step inserting a training sequence with flat spectral characteristics into the signal at the transmitting end;
  • the second step at the receiving end, after the front-end signal processing, the received training sequence is filtered by the FIR filter to achieve channel equalization.
  • the FIR filter coefficients are updated using the RLS algorithm criteria.
  • the third step using the time domain FIR filter obtained in the second step to filter the data signal in the time domain to achieve channel equalization.
  • the receiving end first performs front end data processing on the received signal, including dispersion coarse compensation and carrier frequency. Rate recovery, receive matched filtering, and digital synchronization; and after the third step, back-end data processing, including carrier phase recovery.
  • the signal at the transmitting end is frame-transmitted.
  • the frame structure of each frame includes two polarization directions, each of which includes a training sequence and a data signal.
  • the training sequence in the X polarization direction is the sequence t 1 arranged in time in the period
  • the training sequence in the Y polarization direction is the sequence t 2 which is periodically arranged in time, and:
  • t x and t y are M sequences, and "0" represents a sequence having a length equal to 0 in length and M sequence.
  • the selection of the M sequence length is determined by the channel carrier frequency offset and the degree of phase drift; the selection of the number of M sequences is determined by the intensity of the spontaneous radiated noise in the channel; the length of the data signal (data after each frame training sequence) The choice is determined by the degree of drift of the channel transfer function.
  • An equalization system based on time domain channel estimation for implementing the above method, comprising a transmitting end and a receiving end,
  • the transmitting end includes:
  • a training sequence insertion module for inserting a training sequence having flat spectral characteristics into a signal at a transmitting end
  • the receiving end includes:
  • the FIR filter uses the time domain filter tap coefficients to filter the data signal in the time domain to achieve channel equalization.
  • the training sequence comparison module is connected to the FIR filter module for performing a difference between the training sequence and the data signal to obtain an error value e.
  • the filter coefficient updating module is connected to the training sequence comparison module to update the FIR filter coefficients by using the RLS criterion according to the error value e.
  • the front end data processing module is configured to preprocess the signal received from the transmitting end and then send the signal to the FIR filter module.
  • a back-end data processing module is coupled to the FIR filter for carrier phase recovery.
  • the preprocessing performed by the front end data processing module includes: coarse dispersion compensation, carrier frequency recovery, receive matching filtering, and digital synchronization.
  • a decision module is further included, and the back end data processing module is connected to restore the received signal information into binary data.
  • the present invention utilizes a training sequence and a time domain filter for channel equalization.
  • the method has different frame structures and different time domain filter updating algorithms.
  • the training sequence is partially between the M sequence and the 0 sequence.
  • the interpolation structure facilitates the equalization of the polarization crosstalk received by the signal by the time domain filter, thereby unlocking the polarization multiplexing.
  • the RLS algorithm has better convergence than the traditional time domain blind equalization (CMA). Therefore, the present invention only uses the training sequence part to update the time domain filter coefficients, and the algorithm complexity is small, which can save computation time.
  • the modulation format is not sensitive and has wide applicability.
  • FIG. 1 is a flow chart of a time domain channel estimation based equalization method according to an embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing the structure of a signal frame according to an embodiment of the present invention.
  • FIG. 3 is a schematic diagram of filter coefficient update according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram showing experimental results of a 400 km transmission of a 1.24 Tb/s 64QAM signal according to an embodiment of the present invention.
  • the first step is to insert a training sequence at the front end of the signal at the transmitting end, and design according to the frame structure. Several M sequences with flat spectral characteristics are selected.
  • the second step at the receiving end, after the front end signal processing, the received training sequence is filtered by the FIR filter.
  • the filter coefficients are updated according to well-known RLS algorithm criteria.
  • the third step using the time domain filter obtained in the second step to filter the data signal in the time domain to achieve channel equalization.
  • the fourth step the back-end signal processing, carrier phase recovery, and decision.
  • Receiver signal processing is based on the well-known RLS (Recursive Least Squares) algorithm.
  • RLS Recursive Least Squares
  • the FIR filter has a vector coefficient w(n) at time n and a cost function value J(n) at time n.
  • the training sequence in the data of the transmitting end be d TS (n)
  • the training sequence in the data of the receiving end be u TS (n)
  • the signal part in the data is u(n)
  • the filtering output training sequence is y TS (n)
  • the filtered output signal part is y(n)
  • ⁇ is the forgetting factor.
  • the effect of introducing the forgetting factor is that the error near the n-time is assigned a larger weight, and the error far from the n-time is given a smaller weight, ensuring that the observation data in a certain period of time in the past is "forgotten".
  • R(n) and r(n) are the correlation matrix of the data u TS .
  • N 1, 2, 3...N, where N is the number of filter updates, determined by the difference between the length of the training sequence and the length of the filter.
  • the receiver signal u(n) is convolved with W to obtain a channel-equalized signal y(n).
  • the back-end signal processing that is, the carrier phase recovery, is performed and judged.
  • Figure 4 is a schematic diagram showing the experimental results of a 400km transmission of a 1.24Tb/s 64QAM signal.
  • the horizontal axis is the fiber input power of the signal.
  • CMA norm algorithm
  • CMMA cascading multimode algorithm
  • D_LMS direct decision minimum mean square error

Abstract

L'invention concerne un procédé et système d'égalisation de canaux basés sur une estimation de canaux dans le domaine temporel. Le procédé comporte les étapes consistant: en premier lieu, à insérer une séquence d'apprentissage dans un signal d'extrémité d'émission; puis à effectuer une égalisation de canaux de la partie reçue de la séquence d'apprentissage sur une extrémité de réception en utilisant un filtre, et à actualiser un coefficient du filtre; et à filtrer un signal de données dans un domaine temporel en utilisant le filtre actualisé à l'étape précédente, de façon à mettre en œuvre l'égalisation de canaux. Dans la présente invention, l'égalisation de canaux est effectuée en utilisant une séquence d'apprentissage et un filtre dans le domaine temporel. Une structure de trame d'une séquence d'apprentissage part est formée de séquences M et de séquences 0 de manière entrelacée, ce qui aide le filtre dans le domaine temporel à égaliser la diaphonie de polarisation rencontrée par un signal, de façon à débloquer le multiplexage en polarisation; de plus, un coefficient du filtre dans le domaine temporel est actualisé en utilisant un algorithme RLS, la complexité de l'algorithme est faible, un gain de temps de calcul est possible, la sensibilité à un format de modulation est absente et l'applicabilité est étendue.
PCT/CN2014/086212 2014-02-24 2014-09-10 Procédé et système d'égalisation de canaux basés sur une estimation de canaux dans le domaine temporel WO2015123989A1 (fr)

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CN201410062434.4A CN103812806B (zh) 2014-02-24 2014-02-24 一种基于时域信道估计的信道均衡方法和系统

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CN103812806B (zh) * 2014-02-24 2017-10-10 北京大学 一种基于时域信道估计的信道均衡方法和系统
CN105071856A (zh) * 2015-08-17 2015-11-18 哈尔滨理工大学 基于ofdm的led可见光通信系统
CN106059967B (zh) * 2016-07-01 2020-06-05 晶晨半导体(上海)股份有限公司 一种单载波信道估计方法
CN108259091B (zh) * 2016-12-29 2020-02-14 华为技术有限公司 一种时域滤波装置方法和装置
CN106888054B (zh) * 2017-03-08 2019-03-26 北京理工大学 一种加权优化的fir时域色散均衡的方法
CN107248965B (zh) * 2017-05-26 2019-11-22 华中科技大学 一种数据处理方法及通信设备
CN109600179B (zh) 2017-09-30 2021-04-27 富士通株式会社 信道间线性串扰的估计方法、装置和接收机
CN108123908B (zh) * 2017-12-14 2020-10-27 杭州电子科技大学 一种用于ng-pon的改进svm均衡方法及系统
EP3837780B1 (fr) 2018-09-11 2023-11-01 Huawei Technologies Co., Ltd. Dispositif d'égalisation pour compenser des changements d'état rapide de changements de polarisation d'un signal optique
CN109525336A (zh) * 2018-10-29 2019-03-26 上海大学 非同步时钟下基于频差检测时域补偿的无线通信信道测试方法
JP6876099B2 (ja) * 2019-06-21 2021-05-26 Ｎｔｔエレクトロニクス株式会社 適応等化器、適応等化方法及び光通信システム
CN112615678B (zh) * 2020-12-15 2022-02-01 武汉邮电科学研究院有限公司 基于导频信号的信道均衡方法及设备

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