CN106559370B - A kind of method of low complexity OFDM-PON system sample clock frequency deviation compensation - Google Patents

A kind of method of low complexity OFDM-PON system sample clock frequency deviation compensation Download PDF

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CN106559370B
CN106559370B CN201610966929.9A CN201610966929A CN106559370B CN 106559370 B CN106559370 B CN 106559370B CN 201610966929 A CN201610966929 A CN 201610966929A CN 106559370 B CN106559370 B CN 106559370B
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ofdm
clock frequency
channel response
frequency deviation
symbol
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CN106559370A (en
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宋英雄
岳露露
张镇
张卫宾
邝彩霞
张俊杰
陈健
李迎春
张倩武
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University of Shanghai for Science and Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects

Abstract

The present invention provides a kind of method of low complexity OFDM-PON system sample clock frequency deviation compensation, phase rotation coefficient caused by sample clock frequency deviation is eliminated using subcarrier sampling frequency offset increment of rotation, sign synchronization is carried out to the collected data of ADC in receiving end, find the position of FFT window, training sequence and data symbol are extracted respectively using the training sequence frequency domain value for extracting obtained training sequence frequency domain value and local, estimate the channel response initial value of system, the channel response more positive value at each symbol is obtained through recursion and feedback system using the channel response initial value of system, phase rotation caused by systematic sampling clock frequency deviation is compensated according to the system channel response coefficient updated.The present invention is easy to hardware realization, economizes on resources, while significantly reducing the computation complexity of OFDM-PON sample clock frequency deviation backoff algorithm.

Description

A kind of method of low complexity OFDM-PON system sample clock frequency deviation compensation
Technical field
The present invention relates to a kind of low complexity OFDM-PON (Orthogonal Frequency Division Multiplexing-Passive Optical Network, orthogonal frequency division multiplexing passive optical network) system sampling clock frequency The method of deviation compensation, belongs to digital technology.
Background technique
OFDM-PON technology is ofdm system to be merged with PON.Because with transmission capacity, (uplink and downlink rate be can reach greatly for it 40Gbit/s even 100Gbit/S), it is capable of providing the business of various types, various broadbands and various qos requirements, traffic scheduling And broadband manages the advantages that very flexible, in (the Next Generation Passive of next-generation passive optical network -2 Optical Network 2, NG-PON2) in show huge potentiality.
The basic principle of light OFDM is similar to electricity OFDM, and the two difference is that signal is become from the transmission of the wireless channel of electrical domain The fibre channel transmission of area of light, therefore OFDM-PON the shortcomings that there are OFDM technologies, are mainly reflected in OFDM-PON system Symbol timing error (Symbol Time Offset, STO), carrier frequency shift (Carrier Frequency Offset, ) and sampling clock deviation (Sampling Frequency Offset, SFO) CFO.Sampling clock deviation is mostly derived from transmitting A/D converter (the Analog- of D/A converter (the Digital-to-Analog Converter, DAC) and receiver of machine To-Digital Converter, ADC) crystal oscillator can not have identical clock cycle and phase, both cause Deviation can be generated between sampling interval, to bring serious influence to the performance of whole system: one is the son through over-sampling Orthogonality is no longer kept between carrier wave, generates interchannel interference；The other is the time-varying timing offset that sampling frequency offset generates, passes through It will lead to the phase change of time-varying after discrete Fourier transform (Discrete Fourier Transformation, DFT).
Sample clock frequency in the OFDM-PON data transmission system of high speed, for transmitting terminal DAC and receiving end ADC Usually in several GSps, and the system clock for being used for the FPGA of real time signal processing only has several hundred MHz, when being much smaller than sampling Clock, therefore the Digital Signal Processing of OFDM-PON is needed using parallel processing technique.The parallel processing of multichannel means that logic provides The increase of source consumption, therefore be particularly important in OFDM-PON using the signal processing algorithm of low complex degree.Most of In the OFDM-PON system sampling clock deviation compensation method of open report, most of is all to use for reference to use in Wireless OFDM System By Shafiee et al. propose classical synchronized algorithm, i.e., frequency departure is estimated using pilot frequency information.This synchronized algorithm Need to calculate phase rotation coefficient exp (the jd θ of each OFDM symboll,k), it needs to use when FPGA hardware is realized to be configured to cos& The CORDIC core of sin mode, the complexity of the significant wastage and realization that will lead to resource are relatively high.
Summary of the invention
For the existing biggish defect of sampling clock compensation technique resource consumption, the purpose of the present invention is to provide one kind Low complexity OFDM-PON system sample clock frequency deviation compensation method.It is eliminated using subcarrier sampling frequency offset increment of rotation Fall phase rotation coefficient caused by sample clock frequency deviation, so that it is hard to improve FPGA in traditional sampling Clock Frequency Offset Compensation method Part calculates phase rotation coefficient exp (the jd θ of each OFDM symboll,k) when caused by the wasting of resources and delay it is big the disadvantages of；Benefit The frequency channels response of initial OFDM symbol subcarrier is obtained with the algorithm of recurrence thought, and then each OFDM symbol is adopted The compensation of sample frequency deviation of clock, will greatly reduce computation complexity.
Inventive method assumes that ofdm system has been realized in correct sign synchronization, and sampling clock frequency deviation is obtained Estimated value.To achieve the above object, the present invention adopts the following technical scheme:
A kind of method of low complexity OFDM-PON system sample clock frequency deviation compensation, the specific steps are as follows:
1) the sampling clock offset estimation value estimated by OFDM-PON system receiving terminal, it is adjacent to obtain each subcarrier Phase rotation increment between OFDM symbol；
2) the twiddle factor increment of frequency domain between each subcarrier adjacent OFDM symbol is unfolded by Euler's formula, and approximate It is indicated with phase rotation increment；
3) channel response initial value is combined, according to the approximate twiddle factor increment between adjacent OFDM symbol by the way of recursion Obtain the channel response after each subcarrier extends at each OFDM symbol；
4) sampling clock frequency deviation is compensated according to the channel response after extension.
The phase rotation increment θ of k-th of subcarrier of adjacent OFDM symbol in the step 1)kIt is obtained by following formula Out:
Δ is sample clock frequency relative deviation in formula, and the calculating that N is ofdm system FFT/IFFT is counted, NsIt is one The length of OFDM data symbol, including OFDM data and data cyclic prefix.
In the step 2) between adjacent OFDM symbol k-th of subcarrier phase rotation increment θkIt much smaller than 0, and is solid Definite value, phase rotation coefficient caused by the sampling frequency offset between adjacent OFDM symbolBy the phase between adjacent OFDM symbol Increment of rotation θkApproximate representation:
Channel response in the step 3) at OFDM symbol is provided by previous OFDM symbol channel response, according to channel Response initial value and recurrence formula obtain the channel response of each OFDM symbol, are specifically provided by following formula,
Wherein l is the call number of the OFDM symbol received, and H (0, k) is that system channel responds initial value.
The system channel response coefficient that the step 4) updates mends phase rotation caused by systematic sampling clock frequency deviation It repays, is specifically provided by following formula:
Wherein Y1(l, k) is the reception frequency response of uncompensated frequency departure, and H (l, k) is first of OFDM symbol kth The frequency channels of a subcarrier respond, and this completes sampling frequency offset compensation.
The present invention compared with prior art, has following obvious prominent substantive distinguishing features and marked improvement:
(1) the invention proposes one kind to be easy to hard-wired sampling clock frequency compensation method, in particular to utilizes son Carrier wave sampling frequency offset increment of rotation eliminates phase rotation coefficient caused by sample clock frequency deviation, and utilizes recurrence thought Algorithm obtain initial OFDM symbol subcarrier frequency channels response, and then to each OFDM symbol carry out sampling clock frequency deviation Compensation, has greatly saved resource, has reduced complexity.
(2) the compatible existing OFDM-PON system of sample clock frequency deviation compensation method proposed by the present invention, uses this The signal processing algorithm of low complex degree avoids the increase that logical resource caused by the parallel processing of multichannel consumes in OFDM-PON.
Detailed description of the invention
Fig. 1 is OFDM frame structure schematic diagram in the embodiment of the present invention.
Fig. 2 is sampling clock frequency bias compensation method flow chart of the present invention.
Fig. 3 is that the algorithm in the embodiment of the present invention realizes structural schematic diagram.
Fig. 4 is that channel response of the present invention updates flow diagram.
Fig. 5 is the experimental result bit error rate figure in the embodiment of the present invention.
Specific embodiment
With reference to the accompanying drawing, specific embodiments of the present invention are described further.
Frame structure used by this example training sequence and OFDM symbol as shown in Figure 1, be mainly made of.Training sequence and OFDM symbol all includes cyclic prefix, and wherein training sequence is used to realize the channel equalization and channel compensation of ofdm system.This FFT/IFFT that example uses points are 64, and the length of cyclic prefix is 16 points, and the OFDM symbol number N that every frame includes is 100.
It is illustrated in figure 2 the flow chart that the present invention implements the ofdm system sampling clock frequency bias compensation method, Fig. 3 is this Realization structural schematic diagram in invention example.In conjunction with Fig. 2 and Fig. 3, detailed process is as follows:
1, method assumes that the estimated value Δ of sampling clock frequency deviation has been obtained.It is obtained first according to sampling clock frequency deviation value Δ To the phase rotation increment of each subcarrier, implement according to following formula:
2, sign synchronization is carried out to the collected data of ADC in receiving end, finds the position of FFT window, extracts respectively Training sequence and data symbol.FFT transform is done to the training sequence and OFDM data symbol that extract, obtains the training sequence of frequency domain Train value RtrsWith data Xl,k.Wherein l indicates the call number of the OFDM data symbol received, and k is the subcarrier of OFDM data.
3, local training sequence is stored in the training sequence of transmitting terminal, the training sequence frequency domain value obtained using extraction RtrsWith local training sequence frequency domain value LtrsEstimate the channel response initial value H (0, k) of system.Specific implementation is according to following public Formula:
4, the channel response more positive value at each symbol is obtained in such a way that the channel response initial value of system is through recursion.Mould The structure of block a multiplier and delayer as shown in figure 4, be made of, and specific implementation is according to following formula:
5, equilibrium is carried out to data according to the system channel response coefficient updated, is also to systematic sampling clock while balanced Phase rotation caused by frequency deviation compensates, and specific implementation is as follows according to formula:
It is illustrated in figure 5 the compensation performance verification result of this example, systematic sampling intensity modulated Direct-detection Optical OFDM system System.The data modulation format of system is 16QAM, and transmitting optical power is 7.5dBm, after 25Km single mode optical fiber and optical attenuation Received optical power is -13dBm after device.Under different sampling clock offset frequency situations, before system balance and compensated error code is forthright Can as shown in figure 5, it can be seen from the figure that without compensation, the bit error rate of system with sampling clock frequency deviation increasing Add and sharply increase, and to sampling clock frequency deviation compensation after, the performance of system is effectively improved, when sampling clock frequency deviation- When between 150ppm to 150ppm, the compensated bit error rate almost with 0 frequency deviation when it is equal.Using the method for the present invention compensation and ideal The effect of compensation is about the same.
The above examples are only used to illustrate the technical scheme of the present invention, is not intended to limit the scope of the present invention, all at this Any modifications, equivalent replacements, and improvements etc. done within spirit and principle, contained within protection scope of the present invention.

Claims (5)

1. a kind of low complexity OFDM-PON system sample clock frequency deviation compensation method, which is characterized in that specific steps It is as follows:
1) the sampling clock offset estimation value estimated by OFDM-PON system receiving terminal obtains each subcarrier adjacent OFDM symbol Phase rotation increment between number；
2) the twiddle factor increment of frequency domain between each subcarrier adjacent OFDM symbol is unfolded by Euler's formula, and approximation phase Position increment of rotation indicates；
3) channel response initial value is combined, is obtained by the way of recursion according to the approximate twiddle factor increment between adjacent OFDM symbol Channel response of each subcarrier after extension at each OFDM symbol；
4) sampling clock frequency deviation is compensated according to the channel response after extension；
Sampling clock frequency has been obtained in the low complexity OFDM-PON system sample clock frequency deviation compensation method hypothesis Inclined estimated value Δ；The phase rotation increment of each subcarrier is obtained according to sampling clock frequency deviation value Δ first, specific implementation according to According to following formula:
Sign synchronization is carried out to the collected data of ADC in receiving end, the position of FFT window is found, extracts trained sequence respectively Column and data symbol；FFT transform is done to the training sequence and OFDM data symbol that extract, obtains the training sequence value of frequency domain RtrsWith data Xl,k；Wherein l indicates the call number of the OFDM data symbol received, and k is the subcarrier of OFDM data；
Local training sequence is stored in the training sequence of transmitting terminal, the training sequence frequency domain value R obtained using extractiontrsWith Local training sequence frequency domain value LtrsEstimate the channel response initial value H (0, k) of system；Specific implementation is according to following formula:
The channel response more positive value at each symbol is obtained in such a way that the channel response initial value of system is through recursion；Module is by one A multiplier and delayer composition, implement according to following formula:
Equilibrium is carried out to data according to the system channel response coefficient updated, is also to draw while balanced to systematic sampling clock frequency deviation The phase rotation risen compensates, and specific implementation is as follows according to formula:
2. low complexity OFDM according to claim 1-PON system sample clock frequency deviation compensation method, special Sign is, the phase rotation increment θ of k-th of subcarrier of adjacent OFDM symbol in the step 1)kIt is obtained by following formula:
Δ is sample clock frequency relative deviation in formula, and the calculating that N is ofdm system FFT/IFFT is counted, NsFor an OFDM number According to the length of symbol, including OFDM data and data cyclic prefix.
3. low complexity OFDM according to claim 1-PON system sample clock frequency deviation compensation method, special Sign is, in the step 2) between adjacent OFDM symbol k-th of subcarrier phase rotation increment θkIt much smaller than 0, and is solid Definite value, phase rotation coefficient caused by the sampling frequency offset between adjacent OFDM symbolBy the phase between adjacent OFDM symbol Increment of rotation θkApproximate representation:
4. low complexity OFDM according to claim 1-PON system sample clock frequency deviation compensation method, special Sign is that the channel response in the step 3) at OFDM symbol is provided by previous OFDM symbol channel response, according to channel Response initial value and recurrence formula obtain the channel response of each OFDM symbol, are specifically provided by following formula,
Wherein l is the call number of the OFDM symbol received, and H (0, k) is that system channel responds initial value.
5. low complexity OFDM according to claim 1-PON system sample clock frequency deviation compensation method, special Sign is that the system channel response coefficient that the step 4) updates mends phase rotation caused by systematic sampling clock frequency deviation It repays, is specifically provided by following formula:
Wherein Y1(l, k) is the reception frequency response of uncompensated frequency departure, and H (l, k) is that first of OFDM symbol, k-th of son carries The frequency channels of wave respond, and this completes sampling frequency offset compensation.
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* Cited by examiner, † Cited by third party
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CN107204950A (en) * 2017-07-12 2017-09-26 东南大学 A kind of sampling clock synchronous method based on pilot tone
CN112291013A (en) * 2020-09-25 2021-01-29 湖南工业大学 Sampling clock frequency offset blind estimation method of optical OFDM system
CN114338321A (en) * 2020-09-29 2022-04-12 中国船舶重工集团公司第七二四研究所 Method for estimating arrival time of orthogonal frequency division multiplexing system
CN112468429B (en) * 2020-12-13 2022-03-01 湖南师范大学 Sampling frequency deviation estimation method applied to asynchronous optical fiber discrete multi-audio system
CN113364716B (en) * 2021-06-04 2022-03-11 深圳智微电子科技有限公司 Phase compensation method for sampling frequency offset in OFDM system
CN114430290B (en) * 2022-01-13 2023-04-18 芯象半导体科技(北京)有限公司 Residual sampling clock deviation compensation method and device based on BPLC system
CN114465691A (en) * 2022-02-15 2022-05-10 上海兆煊微电子有限公司 Low-complexity constant envelope phase modulation signal sampling deviation estimation and compensation method and system
CN115987742B (en) * 2023-03-20 2023-06-16 四川创智联恒科技有限公司 OFDM communication system-based frequency domain Doppler frequency offset expansion resisting method
CN116055928B (en) * 2023-04-03 2023-06-02 深圳市紫光同创电子有限公司 Data sampling method, device, electronic equipment and storage medium

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105141561A (en) * 2015-05-19 2015-12-09 上海大学 Low resource consumption high precision OFDM-PON system symbol synchronization method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2489922A (en) * 2011-04-06 2012-10-17 Univ Bangor Synchronising optical OFDM signal with pattern of DC offset levels superimposed upon OFDM symbols

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105141561A (en) * 2015-05-19 2015-12-09 上海大学 Low resource consumption high precision OFDM-PON system symbol synchronization method

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
An OFDM-PON symbol synchronization technology based on absolute value error of training sequence;陈健 等;《3rd International Conference on Consumer Electronics Communications and Networks 》;20131122;第125-129页
基于OFDM-PON的短训练序列分配方案;陈曦 等;《上海大学学报（自然科学版）》;20151031;第21卷(第5期);第560-569页
基于训练序列的OOFDM采样时钟频率偏差估计算法;张镇 等;《上海大学学报（自然科学版）》;20170228;第23卷(第1期);第128-146页

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