CN108964783A - Coherent optical heterodyne communicatio carrier synchronization method under big Frequency Offset - Google Patents
Coherent optical heterodyne communicatio carrier synchronization method under big Frequency Offset Download PDFInfo
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- CN108964783A CN108964783A CN201810853929.7A CN201810853929A CN108964783A CN 108964783 A CN108964783 A CN 108964783A CN 201810853929 A CN201810853929 A CN 201810853929A CN 108964783 A CN108964783 A CN 108964783A
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- compensation
- frequency deviation
- phase
- carrier synchronization
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6164—Estimation or correction of the frequency offset between the received optical signal and the optical local oscillator
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6165—Estimation of the phase of the received optical signal, phase error estimation or phase error correction
Abstract
The invention discloses coherent optical heterodyne communicatio carrier synchronization methods under a kind of big Frequency Offset, it is related to the compensation of optical communication field frequency deviation and difference compensation.Preliminary frequency deviation compensation is carried out to signal is received first with the frequency deviation backoff algorithm based on phase increment, there may be residual frequency deviations after compensation；Then preliminary difference compensation is carried out to signal using classical phase estimation algorithm, there may be phase rotatioies after compensation；Finally residual frequency deviation and phase rotation are compensated using data frame head, realize carrier synchronization.The accurate compensation of arbitrarily large frequency deviation and carrier phase theoretically may be implemented under conditions of increasing small-amount algorithm complexity in the present invention, suitable for star the fields such as high speed optical communication.
Description
Technical field
The present invention relates to coherent optical heterodyne communicatio carrier synchronizations under technical field of photo communication more particularly to a kind of big Frequency Offset
Method.
Background technique
With the raising of social informatization degree, the demand to data transmission is sharply increased.Coherent light communication and intensity tune
Communication mode processed, which is compared, has communication band roomy and the advantages such as sensitivity is high, is the emphasis of the following high-speed communication research.But phase
Modulation, relevant detection communication mode by frequency difference between local oscillator light source and signal optical source, differ and Doppler frequency shift influenced it is tight
Weight, therefore need to carry out carrier synchronization before signal demodulation.
Phase-modulation coherent light communication carrier synchronization can be generally divided into frequency deviation compensation and difference two steps of compensation carry out, certainly
It is carried out it is also contemplated that the two is synchronous.It can be divided into using more carrier synchronization method based on training sequence (data at present
Auxiliary) method and carrier wave blind synchronization method.Method based on training sequence can eliminate modulation intelligence using training sequence, past
Toward with bigger compensation range.But due to joined training sequence, link burden is inevitably increased, and algorithm is complicated
It spends higher.Blind carrier synchronization method based on phase increment has many advantages, such as to realize that simple, calculation amount is small, by the relevant technologies people
The favor of member.But due to eliminating phase-modulated information using method is multiplied, the compensation range of this method is smaller.Local oscillator light source and
Frequency deviation and difference between signal optical source are drifted about at any time, are more up to by the Doppler frequency shift of the mobile introducing of communication ends several
G hertz, it is therefore desirable to improve the compensation range of existing method.
Summary of the invention
It is an object of the invention to the deficiency for above-mentioned background technique one kind is provided, big frequency deviation and difference may be implemented
Under the conditions of carrier synchronization method, compensated by preliminary frequency deviation and difference compensation and the subsequent blurring process that disappears may be implemented to appoint
The accurate compensation of big frequency deviation of anticipating and difference.
Effective object default of the invention is the receiver signal by preliminary treatment, these processing include going inclination, just
Friendshipization, Timing Synchronization and polarization demultiplexing.
The object of the present invention is achieved like this, coherent optical heterodyne communicatio carrier synchronization method under a kind of big Frequency Offset, it
The following steps are included:
(1) preliminary offset estimation and benefit are carried out to signal is received using the blind frequency excursion algorithm based on phase increment
It repays, after preliminary frequency deviation compensation, remaining frequency deviation
(2) difference compensation is carried out to by the compensated signal of preliminary frequency deviation using V-V algorithm, after difference compensation,
Phase rotation angle
(3) compensated signal is compensated and differed to the preliminary frequency deviation of process in the way of traversal carry out residual frequency deviation compensation
Disappear with phase fuzzy, and compensated signal and frame head will match each time, can be realized one group of frame head complete match
As correctly compensated one group of residual frequency deviation and phase rotation angle completes coherent optical heterodyne communicatio carrier synchronization.
Wherein, step (3) specifically: using frame head removal process (1) and (2) in remaining frequency deviation and phase rotation angle
Degree, compensation formula are as follows:
Compensation formula needs to carry out repeatedly, chooses different frequency deviation Δ f each timereWith rotation angleIt is combined, obtains
It to compensated data, is successively matched with compensated data block using frame head, matching correctly is then completed to compensate, and completes phase
Dry photoreceiver carrier synchronization；Wherein, X "kTo compensate and differing compensated signal, T by preliminary frequency deviationsFor adjacent symbol
Time interval.
Wherein, when compensating, X " is chosenkAt least two frame of length length.
It has the advantages that compared with the background technology, the present invention
Coherent optical heterodyne communicatio carrier synchronization process is integrally divided into two stages by the present invention, is estimated first with typical frequency deviation
Meter and difference estimation method carry out preliminary frequency deviation compensation and difference to reception signal and compensate, and then utilize the method for searching for frame head
The compensation for realizing residual frequency deviation and phase rotation, finally realizes the accurate compensation of big frequency deviation and difference.The present invention solves existing
The problem of frequency deviation compensation range of algorithm is small, phase developing method is only applicable in the case of difference is changed from small to big, may be implemented to appoint
The accurate compensation for the size frequency deviation and carrier phase of anticipating.
Detailed description of the invention
Fig. 1 is carrier synchronization method flow chart proposed by the present invention.
Fig. 2 is the preliminary frequency deviation compensation flow chart that the present invention uses.
Fig. 3 is the preliminary difference compensation flow chart that the present invention uses.
Fig. 4 is the data frame structure schematic diagram that the present invention uses.
Fig. 5 is that the present invention carries out frame head matching process schematic diagram.
Specific embodiment
Technical solution of the present invention is more clearly and detailedly described below in conjunction with accompanying drawings and embodiments, but this
The protection scope of invention is not limited thereto.
QPSK modulation system spectrum efficiency with higher is the mainstream modulation system of the current and following optical communication applications.
The present invention is described in detail technical solution of the present invention by taking single carrier qpsk modulation signal as an example, order of modulation M=4.
Flow chart is as shown in Figure 1；
(1) carry out preliminary frequency deviation to the reception signal Jing Guo pre-processing first to compensate, this step is using based on phase
The frequency excursion algorithm realization of increment, work flow diagram such as Fig. 2.For message transmission rate, frequency deviation is that slow become is believed
Number, therefore by the way of block processing.
Previous symbol in each data block is taken and makees product with the latter symbol after being conjugated；
4 power operations are carried out to gained product；
Symbol amplitude after power is normalized, the average value of block of symbols is sought；
It takes the phase of previous step averaging of income value and divided by 4, obtains the phase increment between adjacent symbol；
Frequency deviation compensation is carried out to the data block.
(2) carry out preliminary difference to the signal by the compensation of preliminary frequency deviation to compensate, work flow diagram such as Fig. 3.Laser
Phase jitter equally may be considered slow varying signal, use block processing to reduce random error.
4 power operations successively are carried out to each code element in data block；
By the amplitude normalization of symbol, the average value of symbol in each piece is sought；
The phase that is averaged and divided by 4；
The phase jitter introduced to laser compensates.
(3) remaining frequency deviation and phase ambiguity are compensated using known frame head.
The possibility value collection of residual frequency deviation is combined intoThe possibility value collection of Phase aberration is combined into
It is handled by frame data are received, the data structure of use of the invention is as shown in Figure 4.Choose the length of data block
Degree is the length of two frame data, is successively compensated according to the various combination of residual frequency deviation and Phase aberration to it；
The matching of frame head is carried out to the sequence that each compensation obtains, matching process is as shown in figure 5, best by matching degree
One group as final compensated data.
Step (1) in, take conjugate product operation can with take 4 power operation exchanges sequences, but first carry out conjugate product operation
It can reduce by a power operation；
Step (1) in, code fetch member mean operation can with take phase operation exchange sequence, first take mean value to need to carry out amplitude
Normalization, first takes phase can be without amplitude normalization.
(1) and (2) step is to weaken the interference of random noise using the method that multiple elements are averaging.
The specific algorithm process of step (1) is as follows:
Signal with frequency deviation and phase rotation can be generally expressed as
Wherein, XkIt is the sequence of symhols for receiving signal, AkIt is XkAmplitude, Δ f is frequency deviation, TsIt is the time of adjacent symbol
Interval, dkIt is phase-modulated information,Or It is by laser linewidth
The phase jitter of introducing, θkIt is the random noise of the introducings such as optoelectronic receiver.
The result of adjacent symbol conjugate multiplication is
Asterisk expression takes conjugation,For the difference of former and later two symbol phase modulations,With Δ θk=θk+1-θkIt is a small amount of of random distribution.
It can use the influence that phase modulation information is eliminated in 4 power operations in this way
The influence that random disturbances can be eliminated substantially by the method that multiple elements are averaging, finally acquires adjacent symbol phase
The desired value of position increment,
It finally obtains the estimated value of frequency deviation and it is compensated
Due to first having carried out multiplying 4 operations to phase increment, and the operation divided by 4 is carried out to it, therefore finally acquire
That is, there is frequency deviation and obscure or have residual frequency deviation in the integral multiple that 2 π are not necessarily differed between phase increment and original phase increment,
(2) step is not required to consider the part of frequency deviation, specific algorithm is as follows:
It is by the symbol that preliminary frequency deviation compensates
The influence of phase-modulated information is eliminated also with 4 power operations,
WhereinIt is the phase jitter introduced by laser linewidth, is slow varying signal, θkIt is the introducings such as optoelectronic receiver
Random noise is random interfering signal.
Weaken the influence of random interfering signal using the method that multiple symbols are averaging, the desired value for obtaining phase error is
Due to eliminating phase-modulated information, finally obtained phase error desired value also with 4 power operationsWith
True phase error desired valueBetween difference be not necessarily the integral multiple of 2 π, that is, there is phase ambiguity,
(3) step utilizes frame head removal process (1) and (2) remaining frequency deviation and phase ambiguity, compensation formula are
Wherein, X "kFor the signal that compensation is compensated and differed by preliminary frequency deviation.By step (1) and (2) it is found that shown in formula (9)
Compensation formula need carry out repeatedly, choose different Δ f each timereWithCombination, share 16 kinds of possible situations.Benefit
It is successively matched with compensated data block with frame head, until obtaining the result of perfect matching.In order to ensure matched every time
Complete preamble sequence is contained at least one in sequence, the data block length of processing is chosen for the length of two frames.
In the present invention there are three the effects of frame head: determining the position (frame synchronization) of each frame, eliminate residual frequency deviation and disappear
Except phase ambiguity.
The foregoing is merely the specific embodiment of the present invention in embodiment, but protection scope of the present invention is not limited to
In this, in the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of for anyone skilled in the art,
Should all it cover within that scope of the present invention.
Claims (3)
1. coherent optical heterodyne communicatio carrier synchronization method under a kind of big Frequency Offset, which comprises the following steps:
(1) preliminary offset estimation and compensation are carried out to signal is received using the blind frequency excursion algorithm based on phase increment, passed through
After crossing preliminary frequency deviation compensation, remaining frequency deviation
(2) difference compensation is carried out to by the compensated signal of preliminary frequency deviation using V-V algorithm, after difference compensation, phase
Rotate angle
(3) compensated signal is compensated and differed to the preliminary frequency deviation of process in the way of traversal carry out residual frequency deviation compensation and phase
Position disappears fuzzy, and compensated signal and frame head will match each time, one group for can be realized frame head complete match is
Correctly compensated one group of residual frequency deviation and phase rotation angle completes coherent optical heterodyne communicatio carrier synchronization.
2. coherent optical heterodyne communicatio carrier synchronization method under big Frequency Offset according to claim 1, which is characterized in that step
(3) specifically: using frame head removal process (1) and (2) in remaining frequency deviation and phase rotation angle, compensation formula are as follows:
Yk=X "k·exp[-j(2πΔfre·kTs+φre)]
Compensation formula needs to carry out repeatedly, chooses different frequency deviation Δ f each timereWith rotation angleIt is combined, is mended
Data after repaying successively are matched with compensated data block using frame head, and matching correctly is then completed to compensate, and complete coherent light
Receiver carrier synchronization；Wherein, X "kTo compensate and differing compensated kth frame signal, T by preliminary frequency deviationsFor adjacent symbol
Time interval.
3. coherent optical heterodyne communicatio carrier synchronization method under big Frequency Offset according to claim 2, which is characterized in that carry out
When compensation, X " is chosenkAt least two frame of length length.
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| CN109862545A (en) * | 2019-01-15 | 2019-06-07 | 珠海市杰理科技股份有限公司 | Frequency bias compensation method, device, computer equipment and the storage medium of Bluetooth signal |
| CN110380786A (en) * | 2019-06-20 | 2019-10-25 | 华南师范大学 | A kind of frequency difference blind estimating method under probability shaping constellation |
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