CN102318305B  Method, equipment and system to deal with optical orthogonal frequency division multiplexing (OFDM) signal  Google Patents
Method, equipment and system to deal with optical orthogonal frequency division multiplexing (OFDM) signal Download PDFInfo
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 CN102318305B CN102318305B CN201180001550.XA CN201180001550A CN102318305B CN 102318305 B CN102318305 B CN 102318305B CN 201180001550 A CN201180001550 A CN 201180001550A CN 102318305 B CN102318305 B CN 102318305B
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Classifications

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B10/00—Transmission systems employing electromagnetic waves other than radiowaves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
 H04B10/60—Receivers
 H04B10/66—Noncoherent receivers, e.g. using direct detection
 H04B10/69—Electrical arrangements in the receiver

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L27/00—Modulatedcarrier systems
 H04L27/26—Systems using multifrequency codes
 H04L27/2601—Multicarrier modulation systems
 H04L27/2647—Arrangements specific to the receiver only
 H04L27/2655—Synchronisation arrangements
 H04L27/2662—Symbol synchronisation

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L27/00—Modulatedcarrier systems
 H04L27/26—Systems using multifrequency codes
 H04L27/2601—Multicarrier modulation systems
 H04L27/2647—Arrangements specific to the receiver only
 H04L27/2655—Synchronisation arrangements
 H04L27/2668—Details of algorithms
 H04L27/2673—Details of algorithms characterised by synchronisation parameters
 H04L27/2675—Pilot or known symbols

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L27/00—Modulatedcarrier systems
 H04L27/26—Systems using multifrequency codes
 H04L27/2601—Multicarrier modulation systems
 H04L27/2697—Multicarrier modulation systems in combination with other modulation techniques
Abstract
This invention provides a Method, equipment and system to deal with optical orthogonal frequency division multiplexing (OFDM) signal, which is related to the area of communication technology. The mentioned methods include: the receiving terminal receives OFDM signal, and obtains its sample signal. The mentioned OFDM signal is equipped with synchronous training sequence, which is used to achieve synchronization of the receiving terminal and transmitting terminal; the first sample point is obtained according to the mentioned sample signal; the second sample point is gained through the mentioned first sample point, and the starting point of OFDM signal is acquired through the second sample point. This invention ascertains the starting point of OFDM signal by means of three levels synchronization method, which greatly increases the accuracy of obtaining the OFDM starting point, and can reduce achieve synchronization error, and achieve the accurate synchronization of signals in cases of feeble signal.
Description
Technical field
The present invention relates to communication technical field, particularly a kind of methods, devices and systems of processing light orthogonal frequencydivision multiplex singal.
Background technology
Light OFDM(Orthogonal Frequency Division Multiplexing, OFDM) be the OFDM technology in wireless to be incorporated into a kind of new technique of optical communication field, it both can regard a kind of modulation technique as, also can regard a kind of multiplex technique as.The basic principle of light ofdm signal is: by the division of signal of time domain high speed serial, be a plurality of lowspeed parallel signals, frequency domain channel is divided into some orthogonal subchannels (being light OFDM symbol subcarrier), then lowspeed parallel signal is modulated on every subchannels and is transmitted.But because light OFDM is a kind of multicarrier modulation technology, it to synchronous error than singlecarrier system sensitivity many, so in optical OFDM system, very important when how light ofdm signal is processed, especially timing synchronization algorithm is extremely important accurately for receiving terminal, it can provide correct symbol original position, so that the demodulation that transmission data can be correct.
In prior art, receiving terminal adopts the method for singlestage Timing Synchronization to realize the sign synchronization sending with transmitting terminal.The method of singlestage Timing Synchronization is mainly utilized the characteristic of synchronous training sequence self, carries out, after related operation, obtaining the peak value of synchronous training sequence, thus the starting point of definite optical character.Concrete, at transmitting terminal, produce a PN(PseudoNoise, pseudo noise) synchronous training sequence, wherein, supposes that an OFDM symbol lengths is N, PN training sequence length is also taken as N, then training sequence is divided into 4 parts, every partiallength is N/4, and this 4 part is called after A, B, C, D respectively.In A, B, C, D, the data of A and B are the same, the data of C and D the same and with A, B contrary sign.There is the sequence of abovementioned feature through IFFT(Inverse Fast Fourier Transform, inverse Fourier transform) after conversion, just obtained time domain data corresponding to training sequence, afterwards, again training sequence is placed in to the front end of light ofdm signal, sends into transmission and send to together receiving terminal.At receiving terminal, signal after the light ofdm signal receiving is carried out being sampled after relevant treatment, signal after sampling is carried out to serial to parallel conversion, to after the signal lag carrying out after serial to parallel conversion, carry out autocorrelation computation with self again, obtain autocorrelation function M (d), wherein, d refers to d sampled point of signal, if M (d) is greater than the threshold value of setting, to get maximum place be the initiating terminal of light ofdm signal to M (d), completes synchronous.
But at least there is following problem in prior art: adopt the method for singlestage Timing Synchronization, in the situation that signal to noise ratio is lower, regularly spike is not obvious for autocorrelation function, and synchronous error is larger, even cannot realize synchronously serious system for restricting performance.
Summary of the invention
In order to solve the problem that receiving terminal and transmitting terminal synchronous error are larger, the embodiment of the present invention provides a kind of methods, devices and systems of processing light orthogonal frequencydivision multiplex singal.Described technical scheme is as follows:
On the one hand, provide a kind of method of processing light orthogonal frequencydivision multiplex singal, described method comprises:
Receive light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, described the 4th part is the repetition of second portion, and described synchronous training sequence length equals 1 light orthogonal frequency division multiplex OFDM symbol lengths;
According to the repeat property existing in described synchronous training sequence, described sampled signal is processed and obtained the first sampled point;
According to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point;
According to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol.
On the other hand, also provide a kind of device of processing light orthogonal frequencydivision multiplex singal, described device comprises:
Receiver module, be used for receiving light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, described the 4th part is the repetition of second portion, and described synchronous training sequence length equals 1 light orthogonal frequency division multiplex OFDM symbol lengths;
The first acquisition module, for the repeat property existing according to described synchronous training sequence, processes and obtains the first sampled point described sampled signal;
The second acquisition module, for according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtains the second sampled point;
The 3rd acquisition module, for according to the conjugate symmetry of described the second sampled point and described synchronous training sequence first and second portion and zero cross correlation, obtains the starting point of light OFDM symbol.
Another fermentation, also provides a kind of system that receives light orthogonal frequencydivision multiplex singal, and described system comprises:
The device of abovementioned processing optical frequency division multiplex signal, be used for receiving light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, described the 4th part is the repetition of second portion, described synchronous training sequence length equals 1 light orthogonal frequency division multiplex OFDM symbol lengths, according to the repeat property existing in described synchronous training sequence, described sampled signal is processed and obtained the first sampled point, according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point, according to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol,
Serial to parallel conversion module, for after getting the starting point of described smooth OFDM symbol, starts to extract light OFDM symbol from described starting point, and is N channel parallel data by described smooth OFDM symbol serial to parallel conversion; Described N is greater than 1 natural number;
Going cyclic prefix module, is the Cyclic Prefix that described smooth OFDM symbol adds for removing transmitting terminal;
Fourier transform module, for going the data after cyclic prefix module is processed to carry out Fourier transform to described, obtains constellation mapping data;
Channel equalization module, for carrying out dispersion compensation, phase correction processing to the described constellation mapping data that obtain;
Constellation demodulation module, for reverting to the parallel binary data in N road by the data after described channel equalization resume module;
Parallel serial conversion module, is reduced to serial binary data for the data after described constellation demodulation module is processed.
Another fermentation, also provides a kind of system of processing light orthogonal frequencydivision multiplex singal, and described system comprises: the system of the system of transmission light orthogonal frequencydivision multiplex singal and abovementioned reception light orthogonal frequencydivision multiplex singal, wherein,
The system of described transmission light orthogonal frequencydivision multiplex singal, for generation of for the synchronous synchronous training sequence of light OFDM symbol, and described synchronous training sequence is placed in to the front end of the light OFDM symbol that will transmit, send to together the device of described reception light orthogonal frequencydivision multiplex singal; Described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, described the 4th part is the repetition of second portion, and described synchronous training sequence length equals 1 light orthogonal frequency division multiplex OFDM symbol lengths;
The system of described reception light orthogonal frequencydivision multiplex singal, the light OFDM symbol and the described synchronous training sequence that for receiving the device of described transmission light orthogonal frequencydivision multiplex singal, send, and find the starting point of described smooth OFDM symbol according to described synchronous training sequence, thereby optical frequency division multiplex symbol described in demodulation.
The beneficial effect of the technical scheme that the embodiment of the present invention provides is: by obtaining the first sampled point, the second sampled point, thereby determine again the light ofdm signal synchronous method of the starting point of light OFDM symbol, greatly increased the accurate positioning to optical character, even in the situation that signal to noise ratio is lower, also can realize the accurate synchronization of signal, reduce synchronous error.
Accompanying drawing explanation
Fig. 1 is a kind of flow chart of processing the method for light orthogonal frequencydivision multiplex singal that the embodiment of the present invention provides;
Fig. 2 is a kind of flow chart of processing the method for light orthogonal frequencydivision multiplex singal that another embodiment of the present invention provides;
Fig. 3 is the structure chart of a kind of synchronous training sequence of providing of another embodiment of the present invention;
Fig. 4 is a kind of schematic diagram that sends the device of light orthogonal frequencydivision multiplex singal that another embodiment of the present invention provides;
Fig. 5 is a kind of schematic diagram that receives the device of light orthogonal frequencydivision multiplex singal that another embodiment of the present invention provides;
Fig. 6 is a kind of schematic diagram of processing the device of light orthogonal frequencydivision multiplex singal that another embodiment of the present invention provides;
Fig. 7 is a kind of schematic diagram that receives the system of light orthogonal frequencydivision multiplex singal that another embodiment of the present invention provides;
Fig. 8 is a kind of schematic diagram of processing the system of light orthogonal frequencydivision multiplex singal that another embodiment of the present invention provides.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, embodiment of the present invention is described further in detail.
Referring to Fig. 1, the embodiment of the present invention provides a kind of method of processing light orthogonal frequencydivision multiplex singal, comprising:
101: receive light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, and second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, and described the 4th part is the repetition of second portion;
102: according to the repeat property existing in described synchronous training sequence, described sampled signal is processed and obtained the first sampled point;
103: according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point;
104: according to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol.
Preferably, in the present embodiment, according to the repeat property existing in described synchronous training sequence, described sampled signal is processed and is obtained the first sampled point, comprising:
By the described default time of sampled signal time delay of obtaining, obtain the sampled signal after time delay;
Sampled signal after described sampled signal and described time delay is carried out to autocorrelation computation, and obtain thick timing estimation function according to the repeat property existing in described synchronous training sequence;
According to described thick timing estimation function, obtain the first sampled point.
Preferably, in the present embodiment, according to described thick timing estimation function, obtain the first sampled point, comprising:
Obtain first and make described thick timing estimation functional value be greater than the sampled point of predetermined threshold value, obtain the first sampled point.
Preferably, in the present embodiment, according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point, comprising:
From described the first sampled point, light orthogonal frequencydivision multiplex singal corresponding to the later sampled point of described the first sampled point carried out to autocorrelation computation, obtain timing slip function;
According to the permanent envelope of described synchronous training sequence and zero their cross correlation, described the first sampled point of take is starting point, searches for the maximum of described timing slip function, will make described timing slip function obtain peaked sampled point and be designated as the second sampled point.
Preferably, in the present embodiment, according to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol, comprising:
Centered by described the second sampled point, search makes to become with described timing slip function maximum the position of the sampled point of preset ratio, obtains primary importance and the second place;
Light orthogonal frequencydivision multiplex singal between described primary importance and the described second place is carried out to autocorrelation computation, obtain new timing slip function;
According to the conjugate symmetry of first and second portion in described synchronous training sequence and zero cross correlation, obtain and make described new timing slip function obtain peaked sampled point, described in make described new timing slip function obtain the starting point that peaked sampling point position is exactly light OFDM symbol.
The beneficial effect of the technical scheme that the embodiment of the present invention provides is: by obtaining the first sampled point, the second sampled point, thereby determine again the light ofdm signal synchronous method of the starting point of light OFDM symbol, greatly increased the accurate positioning to optical character, even in the situation that signal to noise ratio is lower, also can realize the accurate synchronization of signal, reduce synchronous error.
Referring to Fig. 2, another embodiment of the present invention provides a kind of method of processing light orthogonal frequencydivision multiplex singal, comprising:
Step 201: receive light ofdm signal, obtain the sampled signal of this signal.
In the present embodiment, receiving terminal receives light ofdm signal, and wherein light ofdm signal comprises synchronous training sequence symbol and light OFDM symbol.Light OFDM symbol is exactly the data that need transmission, and synchronous training sequence is the signal for light OFDM sign synchronization.
Wherein, transmitting terminal produces the training sequence for light OFDM sign synchronization, preferably, the training sequence that transmitting terminal produces for light OFDM sign synchronization can be specifically CAZAC(Const Amplitude Zero AutoCorelation, permanent envelope sequence), its training sequence structure as shown in Figure 3.Wherein, first is CAZAC sequence, and its excessthree is partly conjugation symmetric body or the repetition of CAZAC sequence.Concrete, training sequence length equals 1 light OFDM symbol lengths N(and conventionally gets N=2
^{m}, wherein m is greater than 8), training sequence is comprised of 4 parts, and every partiallength is N/4.The part 1 of training sequence is that abovementioned length is the time domain sequences that the CAZAC sequence of N/4 generates after IFFT, and part 2 is the conjugation symmetric body of part 1; 3rd, 4 parts are repetitions of the 1st, 2 parts.Permanent envelope sequence has good their cross correlation, and peaktoaverage force ratio is low, and remains CAZAC sequence after IFFT.
Referring to Fig. 4, in the present embodiment, before producing synchronous training sequence, first binary data is delivered in the light OFDM sending module shown in Fig. 4 and modulated.The binary data of serial, after serial to parallel conversion, becomes N channel parallel data; Each channel parallel data carries out constellation mapping (as mQAM, mPSK etc.) again, then the signal after constellation mapping is carried out to inverse Fourier transform IFFT, obtains the timedomain information of light ofdm signal.After producing training sequence, training sequence is placed in to the light OFDM symbol front end that will transmit, then the light OFDM symbol with training sequence is added to Cyclic Prefix (length of note Cyclic Prefix is Ng), and then parallel serial conversion is to serial signal, transmits.
In the present embodiment, the effect of Cyclic Prefix is for overcoming because the time delay of optical fiber dispersion is expanded the light ofdm signal intersymbol interference causing.The length of Ng is relevant with the transmission range of light ofdm signal, is generally greater than the maximum delay in transmission range.Alternatively, Ng is 1/8～1/16 of N length.
Referring to Fig. 5, in the present embodiment, receiving terminal receives after light ofdm signal, first the signal receiving is carried out to analogtodigital conversion, obtains sampled signal, and then carries out three grades synchronously, determines the starting point of light OFDM symbol.Wherein, the concrete step 203205 below that passes through realizes three grades synchronously.
Step 202: according to the repeat property existing in synchronous training sequence, sampled signal is processed and obtained the first sampled point.
In the present embodiment, adopt three grades of synchronous methods to realize the sign synchronization of receiving terminal and transmitting terminal, wherein the first step is exactly to obtain the initial synchronization of the first sampled point.Concrete: by the described default time of sampled signal time delay of obtaining, obtain the sampled signal after time delay; According to the repeat property existing in described synchronous training sequence, the sampled signal after described sampled signal and described time delay is carried out to autocorrelation computation, obtain thick timing estimation function; According to described thick timing estimation function, obtain the first sampled point.Wherein d is sampled point, and Preset Time is generally the integral multiple of Ng, in order to guarantee the accuracy of thick timing estimation function, must be more than or equal to Ng, if overlong time will increase operand, is preferably 2Ng, and this present embodiment is not specifically limited this.
Concrete, according to thick timing function, obtaining the first sampled point comprises: by M (d) and the threshold value ζ comparison of setting, if M (d) > is ζ, think that signal arrives, realize initial synchronisation, the sampled point that first is greater than to the M (d) of ζ is designated as d1, is defined as the first sampled point.
Further, in the present embodiment, threshold value ζ chooses as follows: under desirable transmission conditions, carry out to the received signal carrying out autocorrelation computation after 2*Ng time delay, obtain an autocorrelation function M (d), choose M (d) peaked 75%, as the size of threshold value.
Step 203: according to the permanent envelope of the first sampled point and synchronous training sequence and zero their cross correlation, obtain the second sampled point.
In the present embodiment, according to the permanent envelope of the first sampled point and synchronous training sequence and zero their cross correlation, obtain the second sampled point, thick synchronous to realize.Concrete, according to the permanent envelope of described synchronous training sequence and zero their cross correlation, from described the first sampled point, light orthogonal frequencydivision multiplex singal corresponding to the later sampled point of described the first sampled point carried out to autocorrelation computation, obtain timing slip function; Described the first sampled point of take is starting point, searches for the maximum of described timing slip function, will make described timing slip function obtain peaked sampled point and be designated as the second sampled point.In the present embodiment, will make timing slip function obtain peaked sampled point and be designated as the second sampled point d2, complete thick synchronous.
In the present embodiment, if the synchronous training sequence that transmitting terminal produces is permanent envelope sequence, due to tetrameric architectural characteristic, also be that first half section is identical with the second half section, and first and third part and second portion and the 4th part, or first and the 4th part and second portion and third part.
Step 204: according to the conjugate symmetry of first and second portion in the second sampled point and synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol.
In the present embodiment, according to the second sampled point, finally obtain the starting point of light OFDM symbol, the process of carefully synchronizeing with transmitting terminal to realize receiving terminal.Concrete, centered by described the second sampled point, search makes to become with described timing slip function maximum the position of the sampled point of preset ratio, obtains primary importance and the second place; According to the conjugate symmetry of first and second portion in described synchronous training sequence and zero cross correlation, the light orthogonal frequencydivision multiplex singal between described primary importance and the described second place is carried out to autocorrelation computation, obtain new timing slip function; Obtain and make described new timing slip function obtain peaked sampled point, wherein, the position that makes new timing slip function obtain peaked sampled point is exactly the starting point of light OFDM.In the present embodiment, preset ratio is lower, and thin synchronous scope is just wider, but due to thick synchronous in, the peaked position of timing slip function obtaining has extremely approached tram, therefore preferably, preset ratio is 90%, and this present embodiment is not specifically limited.
In the present embodiment, centered by d2, the sampling point position of search timing slip function M (d) maximum 90%, is designated as respectively d3 and d4.In [d3, d4] scope, calculate new timing slip function M1 (d), the signal being about in [d3, d4] scope carries out autocorrelation computation.According to the conjugate symmetry of CAZAC training sequence, in autocorrelation computation, because training sequence and time delay n(n are not equal to the symbol lengths of training sequence) training sequence uncorrelated, and CAZAC sequence crosscorrelation value is close to zero, therefore the timing slip function M1 (d) that autocorrelation calculation obtains will be a very sharppointed curve chart, only when accurate synchronization, there will be peak value.Therefore, M1 (d) gets the starting point that peaked position is light OFDM symbol, is designated as d5, has now just completed light ofdm signal synchronous.
Referring to Fig. 5, in the present embodiment, after finding the starting point d5 of light OFDM, from d5, start to extract OFDM symbol, through serial to parallel conversion, be N channel parallel data, and remove the Cyclic Prefix that transmitting terminal adds; After Fourier transform (FFT), obtain the data of mQAM or mPSK mapping, then data are carried out the channel equalization such as dispersion compensation, phase correction.Finally, the data after channel equalization, by constellation demodulation, are reverted to the parallel binary data in N road.Then through parallel serial conversion, be reduced to serial binary data.
The beneficial effect of the embodiment of the present invention is: by obtaining the first sampled point, the second sampled point, thereby determine again the synchronous method of light ofdm signal of the starting point of light OFDM symbol, greatly increased the accurate positioning to optical character, even in the situation that signal to noise ratio is lower, also can realize the accurate synchronization of signal, reduce synchronous error.In addition, the present invention adopts CAZAC sequence as training sequence, has reduced the peaktoaverage force ratio of training sequence, has further promoted net synchronization capability.
Referring to Fig. 6, another embodiment of the present invention provides a kind of device of processing light orthogonal frequencydivision multiplex singal, comprising: receiver module 301, the first acquisition module 302, the second acquisition module 303, the 3rd acquisition module 304.
Receiver module 301, be used for receiving light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of light orthogonal frequencydivision multiplex singal, light orthogonal frequencydivision multiplex singal is with synchronous training sequence, and described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, and third part is the repetition of described first, and described the 4th part is the repetition of second portion;
The first acquisition module 302, for the repeat property existing according to described synchronous training sequence, processes and obtains the first sampled point described sampled signal;
The second acquisition module 303, for according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtains the second sampled point;
The 3rd acquisition module 304, for according to the conjugate symmetry of described the second sampled point and described synchronous training sequence first and second portion and zero cross correlation, obtains the starting point of light OFDM symbol.
Wherein, preferably, the first acquisition module 302, comprising:
Delay unit, for by the described default time of sampled signal time delay of obtaining, obtains the sampled signal after time delay;
The first computing unit, for the sampled signal after described sampled signal and described time delay is carried out to autocorrelation computation, and obtains thick timing estimation function according to the repeat property existing in described synchronous training sequence;
The first acquiring unit, for obtaining the first sampled point according to described thick timing estimation function.
Preferably, acquiring unit, specifically for:
Obtain first and make described thick timing estimation functional value be greater than the sampled point of predetermined threshold value, obtain the first sampled point.
In the present embodiment, preferably, the second acquisition module 303, comprising:
The second computing unit, be used for according to the permanent envelope of described synchronous training sequence and zero their cross correlation, from described the first sampled point, light orthogonal frequencydivision multiplex singal corresponding to the later sampled point of described the first sampled point carried out to autocorrelation computation, obtain timing slip function;
Second acquisition unit, is starting point for take described the first sampled point, searches for the maximum of described timing slip function, will make described timing slip function obtain peaked sampled point and be designated as the second sampled point.
Preferably, the 3rd acquisition module 304, comprising:
Search unit, for centered by described the second sampled point, search makes to become with described timing slip function maximum the position of the sampled point of preset ratio, obtains primary importance and the second place;
The 3rd computing unit, be used for according to the conjugate symmetry of described synchronous training sequence first and second portion and zero cross correlation, light orthogonal frequencydivision multiplex singal between described primary importance and the described second place is carried out to autocorrelation computation, obtain new timing slip function;
The 3rd acquiring unit, makes described new timing slip function obtain peaked sampled point for obtaining, described in make described new timing slip function obtain the starting point that peaked sampling point position is exactly light OFDM symbol.
Referring to Fig. 7, the embodiment of the present invention provides a kind of system that receives light orthogonal frequencydivision multiplex singal, comprising: process optical frequency division multiplex signal device 401, serial to parallel conversion module 402, go cyclic prefix module 403, Fourier transform module 404, channel equalization module 405, constellation demodulation module 406, parallel serial conversion module 407.Wherein, the device 401 of processing optical frequency division multiplex signal can be the device of arbitrary processing optical frequency division multiplex signal of describing in embodiment above.
Process the device 401 of optical frequency division multiplex signal, be used for receiving light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, and described the 4th part is the repetition of second portion; According to the repeat property existing in described synchronous training sequence, described sampled signal is processed and obtained the first sampled point; According to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point; According to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol;
Serial to parallel conversion module 402, for after getting the starting point of described smooth OFDM symbol, starts to extract light OFDM symbol from described starting point, and is N channel parallel data by described smooth OFDM symbol serial to parallel conversion; Described N is greater than 1 natural number;
Going cyclic prefix module 403, is the Cyclic Prefix that described smooth OFDM symbol adds for removing transmitting terminal;
Fourier transform module 404, for going the data after cyclic prefix module is processed to carry out Fourier transform to described, obtains constellation mapping data data;
Channel equalization module 405, for carrying out dispersion compensation, phase correction processing to the described constellation mapping data that obtain;
Constellation demodulation module 406, for reverting to the parallel binary data in N road by the data after described channel equalization resume module;
Parallel serial conversion module 407, is reduced to serial binary data for the data after described constellation demodulation module is processed.
Referring to Fig. 8, the embodiment of the present invention also provides a kind of system of processing light orthogonal frequencydivision multiplex singal, system comprises: send the system 300 of light orthogonal frequencydivision multiplex singal and the system 400 of reception light orthogonal frequencydivision multiplex singal, wherein, the system 400 that receives light orthogonal frequencydivision multiplex singal can be the system of the reception light orthogonal frequencydivision multiplex singal described in embodiment above.
The system 300 of described transmission light orthogonal frequencydivision multiplex singal, for generation of for the synchronous synchronous training sequence of light OFDM symbol, and described synchronous training sequence is placed in to the front end of the light OFDM symbol that will transmit, send to together the device of described reception light orthogonal frequencydivision multiplex singal; Described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, and second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, and described the 4th part is the repetition of second portion;
The system 400 of described reception light orthogonal frequencydivision multiplex singal, the light OFDM symbol and the described synchronous training sequence that for receiving the device of described transmission light orthogonal frequencydivision multiplex singal, send, and find the starting point of described smooth OFDM symbol according to described synchronous training sequence, thereby optical frequency division multiplex symbol described in demodulation.
The beneficial effect that device embodiment provided by the invention provides is: by obtaining the first sampled point, the second sampled point, it is synchronous that thereby three grades of timings determining again the starting point of light OFDM symbol realize light ofdm signal, greatly increased the accurate positioning to optical character, even in the situation that signal to noise ratio is lower, also can realize the accurate synchronization of signal, reduce synchronous error.
The device that the present embodiment provides, system, specifically can belong to same design with embodiment of the method, and its specific implementation process refers to embodiment of the method, repeats no more here.
The embodiment of the present invention can utilize software to realize, and corresponding software program can be stored in the storage medium can read, for example, and in the hard disk of computer, buffer memory or CD.
The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (10)
1. a method of processing light orthogonal frequencydivision multiplex singal, is characterized in that, described method comprises:
Receive light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, the 4th part is the repetition of described second portion, and the length of described synchronous training sequence equals 1 light orthogonal frequency division multiplex OFDM symbol lengths;
According to the repeat property existing in described synchronous training sequence, the sampled signal of the described light orthogonal frequencydivision multiplex singal getting is processed and obtained the first sampled point;
According to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point;
According to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol;
Wherein, described according to the repeat property existing in described synchronous training sequence, the sampled signal of the described light orthogonal frequencydivision multiplex singal getting is processed and obtained the first sampled point, comprising:
The default time of sampled signal time delay by the described light orthogonal frequencydivision multiplex singal getting, obtain the sampled signal after time delay; The described default time is 2Ng, the length of the Cyclic Prefix that Ng is described smooth orthogonal frequencydivision multiplex singal;
According to the repeat property existing in described synchronous training sequence, the sampled signal after the sampled signal of the described light orthogonal frequencydivision multiplex singal getting and described time delay is carried out to autocorrelation computation, obtain thick timing estimation function;
According to described thick timing estimation function, obtain the first sampled point.
2. method according to claim 1, is characterized in that, describedly according to described thick timing estimation function, obtains the first sampled point, comprising:
Obtain the sampled point that first value that makes described thick timing estimation function is greater than predetermined threshold value, obtain the first sampled point.
3. method according to claim 1 and 2, is characterized in that, describedly according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtains the second sampled point, comprising:
According to the permanent envelope of described synchronous training sequence and zero their cross correlation, from described the first sampled point, light orthogonal frequencydivision multiplex singal corresponding to the later sampled point of described the first sampled point carried out to autocorrelation computation, obtain timing slip function;
Described the first sampled point of take is starting point, searches for the maximum of described timing slip function, will make described timing slip function obtain peaked sampled point and be designated as the second sampled point.
4. method according to claim 3, described according to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtains the starting point of light OFDM symbol, comprising:
Centered by described the second sampled point, search makes to become with described timing slip function maximum the position of the sampled point of preset ratio, obtains primary importance and the second place;
According to the conjugate symmetry of first and second portion in described synchronous training sequence and zero cross correlation, the light orthogonal frequencydivision multiplex singal between described primary importance and the described second place is carried out to autocorrelation computation, obtain new timing slip function;
Obtain and make described new timing slip function obtain peaked sampled point, described in make described new timing slip function obtain the starting point that peaked sampling point position is exactly light OFDM symbol.
5. a device of processing light orthogonal frequencydivision multiplex singal, is characterized in that, described device comprises:
Receiver module, be used for receiving light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, the 4th part is the repetition of described second portion, and the length of described synchronous training sequence equals 1 light orthogonal frequency division multiplex OFDM symbol lengths;
The first acquisition module, for the repeat property existing according to described synchronous training sequence, processes and obtains the first sampled point the sampled signal of the described light orthogonal frequencydivision multiplex singal getting;
The second acquisition module, for according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtains the second sampled point;
The 3rd acquisition module, for according to the conjugate symmetry of described the second sampled point and described synchronous training sequence first and second portion and zero cross correlation, obtains the starting point of light OFDM symbol;
Wherein, described the first acquisition module, comprising:
Delay unit, for by the default time of sampled signal time delay of the described light orthogonal frequencydivision multiplex singal getting, obtains the sampled signal after time delay; The described default time is 2Ng, the length of the Cyclic Prefix that Ng is described smooth orthogonal frequencydivision multiplex singal;
The first computing unit, for the sampled signal after the sampled signal of the described light orthogonal frequencydivision multiplex singal getting and described time delay is carried out to autocorrelation computation, and obtains thick timing estimation function according to the repeat property existing in described synchronous training sequence;
The first acquiring unit, for obtaining the first sampled point according to described thick timing estimation function.
6. device according to claim 5, is characterized in that, described the first acquiring unit, specifically for:
Obtain the sampled point that first value that makes described thick timing estimation function is greater than predetermined threshold value, obtain the first sampled point.
7. according to the device described in claim 5 or 6, it is characterized in that, described the second acquisition module, comprising:
The second computing unit, be used for according to the permanent envelope of described synchronous training sequence and zero their cross correlation, from described the first sampled point, light orthogonal frequencydivision multiplex singal corresponding to the later sampled point of described the first sampled point carried out to autocorrelation computation, obtain timing slip function;
Second acquisition unit, is starting point for take described the first sampled point, searches for the maximum of described timing slip function, will make described timing slip function obtain peaked sampled point and be designated as the second sampled point.
8. device according to claim 7, described the 3rd acquisition module, comprising:
Search unit, for centered by described the second sampled point, search makes to become with described timing slip function maximum the position of the sampled point of preset ratio, obtains primary importance and the second place;
The 3rd computing unit, be used for according to the conjugate symmetry of described synchronous training sequence first and second portion and zero cross correlation, light orthogonal frequencydivision multiplex singal between described primary importance and the described second place is carried out to autocorrelation computation, obtain new timing slip function;
The 3rd acquiring unit, makes described new timing slip function obtain peaked sampled point for obtaining, described in make described new timing slip function obtain the starting point that peaked sampling point position is exactly light OFDM symbol.
9. a system that receives light orthogonal frequencydivision multiplex singal, is characterized in that, described system comprises:
The device of the processing light orthogonal frequencydivision multiplex singal as described in claim 5 to 8 any one, be used for receiving light orthogonal frequencydivision multiplex singal, and obtain the sampled signal of described smooth orthogonal frequencydivision multiplex singal, described smooth orthogonal frequencydivision multiplex singal is with synchronous training sequence, described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, the 4th part is the repetition of described second portion, the length of described synchronous training sequence equals 1 light orthogonal frequency division multiplex OFDM symbol lengths, according to the repeat property existing in described synchronous training sequence, the sampled signal of the described light orthogonal frequencydivision multiplex singal getting is processed and obtained the first sampled point, according to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point, according to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol, wherein, described according to the repeat property existing in described synchronous training sequence, the sampled signal of the described light orthogonal frequencydivision multiplex singal getting is processed and obtained the first sampled point, comprise: the default time of sampled signal time delay by the described light orthogonal frequencydivision multiplex singal getting, obtain the sampled signal after time delay, the described default time is 2Ng, the length of the Cyclic Prefix that Ng is described smooth orthogonal frequencydivision multiplex singal, according to the repeat property existing in described synchronous training sequence, the sampled signal after the sampled signal of the described light orthogonal frequencydivision multiplex singal getting and described time delay is carried out to autocorrelation computation, obtain thick timing estimation function, according to described thick timing estimation function, obtain the first sampled point,
Serial to parallel conversion module, for after getting the starting point of described smooth OFDM symbol, starts to extract light OFDM symbol from described starting point, and is N channel parallel data by described smooth OFDM symbol serial to parallel conversion; Described N is greater than 1 natural number;
Going cyclic prefix module, is the Cyclic Prefix that described smooth OFDM symbol adds for removing transmitting terminal;
Fourier transform module, for going the data after cyclic prefix module is processed to carry out Fourier transform to described, obtains constellation mapping data;
Channel equalization module, for carrying out dispersion compensation, phase correction processing to the described constellation mapping data that obtain;
Constellation demodulation module, for reverting to the parallel binary data in N road by the data after described channel equalization resume module;
Parallel serial conversion module, is reduced to serial binary data for the data after described constellation demodulation module is processed.
10. a system of processing light orthogonal frequencydivision multiplex singal, is characterized in that, described system comprises: send the system of light orthogonal frequencydivision multiplex singal and the system of reception light orthogonal frequencydivision multiplex singal as claimed in claim 9, wherein,
The system of described transmission light orthogonal frequencydivision multiplex singal, for generation of for the synchronous synchronous training sequence of light OFDM symbol, and described synchronous training sequence is placed in to the front end of the light OFDM symbol that will transmit, send to together the device of described reception light orthogonal frequencydivision multiplex singal; Described synchronous training sequence at least comprises four parts, wherein, first is permanent envelope zero autocorrelation sequence, second portion is the conjugation symmetric body of described permanent envelope zero autocorrelation sequence, third part is the repetition of described first, the 4th part is the repetition of described second portion, and the length of described synchronous training sequence equals 1 light orthogonal frequency division multiplex OFDM symbol lengths;
The system of described reception light orthogonal frequencydivision multiplex singal, the light OFDM symbol and the described synchronous training sequence that for receiving the system of described transmission light orthogonal frequencydivision multiplex singal, send, and find the starting point of described smooth OFDM symbol according to described synchronous training sequence, thereby light OFDM symbol described in demodulation;
Wherein, the described starting point that finds described smooth OFDM symbol according to described synchronous training sequence, comprise: the sampled signal of obtaining described smooth OFDM symbol, according to the repeat property existing in described synchronous training sequence, the sampled signal of the described light OFDM symbol getting is processed and obtained the first sampled point; According to the permanent envelope of described the first sampled point and described synchronous training sequence and zero their cross correlation, obtain the second sampled point; According to the conjugate symmetry of first and second portion in described the second sampled point and described synchronous training sequence and zero cross correlation, obtain the starting point of light OFDM symbol;
Described according to the repeat property existing in described synchronous training sequence, the sampled signal of the described light OFDM symbol getting is processed and obtained the first sampled point, comprise: the default time of sampled signal time delay by the described light OFDM symbol getting, obtain the sampled signal after time delay; The described default time is 2Ng, the length of the Cyclic Prefix that Ng is described smooth orthogonal frequencydivision multiplex singal; According to the repeat property existing in described synchronous training sequence, the sampled signal after the sampled signal of the described light OFDM symbol getting and described time delay is carried out to autocorrelation computation, obtain thick timing estimation function; According to described thick timing estimation function, obtain the first sampled point.
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