CN105282080A - OFDM symbol synchronization position search method and synchronization device - Google Patents
OFDM symbol synchronization position search method and synchronization device Download PDFInfo
- Publication number
- CN105282080A CN105282080A CN201410295484.7A CN201410295484A CN105282080A CN 105282080 A CN105282080 A CN 105282080A CN 201410295484 A CN201410295484 A CN 201410295484A CN 105282080 A CN105282080 A CN 105282080A
- Authority
- CN
- China
- Prior art keywords
- peak
- symbol
- synchronous
- correlation
- absolute value
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Abstract
The invention discloses an OFDM symbol synchronization position search method which comprises the following steps: to begin with, carrying out edge detection on relevant values of a P1 symbol by utilizing relevant results of the P1 symbol, wherein the step is specifically characterized by carrying out difference on relevant value signals and then, carrying out moving average; and then, searching the absolute value of output signals of the moving average, and if the absolute value is larger than a preset threshold value, continuing to search 5760Samples; when searching the maximum peak, giving two synchronization candidate points according to the polarity thereof; and finally, calculating peak value noise ratio according to the given two synchronization candidate points, and selecting the synchronization candidate point, of which the peak value noise ratio is larger, as the final synchronization point position. The invention further discloses an OFDM symbol synchronization device for the method. P1 symbol synchronization error can be reduced under severe multipath interference; P1 symbol detection and decoding and P2 symbol decoding performances are improved; and deterioration of system performance due to large P1 symbol synchronization error can be prevented.
Description
Technical field
The present invention relates to the communications field, particularly relate to OFDM (OFDM) the sign synchronization position search method of second generation European terrestrial digital TV (DVB-T2).The invention still further relates to a kind of OFDM symbol synchronizer for described method.
Background technology
OFDM technology is widely used in Modern Communication System.As the second generation terrestrial digital TV standard in Europe, DVB-T2 (" DigitalVideoBroadcasting (DVB); Framestructurechannelcodingandmodulationforasecondgenera tiondigitalterrestrialtelevisionbroadcastingsystem (DVB-T2); " ETSIEN302755), inherit the OFDM technology of first generation standard DVB-T, the elementary cell of its data is called T2 frame.Be illustrated in figure 1 the structure chart of T2 frame, every frame comprises P1 leading symbol, P2 leading symbol and data symbol following closely.The P1 sign synchronization of DVB-T2 system is the first step of DVB-T2 system synchronization.The every frame of P1 symbol occurs once, and at the initial position of every frame, it indicates the beginning of each T2 frame or each FEF frame.P1 sign synchronization mainly can complete:
(1) whether what receiver was determined rapidly to receive is DVB-T2 signal;
(2) confirm that present frame is T2 frame or FEF frame;
(3) signaling message S1, S2 decoding, obtains, as parameters such as FFT length, possibility GI combinations, facilitating subsequent module to receive process;
(4) detect and compensate initial carrier frequency deviation.
Be illustrated in figure 2 the pie graph of P1 symbol, P1 symbol comprises three parts: part A, is the OFDM symbol of 1K; C part, by front 542 sampled points of part A through frequency displacement f
sHobtain; Part B, is obtained through frequency displacement by rear 482 sampled points of part A.P1 symbol lengths is fixed, not by FFT length or GI effect length.And due to the design feature of P1 symbol self, namely the front end C part of P1 symbol and rear end part B are obtained by the part A frequency displacement of P1 symbol respectively, and this Data duplication through frequency displacement, even if can make P1 symbol also be easy to be detected under large frequency deviation.
As shown in Figure 3, be usual receiver schematic diagram.It comprises P1 symbol detection (P1_DET), FFT window adjusting device, and FFT, P1 symbol confirms (P1_VALID) and P1 symbol substitution device (P1_DEC).Wherein, P1_DET calculates the correlation peak of input P1 symbol; If correlation peak is greater than predetermined threshold, namely show the existence of P1 symbol, in predetermined scope, then search for the position of maximum correlation peaks, this position is P1 sign synchronization position.Further, according to obtained maximum correlation peaks, estimate fractional frequency deviation, line frequency of going forward side by side compensates.According to P1 sign synchronization position, determine the initial of FFT window, then carry out FFT conversion.Due to P1 symbol carry information in multiple subcarrier, P1_VALID identifies whether incoming symbol meets distribution of carriers.Do correlation computations by the subcarrier distribution of the signal that will receive with desirable CDS (Carrier-DistributionSequence, distribution of carriers sequence), if the correlation obtained is greater than predetermined threshold, show really there is P1 symbol.Meanwhile, according to the subcarrier sequence of input signal and the relative position of desirable subcarrier sequence, the integer carrier frequency deviation in input signal is calculated.After frequency compensation being carried out to the signal after FFT with this frequency departure, send into P1_DEC and carry out decoding, finally obtain signaling message S1 and S2 entrained by P1 symbol.
The correlation peak method of above-mentioned P1 symbol detection, can resist various serious interference and noise, but its shortcoming is: the error of sync bit is very large.J.G.Doblado (" CoarsetimesynchronizationforDVB-T2; " IEEElec.letters, Vol.46, No.11, May2010) innovatory algorithm proposed can improve synchronous error performance, but it is under heavy multipath interference channel, particularly interference footpath is the two footpath channels of 0dB, and synchronous error performance sharply worsens.M.Rotoloni, (" Oncorrelation-basedsynchronizationforDVB-T2; " IEEEComm.Letters, vol.14, No.3, pp.248-250, Mar.2010) propose Edge Detection, tackle severe jamming channel, two footpath Signal averaging problems when particularly two footpath channel disturbance are 0dB.But this algorithm has following point:
1) positive correlation peaks can not ensure the Shi Qian footpath, footpath (in like manner, negative correlation can not ensure rear footpath) of detection;
2) Pre/PostEcho (namely D/U is not equal to the two footpath channels of 0dB) cannot be processed;
3) correlation peak can not be distinguished and whether really contain synergistic effect.
How to improve the performance of P1 symbol synchronization error, the performance particularly under heavy multipath interference channel, remaining one has problem to be solved.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of second generation European terrestrial digital TV (DVB-T2) OFDM (OFDM) sign synchronization position search method that can reduce P1 symbol synchronization error under heavy multipath interference channel.For this reason, the present invention also will provide a kind of OFDM symbol synchronizer for described method.
For solving the problems of the technologies described above, OFDM symbol sync bit searching method, comprising:
1) according to the correlation result of input signal, correlation is detected; Described related operation, is a kind of known computing in this area, adopts P1 symbol correlator to carry out;
2) carry out Edge check to P1 symbol correlation, concrete grammar is: carry out difference to correlation value signal, then carries out rolling average;
3) absolute value of the output signal of rolling average is searched for, if the absolute value of the output signal of rolling average is less than or equal to synchronous detection predetermined threshold, think noise, if the absolute value of the output signal of rolling average is greater than synchronous detection predetermined threshold P1_DET_TH, continue search 5760Samples, described Samples is sampling (corresponding maximum GI+896, GI and GuardInterval, protection interval), search peak-peak, and according to its polarity, provide two synchronous candidate points;
4) with above-mentioned two sync bit candidate points, calculate peak noise ratio (PNR:Peak-Noise-Ratio), select peak noise to be final synchronous point position than large synchronous candidate point;
Synchronous detection predetermined threshold P1_DET_TH: search for the absolute value of the output signal of rolling average, if be less than or equal to synchronous detection predetermined threshold P1_DET_TH, thinks noise, otherwise, think there is P1 symbol.Only when being greater than predetermined threshold P1_DET_TH, when namely thinking and may there is P1 symbol, carry out peak value searching again, predetermined threshold P1_DET_TH span [4E-5,8E-5].
The invention provides a kind of OFDM symbol synchronizer for said method, comprising:
P1 symbol correlation unit, calculates correlation result (related operation is a kind of known computing of the industry, adopts P1 symbol correlator to carry out) according to input signal;
Difference averaging unit, carries out difference to correlation value signal, then carries out rolling average;
Peak search element, signal after difference rolling average is taken absolute value, and compare with the synchronous predetermined threshold that detects, signal after average to difference takes absolute value and is less than or equal to the synchronous predetermined threshold that detects and thinks noise, signal after average to difference takes absolute value and is greater than synchronous when detecting predetermined threshold, continues search 5760Samples (corresponding maximum GI+896), searches peak-peak, and according to its polarity, provide two sync bit candidate points;
Sync bit determining unit, with above-mentioned two sync bit candidate points, calculates peak noise ratio (PNR:Peak-Noise-Ratio), selects peak noise to be final synchronous point position than large synchronous candidate point.
First the present invention utilizes P1 symbol correlated results, and carry out Edge check to P1 symbol correlation, concrete grammar is: carry out difference to correlation value signal, then carries out rolling average; Again the absolute value of the output signal of rolling average is searched for, if be greater than predetermined threshold (P1_DET_TH), continue search 5760Samples (corresponding maximum GI+896).Search peak-peak, and according to its polarity, provide two synchronous candidate points.Finally with these two the sync bit candidate points provided, calculate peak noise ratio (PNR:Peak-Noise-Ratio) and select, peak noise is final synchronous point position than large synchronous candidate point.For all distortion that P1 symbol waveform correlation under serious fading channel produces, method of the present invention can carry out difference to them, and select by calculating peak noise ratio, thus ensure that the correctness of sync bit, and then improve P1 symbol synchronization error performance, improve the performance of P1 symbol detection and decoding and P2 symbol substitution, avoid large by P1 symbol synchronization error and cause system performance degradation.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the present invention is further detailed explanation:
Fig. 1 is T2 frame structure schematic diagram.
Fig. 2 is that P1 symbol forms schematic diagram.
Fig. 3 is receiver structure schematic diagram.
Fig. 4 is OFDM symbol synchronizer structural representation.
Fig. 5 is a kind of existing P1 symbol correlator.
Fig. 6 is P1 symbol waveform correlation figure.
Fig. 7 is two footpath channel correlation output waveform schematic diagrames.
Fig. 8 is the schematic diagram of difference averaging unit one embodiment of the present invention.
Fig. 9 is two kinds of representative average output waveform figures of typical difference.
Figure 10 is the schematic diagram of peak search element one embodiment of the present invention.
Figure 11 is the schematic diagram of sync bit determining unit one embodiment of the present invention
Description of reference numerals
P1 symbol correlation unit 10
Difference averaging unit 20
Peak search element 30
Sync bit determining unit 40
Embodiment
As shown in Figure 4, be OFDM symbol synchronizer structural representation of the present invention, comprise:
P1 symbol correlation unit, using a kind of existing P1 symbol correlator as shown in Figure 5 as the P1 symbol correlation unit of the embodiment of the present invention, delayer, conjugation multiplier and moving average filter form a correlator jointly, detect the C after frequency displacement and part B respectively.C, part B branch road be corresponding upper and lower two correlators respectively.This creates the terminal two correlators and export pulse, they are trapezoidal pulse, and the total duration of pulse equals (T
a+ T
x).Wherein, the duration of trapezoidal hypotenuse is T
x, the duration on trapezoidal upper top is (T
a-T
x).Corresponding to C, B branch road, T
xvalue be T respectively
cand T
b.Then, the output of upper correlator is again through a time delay T
a, make it align in time with the output of lower correlator, latter two pulse is multiplied, obtains final result.Fig. 6 shows the waveform of correlation computations process.The output of what wherein left figure showed is two correlators, right figure is that they align and the result be multiplied in time domain.When channel is the two footpath channels of 0dB and the phase place in two footpaths is contrary, due to two footpath synergistic effects, after two trapezoidal superpositions, become two triangles, as shown in Figure 7.
Figure 8 shows that difference averaging unit.P1 symbol correlation output is sent into difference engine and is carried out difference, and differential delay is the preferred span of L is 64 ~ 512, its representative value 256.Differential signal sends into rolling average, rolling average length M=L.The Edge check function utilizing difference average, the waveform obtained is such as shown in Fig. 9, and in figure, positive peak corresponds to rising edge, and negative peak corresponds to trailing edge.
Further, two kinds of representative average output waveform figures of typical difference of Fig. 9 display.Wherein, when the multipath of two footpath channels delay much larger than 512 time, the distance=512+256=768 between positive negative peak, wherein 512 is the length of trapezoidal top in Fig. 7, and 256 is rolling average length.And when to delay be 512 to multipath (or near), synergistic effect as shown in Figure 7, two trapezoidal distortions are two triangles; After difference is average, between positive negative peak, distance is rolling average length 256; Meanwhile, the distance=multipath in rear footpath and front footpath delays+512.Therefore, any peak value, can be summarized as one of following four kinds of situations:
Positive peak:
One, peak=synchronous point position (the front footpath of DELAY512, DELAY2000)
Two, peak-512=synchronous point position (the rear footpath of DELAY512)
Negative peak:
Three, peak-256=synchronous point position (the front footpath of DELAY512)
Four, peak-768=synchronous point position (the rear footpath of DELAY512, DELAY2000)
No matter which kind of channel, any one peak as shown in Figure 9, always can calculate the sync bit in the main footpath (maximum diameter) of multipath channel.
Peak search element can adopt embodiment as shown in Figure 10 to realize its function (its execution mode is not limited only to content shown in this embodiment); First, after difference is average, the absolute value of signal compares with the synchronous predetermined threshold P1_DET_TH that detects, and when being greater than synchronous detection predetermined threshold, shows to search P1 symbol.Next, in follow-up 5760 (corresponding maximum GI+896) scope, maximum is searched for.Finally, obtain maximum (peak value) position m, m ∝ { n, n+5760}.Further, according to the polarity of D (m), peak is chosen further.When peak value is positive polarity, obtaining two synchronous point candidates is: sync bit=m or sync bit=m-512; When peak value is negative polarity, obtaining two synchronous point candidates is: sync bit=m-256 or sync bit=m-768.
Two sync bits that peak search element obtains, as sync bit candidate point, obtain the Received signal strength synchronously, send into sync bit determining unit at twice.Sync bit determining unit adopts embodiment as shown in figure 11 to realize its function (its execution mode is not limited only to content shown in this embodiment); According to common practise CDS relevant treatment, do correlation computations by from the subcarrier distribution that obtains in Received signal strength with desirable CDS (Carrier-DistributionSequence, distribution of carriers sequence), obtain correlation; Next carry out maximum value search, obtain correlation peak.Next step, take absolute value correlation side lobes and be averaged, obtaining noise level.Finally, with correlation peak divided by noise, obtain peak noise ratio (PNR:Peak-Noise-Ratio).Carry out same process with the Received signal strength corresponding to two sync bit candidate points, obtain two peak noise ratios.And select peak noise to be final synchronous point position than large synchronous candidate point.
Above by specific embodiment to invention has been detailed description, but these are not construed as limiting the invention.Without departing from the principles of the present invention, those skilled in the art also can make many distortion and improvement, and these also should be considered as protection scope of the present invention.
Claims (2)
1. an OFDM symbol sync bit searching method, is characterized in that, comprising:
1) according to the correlation result of input signal, correlation is detected;
2) carry out Edge check to P1 symbol correlation, concrete grammar is: carry out difference to correlation value signal, then carries out rolling average;
3) absolute value of the output signal of rolling average is searched for, if the absolute value of the output signal of rolling average is less than or equal to synchronous detection predetermined threshold, think noise, if the absolute value of the output signal of rolling average is greater than synchronously detect predetermined threshold, continue search 5760Samples, search peak-peak, and according to its polarity, provide two synchronous candidate points; Described predetermined threshold span is 4E-5 to 8E-5;
4) with above-mentioned two sync bit candidate points, calculate peak noise ratio, select peak noise to be final synchronous point position than large synchronous candidate point.
2., for an OFDM symbol synchronizer for method described in claim 1, it is characterized in that, comprising:
P1 symbol correlation unit, calculates correlation result according to input signal;
Difference averaging unit, carries out difference to correlation value signal, then carries out rolling average;
Peak search element, signal after difference rolling average is taken absolute value, and compare with the synchronous predetermined threshold that detects, signal after average to difference takes absolute value and is less than or equal to the synchronous predetermined threshold that detects and thinks noise, signal after average to difference takes absolute value and is greater than synchronous when detecting predetermined threshold, continues search 5760Samples, searches peak-peak, and according to its polarity, provide two sync bit candidate points;
Sync bit determining unit, two the sync bit candidate points obtained by peak search element, calculate peak noise ratio, select peak noise to be final synchronous point position than large synchronous candidate point.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410295484.7A CN105282080B (en) | 2014-06-26 | 2014-06-26 | OFDM symbol sync bit searching method and its synchronizing device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410295484.7A CN105282080B (en) | 2014-06-26 | 2014-06-26 | OFDM symbol sync bit searching method and its synchronizing device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN105282080A true CN105282080A (en) | 2016-01-27 |
| CN105282080B CN105282080B (en) | 2018-08-07 |
Family
ID=55150422
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410295484.7A Active CN105282080B (en) | 2014-06-26 | 2014-06-26 | OFDM symbol sync bit searching method and its synchronizing device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN105282080B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110290084A (en) * | 2019-07-04 | 2019-09-27 | 电子科技大学 | A kind of blind symbol timing synchronization method of short wave channel based on data frequency energy peak |
| CN113556202A (en) * | 2021-09-18 | 2021-10-26 | 广州慧睿思通科技股份有限公司 | Time domain synchronization point acquisition method, device, equipment and storage medium |
| CN113640635A (en) * | 2021-10-18 | 2021-11-12 | 广东电网有限责任公司惠州供电局 | Power cable insulation state online monitoring method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101884202A (en) * | 2007-11-02 | 2010-11-10 | 诺基亚公司 | OFDM synchronization using two pilot symbols having a predetermined frequency shift between each other |
| CN101945077A (en) * | 2009-06-03 | 2011-01-12 | 索尼公司 | Data processing equipment and method |
| US20120176550A1 (en) * | 2011-01-06 | 2012-07-12 | Hendrickson Alan F | Receiver and Method of Receiving Analog and Digital Television Signals |
| CN102891814A (en) * | 2012-09-06 | 2013-01-23 | 天津市德力电子仪器有限公司 | Method for implementing channel multi-path detection based on P1 sign |
| CN103281282A (en) * | 2013-06-13 | 2013-09-04 | 湖南国科微电子有限公司 | Frequency offset estimation method in DVB-T2 system |
| CN103346990A (en) * | 2013-06-13 | 2013-10-09 | 湖南国科微电子有限公司 | Method for correcting symbols regularly in DVB-T2 system |
-
2014
- 2014-06-26 CN CN201410295484.7A patent/CN105282080B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101884202A (en) * | 2007-11-02 | 2010-11-10 | 诺基亚公司 | OFDM synchronization using two pilot symbols having a predetermined frequency shift between each other |
| CN101945077A (en) * | 2009-06-03 | 2011-01-12 | 索尼公司 | Data processing equipment and method |
| US20120176550A1 (en) * | 2011-01-06 | 2012-07-12 | Hendrickson Alan F | Receiver and Method of Receiving Analog and Digital Television Signals |
| CN102891814A (en) * | 2012-09-06 | 2013-01-23 | 天津市德力电子仪器有限公司 | Method for implementing channel multi-path detection based on P1 sign |
| CN103281282A (en) * | 2013-06-13 | 2013-09-04 | 湖南国科微电子有限公司 | Frequency offset estimation method in DVB-T2 system |
| CN103346990A (en) * | 2013-06-13 | 2013-10-09 | 湖南国科微电子有限公司 | Method for correcting symbols regularly in DVB-T2 system |
Non-Patent Citations (1)
| Title |
|---|
| 王旋: "DVB-T2系统初始同步算法的研究", 《中国优秀硕士学位论文全文数据库》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110290084A (en) * | 2019-07-04 | 2019-09-27 | 电子科技大学 | A kind of blind symbol timing synchronization method of short wave channel based on data frequency energy peak |
| CN113556202A (en) * | 2021-09-18 | 2021-10-26 | 广州慧睿思通科技股份有限公司 | Time domain synchronization point acquisition method, device, equipment and storage medium |
| CN113640635A (en) * | 2021-10-18 | 2021-11-12 | 广东电网有限责任公司惠州供电局 | Power cable insulation state online monitoring method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN105282080B (en) | 2018-08-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110224968B (en) | Frame timing synchronization method and device in OFDM communication system | |
| US7424067B2 (en) | Methods and apparatus for synchronization of training sequences | |
| CN101317339B (en) | Pilot sequence detection | |
| US8553812B2 (en) | Synchronization structure and method for a receiving apparatus of a communication system | |
| KR100585173B1 (en) | Method of receiving of ofdm signal having repetitive preamble signals | |
| CN103023853B (en) | Orthogonal frequency division multiplexing received frame synchronizing method for co-training sequence mutual-correlation information | |
| KR101105399B1 (en) | Apparatus and method for detecting time synchronization of ofdm system and apparatus for receiving | |
| US20110293040A1 (en) | Method and apparatus for signal acquisition in ofdm receivers | |
| US20070092044A1 (en) | Method for symbol timing synchronization and apparatus thereof | |
| CN107241794B (en) | Rapid synchronous tracking method and device for TDD-OFDM downlink | |
| US9225574B2 (en) | Synchronization and acquisition in radio communication systems | |
| KR20070056881A (en) | Apparatus and method for recovering frequency in orthogonal frequency division multiple system | |
| CN102143117A (en) | Time-frequency synchronization joint estimation method based on multi-carrier receiver of digital television media broadcast (DTMB) system | |
| CN101621491A (en) | Receiver and method for receiving digital signal | |
| CN1722720A (en) | Detect the equipment and the method for the time synchronized of frame and code element | |
| CN113612527B (en) | Initial synchronization method for low-earth-orbit satellite mobile communication system | |
| CN104717174A (en) | Orthogonal frequency division multiplexing (OFDM) anti-interference synchronization method under complex multipath channel | |
| US20050063297A1 (en) | Receiver for burst signal including known signal | |
| CN110798421A (en) | Method and device for receiving preamble symbol | |
| CN105282080A (en) | OFDM symbol synchronization position search method and synchronization device | |
| CN101394198A (en) | Frequency bias capture method for block signal with relatively large frequency bias | |
| CN102377726A (en) | Timing synchronization method of OFDM (Orthogonal Frequency Division Multiplexing) system | |
| US20170078131A1 (en) | Receiver controller | |
| CN103873421A (en) | Symbol synchronizing method of multi-path channel | |
| CN101047686A (en) | Receiving symbolic synchronous method for WiMAX system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |