CN1976331B - Symbol timing synchronizing method and apparatus using the same method - Google Patents
Symbol timing synchronizing method and apparatus using the same method Download PDFInfo
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- CN1976331B CN1976331B CN200510126943XA CN200510126943A CN1976331B CN 1976331 B CN1976331 B CN 1976331B CN 200510126943X A CN200510126943X A CN 200510126943XA CN 200510126943 A CN200510126943 A CN 200510126943A CN 1976331 B CN1976331 B CN 1976331B
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Abstract
A method for synchronizing code element timing includes calculating correlation of sampling sequence and delay sampling sequence of sampling sequence delay length N for generating correlation sequence, generating cross correlation sequence by taking a moving average on correlation sequence, carrying out differential operation on cross correlation sequence to generate differential post sequence, generating a moving average post sequence by taking a moving average on differential sequence, detecting peak value position of moving average post sequence for obtaining correct code element timing.
Description
Technical field
The invention relates to a kind of symbol timing (symbol timing synchronization) synchronously, and particularly relevant for a kind of OFDM (orthogonal frequency divisionmultiplexing, OFDM) synchronous method and the device of the symbol timing of receiver in the system.
Background technology
In the OFDM communication system, receiver must detect the original position of each code element (symbol), and correctly to reply the information that transmits from transmitter, it is synchronous that such operation is called symbol timing.For some ofdm systems, for example WLAN (WLAN) or digital audio broadcasting (DAB) system, its transmitter will transmit some advance data (preamble) or training sequence (training sequence) is synchronous so that receiver is used to do symbol timing.But, for some for other the ofdm system, terrestrial digital video broadcasting (DVB-T) system for example, its transmitter does not transmit these advance data or training sequence.The general normal characteristic of guard interval of utilizing of these systems comes detected symbol regularly.
Fig. 1 illustrates to a kind of known ofdm system utilizes guard interval under additivity white Gaussian noise (AWGN) channel and comes detected symbol schematic diagram regularly.Please refer to Fig. 1, r[n] ofdm signal received of expression is through the sampling sequence after the analog-digital conversion, and r[n-N] expression is sampling sequence r[n] postpone the sequence of N sampling point.Sampling sequence r[n] formed by a plurality of code element, for example comprise code element 110 and 120.Each code element is that guard interval and a length of Ng (or having Ng sampling point) is formed by the useful data of N (or having N sampling point) by a length; wherein guard interval is placed on the front end of useful data, and is the end section that duplicates from useful data.
For example, the guard interval 111 of code element 110 duplicates the end section 112 from its useful data, and code element 110 is postponed N sampling point is code element 110 '.What can know is, data identical (the two difference is having a delay) in the guard interval 111 ' and 111, and guard interval 111 duplicates from end section 112, so the interior data of guard interval 111 ' and end section 112 are identical.
Because the structure (such as guard interval 111 duplicates from end section 112) of repetition is arranged, in each code element so at sequence r[n] and r[n-N] between have some correlations.For example, by with sequence r[n] and r[n-N] the two one of them get conjugate complex number and multiply each other with another sequence of not getting conjugate complex number (to call this process in the following text) for getting correlation function, promptly (r*[n] * r[n-N]) or (r[n] * r*[n-N]), then can produce correlation sequence j[n].At correlation sequence j[n] in, interval 113 expression sequence r[n] and r[n-N] correlation of height had in this interval.At last, to correlation sequence j[n] get rolling average and produce crosscorrelation sequence c[n], the position of detecting its peak value 114 again is to obtain the correct original position of next code element (such as code element 120).
In addition,, in No. 406, utilize the correlation sequence of a plurality of code elements that add up,, improve the reliability of detection peak position by this so that the peak value of crosscorrelation sequence is more obvious at United States Patent (USP) the 6th, 088.Yet for time dispersion (time-dispersive) channel, the reliability of above-mentioned symbol timing detection method is not enough.Especially for having the time distributed channel that long echo postpones (long echo delay), for example (its reliability is still not enough for single frequency network, SFN) channel for the single frequency network that often uses of broadcast system.This be since in the SFN channel peak value of crosscorrelation sequence not if in awgn channel obviously.
Fig. 2 illustrates to symbol timing synchronization method shown in Figure 1 being applied to the schematic diagram of the SFN channel with two paths, and wherein the gain of two paths is identical, and path difference is Ng, and therefore behind this SFN channel of ofdm signal process, receiver obtains sampling sequence r from a path
1[n] and obtain sampling sequence r from another path
2[n], i.e. sampling sequence r[n] be by sequence r
1[n] and r
2[n] forms.
With sampling sequence r
1Code element 210 in [n] is an example, at sampling sequence r
2The code element 220 identical with data in the code element 210 is that code element 210 postpones Ng sampling point in [n].As sequence r
1[n] and r
2[n] through after getting correlation function and getting rolling average, it produces sequence c respectively respectively
1[n] and c
2[n].Therefore, can be with crosscorrelation sequence c[n] be considered as by sequence c
1[n] and c
2[n] combines.With the crosscorrelation sequence c[n in awgn channel shown in Figure 1] compare, crosscorrelation sequence c[n in the SFN channel shown in Figure 2] no longer have a tangible peak value, the substitute is a peak region, and the value of sampling point in this zone is all identical and be maximum in the ideal case.Unfortunately, when making the sampling point value of peak region no longer identical when the influence that is subjected to noise and interference signal, can make the detection difficulty more of correct element position 214.
In the time distributed channel of SFN channel for example, there is element position to be difficult for the shortcoming that detects in order to overcome above-mentioned symbol timing synchronization method, at United States Patent (USP) the 6th, 421, disclose another kind of method No. 401, it is got correlator by two of uses and gets correlation function, therefore can provide tangible peak value.But this method obviously needs extra correlator, and this meaning needs more multiplier and storage device and makes structure more become complicated.In addition, whether in the paper " Enhanced symbol synchronization method for OFDMsystem in SFN channels " that is proposed in IEEE Globecom meeting in 1998 by A.Palin and J.Rinne, proposing symbol timing can be cumulative to assessing above preset critical by the amplitude of judging sampling point in the crosscorrelation sequence.But, dissimilar time distributed channel will cause the amplitude range difference of sampling point in the crosscorrelation sequence, and therefore being difficult to choose suitable critical value meets all types of time distributed channel.
Summary of the invention
Purpose of the present invention is exactly in the symbol timing detection method that a kind of communication system that is used in OFDM (OFDM) is provided and uses the device of this method, have low complex degree and high-reliability, and be applicable to all types of channels, especially be applicable to have the time distributed channel that long echo postpones.
The present invention proposes a kind of symbol timing synchronization method, and it is applicable to for example receiver of the communication system of OFDM (OFDM), and is applicable to all types of channels, especially is applicable to have the time distributed channel that long echo postpones.This symbol timing synchronization method at first calculates sampling sequence and postpones the two correlation of sampling sequence to produce the correlation sequence, wherein postponing sampling sequence is that sampling sequence postpones N sampling point, and wherein N is the sampling point number of the useful data of code element in the sampling sequence.Then, the correlation sequence is got rolling average to produce the crosscorrelation sequence, again the crosscorrelation sequence is carried out calculus of differences to produce sequence after the difference.Then, sequence after the difference is got rolling average producing sequence after the rolling average, and detect the peak of sequence after the rolling average, wherein peak is that to be used to obtain correct symbol timing synchronous.
In one embodiment, above-mentioned symbol timing synchronization method also is included in the crosscorrelation sequence is carried out calculus of differences to produce after the difference before the sequence, earlier the crosscorrelation sequence is carried out M code element on average or add up, and wherein M is a positive integer.Moreover, above-mentioned symbol timing synchronization method also comprises provides index, it is the minimum value that the peak value (being maximum) of sequence after the rolling average deducts sequence after the rolling average, wherein index be used for the preset critical comparison to judge whether sampling sequence exists code element.
The present invention proposes a kind of symbol timing synchronizer, and it comprises in one embodiment gets correlator, difference engine, gets rolling average device and peak detector.In this embodiment, get correlator and be used to receive sampling sequence, calculate sampling sequence and sampling sequence and postpone the two the correlation of delay sampling sequence of N sampling point with generation correlation sequence, and the correlation sequence got rolling average to produce the crosscorrelation sequence, wherein N is the sampling point number of the useful data of code element in the sampling sequence.Difference engine is coupled to gets correlator, is used for the crosscorrelation sequence is carried out calculus of differences to produce sequence after the difference.Get the rolling average device and be coupled to difference engine, be used for sequence after the difference is got rolling average to produce sequence after the rolling average.Peak detector is coupled to gets the rolling average device, is used to detect the peak of sequence after the rolling average, and wherein to be used to obtain correct symbol timing synchronous for peak.
In one embodiment, above-mentioned symbol timing synchronizer also comprises code fetch unit averager (or code fetch unit accumulator).This code fetch unit averager (or code fetch unit accumulator) is coupled to and gets between correlator and the difference engine, is used for the crosscorrelation sequence is carried out M code element average (or adding up) to produce the on average crosscorrelation sequence after (or adding up) of code fetch unit, and wherein M is a positive integer.Moreover, peak detector in the above-mentioned symbol timing synchronizer also produces index, it is the minimum value that the peak value of sequence deducts sequence after the rolling average after the rolling average, wherein index be used for the preset critical comparison to judge whether sampling sequence exists code element.
The present invention gets the rolling average device again because of the crosscorrelation sequence is carried out calculus of differences earlier, even ofdm signal also can produce tangible peak value through the time distributed channel with long echo delay, the symbol timing that therefore has high-reliability detects.
For above and other objects of the present invention, feature and advantage can be become apparent, preferred embodiment cited below particularly, and cooperate appended graphicly, be described in detail below.
Description of drawings
Fig. 1 illustrates to a kind of known ofdm system utilizes guard interval under awgn channel and comes detected symbol schematic diagram regularly.
Fig. 2 illustrates to symbol timing synchronization method shown in Figure 1 being applied to the schematic diagram of the SFN channel with two paths, and wherein the gain of two paths is identical, and path difference is Ng.
Fig. 3 A and Fig. 3 B are the flow chart according to the symbol timing synchronization method that the embodiment of the invention illustrated.
Fig. 4 A and Fig. 4 B are respectively schematic diagram and the analogous diagram according to the relevant signal of symbol timing synchronization method shown in the embodiment of the invention.
Fig. 5 A and Fig. 5 B are the calcspar according to the symbol timing synchronizer that the embodiment of the invention illustrated, and it corresponds to the symbol timing synchronization method shown in Fig. 3 A and the 3B respectively.
Fig. 6 A and 6B are according to the calcspar of getting correlator in the symbol timing synchronizer that the embodiment of the invention illustrated.
Fig. 7 is according to the calcspar of getting the rolling average device in the symbol timing synchronizer that the embodiment of the invention illustrated.
Fig. 8 A and Fig. 8 B are respectively the calcspar of unit's averager of code fetch in the symbol timing synchronizer that illustrates according to the embodiment of the invention and code fetch unit accumulator.
[main element label declaration]
S311～S315: according to the process step of the symbol timing synchronization method that one embodiment of the invention illustrated
S351～S356: according to the process step of the symbol timing synchronization method that another embodiment of the present invention illustrated
R[n], r
1[n], r
2[n], r[n-N]: sampling sequence
J[n]: the correlation sequence
C[n], c
1[n], c
2[n]: crosscorrelation sequence
C ' [n]: the crosscorrelation sequence after code fetch unit is average
110,110 ', 120,120 ', 210,220: code element
111,111 ': guard interval
112,112 ': end section
113: interval (it represents the correlation of tool height)
114,214,414,424: peak value (being maximum)
425: minimum value
500,505: the symbol timing synchronizer
510: get correlator
520: code fetch unit averager
530: difference engine
550: get the rolling average device
570: peak detector
590: the phase place getter
610,615: delayer
630,635: get the conjugate complex number device
650,655: multiplier
670,675: get the rolling average unit
710,740: delayer
720: adder
730: subtracter
810: divider
820: adder
830: delayer
Ng: the guard interval length of code element (or sampling point number)
N: the valid data length of code element (or sampling point number)
N+Ng: Baud Length (or sampling point number)
Embodiment
For the purpose of the convenient explanation of embodiment, following communication system is an example to utilize guard interval to come detected symbol OFDM (OFDM) system regularly.After passing through analog-digital conversion with the ofdm signal of receiving, the receiver of ofdm system produces sampling sequence r[n], must detect sampling sequence r[n this moment] in the original position of each code element, correctly to reply the information that transmits from transmitter, it is synchronous that such operation is called symbol timing.
Fig. 3 A is for according to the flow chart of the symbol timing synchronization method that one embodiment of the invention illustrated, and Fig. 4 A is the schematic diagram of the signal relevant with symbol timing synchronization method shown in Fig. 3 A.Please be simultaneously with reference to Fig. 3 A and Fig. 4 A, at step S311, at first calculate sampling sequence r[n] and its postpone delay sampling sequence r[n-N behind N the sampling point] the two correlation to be to produce correlation sequence j[n], wherein N is sampling sequence r[n] the sampling point number of the useful data of middle code element.Here, correlation sequence j[n] for example be (r*[n] * r[n-N]) or (r[n] * r*[n-N]), even multiplication wherein can be substituted in the subtraction mode, perhaps multiplication is wherein substituted in power subtraction (power subtraction) mode.Then, at step S312, to correlation sequence j[n] get rolling average to produce crosscorrelation sequence c[n].Therefore significantly, the process of step S311 to S312 and Fig. 1 or shown in Figure 2 identical produce the crosscorrelation sequence c[n shown in Fig. 4 A through step S311 to S312] associated description no longer do explanation at this more.
Come again, at step S313, to crosscorrelation sequence c[n] carry out calculus of differences to produce sequence d[n after the difference], wherein calculus of differences has many kinds of modes to realize, such as d[n]=c[n]-c[n-1] or d[n]=c[n]-c[n+1] promptly be to realize difference in the subtraction mode.Then, at step S314, to sequence d[n after the difference] get rolling average to produce sequence e[n after the rolling average], and after step S315 detects rolling average sequence e[n] peak value 414 positions, wherein peak value 414 positions are that to be used to obtain correct symbol timing synchronous.
Fig. 3 B is for according to the flow chart of the symbol timing synchronization method that another embodiment of the present invention illustrated, and the analogous diagram of Fig. 4 B relevant signal when being applied to the SFN channel with two paths for symbol timing synchronization method shown in Fig. 3 B.Please be simultaneously with reference to Fig. 3 B and Fig. 4 B, in fact step S311, S312, S313, S314 and the S315 with Fig. 3 A is identical respectively with S356 for the step S351 of Fig. 3 B, S352, S354, S355.So, the difference of method shown in Fig. 3 B and Fig. 3 A is to correlation sequence j[n] get rolling average to produce crosscorrelation sequence c[n] (being step S312 or S352) afterwards, and to crosscorrelation sequence c[n] carry out calculus of differences to produce sequence d[n after the difference] (being step S313 or S354) before, earlier to crosscorrelation sequence c[n] carry out M code element average or add up (being step S353), wherein M is a positive integer.
Can find out crosscorrelation sequence c[n from Fig. 4 B] the crosscorrelation sequence c ' [n] that produces through the average back of code element, its noise level descends and produces significantly peak region, the sequence e[n that at this moment carries out difference and rolling average again and produced] have tangible peak value 424 positions and no longer be a mild zone.Moreover, can utilize sequence e[n] peak value (being maximum) 424 provide an index with minimum value 425 the two difference.When this referred to target value greater than preset critical, the pickup electrode that this expression receives may contain the code element of ofdm signal, therefore this index can be applied to such as accelerate to scan the speed of channel.
Fig. 5 A and 5B are the calcspar according to the symbol timing synchronizer that the embodiment of the invention illustrated, and it corresponds to the symbol timing synchronization method shown in Fig. 3 A and the 3B respectively.Please refer to Fig. 5 A, symbol timing synchronizer 500 comprise get correlator 510, difference engine 530, get rolling average device 550, peak detector 570 and phase place getter 590.Get correlator 510 and be used to receive sampling sequence r[n], calculate sampling sequence r[n] and its postpone the delay sampling sequence r[n-N of N sampling point] the two correlation is with generation correlation sequence, and the correlation sequence got rolling average to produce crosscorrelation sequence c[n], wherein N is sampling sequence r[n] in the sampling point number of useful data of code element.Difference engine 530 is coupled to gets correlator 510, is used for crosscorrelation sequence c[n] carry out calculus of differences to produce sequence d[n after the difference].Get rolling average device 55O and be coupled to difference engine 530, be used for sequence d[n after the difference] get rolling average to produce sequence e[n after the rolling average].
Please refer to Fig. 5 B, symbol timing synchronizer 505 is similar to symbol timing synchronizer 500, and the two difference is that symbol timing synchronizer 505 also comprises device 520, and device 520 can be a code fetch unit averager, can also be code fetch unit accumulator.Code fetch unit averager (or code fetch unit accumulator) 520 is coupled to be got between correlator 510 and the difference engine 530, be used for crosscorrelation sequence c[n] carry out M code element average (or adding up) to produce the crosscorrelation sequence c ' [n] after the code fetch unit average (or adding up), wherein M is a positive integer.At this moment, phase place getter 590 is coupled to the output of code fetch unit averager (or code fetch unit accumulator) 520 output, the input of difference engine 530 and peak detector 570.
Fig. 6 A and 6B are according to the calcspar of getting correlator in the symbol timing synchronizer that the embodiment of the invention illustrated.Please refer to Fig. 6 A, get that correlator 510 comprises delayer 610, gets conjugate complex number device 630, multiplier 650 and get rolling average unit 670.Delayer 610 receives sampling sequence r[n] and postpone N sampling point to produce sequence r[n-N].Get conjugate complex number device 630 and receive sampling sequence r[n] and it is got conjugate complex number to produce sequence r*[n].Multiplier 650 is coupled to delayer 610 and the output of getting conjugate complex number device 630, and with the sequence r[n-N that receives] with r*[n] multiply by mutually produce correlation sequence j[n].Get rolling average unit 670 and be coupled to the output of multiplier 650, and to correlation sequence j[n] get rolling average to produce crosscorrelation sequence c[n].
Another kind is got the implementation method of correlator 510 shown in Fig. 6 B, gets that correlator 510 comprises delayer 615, gets conjugate complex number device 635, multiplier 655 and get rolling average unit 675.Delayer 615 receives sampling sequence r[n] and postpone N sampling point to produce sequence r[n-N].Get conjugate complex number device 635 and be coupled to the output of delayer 615, and to sequence r[n-N] get conjugate complex number to produce sequence r*[n-N].Multiplier 655 is coupled to the output of getting conjugate complex number device 635, and with the sequence r[n that receives] with r*[n-N] multiply by mutually produce correlation sequence j[n].Get rolling average unit 675 and be coupled to the output of multiplier 655, and to correlation sequence j[n] get rolling average to produce crosscorrelation sequence c[n].
Fig. 7 is according to the calcspar of getting the rolling average device in the symbol timing synchronizer that the embodiment of the invention illustrated.Please refer to Fig. 7, get rolling average device 550 and comprise first delayer 710, second delayer 740, adder 720 and subtracter 730.The input of delayer 710 receives sequence d[n after the difference], and with sequence d[n after the difference] postpone to send by the output of delayer 710 behind Ng sampling point, wherein Ng is sampling sequence r[n] the sampling point number of the guard interval of middle code element.Adder 720 is sent by its output after with its first input end signal and its second input end signal addition, and wherein the first input end of adder 720 receives sequence d[n after the difference], and second input of adder 720 is coupled to the output of delayer 740.Delayer 740 is used for its input end signal is postponed to be sent by its output behind a sampling point, and wherein the input of delayer 740 is coupled to the output of adder 720, and the output of delayer 740 is coupled to second input of adder 720.Subtracter 730 subtracts each other back (promptly produce rolling average after sequence e[n]) with its first input end signal and its second input end signal and is sent by its output, wherein the first input end of subtracter 730 is coupled to the output of adder 720, and second input of subtracter 730 is coupled to the output of delayer 710.
Fig. 8 A and Fig. 8 B are respectively the calcspar of unit's averager of code fetch in the symbol timing synchronizer that illustrates according to the embodiment of the invention and code fetch unit accumulator.Please refer to Fig. 8 A, code fetch unit averager 520 comprises divider 810, adder 820 and delayer 830.The input of divider 810 receives crosscorrelation sequence c[n], and with crosscorrelation sequence c[n] divided by being sent by the output of divider 810 behind the M, wherein M is the code element number that is averaged.Adder 820 is produced the crosscorrelation sequence c ' [n] after average of code fetch unit mutually with its first input end signal and its second input end signal, and send by the output of adder 820, wherein the first input end of adder 820 is coupled to the output of divider 810, and second input of adder 820 is coupled to the output of delayer 830.Delayer 830 is used for its input end signal is postponed to be sent by its output behind (N+Ng) individual sampling point, and wherein the input of delayer 830 is coupled to the output of adder 820, and the output of delayer 830 is coupled to second input of adder 820.
And the device 520 shown in Fig. 5 B can also be the code fetch unit accumulator 520 shown in Fig. 8 B except being the code fetch unit averager 520 shown in Fig. 8 A.Please refer to Fig. 8 B, code fetch unit accumulator 520 in fact promptly is that the divider 810 in the unit of code fetch shown in Fig. 8 A averager 520 is removed, and promptly direct first input end by adder 820 receives crosscorrelation sequence c[n].
In sum, symbol timing synchronization method of the present invention and the device that uses this method are because of to crosscorrelation sequence c[n] carry out calculus of differences earlier and get rolling average again, even ofdm signal also can produce tangible peak value through the time distributed channel with long echo delay, the symbol timing that therefore has high-reliability detects.Natch, method of the present invention and device also are applicable to the channel of other type, such as AWGN, Rayleigh or SFN channel.
Though the present invention discloses as above with preferred embodiment; so it is not to be used to limit the present invention; any those skilled in the art; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion when looking appended the claim scope person of defining.
Claims (20)
1. symbol timing synchronization method is applicable to the receiver of communication system, and this symbol timing synchronization method comprises:
Calculate sampling sequence and postpone the two correlation of sampling sequence to produce the correlation sequence;
This correlation sequence is got rolling average to produce the crosscorrelation sequence;
This crosscorrelation sequence is carried out calculus of differences to produce sequence after the difference;
Sequence after this difference is got rolling average to produce sequence after the rolling average; And
Detect the peak of sequence after this rolling average, wherein to be used to obtain correct symbol timing synchronous for this peak;
Wherein, this postpones sampling sequence and postpones N sampling point for this sampling sequence, and N is the sampling point number of the useful data of code element in this sampling sequence.
2. symbol timing synchronization method according to claim 1 also is included in this crosscorrelation sequence is carried out calculus of differences to produce after this difference before the sequence, earlier this crosscorrelation sequence is carried out M code element on average or accumulation calculating, and wherein M is a positive integer.
3. symbol timing synchronization method according to claim 1 also comprises index is provided, and this index and preset critical comparison are to judge whether there is code element in this sampling sequence, and wherein this index is the peak value of sequence after this rolling average and the difference of its minimum value.
4. symbol timing synchronization method according to claim 1, wherein this communication system comprises ofdm system.
5. symbol timing synchronization method according to claim 1, wherein this correlation sequence is that this sampling sequence and this delay sampling sequence of getting behind the conjugate complex number multiplies each other.
6. symbol timing synchronization method according to claim 1, wherein this correlation sequence is this sampling sequence and this delay sampling sequence of getting behind the conjugate complex number multiplies each other.
7. symbol timing synchronization method according to claim 1, wherein this correlation sequence is this sampling sequence and this delay sampling sequence subtracts each other or power subtracts each other.
8. symbol timing synchronization method according to claim 1, wherein sequence is that this crosscorrelation sequence deducts this crosscorrelation sequence that postpones behind the sampling point after this difference.
9. symbol timing synchronizer is applicable to the receiver of communication system, and this symbol timing synchronizer comprises:
Get correlator, be used to receive sampling sequence, the correlation of calculating this sampling sequence and postponing this sampling sequence to be producing the correlation sequence, and this correlation sequence is got rolling average to produce the crosscorrelation sequence;
Difference engine is coupled to this and gets correlator, and this difference engine is used for this crosscorrelation sequence is carried out calculus of differences to produce sequence after the difference;
Get the rolling average device, be coupled to this difference engine, this is got the rolling average device and is used for sequence after this difference is got rolling average to produce sequence after the rolling average; And
Peak detector is coupled to this and gets the rolling average device, and this peak detector is used to detect the peak of sequence after this rolling average, and wherein to be used to obtain correct symbol timing synchronous for this peak;
Wherein, this postpones sampling sequence and postpones N sampling point for this sampling sequence, and N is the sampling point number of the useful data of code element in this sampling sequence.
10. symbol timing synchronizer according to claim 9 also comprises the phase place getter, is coupled to the output that this gets correlator and this peak detector, and this phase place getter is used to obtain the phase place of this crosscorrelation sequence.
11. symbol timing synchronizer according to claim 9, also comprise code fetch unit averager, being coupled to this gets between correlator and this difference engine, this code fetch unit averager is used for this crosscorrelation sequence is carried out M code element on average to produce code fetch unit this crosscorrelation sequence after on average, and wherein M is a positive integer.
12. symbol timing synchronizer according to claim 9, also comprise code fetch unit accumulator, being coupled to this gets between correlator and this difference engine, this code fetch unit accumulator is used for that this crosscorrelation sequence is carried out M code element and adds up to produce this crosscorrelation sequence after code fetch unit adds up, and wherein M is a positive integer.
13. according to claim 11 or 12 described symbol timing synchronizers, also comprise the phase place getter, be coupled between the output of the input of this difference engine and this peak detector, this phase place getter be used to obtain code fetch unit average or add up after the phase place of this crosscorrelation sequence.
14. symbol timing synchronizer according to claim 9, wherein this peak detector also provides index, this index and preset critical comparison are to judge whether there is code element in this sampling sequence, and wherein this index is the peak value of sequence after this rolling average and the difference of its minimum value.
15. symbol timing synchronizer according to claim 9, wherein this communication system comprises ofdm system.
16. symbol timing synchronizer according to claim 9, wherein this is got correlator and comprises:
Delayer is used to receive this sampling sequence, and produces the delay sampling sequence that this sampling sequence is postponed N sampling point;
Get the conjugate complex number device, be used to receive this sampling sequence, and produce the conjugate complex number sampling sequence of this sampling sequence being got conjugate complex number;
Multiplier is coupled to this delayer and this gets the conjugate complex number device, and this multiplier is used for this delay sampling sequence and this conjugate complex number sampling sequence are multiplied each other, to produce this correlation sequence; And
Get the rolling average unit, be coupled to this multiplier, this is got the rolling average unit and is used for this correlation sequence is got rolling average to produce this crosscorrelation sequence.
17. symbol timing synchronizer according to claim 9, wherein this is got correlator and comprises:
Delayer is used to receive this sampling sequence, and produces the delay sampling sequence that this sampling sequence is postponed N sampling point;
Get the conjugate complex number device, be coupled to this delayer, this is got the conjugate complex number device and is used for this delay sampling sequence is got conjugate complex number, postpones sampling sequence to produce conjugate complex number;
Multiplier is coupled to this sampling sequence and this and gets the conjugate complex number device, and this multiplier is used for that this conjugate complex number is postponed sampling sequence and this sampling sequence, and the two multiplies each other, to produce this correlation sequence; And
Get the rolling average unit, be coupled to this multiplier, this is got the rolling average unit and is used for this correlation sequence is got rolling average to produce this crosscorrelation sequence.
18. symbol timing synchronizer according to claim 9, wherein this is got the rolling average device and comprises:
First delayer, have input and receive sequence and output after this difference, this first delayer is used for and will be sent by the output of this first delayer behind the sequence delays Ng sampling point after this difference, and wherein Ng is the sampling point number of the guard interval of code element in this sampling sequence;
Adder has first input end and receives sequence after this difference, second input and output, is sent by the output of this adder after the second input end signal addition of this adder with the first input end signal of this adder and this adder;
Second delayer, have input and be coupled to the output of this adder and second input that output is coupled to this adder, this second delayer is used for the input end signal of this second delayer is postponed to be sent by the output of this second delayer behind a sampling point; And
Subtracter, have first input end and be coupled to the output of this adder, output and the output that second input is coupled to this first delayer, this subtracter subtracts each other second input end signal of the first input end signal of this subtracter and this subtracter producing sequence after this rolling average, and sends sequence after this rolling average by the output of this subtracter.
19. symbol timing synchronizer according to claim 11, wherein this code fetch unit averager comprises:
Divider has the input and the output that are used to receive this crosscorrelation sequence, and this divider is used for this crosscorrelation sequence is sent by the output of this divider after divided by M;
Adder, have first input end and be coupled to output, second input and the output of this divider, this adder is produced code fetch unit this crosscorrelation sequence after average mutually with the first input end signal of this adder and second input end signal of this adder, and sends code fetch unit this crosscorrelation sequence after average by the output of this adder; And
Delayer, have input and be coupled to the output of this adder and second input that output is coupled to this adder, this delayer is used for the input end signal of this delayer is postponed to be sent by the output of this delayer behind (N+Ng) individual sampling point, and wherein (N+Ng) is a Baud Length.
20. symbol timing synchronizer according to claim 12, wherein this code fetch unit accumulator comprises:
Adder, have first input end and receive crosscorrelation sequence, second input and output, this crosscorrelation sequence after this adder is produced the first input end signal of this adder and second input end signal of this adder mutually code fetch unit and adds up, and this crosscorrelation sequence after sending code fetch unit and add up by the output of this adder; And
Delayer, have input and be coupled to the output of this adder and second input that output is coupled to this adder, this delayer is used for the input end signal of this delayer is postponed to be sent by the output of this delayer behind (N+Ng) individual sampling point, and wherein (N+Ng) is a Baud Length.
Priority Applications (1)
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| CN1976331B true CN1976331B (en) | 2011-06-08 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6088406A (en) * | 1996-08-23 | 2000-07-11 | Sony Corporation | Reception method, reception apparatus and timing detecting apparatus |
| US6421401B1 (en) * | 1998-05-07 | 2002-07-16 | Nokia Corporation | Method and apparatus for achieving and maintaining symbol synchronization particularly in an OFDM system |
| CN1578291A (en) * | 2003-07-03 | 2005-02-09 | 三星电子株式会社 | Symbol timing recovering apparatus for quadrature frequency division multiplexing receiver |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6088406A (en) * | 1996-08-23 | 2000-07-11 | Sony Corporation | Reception method, reception apparatus and timing detecting apparatus |
| US6421401B1 (en) * | 1998-05-07 | 2002-07-16 | Nokia Corporation | Method and apparatus for achieving and maintaining symbol synchronization particularly in an OFDM system |
| CN1578291A (en) * | 2003-07-03 | 2005-02-09 | 三星电子株式会社 | Symbol timing recovering apparatus for quadrature frequency division multiplexing receiver |
Non-Patent Citations (2)
| Title |
|---|
| JP特开2000-165338A 2000.06.16 |
| JP特开平11-163824A 1999.06.18 |
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