CN101309250A - Timing synchronizing method and apparatus for communication system and receiver - Google Patents
Timing synchronizing method and apparatus for communication system and receiver Download PDFInfo
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Abstract
The invention discloses a communication system timing synchronization method, a device and a receiver of the communication system, which process the moving correlated operation towards the differentiated and received data and the pre-stored whole difference result of the lead code; on one hand, the difference method is adopted to overcome most of the frequency deviation influence; on the other hand, a plurality of repetition blocks of the whole lead code are adopted to enable the peak amplitude after the moving correlated operation to be increased greatly, compared with the peak amplitude obtained through a repletion block in the traditional method; good timing synchronization effect can be obtained even under the low signal-to-noise ratio situation; thereby, the communication system timing synchronization method in the invention can provide accurate symbol timing synchronization under the situations of high frequency deviation and low signal-to-noise ratio.
Description
Technical field
The present invention relates to communication technical field, particularly regularly synchronous method, device and the receiver of the communication system in the mobile communication technology field.
Background technology
At present, mobile communication technology has all obtained using widely in the world, GSM (Global System forMobile Communication for example, whole world digital mobile communication system), CDMA (Code-Division Multiple Access, CDMA mobile communication systems), WCDMA (Wideband Code-Division Multiple Access, WCDMA mobile communication system) or the like, development along with mobile communication technology, can provide the business support service for more mobile communication terminal, yet, identical or different business at each terminal processes, need the transmission lot of data, thereby need higher transmission rate, in the single-carrier system of routine, if use higher transmission rate, reception brings certain difficulty to signal because intersymbol interference (ISI, Inter-Symbol Interference) and frequency decline in meeting.
OFDM (Orthogonal Frequency Division Multiplexing, OFDM) technology since by with the data parallel of serial be modulated on the subcarrier of a plurality of quadratures, make the chip rate of each subcarrier reduce greatly, thereby improved the anti-fading and antijamming capability of system, in addition, because the pairwise orthogonal of each subcarrier, can fully they be made a distinction at receiving terminal, therefore the OFDM technology has obtained extensive use in numerous areas, for example, by WMAN (WirelessMetropolitan Area Network, wireless MAN) adopts, the wireless metropolitan area network standard that picture IEEE tissue (Institute of Electrical andElectronics Engineers, U.S. electric and electronics engineers) is formulated comprises standards such as IEEE802.16-2004 and IEEE802.16-2005.
Regularly simultaneous techniques is one of important technology in the communication technology, is example with the ofdm system, and the time synchronization method of ofdm system generally is divided into two classes, based on preamble word (Preamble) synchronously and based on Cyclic Prefix (CP) synchronously.Because based on Cyclic Prefix (CP, Cyclic Prefix) synchronized algorithm generally needs long convergence time, in the practical project utilization, can not put up with, so more be applicable to actual OFDM transmission system based on the timing synchronized algorithm of preamble word (Preamble).
As shown in Figure 1, be the preamble word structural representation of IEEE802.16-2004 ofdm system in the prior art, first OFDM symbol has 4 64 repeatable block, is referred to as short leading; An OFDM symbol afterwards has 2 128 repeatable block, is referred to as long preambles.CP represents Cyclic Prefix, is that the afterbody from current OFDM symbol duplicates, and is used to eliminate ISI (intersymbol interference) and ICI (inter-carrier interference).
As shown in Figure 2, be Domain Synchronous schematic flow sheet in the prior art, the influence of various noises and multipath because the data that receive have superposeed, therefore, after receiving the reception data, at first need to detect the probable ranges that processing procedure comes specified data to arrive by frame; After having determined probable ranges,, obtain the accurate initial sampling point of preamble word by thin timing synchronization processing procedure; Again the sequence after the thin timing synchronization is carried out the frequency offset estimating and the correction of time domain, eliminate the influence of fractional part of frequency offset, so far, whole Domain Synchronous process finishes.
In Domain Synchronous flow process shown in Figure 2, when carrying out thin timing synchronization processing procedure, traditional processing procedure is to adopt in advance leading repeatable block of the weak point that stores and receiving sequence to do the slip cross-correlation operation, as shown in Figure 3, it is the emulation schematic diagram of this traditional thin symbol Timing Processing mode, yet, this thin symbol Timing Processing mode, very sensitive to frequency deviation, Fig. 4 is this traditional leading cross-correlation peak value figure of the thin weak point of symbol Timing Processing mode when frequency deviation is 75khz, as shown in the figure, frequency deviation makes short leading cross-correlation peak value be subjected to serious the interference and is beyond recognition.
In order to overcome the influence of frequency deviation, in the prior art this thin timing synchronization processing mode is improved, it is when handling, carry out difference to receiving data earlier, the leading repeatable block of weak point that this locality is stored is in advance done difference again, then difference result and the difference result that receives data is done the slip cross-correlation, wherein, the process of difference is with last bit data and back to back data conjugate multiplication, is reflected in frequency deviation on the imaginary part with elimination.As shown in Figure 5, be the leading cross-correlation peak value schematic diagram of the weak point of improved thin symbol timing algorithm when different frequency deviation, according to this improved thin timing synchronization processing mode, when signal to noise ratio is 20dB, under different frequency deviation states, short leading cross-correlation peak value is not subjected to the influence of frequency deviation.
Yet, in this improved mode, owing to be only to adopt the difference sequence of a leading repeatable block of weak point and the difference sequence that receives data to do the slip cross-correlation operation, the correlation peak amplitude that obtains is limited, when signal to noise ratio is low, peak value is easy to be flooded by the noise behind the associative operation, as shown in Figure 6, be the cross-correlation peak value schematic diagram of this improved thin timing synchronization processing mode when signal to noise ratio is 5dB, at this moment, short leading cross-correlation peak value has been submerged among the noise behind the associative operation, and under the lower situation of signal to noise ratio, this situation will be more serious.
Summary of the invention
At existing problem in the above-mentioned prior art, first purpose of the present invention is to provide a kind of communication system timing synchronous method, and it can provide accurate sign synchronization under the situation of low signal-to-noise ratio.
For achieving the above object, the present invention by the following technical solutions:
The method that a kind of communication system is regularly synchronous comprises step:
Receive data;
The described reception data and the lead code integral body of storage are in advance made the slip cross-correlation operation, and described lead code comprises plural at least repeatable block;
With the initial sampling point of the pairing sampled point of peak-peak after the described slip cross-correlation operation as described reception data.
According to communication system time synchronization method of the present invention, it is the lead code integral body that will receive data and the storage in advance operation that is in sliding cross-correlation, because lead code has a plurality of repeatable blocks, the repeatable block that utilizes lead code integral body to be had is many more, correspondingly the number of the sampled point that is used is also many more, make that the amplitude of the peak value after the slip cross-correlation operation is also bigger, thereby be not easy to be flooded by the noise behind the associative operation, even under the situation of low signal-to-noise ratio, also can obtain well regularly synchronous effect, therefore, the synchronous method of communication system timing of the present invention can provide accurate sign synchronization under the situation of low signal-to-noise ratio.
Second purpose of the present invention is to provide a kind of communication system timing synchronous device, and it can provide accurate sign synchronization under the situation of low signal-to-noise ratio.
The device that a kind of communication system is regularly synchronous comprises:
The Data Receiving unit is used to receive data;
Memory cell is used for storing predetermined lead code, and described lead code comprises plural at least repeatable block;
The slip cross-correlation unit, this slip cross-correlation unit is connected with described Data Receiving unit, described memory cell respectively, is used for described reception data and the whole slip cross-correlation operation of carrying out of described lead code.
According to timing synchronization device of the present invention, it is the lead code integral body that will receive data and the storage in advance operation that is in sliding cross-correlation, owing to be to operate at the integral body of lead code, and a plurality of repeatable blocks that lead code integral body has, correspondingly the number of the sampled point that is used is also many more, make that the peak amplitude after the slip cross-correlation operation is very big, be not easy to be flooded by the noise behind the associative operation, therefore, even under the situation of low signal-to-noise ratio, also can obtain well regularly synchronous effect, therefore, communication system of the present invention regularly synchronous device can obtain the accurate initial sampling point of lead code under the situation of low signal-to-noise ratio, accurate sign synchronization is provided.
The 3rd purpose of the present invention is to provide a kind of receiver of communication system, and it can provide accurate sign synchronization under the situation of low signal-to-noise ratio.
For achieving the above object, the present invention by the following technical solutions:
Receiver in a kind of communication system comprises:
The Data Receiving unit is used to receive data;
Memory cell is used for storing predetermined lead code, and described lead code comprises at least two repeatable blocks;
The slip cross-correlation unit, this slip cross-correlation unit is connected with described Data Receiving unit, described memory cell respectively, is used for described reception data and the whole slip cross-correlation operation of carrying out of described lead code.
Receiver according to communication system of the present invention, it is the lead code integral body that will receive data and the storage in advance operation that is in sliding cross-correlation, owing to be to operate at the integral body of lead code, and lead code integral body has a plurality of repeatable blocks, correspondingly the number of the sampled point that is used is also many more, make that the peak amplitude after the slip cross-correlation operation is very big, be not easy to be flooded by the noise behind the associative operation, therefore, even under the situation of low signal-to-noise ratio, also can obtain well regularly synchronous effect, therefore, communication system of the present invention regularly synchronous device can obtain the accurate initial sampling point of lead code under the situation of low signal-to-noise ratio, accurate sign synchronization is provided.
Description of drawings
Fig. 1 is the preamble word structural representation of IEEE802.16-2004 ofdm system in the prior art;
Fig. 2 is a Domain Synchronous schematic flow sheet in the prior art;
Fig. 3 is the emulation schematic diagram of thin symbol timing algorithm traditional in the prior art;
Fig. 4 is thin symbol timing algorithm traditional in the prior art at frequency deviation short leading cross-correlation peak value figure during for 75KHz;
Fig. 5 is the leading cross-correlation peak value schematic diagram of the weak point of improved thin symbol timing algorithm when different frequency deviation in the prior art;
Fig. 6 is the cross-correlation peak value schematic diagram of improved thin symbol timing algorithm when signal to noise ratio is 5dB in the prior art;
Fig. 7 is the schematic flow sheet of time synchronization method embodiment one of the present invention;
Fig. 8 is the cross-correlation peak value schematic diagram of time synchronization method when frequency deviation is 0Hz, different signal to noise ratio among the time synchronization method embodiment one of the present invention;
Fig. 9 is the schematic flow sheet of time synchronization method embodiment two of the present invention;
Figure 10 is the cross-correlation peak value schematic diagram of time synchronization method when frequency deviation is 100KHz, different signal to noise ratio among the time synchronization method embodiment two of the present invention;
Figure 11 is that the time synchronization method among the time synchronization method embodiment two of the present invention is that 100KHz, signal to noise ratio are 0 o'clock auto-correlation peak value schematic diagram in frequency deviation;
Figure 12 is that the time synchronization method among the time synchronization method embodiment two of the present invention is that 100KHz, signal to noise ratio are 0 o'clock cross-correlation peak value schematic diagram in frequency deviation;
Figure 13 is the structural representation of communication system timing synchronization device embodiment one of the present invention;
Figure 14 is the structural representation of communication system timing synchronization device embodiment two of the present invention;
Figure 15 is the structural representation of communication system timing synchronization device embodiment three of the present invention;
Figure 16 is the structural representation of communication system timing synchronization device embodiment four of the present invention.
Embodiment
Below be elaborated at the specific embodiment of the present invention, at first be elaborated at time synchronization method of the present invention.
Embodiment one:
In present embodiment one, time synchronization method of the present invention is when carrying out timing simultaneous operation, by receiving the operation that is in sliding cross-correlation of lead code integral body that data and receiving terminal store in advance.
As shown in Figure 7, in the present embodiment, time synchronization method of the present invention comprises step:
Step S101: receive the reception data, enter step S103;
Step S103: the lead code integral body that described reception data and receiving terminal are stored the in advance operation that is in sliding cross-correlation enters step S104;
Step S104: get peak-peak after the slip cross-correlation operation as receiving the short leading initial sampling point of data, obtain the accurate initial sampling point of lead code.
According to the time synchronization method in the present embodiment, it is the lead code integral body that will receive data and the storage in advance operation that is in sliding cross-correlation, suppose that this lead code integral body has N repeatable block, with respect to getting the scheme that a short leading repeatable block is in sliding cross-correlation and operates in the prior art, utilize the number of repeatable block to get over for a long time, correspondingly the number of the sampled point that is used is many more, thereby therefore the peak value size during the timing simultaneous operation in the present embodiment is not easy to be flooded by the noise behind the associative operation with respect to improving N in the prior art doubly; Even under the situation of low signal-to-noise ratio, also can obtain well regularly synchronous effect, be easy to obtain the accurate initial sampling point of lead code.Wherein, the size of this N value, difference according to the structure of the lead code of each communication protocol defined can be different, the lead code of 802.16 system's defineds for example shown in Figure 1 has 4 leading repeatable blocks of weak point and 2 long preambles repeatable blocks, and the short lead code of the 802.11a agreement defined of local area network (LAN) has 10 repeatable blocks.
Wherein, in described step S103, be in sliding cross-correlation when operation, can be only at a preset range that the receives data operation that is in sliding cross-correlation, can at first determine the general initial scope of data at this moment by modes such as frame synchronization.Wherein, this preset range can be determined according to the length of lead code of storage in advance, in for example identical with the length of this lead code scope or the like.
Leading with weak point below is example, and the method in the present embodiment is described.With the short preamble structure among Fig. 1 is example, and the length of supposing this cyclic prefix CP is 64 points, thereby the leading integral body of whole weak point is 64*5=320 point, at this moment, to the formula that receives the leading slip cross-correlation operation of data and this weak point can be:
Wherein, r (k+n) expression receives the sequence of data, short (k+n)
(5)The short leader sequence that the expression receiving terminal is stored in advance, wherein 5 in the subscript bracket represented and had 5 basic repeatable blocks (comprising CP) in this short leader sequence.
As shown in Figure 8, be in the present embodiment time synchronization method according to above-mentioned formula be 0Hz in frequency deviation, cross-correlation peak value schematic diagram when signal to noise ratio is respectively 20dB, 0dB, its receiving terminal in advance the lead code of storage have 5 basic repeatable blocks, and added 1000 spot noises receiving the data front.As shown in the figure, when signal to noise ratio is 20dB, 8 cross-correlation spikes have appearred, amplitude is incremented to maximum successively, successively decreases then, and 5 basic repeatable blocks that the corresponding respectively receiving terminal of these 8 states is stored in advance align with the lead code integral body of receiving sequence gradually, then once more the dislocation process, the place that reaches peak-peak is the places of 5 basic fast all aligns, the accurate sign-on point of lead code just, promptly initial sampling point.In addition, as shown in Figure 8, when signal to noise ratio is 0dB, still can operate as normal, the spike of tangible largest global cross-correlation is provided.This shows that time synchronization method of the present invention also can provide accurate sign synchronization under the low signal-to-noise ratio situation.
Wherein, in the method for present embodiment, between described step S101 and step S103, can also comprise step:
Step S102: described reception data are carried out the frame synchronization operation, enter step S103 then.
Thereby, after receiving the reception data, can receive data to this earlier and carry out the frame synchronization operation, to obtain the probable ranges of lead code, probable ranges that is obtained after then this frame synchronization being operated and the above-mentioned lead code of storage in advance are in sliding cross-correlation to operate and obtain accurate initial sampling point.Thereby owing to just carry out with a part that receives in the data during slip cross-correlation operation, thereby the amount of calculation can reduce the slip cross-correlation operation time is accelerated position fixing process.Wherein, this frame synchronization is operated the method that is adopted and can be taked Schmidl﹠amp of the prior art; The Cox algorithm also can be the frame synchronization mode that adopts other.
In addition, according to the time synchronization method of present embodiment,, after the operation of described step S104, can also comprise step S105 for effectively identification is synchronously false:
Step S105: whether the length place of judging a repeatable block after described initial sampling point goes out the occurrence peak value, if, then synchronizing process success, and carry out next processing procedure, if not, then explanation is unsuccessful synchronously, returns step S101 and receives data again.
This is because the data that received probably are noise fully, for being for the data of noise signal fully, the pseudo-peak value that noise causes also might occur when being in sliding cross-correlation operation, cause synchronously false.In addition, because the number of the repeatable block that lead code integral body is had is many more, degree of correlation when making cross-correlation operation is big more, the inferior peak value that closes on peak-peak after the cross-correlation operation is also big more, difficultly more flooded by noise, and this time peak value can appear at the position at a sampled point repeatable block place afterwards of peak-peak, therefore, if inferior peak value occurred in this position, then explanation success synchronously, if do not occur, then explanation is made a fault synchronously, and the data that received may be noises.Thereby, utilize after the initial sampling point one to repeat whether time peak, fast place, what can the pseudo-peak of effective recognition caused by noise cause is synchronously false.As shown in Figure 8,64 sample point have a very tangible inferior peak after peak-peak, utilize this time peak as the judgement foundation, realize false synchronous identification.
Whether successful synchronously in order can more accurately to judge regularly, when used according to the invention a plurality of repeatable block, whether the length place that can also judge two repeatable blocks after initial sampling point the third-largest peak value occurred, whether the length place at three repeatable blocks has occurred the fourth-largest peak value or the like once more, further reduce false synchronous probability, and use what minor peaks as judgment basis actually, the difference that needs as the case may be can be different, usually depend on received signal to noise ratio, signal to noise ratio is big more, helping using a plurality of minor peaks to carry out more accurate vacation more judges synchronously, this moment, employed number as this peak value of adjudicating foundation was correspondingly also many, concrete decision process can be same as described above, do not repeat them here.
In addition, according to the time synchronization method of present embodiment,, after the operation of described step S105, can also comprise step in order to realize the Frequency Synchronization on the time domain:
Step S106: the result after the described slip cross-correlation operation is carried out frequency offset estimating and correct operation, thereby eliminate the influence of fractional part of frequency offset, to avoid interference the demodulation of data.
In addition, time synchronization method of the present invention can be applicable to lead codes such as OFDM or OFDMA and has at least two or more and repeat in block structured communication systems.
Wherein, lead code can comprise short leading and long preambles simultaneously, because accurate timing synchronization is estimated extremely important to the integer frequency offset based on long preambles, therefore if it is synchronous just to finish accurate timing in short preamble-phase, this is very significant to the Frequency Synchronization based on long preambles subsequently.And the number of the included sampled point of short leading and long preambles repeatable block is different, for example, preamble structure with the IEEE802.16-2004OFDM system, as shown in Figure 1, short leadingly have four 64 repeatable blocks arranged, long preambles has two 128 repeatable blocks, according to aforesaid analysis, when total sampled point is identical, it is many more that the whole institute of lead code has N repeatable block, then inferior peak value that closes on of the whole cross-correlation operation peak-peak of gained will be big more, utilizes this time peak, and what can the pseudo-peak value of effective recognition caused by noise be caused is false synchronous.Therefore, in the inventive method the pre-lead code that stores can only be short leading integral body, to improve the overall performance of synchronization module, reduce false synchronous probability.
Embodiment two:
In present embodiment two, time synchronization method in the present embodiment is among the embodiment one, difference mainly is, increased the process of the lead code that receives data and pre-stored being carried out difference processing, thereby can eliminate frequency deviation effectively to regularly synchronous influence, especially frequency deviation is to the influence of multicarrier system, for example OFDM/OFDMA system or the like.
As shown in Figure 9, the time synchronization method in the present embodiment specifically comprises step:
Step S201: receive the reception data, enter step S203;
Step S203: described reception data are carried out difference operation, enter step S205;
Step S204: the whole difference operation of carrying out of lead code to receiving terminal is stored in advance enters step S205;
Step S205:, enter step S206 to the operation that is in sliding cross-correlation of the result after the result after the operation of above-mentioned reception data difference and the above-mentioned lead code integral body difference operation;
Step S206: get peak-peak after the slip cross-correlation operation as receiving the short leading initial sampling point of data, obtain the accurate initial sampling point of lead code.
According to the time synchronization method in the present embodiment, it is after receiving data, earlier this is received data and carry out difference operation, and in advance the storage lead code integral body carry out difference operation, again the result after above-mentioned two difference operation is carried out the slip cross-correlation operation, because the process of difference is the conjugate multiplication with last bit data and back to back data, and frequency deviation is reflected on the imaginary part the influence of data, therefore, the conjugate multiplication of difference is equivalent to the imaginary part of data and subtracts each other, can eliminate frequency deviation effectively, that is, the method in the present embodiment both can overcome influence on signal-to-noise ratio (SNR), insensitive to frequency deviation again, make it under big frequency deviation and low signal-to-noise ratio, to realize accurate sign synchronization.
Wherein, in the method for present embodiment, after described step S201 received the reception data, step S203 carried out can also comprising step before the difference operation:
Step S202: described reception data are carried out the frame synchronization operation, and then enter step S203.Thereby, can carry out the frame synchronization operation to receiving data earlier, to obtain the probable ranges of lead code, the result with the probable ranges that is obtained after this frame synchronization operation carries out difference operation then, to reduce amount of calculation, accelerates position fixing process.Wherein, this scope can be determined according to the length of lead code of storage in advance, in for example identical with the length of this lead code scope or the like.In addition, this frame synchronization is operated the method that is adopted and can be taked Schmidl﹠amp of the prior art; The Cox algorithm also can be the frame synchronization mode that adopts other.
Leading with weak point below is example, and the method in the present embodiment is described.With the short preamble structure among Fig. 1 is example, and the length of supposing this cyclic prefix CP is 64 points, thereby the leading integral body of whole weak point is 64*5=320 point, at this moment, to the formula that receives the leading slip cross-correlation operation of data and this weak point can be:
Wherein, r ' (k+n)=r (k+n) r* (k+n+1), the expression receiving data sequence difference, short ' is (k)
(5)The difference of the short leader sequence that=short (k) short* (k+1) expression receiving terminal is stored in advance, wherein 5 in the subscript bracket represented and had 5 basic repeatable blocks (comprising CP) in this short leader sequence.
As shown in figure 10, be that the time synchronization method in the present embodiment is 100KHz according to above-mentioned formula in frequency deviation, the emulation schematic diagram when signal to noise ratio is respectively 10dB, 0dB, wherein, when this emulation, 1000 noise has superposeed before receiving data.As shown in the figure, under situation, can obtain a tangible peak-peak,, the obvious peak value of a maximum be arranged still at the section start (1001 sampling point places shown in the figure) of lead code even when this signal to noise ratio is reduced to 0dB with different signal to noise ratios.
Wherein, in the method for present embodiment, after described step S201 received the reception data, step S203 carried out can also comprising step before the difference operation:
Step S202: described reception data are carried out the frame synchronization operation, and then enter step S203.Thereby, can carry out the frame synchronization operation to receiving data earlier, to obtain the probable ranges of lead code, the result with the probable ranges that is obtained after this frame synchronization operation carries out difference operation then, to reduce amount of calculation, accelerates position fixing process.Wherein, this frame synchronization is operated the method that is adopted and can be taked Schmidl﹠amp of the prior art; The Cox algorithm also can be the frame synchronization mode that adopts other.
In addition, according to the time synchronization method of present embodiment,, after the operation of described step S206, can also comprise step S207 for effectively identification is synchronously false:
Step S207: whether the length place of judging a repeatable block after described initial sampling point goes out the occurrence peak value, if, then synchronizing process success, and carry out next processing procedure, if not, then explanation is unsuccessful synchronously, returns step S201 and receives data again.
This is because the data that received probably are noise fully, for being for the data of noise signal fully, the pseudo-peak value that noise causes also might occur when being in sliding cross-correlation operation, cause synchronously false.In addition, because the number of the repeatable block that lead code integral body is had is many more, degree of correlation when making cross-correlation operation is big more, the inferior peak value that closes on peak-peak after the cross-correlation operation is also big more, difficultly more flooded by noise, and this time peak value can appear at the position at a sampled point repeatable block place afterwards of peak-peak, therefore, if inferior peak value occurred in this position, then explanation success synchronously, if do not occur, then explanation is made a fault synchronously, and the data that received may be noises, thereby, utilize after the initial sampling point one to repeat whether time peak, fast place, what can the pseudo-peak of effective recognition caused by noise cause is synchronously false.As shown in figure 10,64 sample point have a very tangible inferior peak after peak-peak, utilize this time peak as the judgement foundation, can effectively avoid false synchronous situation.
Whether successful synchronously in order can more accurately to judge regularly, when used according to the invention a plurality of repeatable block, whether the length place that can also judge two repeatable blocks after initial sampling point the third-largest peak value occurred, whether the length place at three repeatable blocks has occurred the fourth-largest peak value or the like once more, further reduce false synchronous probability, by that analogy, and use what minor peaks as judgment basis actually, the difference that needs as the case may be can be different, usually depend on received signal to noise ratio, signal to noise ratio is big more, helping using a plurality of minor peaks to carry out more accurate vacation more judges synchronously, this moment, employed number as this peak value of adjudicating foundation was correspondingly also many, concrete decision process can be same as described above, do not repeat them here.
In addition, according to the time synchronization method in the present embodiment,, after the operation of described step S207, can also comprise step in order to realize the Frequency Synchronization on the time domain:
Step S208: the result after the described slip cross-correlation operation is carried out frequency offset estimating and correct operation, thereby to eliminate the influence of fractional part of frequency offset, to avoid interference the demodulation of data.
Adopt the method in the present embodiment to be 100KHz in frequency deviation, when signal to noise ratio is 0dB, to carry out simulation operations that wherein, in this simulation operations, the frame synchornization method that is adopted is Schmidl﹠amp below to receiving data; Auto-correlation peak value schematic diagram after the Cox algorithm, its frame synchronization and the cross-correlation peak value schematic diagram after the slip cross-correlation operation are respectively as Figure 11, shown in Figure 12.
As shown in figure 11, be to use described Schmidl﹠amp; The Cox algorithm is carried out the auto-correlation peak value schematic diagram after the frame synchronization operation.Because signal to noise ratio very low (0dB); therefore; the platform thresholding can be made as 0.2; because The noise; before real platform arrives an of short duration pseudo-platform has appearred, because the protection counting module requires the duration of platform just the platform judgement to be arrived for real greater than certain threshold value at least, therefore; this pseudo-platform can be discerned by the protection computing module, is interval between 850 to 1150 sampling points thereby obtain real flat roof area.
As shown in figure 12, it is the cross-correlation peak value schematic diagram after the slip cross-correlation operation, as shown in the figure, peak-peak appears at the 1001st point sampling point place, because there is the peak one time in 64 distances after this sampled point, and this sampled point is in the scope of above-mentioned peak value platform, thereby can get the starting point of this sampled point as lead code.
Identical among other technologies feature in the present embodiment and the embodiment one do not repeat them here.
Each embodiment at the timing synchronization device of communication system of the present invention is elaborated below.
Embodiment one:
As shown in figure 13, be the structural representation of timing synchronization device embodiment one of the present invention.
As shown in the figure, in the present embodiment, communication system of the present invention regularly synchronized device comprises:
According to timing synchronization device of the present invention, it is the lead code integral body that will receive data and the storage in advance operation that is in sliding cross-correlation, suppose that this lead code integral body has N repeatable block, with respect to getting the scheme that a short leading repeatable block is in sliding cross-correlation and operates in the prior art, N when the number of employed sampled point was for repeatable block of use when the present invention slided cross-correlation operation doubly, resulting peak value size is with respect to improving N in the prior art doubly during slip cross-correlation operation unit 106 in apparatus of the present invention, therefore be not easy to be flooded by the noise behind the associative operation, thereby, even under the situation of low signal-to-noise ratio, also can obtain well regularly synchronous effect, be easy to obtain the accurate initial sampling point of lead code.Wherein, the size of this N value, difference according to the structure of the lead code of each communication protocol defined can be different, the lead code of 802.16 system's defineds for example shown in Figure 1 has 5 leading repeatable blocks of weak point and 2 long preambles repeatable blocks, and the lead code of the 802.11a agreement defined of local area network (LAN) has 10 repeatable blocks.
Wherein, when being in sliding cross-correlation operation, can be only at a preset range that the receives data operation that is in sliding cross-correlation, at this moment, can at first determine the general initial scope of data by modes such as frame synchronization, wherein, this preset range can be determined according to the length of lead code of storage in advance, in for example identical with the length of this lead code scope or the like.
In addition, the timing synchronization device in the present embodiment can also comprise:
With the identifying unit 107 that slip cross-correlation operation unit 106 is connected, be used to judge whether the length place of a repeatable block after initial sampling point goes out the occurrence peak value, if, then judge the synchronizing process success, if not, then judge unsuccessful synchronously.
This is because the data that received probably are noise fully, for being for the data of noise signal fully, the pseudo-peak value that noise causes also might occur when being in sliding cross-correlation operation, cause synchronously false.In addition, because the number of the repeatable block that lead code integral body is had is many more, degree of correlation when making cross-correlation operation is big more, the inferior peak value that closes on peak-peak after the cross-correlation operation is also big more, difficultly more flooded by noise, and this time peak value can appear at the position at a sampled point repeatable block place afterwards of peak-peak, therefore, if inferior peak value occurred in this position, then explanation success synchronously, if do not occur, then explanation is made a fault synchronously, and the data that received may be noises, thereby, utilize after the initial sampling point one to repeat whether time peak, fast place, what can the pseudo-peak of effective recognition caused by noise cause is synchronously false.
Whether successful synchronously in order can more accurately to judge regularly, when used according to the invention a plurality of repeatable block, whether the length place that can judge two repeatable blocks after initial sampling point the third-largest peak value occurred, whether the length place at three repeatable blocks has occurred the fourth-largest peak value or the like once more, further reduce false synchronous probability, by that analogy, and use what minor peaks as judgment basis actually, the difference that needs as the case may be can be different, usually depend on received signal to noise ratio, signal to noise ratio is big more, helping using a plurality of minor peaks to carry out more accurate vacation more judges synchronously, this moment, employed number as this peak value of adjudicating foundation was correspondingly also many, concrete decision process can be same as described above, do not repeat them here.
Wherein, lead code can comprise short leading and long preambles simultaneously, because accurate timing synchronization is estimated extremely important to the integer frequency offset based on long preambles, therefore if it is synchronous just to finish accurate timing in short preamble-phase, this is very significant to the Frequency Synchronization based on long preambles subsequently.And the number of the included sampled point of short leading and long preambles repeatable block is different, for example, preamble structure with the IEEE802.16-2004OFDM system, as shown in Figure 1, short leadingly have four 64 repeatable blocks arranged, long preambles has two 128 repeatable blocks, according to analysis before, when total sampled point is identical, it is many more that the whole institute of lead code has N repeatable block, then inferior peak value that closes on of the whole cross-correlation operation peak-peak of gained will be big more, utilizes this time peak, and what can the pseudo-peak value of effective recognition caused by noise be caused is false synchronous.Therefore, in the inventive method the pre-lead code that stores can only be short leading integral body, to improve the overall performance of synchronization module, reduce false synchronous probability.
In addition, in the regularly synchronous device of communication system of the present invention, described communication system can be that lead codes such as ofdm system, OFDMA system have in the communication system of two or more repeatable blocks at least.
In addition, in order to realize the Frequency Synchronization on the time domain, according to the timing synchronization device in the present embodiment, can also comprise the frequency offset estimating and the correcting unit (not shown) that are connected with described slip interoperability unit 106, be used for the result after the slip interoperability unit 106 slip interoperability is carried out frequency offset estimating and correct operation, thereby can eliminate the influence of fractional part of frequency offset,, realize the Frequency Synchronization on the time domain to avoid interference the demodulation of data.
Embodiment two:
As shown in figure 14, be the structural representation of communication system timing synchronization device embodiment two of the present invention.
As shown in the figure, in the present embodiment, be mainly that the device that communication system of the present invention is regularly synchronous also comprises with the difference of embodiment one:
Be connected in first difference unit 103 between described Data Receiving unit 101 and the described slip cross-correlation unit 106, be used for described reception data are carried out difference operation;
And be connected in second difference unit 104 between described memory cell 102 and the described slip cross-correlation unit 106, be used for the whole difference operation of carrying out of described lead code;
At this moment, described slip cross-correlation unit 106 is used for result after described first difference unit, the 103 execution difference operation and the result after described second difference unit, 104 difference operation are carried out the slip cross-correlation operation.
Because the process of difference operation is the conjugate multiplication with last bit data and back to back data, and frequency deviation is reflected on the imaginary part the influence of data, and therefore, the conjugate multiplication of difference is equivalent to the imaginary part of data subtracts each other, and can eliminate frequency deviation effectively.
Wherein, when first difference unit 103 carries out difference operation, can be only at a preset range that the receives data operation that is in sliding cross-correlation, at this moment, can at first determine the general initial scope of data by modes such as frame synchronization.Wherein, this preset range can be determined for example identical with the length of this lead code scope or the like according to the length of the lead code of storing in advance.
Identical among other technologies feature in the present embodiment and the embodiment one do not repeat them here.
Embodiment three:
As shown in figure 15, be the structural representation of communication system timing synchronization device embodiment three of the present invention.
As shown in the figure, in the present embodiment, be mainly that the device that communication system of the present invention is regularly synchronous also comprises with the difference of embodiment one:
Be connected in the frame synchronization unit 105 between described Data Receiving unit 101 and the described slip interoperability unit 106, the reception data that are used for that described Data Receiving unit 101 is received are carried out the frame synchronization operation, and the data after the frame synchronization operation are sent to described slip interoperability unit 106.
Thereby, after receiving the reception data, can receive data to this earlier and carry out the frame synchronization operation, to obtain the probable ranges of lead code, probable ranges that is obtained after then this frame synchronization being operated and the above-mentioned lead code of storage in advance are in sliding cross-correlation to operate and obtain accurate initial sampling point.Thereby owing to just carry out with a part that receives in the data during slip cross-correlation operation, thereby the amount of calculation can reduce the slip cross-correlation operation time is accelerated position fixing process.Wherein, this frame synchronization is operated the method that is adopted and can be taked Schmidl﹠amp of the prior art; The Cox algorithm also can be the frame synchronization mode that adopts other.
Identical among other technologies feature in the present embodiment and the embodiment one do not repeat them here.
Embodiment four:
As shown in figure 16, be the structural representation of communication system timing synchronization device embodiment four of the present invention.
As shown in the figure, in the present embodiment, be mainly that the device that communication system of the present invention is regularly synchronous also comprises with the difference of embodiment one:
Be connected in first difference unit 103 between described Data Receiving unit 101 and the described slip cross-correlation unit 106, be used for described reception data are carried out difference operation;
Be connected in second difference unit 104 between described memory cell 102 and the described slip cross-correlation unit 106, be used for the whole difference operation of carrying out of described lead code;
Be connected in the frame synchronization unit 105 between described Data Receiving unit 101 and described first difference unit 103, the reception data that are used for that described Data Receiving unit 101 is received are carried out the frame synchronization operation, and the data after the frame synchronization operation are sent to described first difference unit 103;
At this moment, described slip cross-correlation unit 106 is used for result after described first difference unit, the 103 execution difference operation and the result after described second difference unit, 104 difference operation are carried out the slip cross-correlation operation.
Thereby, after receiving the reception data, can receive data to this earlier and carry out the frame synchronization operation, to obtain the probable ranges of lead code, then the probable ranges that is obtained after the operation of this frame synchronization is carried out after the difference result after the difference operation with the above-mentioned lead code of the storage in advance operation that is in sliding cross-correlation and obtained accurate initial sampling point.Thereby, owing to just carry out during the slip cross-correlation operation with a part that receives in the data, thereby the amount of calculation in the time of can reducing the slip cross-correlation operation, accelerate location speed, in addition, difference operation can effectively overcome the influence of frequency deviation, makes that the device in the present embodiment can be realized accurate sign synchronization under big frequency deviation and low signal-to-noise ratio.Wherein, this frame synchronization is operated the method that is adopted and can be taked Schmidl﹠amp of the prior art; The Cox algorithm also can be the frame synchronization mode that adopts other.
Identical among other technologies feature in the present embodiment and the embodiment one do not repeat them here.
The device regularly synchronous according to the communication system among each embodiment of the invention described above, the present invention also can provide the receiver of communication system, and the timing synchronization device that it comprises respectively in the various embodiments described above does not repeat them here.
Above-described embodiment of the present invention does not constitute the qualification to protection range of the present invention.Any modification of being done within the spirit and principles in the present invention, be equal to and replace and improvement etc., all should be included within the claim protection range of the present invention.
Claims (19)
1, the regularly synchronous method of a kind of communication system is characterized in that, comprises step:
Receive data;
The described reception data and the lead code integral body of storage are in advance made the slip cross-correlation operation, and described lead code comprises two or more repeatable block at least;
With the initial sampling point of the pairing sampled point of peak-peak after the described slip cross-correlation operation as described reception data.
2, the regularly synchronous method of communication system according to claim 1 is characterized in that, before carrying out described slip cross-correlation operation, also comprises step:
Described reception data are carried out the frame synchronization operation.
3, the regularly synchronous method of communication system according to claim 1 is characterized in that, before carrying out described slip cross-correlation operation, also comprises step:
Described reception data are carried out difference operation;
The described preamble data integral body of storage is in advance done difference operation.
4, the regularly synchronous method of communication system according to claim 1 is characterized in that, before carrying out described slip cross-correlation operation, also comprises step:
Described reception data are carried out the frame synchronization operation, the data after the described frame synchronization operation are carried out difference operation;
The described preamble data integral body of storage is in advance done difference operation.
5, the regularly synchronous method of communication system according to claim 1 is characterized in that, after obtaining described initial sampling point, also comprises step:
Judge whether a repeatable block length place after the described initial sampling point goes out the occurrence peak value,
If judge success synchronously;
If not, judge synchronously and get nowhere, receive data again.
6, according to the regularly synchronous method of any described communication system of claim 1 to 5, it is characterized in that described lead code is short leading or long preambles.
7, according to the regularly synchronous method of any described communication system of claim 1 to 5, it is characterized in that described communication system is OFDM or OFDMA system.
8, the regularly synchronous device of a kind of communication system is characterized in that, comprising:
The Data Receiving unit is used to receive data;
Memory cell is used for storing predetermined lead code, and described lead code comprises plural at least repeatable block;
The slip cross-correlation unit, this slip cross-correlation unit is connected with described Data Receiving unit, described memory cell respectively, is used for described reception data and the whole slip cross-correlation operation of carrying out of described lead code.
9, the regularly synchronous device of communication system according to claim 8 is characterized in that, also comprises:
Be connected in first difference unit between described Data Receiving unit and the described slip cross-correlation unit, be used for described reception data are carried out difference operation;
Be connected in second difference unit between described memory cell and the described slip cross-correlation unit, be used for the whole difference operation of carrying out of described lead code;
Described slip cross-correlation unit is used for the result of described first difference unit and the result of described second difference unit are carried out the slip cross-correlation operation.
10, the regularly synchronous device of communication system according to claim 8 is characterized in that, also comprises:
Be connected in the frame synchronization unit between described Data Receiving unit and the described slip cross-correlation unit, be used for the data that receive are carried out the frame synchronization operation.
11, the regularly synchronous device of communication system according to claim 8 is characterized in that, also comprises:
With the identifying unit that described slip cross-correlation operation unit is connected, be used to judge whether the length place of a repeatable block after initial sampling point goes out the occurrence peak value, if, then judge the synchronizing process success, if not, then judge unsuccessful synchronously.
12, according to Claim 8 or the regularly synchronous device of 9 or 10 or 11 described communication systems, it is characterized in that described lead code is short leading or long preambles.
13, according to Claim 8 or the regularly synchronous device of 9 or 10 or 11 described communication systems, it is characterized in that described communication system is OFDM or OFDMA system.
14, the receiver in a kind of communication system is characterized in that, comprising:
The Data Receiving unit is used to receive data;
Memory cell is used for storing predetermined lead code, and described lead code comprises at least two repeatable blocks;
The slip cross-correlation unit, this slip cross-correlation unit is connected with described Data Receiving unit, described memory cell respectively, is used for described reception data and the whole slip cross-correlation operation of carrying out of described lead code.
15, the receiver of communication system according to claim 14 is characterized in that, also comprises:
Be connected in first difference unit between described Data Receiving unit and the described slip cross-correlation unit, be used for described reception data are carried out difference operation;
Be connected in second difference unit between described memory cell and the described slip cross-correlation unit, be used for the whole difference operation of carrying out of described lead code;
Described slip cross-correlation unit is used for the result of described first difference unit and the result of described second difference unit are carried out the slip cross-correlation operation.
16, the receiver of communication system according to claim 14 is characterized in that, also comprises:
Be connected in the frame synchronization unit between described Data Receiving unit and the described slip cross-correlation unit, be used for the data that receive are carried out the frame synchronization operation.
17, the receiver of communication system according to claim 14 is characterized in that, also comprises:
With the identifying unit that described slip cross-correlation operation unit is connected, be used to judge whether the length place of a repeatable block after initial sampling point goes out the occurrence peak value, if, then judge the synchronizing process success, if not, then judge unsuccessful synchronously.
According to the receiver of claim 14 or 15 or 16 or 17 described communication systems, it is characterized in that 18, described lead code is short leading or long preambles.
According to the receiver of claim 14 or 15 or 16 or 17 described communication systems, it is characterized in that 19, described communication system is OFDM or OFDMA system.
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