CN107438042B - Preamble symbol detection and analysis device - Google Patents
Preamble symbol detection and analysis device Download PDFInfo
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Abstract
The invention provides a leading symbol detecting and analyzing device, which comprises: the correlator is used for carrying out frequency shift on the received signal by utilizing three-section structural characteristics of the preamble symbol and then carrying out front and back correlation to obtain a correlation value; the peak value detector is used for searching the peak value of the correlation value to calculate the rough position of the preamble symbol, and the phase angle of the peak value correspondingly obtains a decimal frequency multiplication deviation value; the integral frequency offset and spectrum inversion judging module estimates the integral frequency offset and spectrum inversion characteristics of the subcarrier interval by utilizing the frequency domain effective subcarrier power boosting characteristic of the preamble symbol; the time domain timing fine synchronization module is used for synchronizing the data after the frequency offset is removed to obtain the accurate position of the preamble symbol; a time-frequency domain decoder for decoding the data after the fine synchronization in the time domain and the frequency domain respectively; the signaling distinguishing and analyzing module is used for analyzing the signaling, and distinguishing the signaling and then confirming a preamble symbol decoding result if the time-frequency domain decoding results are different; and if the time-frequency domain decoding results are the same, obtaining a preamble symbol decoding result.
Description
The present application is a divisional application of the original, filed on filed application No. 201610361958.2, filed on filed application No. 2016, 5/26.5.10.3, entitled "leading symbol detection and analysis device and method".
Technical Field
The invention relates to frame header detection, frequency offset estimation and signaling information extraction in an OFDM system, in particular to a robust preamble symbol detection device of a DVB _ T2 system.
Background
European second generation Digital television terrestrial Broadcasting standard Digital Video Broadcasting (DVB); frame channel coding and modulation for an a second generation digital modulation (DVB-T2) discloses a special P1 symbol as a frame header symbol of an OFDM system, and as shown in fig. 1, a preamble symbol (referred to as P1 herein) adopts a cyclic prefix-suffix structure C _ a _ B with frequency shift. The british broadcaster elaborates on the design advantage of the P1 symbol in patent document 1, that it is immune to severe Continuous Wave (CW) interference, resistant to "dangerous" multipath, and immune to frequency offset. Meanwhile, the P1 carries signaling information indicating the fourier transform (FFT) size of the system, Guard Interval (GI) range, base/lite (base/lite) mode, single input single output/multiple input single output (SISO/MISO) mode, etc.
The preamble symbol P1 adopts a cyclic prefix-suffix structure with frequency shift, the correlation value is not affected by frequency shift and continuous wave interference, but in some multipath situations, the P1 detection still fails. DVB-T2 implements the guide Digital Video Broadcasting (DVB); simulation results of P1 performance simulation show that the probability of failure of P1 detection is 100% and the probability of failure of signaling analysis is 100% under multipath channels with equal amplitudes and opposite phases in two paths. Patent document 2 makes two enhancements to the implementation method of the implementation guide without changing the basic characteristics of the P1 structure, but does not make a modification to the signaling resolution. P1 occupies 853 subcarriers in the frequency domain, of which 384 effective subcarriers have higher power and the other unused subcarriers are set to 0, as shown in fig. 2. By utilizing the characteristic, the frequency offset of the system can be extracted and whether the frequency spectrum is overturned or not can be identified. The invention provides a robust P1 symbol detection and analysis method, which enlarges the range of frequency offset estimation and identifies whether the frequency spectrum of the system is overturned.
Prior art documents:
patent document
Patent document 1: chinese patent No. CN 200880024926.7 specification 101743731a
Patent document 2: specification of Chinese patent No. 201010196280.X
Non-patent document
[1]Digital Video Broadcasting(DVB)；Frame structure channel coding andmodulation for a second generation digital terrestrial televisionbroadcasting system(DVB-T2)；
[2]Digital Video Broadcasting(DVB)；Implementation guidelines for asecond generation digital terrestrial television broadcasting system(DVB-T2)。
Disclosure of Invention
The problem solved by the invention is that the probability of failure of detecting the preamble symbol under the multipath channel in the prior DVB-T2 is high.
To solve the above problem, an embodiment of the present invention provides a preamble symbol detection and analysis apparatus, including: the correlator is used for carrying out frequency shift on the received signal by utilizing three-section structural characteristics of the preamble symbol and then carrying out front and back correlation to obtain a correlation value; the peak value detector is used for searching the peak value of the correlation value to calculate the rough position of the preamble symbol, and the phase angle of the peak value correspondingly obtains a decimal frequency multiplication deviation value; the integral frequency offset and spectrum inversion judging module estimates the integral frequency offset and spectrum inversion characteristics of the subcarrier interval by utilizing the frequency domain effective subcarrier power boosting characteristic of the preamble symbol; the time domain timing fine synchronization module is used for synchronizing the data after the frequency offset is removed to obtain the accurate position of the preamble symbol; a time-frequency domain decoder for decoding the data after the fine synchronization in the time domain and the frequency domain respectively; the signaling distinguishing and analyzing module is used for analyzing the signaling, and distinguishing the signaling and then confirming a preamble symbol decoding result if the time-frequency domain decoding results are different; and if the time-frequency domain decoding results are the same, obtaining a preamble symbol decoding result.
Optionally, the integer-times frequency offset estimation and spectrum inversion determining module includes: a frequency domain subcarrier preprocessing unit: carrying out amplitude limiting on the frequency domain abnormal subcarriers, and removing in-band interference signals; a cyclic correlation unit: and considering frequency spectrum inversion, using Fourier and inverse Fourier transform to replace correlation operation, and processing the signal after frequency domain subcarrier preprocessing and the effective subcarrier to obtain an integral multiple frequency offset estimation value.
Optionally, the integer-times frequency offset estimation and spectrum inversion discriminating module operates several times, and the starting position of the preamble symbol selected each time is different.
Optionally, the time domain timing fine synchronization module determines the precise position of the preamble symbol while determining the integer frequency offset.
Optionally, the time-frequency domain decoder combines time domain decoding and frequency domain decoding to decode respectively, and the time domain decoding uses the time domain correlation characteristic and the cross-correlation characteristic of the preamble symbols and all preamble symbols to perform correlation to realize time domain decoding; and when the frequency domain coding is carried out, the frequency domain coding is realized by using a frequency domain differential correlation mode.
Optionally, the signaling discrimination analysis module is configured to confirm different decoding results of the time-frequency domain decoder: firstly, the signaling is distinguished, and then the decoding result of the preamble symbol is confirmed.
Optionally, the signaling discrimination analysis module performs time domain correlation on the preamble symbol obtained by time domain decoding and frequency domain decoding and the received preamble symbol sequence to obtain two groups of correlation values, searches for a sum of the first three maximum values of any one group of correlation values and records the positions of the first three maximum values, sums the three correlation values at the positions corresponding to the other group of correlation values, compares the magnitudes, and determines that the decoding result corresponding to the larger value is correct.
In addition, the embodiment of the invention also provides a preamble symbol detection and analysis method, which comprises the following steps: frequency shifting the received signal by utilizing three-section structural characteristics of a preamble symbol and then carrying out front-back correlation to obtain a correlation value; searching a peak value of the correlation value to calculate a rough position of the preamble symbol, wherein a decimal frequency multiplication deviation value is correspondingly obtained by a phase angle of the peak value; estimating integer frequency offset and spectrum turnover characteristics of subcarrier intervals by utilizing the frequency domain effective subcarrier power boosting characteristic of the preamble symbol; synchronizing the data after the frequency offset is removed to obtain the accurate position of a preamble symbol; decoding the data after the fine synchronization in a time domain and a frequency domain respectively; analyzing the signaling, if the time-frequency domain decoding results are different, firstly judging the signaling and then confirming the decoding result of the preamble symbol; and if the time-frequency domain decoding results are the same, obtaining a preamble symbol decoding result.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
according to the preamble symbol detection and analysis device and method, the existence of the frame header signal in DVB-T2 is robustly detected, the characteristics of the preamble symbol P1 are fully utilized, the frequency offset value is accurately estimated, whether the frequency spectrum is overturned or not is identified, the P1 signaling is decoded in the time-frequency domain respectively, and finally the P1 signaling is correctly analyzed, so that the preamble symbol can be robustly detected, the frequency offset estimation range is large, and the decoding result is more robust.
Drawings
Fig. 1 is a schematic diagram of a preamble three-segment structure CAB in the DVB _ T2 standard according to the present invention;
fig. 2 is a diagram of an 8M systematic preamble symbol valid subcarrier distribution in the DVB _ T2 standard according to the present invention;
FIG. 3 is a schematic diagram of a preamble symbol detection and analysis apparatus according to an embodiment of the present invention;
FIG. 4 is a diagram of the C _ A _ B correlator structure according to the present invention;
FIG. 5 is a schematic diagram of the peak detection of C _ A _ B in the present invention;
FIG. 6 is a graph of correlation values of C _ A _ B in two paths of 0db spaced by 1024 symbols, the second path having the same phase as the first path and being opposite to the first path, respectively;
FIG. 7 is a schematic diagram of a single rectification estimation and spectrum inversion identification in the present invention;
FIG. 8 is a schematic diagram of a time domain fine synchronization process according to the present invention;
FIG. 9 is a schematic diagram of a time-domain decoding process according to the present invention;
FIG. 10 is a schematic diagram of a frequency domain decoding process according to the present invention;
FIG. 11 is a flow chart of decoding verification according to the present invention; and
fig. 12 is a schematic diagram of a preamble symbol detection and analysis method according to the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
The invention aims to robustly detect the existence of a DVB-T2 frame header signal, fully utilize the characteristics of a P1 preamble symbol, accurately estimate a frequency offset value, identify whether a frequency spectrum is overturned or not, respectively decode a preamble symbol P1 signaling in a time-frequency domain, and finally correctly analyze a preamble symbol P1 signaling.
In the P1 symbol detection device of the DVB _ T2 system robust, a C _ A _ B correlator carries out front and back delay correlation operations after signal frequency shift according to the structure of the correlator disclosed in the DVB _ T2 standard, and after smoothing processing and delay alignment, multiplication is carried out for finding a leading symbol P1 signal and decimal frequency offset estimation. Frequency of P1 symbol is utilized in integral frequency offset and spectrum inversion discrimination moduleAnd estimating the integral multiple frequency offset and the frequency spectrum transfer characteristic of the 1K subcarrier interval by using the domain effective subcarrier power boosting characteristic. The time domain timing fine synchronization module is obtained by averaging all P1 symbols (in this case, 128P 1 adopting DVB-T2 protocol)
The time domain correlation characteristic accurately finds the starting position of P1, then the time domain and the frequency domain decode the P1 symbol, and the decoding is completed by the time-frequency domain decoder, because the time-frequency domain decoding results are different, the final judgment of the signaling discrimination analysis module is needed to confirm the P1 decoding result.
Another objective of the present invention is to provide a robust preamble symbol detection and parsing method for DVB _ T2 system. Firstly, performing C _ A _ B structure correlation on a received signal, finding an approximate initial position of P1 and estimating decimal frequency offset; estimating the integer frequency offset and the spectrum inversion characteristic of the 1K subcarrier interval in the frequency domain by utilizing the power boosting characteristic of the P1 effective subcarriers in the area range where the P1 exists, carrying out frequency offset compensation on data, and averaging the data according to 128P 1 symbols
Finding out the accurate P1 initial position in a certain area of the approximate initial position by using the time domain correlation characteristic, respectively decoding P1 in the time-frequency domain after finding out the accurate position P1, and finally confirming the decoding result.
Fig. 1 is a schematic diagram of a preamble three-segment structure C _ a _ B in the DVB _ T2 standard according to the present invention;
as shown in fig. 1, in the present embodiment, the preamble symbol has a three-segment structure C _ a _ B, where part a is a 1K (1024) OFDM symbol, and part C is frequency-shifted by f from the first 542 sampling points of part aSH(one subcarrier spacing) is obtained; part B is frequency shifted from the last 482 samples of part a. In an 8MHz system, the duration of the P1 symbol is 224us (2048 samples total). The duration of part a is 112us, and the duration of C and B are 59us (542 samples) and 53us (482 and samples), respectively.
Fig. 2 is a diagram of an 8M systematic preamble symbol valid subcarrier distribution in the DVB _ T2 standard according to the present invention;
as shown in fig. 2, in the present embodiment, 853 subcarriers are available in the 1K symbol, 384 subcarriers are available, and others are set to 0. In an 8MHz system, the signal bandwidth is 7.61MHz (occupying 0-852 subcarriers), there are 766 carriers in the useful 6.83MHz bandwidth, the first 44 and the last 809.
FIG. 3 is a schematic diagram of a preamble symbol detection and analysis apparatus according to an embodiment of the present invention;
as shown in fig. 3, the preamble symbol detection and analysis apparatus in this embodiment includes a C _ a _ B correlator 11, a preamble symbol peak detector 12, an integer frequency offset and spectrum inversion determining module 13, a time domain timing fine synchronization module 14, a time frequency domain decoder 15, and a signaling determining and analyzing module 16.
The C _ a _ B correlator 11 is the classical structure in DVB-T2 implementation guide [2] above, and its basic structure is post-frequency-shifted pre-post correlation.
FIG. 4 is a diagram of the C _ A _ B correlator of the present invention;
as shown in fig. 4, the frequency offset rotation module 11A is configured to remove the frequency offsets of the C-segment and the a-segment in the three-segment structure C _ a _ B, and the first delay module 11E, the second delay module 11B, and the third delay module 11F respectively have corresponding delay lengths of 1024 and 542, and 482. The first conjugate multiplication module 11C and the second conjugate multiplication module 11G respectively perform conjugate multiplication on the signals after frequency offset cancellation delay alignment, the first moving average module 11D and the second moving average module 11H perform moving average processing on the result of the multiplier, and the result is multiplied by the multiplication module 11I after being delayed by 1024 symbols by the third delay module 11F to obtain a correlation value Z. The peak angle of Z corresponds to the fractional octave.
FIG. 5 is a schematic diagram of the peak detection of C _ A _ B in the present invention;
as shown in fig. 5, in the embodiment, the preamble symbol P1 peak detector 12 determines the correlation value of C _ a _ B, and searches the P1 peak to calculate the rough position of P1, and the phase angle of the peak corresponds to the fractional frequency offset. The proper threshold value is set, because the data correlation and noise of non-P1 symbols are consistent, the AGC module in the digital television ground broadcast receiving system adjusts the power to a certain power levelThe correlation value of the data portion is not affected by the reception power of the received signal and the channel condition, and a suitable threshold value may be set, and the portions of the correlation value successively greater than the threshold value are considered to have detected the preamble symbol P1, the first and last of the absolute values of Z crossing the threshold index s1And s2Through s1And s2The midpoint of P1 can be derived from the position of the P1 symbol, as shown in fig. 5, the coarse synchronization position P1_ coarse _ index of P1 is derived from the following formula (1):
in the formula (1), Δ0Is an empirical value (additive computation delay), na＝1024,nc＝542
The decimal frequency offset value is calculated by the following formula (2): may be based on N around the peak positionfThe phase angle mean of the points is determined.
Where z (i) is the correlation result, as shown in FIG. 4,
equation (1) applies to AWGN channel, the peak of C _ a _ B has large difference in amplitude and shape under different multipath conditions, and how to accurately detect the existence and position of P1 by the peak is critical. The performance simulation result of the preamble symbol P1 in the DVB-T2 implementation guideline [2] shows that the probability of P1 detection failure is 100% under 0dB equal path and two-path delay of 1024 symbol channels (the phase difference of two-path signals is 180 degrees).
FIG. 6 is a graph of correlation values of C _ A _ B in two paths of 0db spaced by 1024 symbols, the second path having the same phase as the first path and being opposite to the first path, respectively;
as shown in fig. 6, the correlation values under the two-path channel with 0dB spacing of 1024 symbols are shown, where the continuous line indicates the case of the same symbol, and the dotted line indicates the case of the opposite symbol, it can be seen that, the peak values of C _ a _ B under the case of the same symbol and the opposite symbol have a large difference in amplitude and shape, especially, in the 0dB channel with the opposite symbol, the position of the peak value deviates from the actual position by about 1000 symbols, and the integer multiple frequency offset is performed according to the P1 position obtained by the peak value, which may result in the failure of the estimation of the integer multiple frequency offset, and further the failure of decoding of the preamble symbol P1. In addition to the special channel shown in fig. 5, in other multipath channels, the range of the correlation value of C _ a _ B exceeding the threshold is wide, and the P1 coarse synchronization position is inaccurate. In order to solve the problem of inaccurate position of the P1 coarse synchronization, the position can be obtained in a formula (1) and moved left and right within a certain range, and the position of P1 is tried to be searched, and the searching process is completed by an integer frequency offset and frequency spectrum inversion judging module 13 and a time domain timing fine synchronization module 14.
FIG. 7 is a schematic diagram of a single rectification estimation and spectrum inversion identification in the present invention;
in this embodiment, as shown in fig. 2, there are only 384 valid subcarriers in the preamble symbol P1, and the remaining 469 subcarriers are 0 and have known distribution. The length of the local frequency domain sequence is 1024,384, the position of the subcarrier is 1, the remaining subcarriers are 0, as shown in fig. 7, FFT is performed on a segment a symbols (1024 points) in the three-segment structure in P1 through step 13A, energy correlation is performed on the segment a symbols and the frequency domain sequence shown in fig. 2, and the position of the peak corresponds to the maximum frequency offset. Meanwhile, the possibility of frequency spectrum inversion is considered, and effective subcarriers are in mirror symmetry. As shown in fig. 7, in the present embodiment, the P1_ coarse _ index coarse synchronization position is already found in the peak detection, and the a-segment signal in the C _ a _ B three-segment structure of the data after fractional frequency offset starting with the coarse synchronization position P1_ coarse _ index of the preamble symbol is taken for integer frequency offset estimation, and the fractional frequency offset compensation is similar to the 11A module. Step 13B calculates the energy (I) of each subcarrier2+Q2Representing the sum of the squares of the real and imaginary parts, and the 13C step clips the subcarriers with abnormal energy in consideration of the influence of the in-band interference signal. And step 13F-13I uses an FFT mode to realize circular correlation operation, the circular correlation sets reasonable circulation times according to the frequency offset range of the system, and the related mode of FFT avoids the point. Steps 13D and 13E are the spectrum flipping module flipping, not flipping. Steps 13D and 13F to I are to find the cyclic correlation value when the spectrum is not inverted, steps 13E and 13F to I are to find the cyclic correlation value when the spectrum is inverted, and fig. 7 shows that 1 is the valueSteps after 3E, which are the same as steps 13F to I, are omitted from the figure, and step 13J searches for the maximum value and subscript of the correlation value, the subscript corresponding to the estimated value of the bias adjustment. And comparing the maximum values to obtain a frequency spectrum turnover mark. Next, the coarse synchronization position P1_ coarse _ index of each preamble symbol is shifted by a certain range, in this embodiment, by 1000 symbols. The calculation process shown in fig. 7 is repeated. And finally, obtaining three groups of integer frequency offset values, correlation values and spectrum turnover marks, sequencing the three groups of maximum values to obtain the integer frequency offsets and the spectrum turnover marks of the first two groups, and adding 1 to the frequency offset value of the second group if the frequency offset values of the two groups are consistent.
FIG. 8 is a schematic diagram of a time domain fine synchronization process according to the present invention;
the integral frequency offset and spectrum inversion discrimination module 13 obtains two frequency offset values, and the time domain timing fine synchronization module 14 confirms the frequency offset and finds the accurate position of P1 at the same time. As shown in fig. 8, after removing the integer multiples and decimal frequency offsets in step 14A, the P1 position obtained by the P1 peak detector 12 is searched for the P1 position precisely, and the sequence after removing the frequency offsets and all the mean sequences of P1 are used, in this example, the mean values of 128 kinds of P1 preamble symbols defined in the DVB-T2 protocol are used
(Pk is a P1 sequence) and the mean of the pilot symbols
There is correlation with any one of the P1 sequences, and the position where the peak is the largest corresponds to the precise timing position of P1. The method comprises the following steps of taking data of 4K in total which is formed by adding 1K symbols on the left and right sides of P1 and 3K symbols of body data and using FFT to realize summation on the 4K data
Correlation, using FFT/IFFT to implement correlation calculation, the process is shown in fig. 8. In step 14A, the first group of frequency deviation and frequency deviation inversion flag in the integer frequency deviation and frequency deviation inversion determination module 13 is selected to perform frequency deviation compensation on the 4K data, including fractional frequency deviation and integer frequency deviation, and if the frequency deviation is inverted, the frequency deviation is compensatedThe imaginary part of the data of (1) is inverted. 14B-14D use FFT/IFFT operation to replace correlation calculation, 14B do 4K FFT to the data of de-frequency deviation, 14C do conjugate multiplication to two FFT sequences, one is the 4K length FFT sequence of the data of de-frequency deviation, the other is the FFT sequence
A 4K length FFT sequence; 14D, carrying out IFFT on the conjugate multiplication result of the length of 4K to obtain a correlation value; 14E calculates the magnitude of the correlation value. Since the integral frequency offset and spectrum inversion discrimination module 13 obtains that two frequency offset values are different, the correlation value is affected by the frequency offset, the correct frequency offset correlation value is large, the correlation value corresponding to the incorrect frequency offset is small, and the maximum value of the two sets of correlation values meets a certain proportion condition, the P1 peak position is considered to be correct, the frequency offset estimation is correct, the fine synchronization is finished, the position of the maximum value of the correlation value corresponds to the accurate position of P1, and the C _ a _ B correlator can stop working. Otherwise, P1 peak detection is carried out again until the result of fine synchronization satisfies the condition.
FIG. 9 is a schematic diagram of a time-domain decoding process according to the present invention;
after the position of a strong path of P1 is accurately found, the autocorrelation peak value of a P1 symbol is very high, the cross-correlation peak value is relatively low, and the maximum peak value corresponds to the real P1 sequence when the time domain correlation characteristic and the cross-correlation characteristic of the P1 symbol are utilized to correlate with 128 kinds of P1. The time domain decoding can solve the problem of ultra-long multipath, the length of the P1 sequence is long, the correlation value is not influenced by the signal-to-noise ratio, and the time domain decoding has strong noise resistance. However, under the channel condition of a large number of near paths, the cross-correlation of P1 is poor, and the time domain decoding result is inaccurate. The frequency domain decoding uses a differential correlation mode, so that the influence of a near path can be overcome, the frequency domain subcarriers are more faded under an ultra-long multipath channel, and the frequency domain decoding performance is poor. The advantages of the time domain and the frequency domain can be combined to decode respectively, if the decoding results are the same, the decoding is successful, and if the decoding results of the time domain and the frequency domain are different, the decoding results need to be confirmed.
As shown in fig. 9, in the present embodiment, the processing flow of time-domain decoding in the time-frequency-domain decoder 15 includes the following steps:
step 15a 1: and (3) correlating the signals of the A part of the P1 symbol (subjected to frequency offset compensation) after the timing fine synchronization with the A part of 128P 1, and performing the steps of 15B 1: finding the maximum of each P1 correlation value, step 15C 1: whether the correlation calculation is finished or not is judged, after the 128P 1 correlation traversals are finished, the 128 peaks are compared by a step 15D1, and the maximum value corresponds to the correct P1 sequence.
Fig. 10 is a schematic diagram of frequency-domain decoding, in this embodiment, a processing flow of the frequency-domain decoding in the time-frequency-domain decoder 15 includes the following steps:
step 15a2 and step 15B2 extract 384 subcarriers in the frequency domain to obtain an Active _ Seq of an effective subcarrier sequence, and step 15C2 performs difference on two adjacent subcarriers; the difference formula is Active _ Seq (i +1) × conj (Active _ Seq (i)), the difference is carried out on the effective subcarriers of the local P1 frequency domain, 128 difference sequences are totally obtained, the 15D2 correlates the received difference sequences with the 128 difference sequences, the maximum value is compared, and the maximum value corresponding to the correct P1 sequence is completed by 15D 2-15G 2.
FIG. 11 is a flow chart of decoding verification according to the present invention;
as shown in fig. 11, in this embodiment, if the time-frequency domain decoding results are different, the signaling determining module 16 determines which P1 decoding result is more reliable by comparing the two sequences with the received P1 sequence to perform time-domain correlation according to the magnitude of the correlation value. Step 16A, data of about 1K of P1 positioned after fine synchronization is acquired, all frequency offsets are compensated by the data, step 16B, the data after frequency offset compensation is performed with 4KFFT, a P1 sequence corresponding to time-frequency domain decoding is performed with 4KFFT, and a P1 sequence obtained by time domain and frequency domain decoding is performed with 4KFFT respectively; 16C, the result of 16B is conjugate multiplied by the two 4K frequency domain sequences of P1, step 16D performs IFFT on the multiplied 4K sequences to obtain 4K correlation values, which is the same as the calculation process of timing fine synchronization, and both uses FFT and IFFT to implement correlation operations. And step 16E, calculating the amplitude of the correlator, and respectively obtaining a time domain decoding correlation value denoted as peak _ td and a frequency domain decoding correlation value denoted as peak _ fd. Step 16F searches the first three maximum values and positions of the time domain decoding correlation value peak _ td, calculates the sum peak _ td _ sum of the first three maximum values, finds the value of peak _ fd at the positions of the first three maximum values of peak _ td, calculates the sum peak _ fd _ sum of the three values, and step 16G compares the magnitudes of peak _ td _ sum and peak _ fd _ sum, and the magnitudes are large and correspond to correct decoding results.
Fig. 12 is a schematic diagram of a preamble symbol detection and analysis method according to the present invention.
As shown in fig. 12, in the present embodiment, fig. 12 is a schematic flow chart of a P1 symbol rate detection method according to a preferred embodiment of the invention. The method starts step S51 to perform C _ a _ B correlation on the received signal, and then step S52 determines the correlation value, detects whether a peak occurs, estimates the starting position of P1 if the peak is detected, and calculates the decimal deviation estimation according to the angle of the peak. After obtaining the rough starting position and the decimal frequency offset of P1, step S53 selects three different positions for the P1 symbol after the decimal frequency offset compensation to perform step S54 frequency offset estimation and spectrum inversion judgment, records the integral frequency offset and the spectrum inversion mark with the larger peak value of the former two groups, and the S55 fine synchronization module confirms whether the frequency offset value and the spectrum are inverted, and if the peak value of the step S56 fine synchronization meets the condition, the P1 accurate starting position is given, otherwise, the C _ A _ B peak value is redetected. The next step is to perform time-frequency domain decoding in step S57, and step S58 determines whether the decoding results are the same, if the decoding results are the same, the detection of the preamble symbol P1 is finished, and if the decoding results are not the same, the signaling decision is made in step S59, and finally the decoding result is confirmed.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Claims (7)
1. A preamble symbol detection and analysis device, comprising:
the correlator is used for carrying out frequency shift on the received signal by utilizing three-section structural characteristics of the preamble symbol and then carrying out front and back correlation to obtain a correlation value;
a peak detector for searching the peak value of the correlation value to calculate the rough position of the preamble symbol, wherein the phase angle of the peak value correspondingly obtains a decimal frequency multiplication deviation value;
the integral frequency offset and spectrum inversion judging module estimates the integral frequency offset and spectrum inversion characteristics of the subcarrier intervals by utilizing the frequency domain effective subcarrier power boosting characteristic of the preamble symbol;
the time domain timing fine synchronization module is used for synchronizing the data after the frequency offset is removed to obtain the accurate position of the preamble symbol;
a time-frequency domain decoder for decoding the data after the fine synchronization in the time domain and the frequency domain respectively; and
the signaling distinguishing and analyzing module analyzes the signaling, and if the time domain decoding result is different from the frequency domain decoding result, the signaling is distinguished firstly and then the preamble symbol decoding result is confirmed; and if the time domain decoding result is the same as the frequency domain decoding result, obtaining the preamble symbol decoding result.
2. The preamble symbol detection and analysis apparatus of claim 1, wherein the integer-times frequency offset estimation and spectrum inversion decision module comprises:
the frequency domain subcarrier preprocessing unit is used for carrying out amplitude limiting on the frequency domain abnormal subcarriers and removing in-band interference signals; and
and the cyclic correlation unit is used for processing the signal after frequency domain subcarrier preprocessing and the effective subcarrier to obtain an integral multiple frequency offset estimation value by taking frequency spectrum inversion into consideration and using Fourier and inverse Fourier transform to replace correlation operation.
3. The preamble symbol detection and analysis apparatus of claim 2, wherein the integer-times frequency offset estimation and spectrum inversion decision module operates several times, and the starting position of the preamble symbol selected each time is different.
4. The preamble symbol detection and analysis apparatus of claim 1, wherein the time domain timing fine synchronization module determines the integer frequency offset and the precise position of the preamble symbol.
5. The preamble symbol detection and resolution apparatus according to claim 1,
the time-frequency domain decoder respectively decodes time domain decoding and frequency domain decoding, and the time domain decoding is related to all the preamble symbols by utilizing the time domain related characteristic and the cross-correlation characteristic of the preamble symbols so as to realize time domain decoding; and when the frequency domain coding is carried out, the frequency domain coding is realized by using a frequency domain differential correlation mode.
6. The preamble symbol detection and analysis device of claim 1, wherein the signaling discrimination and analysis module is configured to identify different decoding results generated by the time-frequency domain decoder: firstly, the signaling is distinguished, and then the decoding result of the preamble symbol is confirmed.
7. The preamble symbol detection and resolution apparatus according to claim 1,
the signaling discrimination analysis module performs time domain correlation on the preamble symbol obtained by time domain decoding and frequency domain decoding after fine synchronization and a received preamble symbol sequence to obtain two groups of correlation values, searches and sums the correlation values of the first three arranged from large to small in any group of correlation values, records the positions of the correlation values of the first three arranged from large to small, sums the three correlation values at the corresponding positions in the other group of correlation values, and compares the sizes, wherein the decoding result corresponding to the larger value is correct.
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| CN107438042B (en) * | 2016-05-26 | 2020-09-29 | 上海高清数字科技产业有限公司 | Preamble symbol detection and analysis device |
| CN110868237B (en) * | 2019-11-21 | 2021-08-24 | Oppo广东移动通信有限公司 | Signal synchronization method and device and computer storage medium |
| CN111083080B (en) * | 2019-12-26 | 2022-12-30 | 北京华力创通科技股份有限公司 | Method and device for synchronizing PRACH (physical random Access channel) of broadband satellite communication system |
| CN113746577A (en) * | 2021-08-10 | 2021-12-03 | 青岛鼎信通讯股份有限公司 | Subcarrier signal-to-noise ratio estimation method of OFDM power line communication system |
| CN114070686B (en) * | 2021-11-11 | 2023-10-03 | 成都中科微信息技术研究院有限公司 | Large frequency offset resistant solving method based on 5G random access preamble long sequence |
| CN113904904B (en) * | 2021-11-12 | 2023-09-15 | 北京信息科技大学 | Integer frequency offset estimation method, system, medium and equipment based on OFDM |
| CN115001928B (en) * | 2022-08-01 | 2022-10-25 | 北京智芯半导体科技有限公司 | Frame detection method, automatic gain control locking method, system and chip thereof |
| CN117222041B (en) * | 2023-11-09 | 2024-03-15 | 深圳国人无线通信有限公司 | Method and device for detecting PRACH signal preamble correlation peak in 5G small cell system |
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