CN109743277B - Quick access searching method and quick access searching device for OFDM system - Google Patents
Quick access searching method and quick access searching device for OFDM system Download PDFInfo
- Publication number
- CN109743277B CN109743277B CN201811434319.XA CN201811434319A CN109743277B CN 109743277 B CN109743277 B CN 109743277B CN 201811434319 A CN201811434319 A CN 201811434319A CN 109743277 B CN109743277 B CN 109743277B
- Authority
- CN
- China
- Prior art keywords
- frequency offset
- speed
- calculation
- signal
- access point
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Abstract
The invention relates to a quick access searching method and a quick access searching device of an OFDM system, wherein the method comprises the following steps: collecting OFDM signals, extracting low-speed OFDM signals, and reserving high-speed OFDM signals; carrying out autocorrelation calculation on the low-speed OFDM signal to obtain an OFDM system access point fuzzy interval; carrying out frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval; and carrying out accurate synchronous calculation on the high-speed OFDM signal after the frequency offset calibration and the local synchronous signal to obtain an OFDM system access point. The method utilizes the self-correlation of the low-speed OFDM signal to carry out coarse synchronization to obtain an access point fuzzy interval, then carries out frequency offset calculation and correction on the high-speed OFDM signal in the access point fuzzy interval, and finally utilizes the cross-correlation of the high-speed OFDM signal and a local synchronous signal to obtain an accurate access point, thereby solving the problems of quick cell search and user access of a special network.
Description
Technical Field
The invention relates to the technical field of cell search and terminal access, in particular to a quick access search method and a quick access search device for an OFDM (orthogonal frequency division multiplexing) system.
Background
The cell search/terminal access network is an important physical layer process, is not an independent algorithm, but is formed by a group of related key algorithms, such as time synchronization, frequency offset estimation and other cell search process designs.
Physical resources available for cell search in existing LTE-TDD (Long Term Evolution-Time Division duplex) include downlink synchronization channels SCH such as P-SCH (Primary synchronization Channel) and S-SCH (Secondary synchronization Channel), common reference signals and broadcast channels. The relevant information needed to be obtained in the cell search process is: and detecting the timing of the symbol.
The UE cell search process is completed through each functional module of a cell search channel, and the cell search channel has 5 functional modules:
a low-pass filtering module: signals except the center frequency of the center 1.08MHz are filtered out, and signals of the center frequency are reserved.
A down-sampling module: and obtaining a time domain signal corresponding to the filtered center frequency.
PSS (Primary synchronization Signal) detection module: complete timing detection (Symbol timing), frequency synchronization, cell group number
And (6) detecting.
An SSS (Secondary synchronization Signal) Signal detection module: cell group number
Detection, Frame timing (Frame timing).
PBCH (Physical Broadcast Channel) signal detection module: for system information: system bandwidth, cell configuration (number of cells supported on a base station), and acquisition of antenna configuration information.
The detection method of the synchronous head comprises 3 methods:
cross-correlation (cross-correlation) method: and performing cross-correlation calculation on the received signal and the predicted preamble signal P-SCH, wherein the position of the maximum correlation value is the timing of the synchronization head.
Auto-correlation (auto-correlation) method: since the synchronization symbol P-SCH has a central symmetry or repeated structural feature in the time domain, after receiving a signal, the self-correlation calculation is performed according to the time domain structural feature, and then the corresponding timing information can be obtained.
The mixing method comprises the following steps: the approximate position of a P-SCH symbol is obtained through an autocorrelation algorithm, and then cross-correlation search calculation is carried out in a smaller range by using a predicted P-SCH signal, so that accurate P-SCH timing information can be obtained.
The existing cell search algorithm has complex flow and is not suitable for cell search and user access of a private network.
Therefore, a fast access searching method and a fast access searching device for an OFDM system are provided.
Disclosure of Invention
In view of the above problems, the present invention is proposed to provide a fast access search method and a fast access search apparatus for an OFDM system, which overcome the above problems or at least partially solve the above problems, have a simple flow, and solve the problems of fast cell search and user access for a private network.
According to an aspect of the present invention, a fast access search method for an OFDM system is provided, including:
collecting OFDM signals, extracting low-speed OFDM signals, and reserving high-speed OFDM signals;
carrying out autocorrelation calculation on the low-speed OFDM signal to obtain an OFDM system access point fuzzy interval;
carrying out frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval;
and carrying out accurate synchronous calculation on the high-speed OFDM signal after the frequency offset calibration and the local synchronous signal to obtain an OFDM system access point.
Further, the low-speed OFDM signal is configured such that two adjacent symbols have the same value or a zero value is interpolated in a symbol frequency domain such that two adjacent segments of the sequence have the same waveform in the time domain.
Further, the autocorrelation calculation is performed on the low-speed OFDM signal by the following formula:
wherein, cnIs the autocorrelation value, L is the number of sampling points, NdIs the window length, n is the number of FFT conversion points, rn+kIs the receive sequence.
Further, before performing frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point ambiguity interval, the method further includes: and removing the synchronization head fuzzy area in the access point fuzzy interval.
Further, performing frequency offset calculation on the high-speed OFDM signal in the access point fuzzy interval by using the following formula:
wherein, Δ fcoarseIs frequency offset, L is the number of sampling points, TSIs a sampling period, fsTo be the rate of sampling,
Δ f is r1(k) And r2(k) Are spaced apart from each other.
Further, the high-speed OFDM signal after frequency offset calibration and the local synchronization signal are subjected to accurate synchronization calculation through the following formula:
the sampling method includes the steps of sampling a high-speed OFDM signal, wherein sum _ sample (k) is a cross-correlation value, S (N) is a local synchronous signal, r (N × OSR + k) is the high-speed OFDM signal after frequency offset calibration, k is a sampling sequence number, N is a sampling point, csp is an autocorrelation peak value, OSR is a down-sampling multiple, and Delay is an autocorrelation fuzzy interval value.
According to another aspect of the present invention, there is provided an OFDM system fast access searching apparatus for implementing the above method, including:
the OFDM signal filtering module is used for collecting OFDM signals, extracting low-speed OFDM signals and reserving high-speed OFDM signals;
the self-correlation calculation module is used for carrying out self-correlation calculation on the low-speed OFDM signal so as to obtain an OFDM system access point fuzzy interval;
the frequency offset calculation and calibration module is used for performing frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval;
and the precise synchronization calculation module is used for performing precise synchronization calculation on the high-speed OFDM signal after the frequency offset calibration and the local synchronization signal so as to obtain the access point of the OFDM system.
Further, in the OFDM signal filtering module, the low-speed OFDM signal is configured such that two adjacent symbols have the same value or a zero value is interpolated in a symbol frequency domain such that two adjacent segments of the sequence have the same waveform in the time domain.
Further, in the autocorrelation calculating module, autocorrelation calculation is performed on the low-speed OFDM signal by the following formula:
wherein, cnIs the autocorrelation value, L is the number of sampling points, NdIs the window length, n is the number of FFT conversion points, rn+kIs the receive sequence.
Further, the fast access search apparatus for the OFDM system further includes: and the synchronization head fuzzy area removing module is used for removing the synchronization head fuzzy area in the access point fuzzy interval.
Compared with the prior art, the invention has the following advantages:
the OFDM system fast access searching method and the fast access searching device of the invention use the autocorrelation of the low-speed OFDM signal to carry out the coarse synchronization to obtain the fuzzy interval of the access point, then carry out the frequency offset calculation and the correction to the high-speed OFDM signal in the fuzzy interval of the access point, finally use the cross correlation of the high-speed OFDM signal and the local synchronous signal to obtain the accurate access point, complete the fast access of the OFDM system, so as to use the fuzzy interval of the access point to quickly complete the frequency offset measurement and the search of the accurate synchronous head, and can solve the problems of the fast cell search and the user access of the special network.
Drawings
The invention is further illustrated by the following figures and examples.
FIG. 1 is a diagram of steps of a fast access search method for an OFDM system according to the present invention;
FIG. 2 is a complete flow of the fast access of the OFDM system of the present invention;
FIG. 3 is a schematic diagram of the present invention using two OFDM symbols to communicate a synchronization header;
FIG. 4 is a diagram of the present invention using one OFDM symbol to transmit the synchronization header;
FIG. 5 is a schematic frequency domain zero insertion of the present invention;
FIG. 6 is a schematic diagram of the inversion of the pilot sequence spectrum of the present invention;
FIG. 7 is a simulation diagram of the original configuration of the present invention prior to spectrum inversion;
FIG. 8 is a simulation of the original configuration after the spectrum inversion of the present invention;
FIG. 9 is a flow chart of an autocorrelation method of the present invention;
FIG. 10 shows the same time domain patterns of the previous and following segments after receiving the P-SCH signal;
fig. 11 is a diagram illustrating the coarse correlation peak power point when the SNR is 0 in the autocorrelation calculation of the present invention;
FIG. 12 is a schematic diagram of the present invention of performing frequency offset measurement after removing phase ambiguity after coarse synchronization;
fig. 13 is a schematic diagram of the fine correlation peak power point when the SNR is 0 for the fine synchronization calculation;
fig. 14 is a block diagram of a fast access searcher for an OFDM system according to the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Fig. 1 is a step diagram of a fast access search method for an OFDM system according to the present invention, and referring to fig. 1, the fast access search method for an OFDM system according to the present invention includes:
collecting OFDM signals, extracting low-speed OFDM signals, and reserving high-speed OFDM signals;
carrying out autocorrelation calculation on the low-speed OFDM signal to obtain an OFDM system access point fuzzy interval;
carrying out frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval;
and carrying out accurate synchronous calculation on the high-speed OFDM signal after the frequency offset calibration and the local synchronous signal to obtain an OFDM system access point.
The fast access searching method of the OFDM system utilizes the autocorrelation of low-speed OFDM signals to carry out coarse synchronization to obtain an access point fuzzy interval, then carries out frequency offset calculation and correction on high-speed OFDM signals in the access point fuzzy interval, and finally utilizes the cross correlation of the high-speed OFDM signals and local synchronous signals to obtain an accurate access point, thereby completing the fast access of the OFDM system, rapidly completing the frequency offset measurement and the search of an accurate synchronous head by utilizing the access point fuzzy interval, and solving the problems of the fast cell search and the user access of a special network.
As shown in fig. 2, the complete flow of the fast access of the OFDM system is as follows:
after the ADC collects signals, the ADC performs low-pass filtering to filter out stray signals. Then, OSR times are carried out to extract the physical layer speed phy _ samples, the low-speed signals are carried out with differential correlation (autocorrelation) to find coarse synchronization, and then the fuzzy zone is taken out to measure the frequency deviation. Then corresponding to the high-speed signal which is not extracted, accurate synchronous correlation is carried out in the fuzzy area, and an accurate synchronous point is found. Of course, the frequency offset is first corrected before fine synchronization.
Specifically, after receiving the high-speed ADC output signal hs _ phy, first filtering out the bandwidth spurious signal through digital filtering, dividing the signal into 2 branches, and extracting one branch OSR times as the baseband signal bs _ phy to perform coarse correlation. The other branch is directly output to the precise synchronous signal without extraction. And according to the extracted signals, the signals with the same waveform in the time domain of the front section and the rear section are obtained by utilizing a method that the numerical values of the front symbol and the rear symbol are the same or a zero value is interpolated in the frequency domain by one symbol, so as to carry out coarse synchronization. After the coarse sync header acquisition, the sync header ambiguity region is removed, i.e., coarse sync correlation of FFTSIZE point starts after MAXpos + DELAY. And removing DELAY in front of the synchronization head, and removing DELAY points at the tail, namely, pinching the head and removing the tail to leave the middle FFTSIZE point for frequency offset measurement, namely, using the pilot clear zone for frequency offset measurement. Firstly, frequency offset calibration is carried out on hs _ phy, and an accurate synchronization point is searched in a MAXpos + [ -DELAY: DELAY ] fuzzy area.
Further, the low-speed OFDM signal is configured such that two adjacent symbols have the same value or a zero value is interpolated in a symbol frequency domain such that two adjacent segments of the sequence have the same waveform in the time domain.
Specifically, two designs of synchronization heads are provided according to the number of subcarriers and the subcarrier spacing or the symbol spacing included in an OFDM symbol:
the first scheme is as follows: if one OFDM symbol contains a small number of subcarriers or the subcarrier spacing is large (32KHZ), two OFDM symbols are used to deliver the synchronization header, as shown in fig. 3. Referring to fig. 3, the same synchronization sequence delivered on two OFDM symbols, i.e. the two symbols deliver the same original synchronization code corresponding to the sub-carriers in the frequency domain: such as communicating ZC sequences.
Scheme II: if one OFDM symbol contains a large number of subcarriers or the OFDM subcarriers have a small interval therebetween (e.g., 8KHZ), 1 OFDM symbol is used to deliver the synchronization header, as shown in fig. 4. Referring to fig. 4, if the use of two symbols to convey the synchronization code is too resource-consuming, a frequency-domain zero-insertion method can be used in the frequency domain on the same symbol. The frequency domain zero insertion method is shown in fig. 5: for example, N2048 point FFT, one ZC sequence is placed starting at 385 and one subcarrier is placed at 1663. 1 subcarrier is isolated on a frequency domain to place a ZC sequence, so that a time domain waveform presents symmetry.
Referring to fig. 6, after the pilot sequence is placed, spectrum shifting, i.e., spectrum inversion, is performed. For example, if N is 2048, the middle point is 1024, and the points start from 1025 to 2048 and are placed to the leftmost end. Points 1 and 1024 are placed to the rightmost end. The most obvious sign is that if 1024 points are DC (direct current), the right end is placed after transposition.
p＝floor(N/2)；
idx＝[p+1:N，1:p]；
Referring to fig. 7 and 8, it is further verified that when N2048, the middle point is 1024, and from 1025 to 2048, it is placed to the leftmost end. Points 1 and 1024 are placed to the rightmost end.
The self-correlation calculation is carried out on the low-speed OFDM signal to obtain an OFDM system access point fuzzy interval, and the method is specifically realized as follows:
as shown in fig. 9, autocorrelation (differential correlation) utilizes a delay NdTwo identical training symbols of each sample value are then subjected to conjugate correlation, and the detection of the position of the synchronous head is judged according to the power value of the conjugate correlation.
Specifically, rnFor receiving sequences, the differential correlation is different from the direct correlation method, and the differential correlation operation is performed by using the received sequence rnThe symmetric characteristic of the PSS sequence in (1), i.e. forming a repeated signal in the time domain, as shown in FIG. 10, therefore r is setnAnd
dot-multiply and count the window length N for each NdThe data in each window are summed, the statistical window is shifted according to sampling points one by one, which is equivalent to sliding on the conjugate multiplication sequence, so that the next data in the current statistical window is added with the next data in the same direction, and the difference correlation value of the next statistical window can be conveniently obtained by subtracting the first data in the current statistical window, and the corresponding difference correlation value c (n) is obtained. In the method, a differential correlation function c (n) is only related to the position of a P-SCH sequence in a received sequence, and the maximum value of c (n) is found, so that the optimal timing moment is found.
The autocorrelation calculation is performed on the low-speed OFDM signal by the following formula:
wherein, cnIs the autocorrelation value, L is the number of sampling points, NdIs the window length, n is the number of FFT conversion points, rn+kIs the receive sequence. A decision variable of cnThe time when the maximum value is reached is the optimum timing time.
And (3) analyzing the computational complexity:
(1) receiving data of 9600 sampling points (after down sampling) and 64 sampling points in a half frame (5ms) time; n-1 … N +64
(2) Receive data r (N) and its displacement (r (N + N)d) And carrying out conjugate multiplication on the received data to obtain a differential correlation sequence.
rx_coru(n)＝r(n)conj(r(n+Nd)
(3) Calculating the statistical window length NdAverage of inner differential sequences.
When k is equal to 0, the first step is,
and rx _ cor _ pu(k)＝rx_cor_pu(k)+rx_coru(k-1)+rx_coru(k+64)
In order to overcome the influence of noise, the data of a plurality of subframes can be averaged, so that better detection performance can be obtained.
The decision of the correlation peak of the autocorrelation (differential correlation) is not limited by the frequency offset, which has no effect on the differential correlation. The peak value swings left and right only largely affected by noise, because the statistical window of the differential correlation shifts from one sampling point to another, which is equivalent to sliding on the upper conjugate multiplication sequence, each time only differs by one statistical difference, as can be seen from the lower graph, the peak value of the differential correlation rises slowly, and the peak value is in a jitter state when rising to the top.
Referring to fig. 11, although the maximum correlation peak point can be obtained by coarse correlation, the peak point CSP is not very accurate and has a certain fuzzy interval CSP-DELAY to CSP + DELAY.
Further, before performing frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point ambiguity interval, the method further includes: and removing the synchronization head fuzzy area in the access point fuzzy interval.
After the coarse synchronization measurement is completed, although an accurate synchronization start point cannot be determined, the measurement of the frequency offset may be started. The method for measuring the frequency deviation is to remove the fuzzy interval and measure the frequency deviation in the definite interval of the synchronous head. As shown in fig. 12, after maxPOS is found in the coarse synchronization, there are fuzzy zones in DELAY intervals on the left and right. Therefore, the signal interval of the first segment is the interval of MAXpos + DELAY: MAXpos + DELAY + fftsize-1. MAXPos + MAX _ DELAY + SP _ Len MAXPos + MAX _ DELAY + fftsize-1+ SP _ Len as the signal interval of the second segment, the signal length of both segments being fftsize, then the magnitude of the frequency offset is obtained by the phase difference of the two segments.
The frequency offset measurement may be by
r1＝phy_rcv_signal(MAXpos+DELAY:MAXpos+DELAY+fftsize-1)；
r2＝phy_rcv_signal(MAXpos+MAX_DELAY+SP_Len:MAXpos+MAX_DELAY+fftsize-1+SP_Len)；
freq_corr＝angle(sum(r1.*conj(r2)))./(2*pi*Tb*SP_Len)；
Where Tb is the symbol period.
Because the interval of the time domain correlation peak is only SLEN/2, the principle of conjugate multiplication of the correlation peaks is as follows, and only delta f is unknown in the following formula, so the frequency offset can be calculated by the following formula.
According to the same original data of the front and the back sections, the receiving end calculates the frequency offset by using conjugate multiplication of the front and the back sections
r2(k)＝exp(j2π·Δf·L·Ts)·r1(k)
Wherein, Δ fcoarseIs frequency offset, L is the number of sampling points, TSIs a sampling period, fsTo be the rate of sampling,
Δ f is r1(k) And r2(k) Interval between, corresponding to sampling rate
And after the frequency offset is calculated, carrying out frequency offset calibration on the high-speed signal. And after the frequency offset calibration is completed, the high-speed signal is accurately synchronized.
For example fs-32 Mhz, pi in the L-2048 denominator may be related to the unit in the numerator
And (6) offsetting. f. ofoffsetHas a theoretical value range of [ -3750, 3750 [ -3750 [)]Hz，
Such a frequency offset range is sufficient for a general drone system.
After the timing initial synchronization and the carrier synchronization are completed, since the correction of the frequency offset is completed, and the residual frequency offset cannot affect the signal correlation, the precise timing synchronization can be directly performed at this time to achieve the CHIP accuracy requirement of 1/D (e.g., 1/4).
And performing accurate synchronous calculation on the high-speed OFDM signal and the local synchronous signal after frequency offset calibration by the following formula:
the sampling method includes the steps of sampling a high-speed OFDM signal, wherein sum _ sample (k) is a cross-correlation value, S (N) is a local synchronous signal, r (N × OSR + k) is the high-speed OFDM signal after frequency offset calibration, k is a sampling sequence number, N is a sampling point, csp is an autocorrelation peak value, OSR is a down-sampling multiple, and Delay is an autocorrelation fuzzy interval value.
Only 2 × Delay points around the initial correlation peak need to be searched for the correlation peak point, and the distribution of the correlation peaks is generally shown in fig. 13.
And completing the measurement and correction of frequency offset, and completing the user access process after accurate synchronization.
For simplicity of explanation, the method embodiments are described as a series of acts or combinations, but those skilled in the art will appreciate that the embodiments are not limited by the order of acts described, as some steps may occur in other orders or concurrently with other steps in accordance with the embodiments of the invention. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred and that no particular act is required to implement the invention.
Fig. 2 is a block diagram of an OFDM system fast access search apparatus according to the present invention, and referring to fig. 2, the OFDM system fast access search apparatus according to the present invention includes:
the OFDM signal filtering module is used for collecting OFDM signals, extracting low-speed OFDM signals and reserving high-speed OFDM signals;
the self-correlation calculation module is used for carrying out self-correlation calculation on the low-speed OFDM signal so as to obtain an OFDM system access point fuzzy interval;
the frequency offset calculation and calibration module is used for performing frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval;
and the precise synchronization calculation module is used for performing precise synchronization calculation on the high-speed OFDM signal after the frequency offset calibration and the local synchronization signal so as to obtain the access point of the OFDM system.
The fast access searching device of the OFDM system utilizes the autocorrelation of low-speed OFDM signals to carry out coarse synchronization to obtain an access point fuzzy interval, then carries out frequency offset calculation and correction on high-speed OFDM signals in the access point fuzzy interval, and finally utilizes the cross correlation of the high-speed OFDM signals and local synchronous signals to obtain an accurate access point, thereby completing the fast access of the OFDM system, rapidly completing the frequency offset measurement and the search of an accurate synchronous head by utilizing the access point fuzzy interval, and solving the problems of fast cell search and user access of a special network.
Further, in the OFDM signal filtering module, the low-speed OFDM signal is configured such that two adjacent symbols have the same value or a zero value is interpolated in a symbol frequency domain such that two adjacent segments of the sequence have the same waveform in the time domain.
Further, in the autocorrelation calculating module, autocorrelation calculation is performed on the low-speed OFDM signal by the following formula:
wherein, cnIs the autocorrelation value, L is the number of sampling points, NdIs the window length, n is the number of FFT conversion points, rn+kIs the receive sequence.
Further, the fast access search apparatus for the OFDM system further includes: and the synchronization head fuzzy area removing module is used for removing the synchronization head fuzzy area in the access point fuzzy interval.
For the system embodiment, since it is basically similar to the method embodiment, the description is simple, and for the relevant points, refer to the partial description of the method embodiment.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (5)
1. A fast access searching method of an OFDM system is characterized by comprising the following steps:
collecting OFDM signals, extracting low-speed OFDM signals, and reserving high-speed OFDM signals;
carrying out autocorrelation calculation on the low-speed OFDM signal to obtain an OFDM system access point fuzzy interval;
carrying out frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval;
carrying out accurate synchronous calculation on the high-speed OFDM signal after frequency offset calibration and a local synchronous signal to obtain an OFDM system access point;
the low-speed OFDM signal is configured to have the same value of two adjacent symbols or interpolate a zero value in a symbol frequency domain to ensure that the waveforms of two adjacent sequences are the same in the time domain;
the autocorrelation calculation is performed on the low-speed OFDM signal by the following formula:
wherein, cnIs the autocorrelation value, L is the number of sampling points, NdIs the window length, n is the number of FFT conversion points, rn+kIs a received sequence;
before performing frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval, the method further comprises the following steps: removing a synchronous head fuzzy area in the access point fuzzy interval;
performing frequency offset calculation on the high-speed OFDM signal in the access point fuzzy interval by using the following formula:
wherein, Δ fcoarseIs frequency offset, L is the number of sampling points, TSIs a sampling period, fsTo be the rate of sampling,
Δ f is r1(k) And r2(k) The interval between them;
and performing accurate synchronous calculation on the high-speed OFDM signal and the local synchronous signal after frequency offset calibration by the following formula:
the sampling method includes the steps of sampling a high-speed OFDM signal, wherein sum _ sample (k) is a cross-correlation value, S (N) is a local synchronous signal, r (N × OSR + k) is the high-speed OFDM signal after frequency offset calibration, k is a sampling sequence number, N is a sampling point, csp is an autocorrelation peak value, OSR is a down-sampling multiple, and Delay is an autocorrelation fuzzy interval value.
2. An OFDM system fast access searching apparatus for implementing the method of claim 1, comprising:
the OFDM signal filtering module is used for collecting OFDM signals, extracting low-speed OFDM signals and reserving high-speed OFDM signals;
the self-correlation calculation module is used for carrying out self-correlation calculation on the low-speed OFDM signal so as to obtain an OFDM system access point fuzzy interval;
the frequency offset calculation and calibration module is used for performing frequency offset calculation and frequency offset calibration on the high-speed OFDM signal in the access point fuzzy interval;
and the precise synchronization calculation module is used for performing precise synchronization calculation on the high-speed OFDM signal after the frequency offset calibration and the local synchronization signal so as to obtain the access point of the OFDM system.
3. The OFDM system quick access searching apparatus as claimed in claim 2, wherein in the OFDM signal filtering module, the low-speed OFDM signal is configured such that two adjacent symbols have the same value or a zero value is interpolated in a frequency domain of one symbol so that two adjacent sequences have the same waveform in a time domain.
4. The fast access searcher of claim 3, wherein in the autocorrelation calculating module, the autocorrelation calculation is performed on the low-speed OFDM signal by the following formula:
wherein, cnIs the autocorrelation value, L is the number of sampling points, NdIs the window length, n is the number of FFT conversion points, rn+kIs the receive sequence.
5. The fast access searcher of claim 4, further comprising: and the synchronization head fuzzy area removing module is used for removing the synchronization head fuzzy area in the access point fuzzy interval.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811434319.XA CN109743277B (en) | 2018-11-28 | 2018-11-28 | Quick access searching method and quick access searching device for OFDM system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811434319.XA CN109743277B (en) | 2018-11-28 | 2018-11-28 | Quick access searching method and quick access searching device for OFDM system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109743277A CN109743277A (en) | 2019-05-10 |
| CN109743277B true CN109743277B (en) | 2021-12-10 |
Family
ID=66358189
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811434319.XA Active CN109743277B (en) | 2018-11-28 | 2018-11-28 | Quick access searching method and quick access searching device for OFDM system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109743277B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110139145B (en) * | 2019-05-13 | 2021-06-22 | 周波 | Small unmanned aerial vehicle graph transmission signal analysis and demodulation method |
| CN111130683B (en) * | 2019-12-26 | 2021-09-14 | 江苏科大亨芯半导体技术有限公司 | Method for searching same-frequency adjacent cells of narrow-band Internet of things |
| CN111490955B (en) * | 2020-03-10 | 2023-05-05 | 西安宇飞电子技术有限公司 | Method and device for realizing synchronous head search under large frequency offset |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4786503B2 (en) * | 2006-11-01 | 2011-10-05 | 株式会社エヌ・ティ・ティ・ドコモ | Cell search method, mobile station and base station |
| CN101325450B (en) * | 2008-07-28 | 2012-10-03 | 北京天碁科技有限公司 | Synchronizing process, frequency deviation estimation method, synchronizing apparatus, frequency deviation estimation apparatus |
| CN101753505B (en) * | 2008-12-22 | 2012-09-05 | 北京信威通信技术股份有限公司 | Method for synchronizing downlink time and frequency of OFDM system |
| CN101945071A (en) * | 2009-07-10 | 2011-01-12 | 中兴通讯股份有限公司 | Confirming method of synchronization sequence in multipoint collaborative environment, synchronizing method and device |
| CN101741800B (en) * | 2009-10-14 | 2014-07-09 | 苏州恩巨网络有限公司 | Synchronous searching method |
| CN101719889B (en) * | 2009-11-25 | 2012-07-11 | 意法·爱立信半导体（北京）有限公司 | Method and device for detecting main synchronizing signal |
| CN102457870B (en) * | 2010-10-21 | 2015-04-15 | 电信科学技术研究院 | Method and device for detecting primary synchronization signal and method and system for searching neighborhoods |
| US20160100373A1 (en) * | 2014-10-07 | 2016-04-07 | Mediatek Inc. | Signal Format for Cell Search and Synchronization in Wireless Networks |
| US10200169B2 (en) * | 2016-03-11 | 2019-02-05 | Qualcomm Incorporated | Narrowband wireless communications cell search |
| CN106376057A (en) * | 2016-11-28 | 2017-02-01 | 北京小米移动软件有限公司 | Wireless network access method and device |
| CN107623650A (en) * | 2017-07-17 | 2018-01-23 | 西安宇飞电子技术有限公司 | For the measuring method of ofdm system frequency deviation under high velocity environment and purposes, measurement apparatus |
| CN108123774B (en) * | 2017-12-27 | 2019-10-25 | 中山大学花都产业科技研究院 | A kind of narrowband Internet of Things down link synchronisation method and its system |
| CN108494518B (en) * | 2018-03-26 | 2019-11-08 | 重庆邮电大学 | A kind of LTE system small region search method |
-
2018
- 2018-11-28 CN CN201811434319.XA patent/CN109743277B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN109743277A (en) | 2019-05-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101656700B (en) | Method and device for detecting cyclic prefix type during initial cell search in long-term evolution system | |
| CN102413079B (en) | Initial fraction frequency offset estimation method used in downlink of 3 generation partnership project long term evolution (3GPP-LTE) system | |
| CN109743277B (en) | Quick access searching method and quick access searching device for OFDM system | |
| CN101325450B (en) | Synchronizing process, frequency deviation estimation method, synchronizing apparatus, frequency deviation estimation apparatus | |
| CN111107033B (en) | Downlink frame timing synchronization method for 5G system | |
| CN102065048B (en) | Time-domain joint estimation method for synchronizing frames, frequencies and fine symbols for orthogonal frequency division multiplexing (OFDM) | |
| JP4159030B2 (en) | Timing synchronization method for wireless networks using OFDM | |
| US7027429B2 (en) | Method and apparatus for time and frequency synchronization of OFDM communication systems | |
| TWI271048B (en) | Cell search method for orthogonal frequency division multiplexing based cellular communication system | |
| CN102130883B (en) | Time frequency synchronization method for time division long-term evolution (TD-LTE) system | |
| CN102025671B (en) | Time domain combined estimate method for time coarse synchronization and frequency precise synchronization | |
| CN101394391B (en) | OFDM synchronization method based on four dimensional chaos system | |
| CN1917491B (en) | OFDM synchronization method of using training circulated prefix | |
| CN111132272A (en) | Cell search timing synchronization method for 5G NR system | |
| CN105516045B (en) | A kind of OFDM training sequence structures and synchronous method | |
| CN102461102A (en) | Process for estimating the channel from the pss signal in a lte communication network, and receiver for the same | |
| CN101277290A (en) | Method and apparatus for synchronization of orthogonal frequency division multiplexing system frequency | |
| KR20070073593A (en) | Method for generating downlink signal, and method for searching cell | |
| KR100519919B1 (en) | Method for making transmission frame and apparatus and method for user equipment synchronization in ofdma system thereof | |
| Wung et al. | A robust scheme in downlink synchronization and initial cell search for 3GPP LTE system | |
| CN100559785C (en) | A kind of receiving symbolic synchronous method that is used for the WiMAX system | |
| CN112714448B (en) | Method for detecting master synchronizing signal in dynamic spectrum sharing | |
| CN105007095B (en) | Integer frequency offset estimation method and device during a kind of cell initial search | |
| CN101741800B (en) | Synchronous searching method | |
| CN101667990A (en) | OFDM frequency offset joint estimation method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |