CN110708265B - Frequency offset estimation system and method - Google Patents
Frequency offset estimation system and method Download PDFInfo
- Publication number
- CN110708265B CN110708265B CN201810743424.5A CN201810743424A CN110708265B CN 110708265 B CN110708265 B CN 110708265B CN 201810743424 A CN201810743424 A CN 201810743424A CN 110708265 B CN110708265 B CN 110708265B
- Authority
- CN
- China
- Prior art keywords
- frequency offset
- carrier
- point
- value
- calculating
- 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
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/2659—Coarse or integer frequency offset determination and synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/266—Fine or fractional frequency offset determination and synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
- H04L2027/0028—Correction of carrier offset at passband only
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Monitoring And Testing Of Transmission In General (AREA)
Abstract
The invention discloses a frequency offset estimation system and a method, which are used for calculating a frequency offset value of a carrier, wherein the carrier consists of a plurality of subcarriers, the frequency offset estimation system comprises an operation module, a point coordinate module and a parabola fitting module, the operation module is used for selecting different offsets in a range in which the frequency offset value possibly exists, calculating an autocorrelation function value corresponding to each offset selected in the same subcarrier, the point coordinate module forms different points in a two-dimensional coordinate system according to each offset and the autocorrelation function value corresponding to each offset, and the parabola fitting module is used for selecting a point with the autocorrelation function value as the maximum value and two points adjacent to the point from the two-dimensional coordinate system to perform parabola fitting to calculate the frequency offset value of the carrier. By adopting the technical scheme of the invention, the frequency offset estimation searching precision is improved.
Description
Technical Field
The present invention relates to a signal synchronization system and method for an OFDM receiver in the field of communications technologies, and more particularly, to a frequency offset estimation system and method.
Background
For a communication system, there are many factors that cause frequency difference between a transmitting end and a receiving end, such as a shift between a carrier frequency and a frequency of a local crystal oscillator, a doppler shift caused by movement of the receiving end, and the like. The frequency offset effect from these factors may be referred to as "frequency offset" for short. E.g. transmitting end carrier frequency fcThen the correct carrier frequency at the receiving end should also be fc. But due to the presence of the above-mentioned factors, receiveThe carrier frequency actually received by the terminal is
While
I.e., the frequency offset. For an actual communication system, a receiver needs to be able to correctly estimate a current frequency offset and compensate the frequency offset, so that the system can maintain a good working state.
At present, a general frequency offset estimation system and method performs correlation calculation by using pilot information in a signal, sets a suitable search range to find an offset value that maximizes a correlation (i.e., a similarity), and the offset value represents a current frequency offset value. However, since the set search precision is generally a single carrier size, a finer frequency offset cannot be reflected. Such an inaccurate frequency offset estimation may affect the compensation and stability of the subsequent communication system.
Disclosure of Invention
The invention provides a frequency offset estimation system and a frequency offset estimation method, so that the problem of low frequency offset estimation search precision is solved.
In accordance with the above object, a frequency offset estimation system according to the present invention is a frequency offset estimation system for calculating a frequency offset value of a carrier composed of a plurality of subcarriers, the frequency offset estimation system comprising:
the frequency offset estimation system comprises an operation module, a point coordinate module and a parabola fitting module;
the operation module is used for selecting different offsets in the range where the frequency offset value possibly exists, and calculating the corresponding autocorrelation function value when each offset is selected in the same subcarrier;
the point coordinate module forms different points in a two-dimensional coordinate system according to each offset and the corresponding autocorrelation function value when each offset is selected;
and the parabolic fitting module is used for selecting a point with the maximum correlation function value from the two-dimensional coordinate system and two points adjacent to the point to perform parabolic fitting, and calculating the frequency offset value of the carrier.
Optionally, the subcarrier consists of OFDM symbols, and the method for calculating the autocorrelation function value by the operation module is as follows: and (4) carrying out conjugate multiplication on every two frequency domain data of all adjacent OFDM symbols in the correlation length in the subcarrier to calculate the square sum.
Optionally, the selection of the correlation length is based on the transmission flow of the carrier.
Optionally, the abscissa of each point in the two-dimensional coordinate system is the selected offset, and the ordinate is the autocorrelation function value corresponding to each offset selected.
Optionally, the parabola equation fitted by the parabola fitting module is y ═ ax2A form of + bx + c, where x is the abscissa and y is the ordinate.
Optionally, the parabola fitting module calculates a coordinate of a vertex of the parabola in the two-dimensional coordinate system, and an offset corresponding to an abscissa of the vertex is a frequency offset value of the carrier.
In accordance with the above object, a frequency offset estimation method of the present invention is implemented for calculating a frequency offset value of a carrier, where the carrier is composed of a plurality of subcarriers, and the method comprises the following steps:
step S1: selecting different offsets from the range in which the frequency offset value may exist, selecting the same subcarrier, and calculating the autocorrelation function value corresponding to the same subcarrier when each offset is selected;
step S2: forming a plurality of points in a two-dimensional coordinate system, wherein the abscissa of each point is the selected offset, and the ordinate is the autocorrelation function value corresponding to the same subcarrier when each offset is selected;
step S3: selecting a point with the autocorrelation function value as the maximum value and two points which are adjacent to the point left and right;
step S4: and performing parabolic fitting on the selected three points in a two-dimensional coordinate system, and calculating the frequency offset value of the carrier.
Optionally, in step S1, there is a gap between the subcarriers, and the offset is selected as an integer multiple of the gap between adjacent subcarriers.
Optionally, in step S1, the subcarrier consists of OFDM symbols, and the method for calculating the autocorrelation function value of the subcarrier includes: and (4) carrying out conjugate multiplication on frequency domain data of adjacent OFDM symbols in the correlation length in the subcarrier to calculate the square sum.
Optionally, the selection of the correlation length is based on the transmission flow of the carrier.
Optionally, the parabola equation of the three-point parabola fitting is y ═ ax2A form of + bx + c, wherein x is the abscissa and y is the ordinate.
Optionally, the step S4 further includes the following steps:
step S41, performing parabolic fitting on the three selected points in a two-dimensional coordinate system;
step S42, finding out the vertex of the parabola formed by fitting;
step S43, calculating an abscissa of the vertex, where an offset corresponding to the abscissa of the vertex is a frequency offset value of the carrier.
By adopting the technical scheme of the invention, aiming at the defects of the prior art, a module/method for performing three-point parabolic fitting is added on the basis of a universal frequency offset estimation system/method, so that the frequency offset estimation search precision is improved.
Drawings
FIG. 1 is a schematic diagram of: a structure diagram of a frequency offset estimation system;
FIG. 2 is a diagram of: a flow chart of a method of frequency offset estimation;
FIG. 3 is a diagram of: schematic diagram of a frequency offset estimation method.
Detailed Description
The technical scheme of the invention is further explained by combining the drawings and the embodiment.
As shown in fig. 1, a frequency offset estimation system for calculating a frequency offset value of a carrier, the carrier being composed of a plurality of subcarriers, includes an operation module, a point coordinate module and a parabolic fitting module; the operation module is used for selecting different offsets in the range where the frequency offset value possibly exists, and calculating the corresponding autocorrelation function value when each offset is selected in the same subcarrier; the point coordinate module forms different points in a two-dimensional coordinate system according to each offset and the corresponding autocorrelation function value when each offset is selected; and the parabolic fitting module is used for selecting a point with the maximum correlation function value from the two-dimensional coordinate system and two points adjacent to the point to perform parabolic fitting, and calculating the frequency offset value of the carrier.
It is a general method to obtain the frequency offset according to the offset of the pilot frequency positions of two adjacent OFDM symbols. Assume a set of integer-times frequency offset search ranges, I [ -n ]I,max,+nI,max]Let m be I, m be possible integer frequency offset, and assuming that the position set of the continuous pilot is C, the position of the continuous pilot after FFT can be represented as k is C + m. When the subcarrier k is pilot frequency, carrying out conjugate multiplication Y of frequency domain data of two OFDM symbols before and afterl,kY* l+1,kAnd then carrying out square sum operation, and accumulating num _ T square sums to obtain the maximum RmFurther obtain the estimated value of the integral multiple carrier frequency offset
As shown in fig. 2 and 3, on the basis of the general frequency offset estimation method, a three-point parabolic fitting method is added to obtain a more accurate position of the maximum value, which is a core distinguishing technical feature of the present scheme.
The parabola equation of the three-point parabola fitting is that y is equal to ax2+bx+c，
Since y (0)>y (-1) and y (0)>Y (1), it can be shown that-0.5 < xmax≤0.5。
According to the above-mentioned maximum value position to search for
Finding xmax。
The estimated value of the carrier frequency offset after correction is as follows:
in the DVB _ T project, the optimization method of the frequency offset estimation is adopted. Data is obtained in a test case, and the maximum value y (0) is 3669, the maximum position index is-6, the value before the maximum value is 1159, and the value after the maximum value is 245 according to the flow.
If the maximum value 3669 and the position index thereof are-6 according to the conventional general frequency offset estimation method, the frequency offset estimation result should be-6. And x can be obtained by calculation using the methods described hereinmaxIs-0.077, which is integrated as a fractional part with the maximum index-6, then-6.077 is the exact frequency offset result.
For the general frequency offset estimation method in the prior art, the invention adds a three-point parabolic fitting method, and the obtained frequency offset value is more accurate. The frequency deviation result is used for deviation correction compensation of a subsequent communication system, and the system is more favorable for achieving stability.
Those skilled in the art will recognize that the foregoing description is merely one or more embodiments of the present invention, and is not intended to limit the invention thereto. Any equivalent changes, modifications and equivalents of the above-described embodiments are within the scope of the invention as defined by the appended claims, and all such equivalents are intended to fall within the true spirit and scope of the invention.
Claims (10)
1. A frequency offset estimation system for calculating a frequency offset value of a carrier, the carrier being composed of a plurality of carriers
A number of sub-carriers, characterized in that,
the frequency offset estimation system comprises an operation module, a point coordinate module and a parabola fitting module;
the operation module is used for selecting different offsets in the range where the frequency offset value may exist, and calculating the corresponding autocorrelation function value when each offset is selected in the same subcarrier;
the point coordinate module forms different points in a two-dimensional coordinate system according to each offset and the corresponding autocorrelation function value when each offset is selected;
the parabolic fitting module is used for selecting a point with the maximum correlation function value and two points adjacent to the point from the two-dimensional coordinate system to perform parabolic fitting, and calculating the frequency offset value of the carrier;
the parabola fitting module selects a point with the maximum correlation function value from the two-dimensional coordinate system and two points adjacent to the point to perform parabola fitting, and calculates the frequency offset value of the carrier wave, and the method comprises the following steps:
carrying out parabolic fitting on the selected three points in a two-dimensional coordinate system;
finding out the vertex of a parabola formed by fitting;
and calculating the abscissa of the vertex, wherein the offset corresponding to the abscissa of the vertex is the frequency offset value of the carrier.
2. The frequency offset estimation system of claim 1,
the subcarrier is composed of OFDM symbols, and the method for calculating the autocorrelation function value by the operation module comprises the following steps: and (4) carrying out conjugate multiplication on every two frequency domain data of all adjacent OFDM symbols in the correlation length in the subcarrier to calculate the square sum.
3. The frequency offset estimation system of claim 2,
the selection basis of the correlation length is the transmission flow of the carrier.
4. The frequency offset estimation system of claim 3,
the abscissa of each point in the two-dimensional coordinate system is the selected offset, and the ordinate is the corresponding autocorrelation function value when each offset is selected.
5. The frequency offset estimation system of claim 4,
the parabola equation fitted by the parabola fitting module is that y is ax2A form of + bx + c, where x is the abscissa and y is the ordinate.
6. A frequency offset estimation method for calculating a frequency offset value of a carrier, the carrier being composed of a plurality of subcarriers, the method comprising the steps of:
step S1: selecting different offsets from the range in which the frequency offset value may exist, selecting the same subcarrier, and calculating the autocorrelation function value corresponding to the same subcarrier when each offset is selected;
step S2: forming a plurality of points in a two-dimensional coordinate system, wherein the abscissa of each point is the selected offset, and the ordinate is the autocorrelation function value corresponding to the same subcarrier when each offset is selected;
step S3: selecting a point with the autocorrelation function value as the maximum value and two points which are adjacent to the point left and right;
step S4: performing parabolic fitting on the selected three points in a two-dimensional coordinate system, and calculating a frequency offset value of the carrier;
the step S4 further includes the following steps:
step S41, performing parabolic fitting on the three selected points in a two-dimensional coordinate system;
step S42, finding out the vertex of the parabola formed by fitting;
step S43, calculating the abscissa of the vertex, where the offset corresponding to the abscissa of the vertex is the frequency offset value of the carrier.
7. The frequency offset estimation method of claim 6,
in step S1, there is a gap between the sub-carriers, and the offset is selected as an integer multiple of the gap between adjacent sub-carriers.
8. The frequency offset estimation method of claim 6,
in step S1, the subcarrier consists of OFDM symbols, and the method for calculating the autocorrelation function value of the subcarrier is as follows: and (4) carrying out conjugate multiplication on every two frequency domain data of all adjacent OFDM symbols in the correlation length in the subcarrier to calculate the square sum.
9. The frequency offset estimation method of claim 8,
the selection basis of the correlation length is the transmission flow of the carrier.
10. The frequency offset estimation method of claim 8,
the parabola equation of the three-point parabola fitting is that y is equal to ax2A form of + bx + c, wherein x is the abscissa and y is the ordinate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810743424.5A CN110708265B (en) | 2018-07-09 | 2018-07-09 | Frequency offset estimation system and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810743424.5A CN110708265B (en) | 2018-07-09 | 2018-07-09 | Frequency offset estimation system and method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110708265A CN110708265A (en) | 2020-01-17 |
| CN110708265B true CN110708265B (en) | 2022-07-12 |
Family
ID=69192573
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810743424.5A Active CN110708265B (en) | 2018-07-09 | 2018-07-09 | Frequency offset estimation system and method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110708265B (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4581767A (en) * | 1980-06-25 | 1986-04-08 | The United States Of America As Represented By The Secretary Of The Army | Measurement of jamming effectiveness by cross correlation techniques (C) |
| WO2002062030A1 (en) * | 2001-02-01 | 2002-08-08 | Industrial Research Limited | Maximum likelihood synchronisation for a communications system using a pilot symbol |
| CN102480452A (en) * | 2010-11-26 | 2012-05-30 | 中国科学院微电子研究所 | Carrier frequency synchronous circuit and method of OFDM (Orthogonal Frequency Division Multiplexing) system |
| EP1791314A3 (en) * | 2005-11-29 | 2012-10-03 | Samsung Electronics Co., Ltd. | Apparatus and method for carrier frequency synchronization in an OFDM system |
| CN103901446A (en) * | 2014-03-28 | 2014-07-02 | 哈尔滨工程大学 | Binary offset carrier modulation signal side peak eliminating and main peak capturing method |
| CN108040028A (en) * | 2017-12-22 | 2018-05-15 | 中国人民解放军国防科技大学 | OFDM system anti-interference signal detection and synchronization method based on local sequence cross-correlation detection |
| CN108183879A (en) * | 2017-12-27 | 2018-06-19 | 北京理工大学 | A kind of pseudo-code subcarrier synchronization realizing method for Terahertz communication |
-
2018
- 2018-07-09 CN CN201810743424.5A patent/CN110708265B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4581767A (en) * | 1980-06-25 | 1986-04-08 | The United States Of America As Represented By The Secretary Of The Army | Measurement of jamming effectiveness by cross correlation techniques (C) |
| WO2002062030A1 (en) * | 2001-02-01 | 2002-08-08 | Industrial Research Limited | Maximum likelihood synchronisation for a communications system using a pilot symbol |
| EP1791314A3 (en) * | 2005-11-29 | 2012-10-03 | Samsung Electronics Co., Ltd. | Apparatus and method for carrier frequency synchronization in an OFDM system |
| CN102480452A (en) * | 2010-11-26 | 2012-05-30 | 中国科学院微电子研究所 | Carrier frequency synchronous circuit and method of OFDM (Orthogonal Frequency Division Multiplexing) system |
| CN103901446A (en) * | 2014-03-28 | 2014-07-02 | 哈尔滨工程大学 | Binary offset carrier modulation signal side peak eliminating and main peak capturing method |
| CN108040028A (en) * | 2017-12-22 | 2018-05-15 | 中国人民解放军国防科技大学 | OFDM system anti-interference signal detection and synchronization method based on local sequence cross-correlation detection |
| CN108183879A (en) * | 2017-12-27 | 2018-06-19 | 北京理工大学 | A kind of pseudo-code subcarrier synchronization realizing method for Terahertz communication |
Non-Patent Citations (2)
| Title |
|---|
| Estimating a spectral correlation function and its errors owing to inexact frequencies;Vladimír Šebesta;《20th International Conference Radioelektronika 2010》;20100603;全文 * |
| OFDM通信系统中的同步与频偏估计技术研究与FPGA实现;张坤;《信息科技辑》;20150415;全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN110708265A (en) | 2020-01-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110290581B (en) | Rapid time-frequency synchronization method and terminal in 5G system | |
| US7894539B2 (en) | Method and device for estimating integer carrier frequency offset | |
| US8290002B2 (en) | Coarse timing synchronization acquisition method in a mobile communication system | |
| CN102461291A (en) | RF fingerprinting for location estimation | |
| CN102546514B (en) | Frequency synchronization method and equipment for OFDM system | |
| US9160597B2 (en) | Method for estimating OFDM integer frequency offset, OFDM integer frequency offset estimator and OFDM receiver system | |
| CN108234371B (en) | Frequency offset estimation method in high-speed scene | |
| JP2009049996A (en) | Method and apparatus for synchronizing timing, preamble, method and apparatus for generating the same | |
| US10009096B2 (en) | Method for estimating frequency offset, apparatus and system | |
| US20070242760A1 (en) | Speed estimation method for telecommunication system | |
| CN105897643A (en) | Combined narrowband interference detection, elimination and channel estimation method based on continuous cyclic shift training sequence in OFDM system | |
| CN109495414A (en) | A kind of frequency deviation estimating method, device, equipment and computer readable storage medium | |
| CN101242390B (en) | Carrier frequency deviation estimation algorithm based on known sequence interference self-association | |
| WO2021143644A1 (en) | Carrier phase tracking method and apparatus | |
| CN110708265B (en) | Frequency offset estimation system and method | |
| WO2021027591A1 (en) | Repetitive sequence-based frequency offset estimation method and system | |
| WO2018147821A1 (en) | Carrier frequency offset (cfo) estimation in frequency-hopping ofdm technique using k-means method | |
| US20110007854A1 (en) | Integer carrier frequency offset estimation scheme for orthogonal frequency division multiplexing | |
| CN101014028B (en) | Frequency coarse synchronizing method of using property of phase reference code element | |
| KR101501334B1 (en) | Method for Estimating Frequency Offset based on OFDM System and Apparatus Thereof | |
| CN110224963B (en) | Method and device for determining symbol timing synchronization position and storage medium | |
| CN104935544A (en) | Information processor and information processing method, display device, and program | |
| KR100438570B1 (en) | Frequency error detection mehod for wireless lan receiver | |
| CN101207594B (en) | Method for implementing frequency coarse synchronizing using energy detection technique | |
| Pan et al. | High accurate time-of-arrival estimation with fine-grained feature generation for Internet-of-Things applications |
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 |