CN109495414A - A kind of frequency deviation estimating method, device, equipment and computer readable storage medium - Google Patents

A kind of frequency deviation estimating method, device, equipment and computer readable storage medium Download PDF

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CN109495414A
CN109495414A CN201710817405.8A CN201710817405A CN109495414A CN 109495414 A CN109495414 A CN 109495414A CN 201710817405 A CN201710817405 A CN 201710817405A CN 109495414 A CN109495414 A CN 109495414A
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path
frequency
channel estimation
time domain
domain channel
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CN109495414B (en
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金晓成
徐兵
谢鑫
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China Academy of Telecommunications Technology CATT
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China Academy of Telecommunications Technology CATT
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    • 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
    • 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
    • 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
    • H04L27/2668—Details of algorithms
    • H04L27/2669—Details of algorithms characterised by the domain of operation
    • H04L27/2671—Time domain
    • 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
    • H04L27/2668—Details of algorithms
    • H04L27/2669—Details of algorithms characterised by the domain of operation
    • H04L27/2672—Frequency domain
    • 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

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Measuring Frequencies, Analyzing Spectra (AREA)

Abstract

The present invention provides a kind of frequency deviation estimating method, device, equipment and computer readable storage medium, is related to field of communication technology, to improve the accuracy for carrying out offset estimation under more RRH high-speed rail environment.Frequency deviation estimating method of the invention, comprising: receive the time-domain signal on each diameter that transmitting terminal is sent, and the running time-frequency resource on each diameter is obtained according to the time-domain signal on each diameter；Channel estimation is carried out to the running time-frequency resource on each diameter respectively, obtains the channel estimation in frequency domain value on each diameter；According to the channel estimation in frequency domain value on each diameter, the time domain channel estimated value on each diameter is determined；According to the time domain channel estimated value on each diameter, the frequency deviation on each diameter is determined.The accuracy that offset estimation is carried out under more RRH high-speed rail environment can be improved in the present invention.

Description

Frequency offset estimation method, device and equipment and computer readable storage medium
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a frequency offset estimation method, apparatus, device, and computer readable storage medium.
Background
Under high-speed rails, multiple antennas in the same cell are generally deployed along the high-speed rails by means of a Remote Radio Unit (RRH), so that cell coverage is increased, and switching frequency is reduced to improve network performance. In general, a plurality of RRHs are installed in a high-speed rail environment. Herein, a high-speed rail environment having a plurality of RRHs is referred to as a multi-RRH high-speed rail environment.
However, when a UE (User Equipment) is located between two RRHs in the same cell, the UE receives two (or more) signals with opposite doppler frequency offsets, thereby forming fast fading and seriously affecting the receiving performance.
Carrier frequency offset is mainly due to two reasons: firstly, the local oscillator frequency of a transmitting end and a receiving end has deviation; the second is the bias due to doppler shift caused by relative motion.
The existing Frequency offset estimation method can only estimate a single Frequency offset Δ f in an OFDM (Orthogonal Frequency Division Multiplexing) system. In a high-speed rail environment, multiple RRHs (or multiple paths) may have different frequency offsets, and these different frequency offsets cannot be estimated by using the prior art, so that the frequency offset estimation result by using the prior art is inaccurate.
Disclosure of Invention
In view of the above, the present invention provides a frequency offset estimation method, apparatus, device and computer readable storage medium, so as to improve the accuracy of frequency offset estimation in a multi-RRH high-speed railway environment.
To solve the foregoing technical problem, in a first aspect, an embodiment of the present invention provides a frequency offset estimation method, including:
receiving time domain signals on each path sent by a transmitting terminal, and obtaining time frequency resources on each path according to the time domain signals on each path;
respectively carrying out channel estimation on the time-frequency resources on each path to obtain frequency domain channel estimation values on each path;
determining a time domain channel estimation value on each path according to the frequency domain channel estimation value on each path;
and determining the frequency offset on each path according to the time domain channel estimation value on each path.
The receiving of the time domain signal on each path sent by the transmitting end and the obtaining of the time frequency resource on each path according to the time domain signal on each path include:
receiving time domain signals on each path sent by a transmitting terminal;
and respectively carrying out Fast Fourier Transform (FFT) on the time domain signals on each path to obtain time frequency resources on each path.
Wherein, the performing channel estimation on the time-frequency resources on each path respectively to obtain the frequency domain channel estimation value on each path includes:
and respectively carrying out least square LS channel estimation on the time frequency resources on each path to obtain frequency domain channel estimation values on each path.
Wherein, the determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path includes:
and performing Inverse Discrete Fourier Transform (IDFT) on the sequence consisting of the frequency domain channel estimation values on each path to determine the time domain channel estimation values on each path.
Wherein, the determining the frequency offset on each path according to the time domain channel estimation value on each path includes:
calculating the conjugate of the first time domain channel estimation value to obtain a value for the first time domain channel estimation value and the second time domain channel estimation value in the time domain channel estimation values on each path;
multiplying the value and the second time domain channel estimation value to determine the frequency offset on a first path;
the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
Wherein the method further comprises:
and carrying out automatic frequency tracking on the frequency deviation.
Wherein the performing automatic frequency tracking on the frequency offset includes:
determining a weighted average coefficient corresponding to each path;
calculating the weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and carrying out automatic frequency tracking on the frequency deviation weighted average value.
Calculating a weighted average value of the frequency offset on each path according to the weighted average coefficient corresponding to each path and the frequency offset on each path, including:
calculating the weighted average of the frequency deviation on each path by using the following formula:
where Δ f represents a frequency offset weighted average, P (Δ f)p) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
Wherein the performing automatic frequency tracking on the frequency offset includes:
determining target frequency offset from the frequency offsets on the paths according to a preset rule;
and carrying out automatic frequency tracking on the target frequency offset.
In a second aspect, an embodiment of the present invention provides a frequency offset estimation method, including:
obtaining time-frequency resources on each path;
performing Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path respectively to obtain time-domain signals on each path;
and sending the time domain signals on each path to a receiving end.
In a third aspect, an embodiment of the present invention provides a frequency offset estimation apparatus, including: a transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor;
the transceiver is used for receiving time domain signals on each path sent by the transmitting terminal;
the processor is used for reading the program in the memory and executing the following processes:
obtaining time-frequency resources on each path according to the time-domain signals on each path; respectively carrying out channel estimation on the time-frequency resources on each path to obtain a frequency domain channel estimation value on each path; determining a time domain channel estimation value on each path according to the frequency domain channel estimation value on each path; and determining the frequency offset on each path according to the time domain channel estimation value on each path.
Wherein the processor is further configured to read the program in the memory and execute the following processes: and respectively carrying out Fast Fourier Transform (FFT) on the time domain signals on each path to obtain time frequency resources on each path.
Wherein the processor is further configured to read the program in the memory and execute the following processes: and respectively carrying out least square LS channel estimation on the time frequency resources on each path to obtain frequency domain channel estimation values on each path.
Wherein the processor is further configured to read the program in the memory and execute the following processes: and performing Inverse Discrete Fourier Transform (IDFT) on the sequence consisting of the frequency domain channel estimation values on each path to determine the time domain channel estimation values on each path.
Wherein the processor is further configured to read the program in the memory and execute the following processes:
calculating the conjugate of the first time domain channel estimation value to obtain a value for the first time domain channel estimation value and the second time domain channel estimation value in the time domain channel estimation values on each path;
multiplying the value and the second time domain channel estimation value to determine the frequency offset on a first path;
wherein the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
Wherein the processor is further configured to read the program in the memory and execute the following processes:
and carrying out automatic frequency tracking on the frequency deviation.
Wherein the processor is further configured to read the program in the memory and execute the following processes:
determining a weighted average coefficient corresponding to each path;
calculating the weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and carrying out automatic frequency tracking on the frequency deviation weighted average value.
Wherein the processor is further configured to read the program in the memory and execute the following processes:
calculating the weighted average of the frequency deviation on each path by using the following formula:
where Δ f represents a frequency offset weighted average, P (Δ f)p) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
Wherein the processor is further configured to read the program in the memory and execute the following processes:
determining target frequency offset from the frequency offsets on the paths according to a preset rule;
and carrying out automatic frequency tracking on the target frequency offset.
In a fourth aspect, an embodiment of the present invention provides a frequency offset estimation apparatus, including: a transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor;
the processor is used for reading the program in the memory and executing the following processes:
obtaining time-frequency resources on each path; respectively carrying out fast Fourier inverse transform (IFFT) on the time-frequency resources on each path to obtain time-domain signals on each path;
and the transceiver is used for transmitting the time domain signals on each path to a receiving end.
In a fifth aspect, an embodiment of the present invention provides a frequency offset estimation apparatus, including:
the first acquisition module is used for receiving the time domain signals on each path sent by the transmitting terminal and acquiring the time frequency resources on each path according to the time domain signals on each path;
a second obtaining module, configured to perform channel estimation on the time-frequency resources on each path, respectively, to obtain frequency domain channel estimation values on each path;
a first determining module, configured to determine, according to the frequency domain channel estimation value on each path, a time domain channel estimation value on each path;
and a second determining module, configured to determine the frequency offset in each path according to the time domain channel estimation value in each path.
Wherein the second determining module comprises:
a calculating submodule, configured to calculate a conjugate of a first time domain channel estimation value and a second time domain channel estimation value in the time domain channel estimation values on the paths, so as to obtain a value;
the determining submodule is used for multiplying the numerical value and the second time domain channel estimation value to determine the frequency offset on a first path;
wherein the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
Wherein the apparatus further comprises:
and the tracking module is used for carrying out automatic frequency tracking on the frequency deviation.
Wherein the tracking module comprises:
the determining submodule is used for determining a weighted average coefficient corresponding to each path;
the calculating submodule is used for calculating the weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and the tracking submodule is used for carrying out automatic frequency tracking on the frequency deviation weighted average value.
In a sixth aspect, an embodiment of the present invention provides a frequency offset estimation apparatus, including:
the first acquisition module is used for acquiring time-frequency resources on each path;
a second obtaining module, configured to perform Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path, respectively, to obtain time-domain signals on each path;
and the sending module is used for sending the time domain signals on each path to a receiving end.
In a seventh aspect, an embodiment of the present invention provides a computer-readable storage medium for storing a computer program, where the computer program, when executed by a processor, implements the steps in the method according to the first aspect; or which when executed by a processor implements the steps in the method according to the second aspect.
The technical scheme of the invention has the following beneficial effects:
in the embodiment of the invention, the time-frequency resources on each path are obtained according to the time-domain signals on the multipath, and the channel estimation is respectively carried out on the time-frequency resources on each path to obtain the frequency-domain channel estimation value on each path. And then, determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path, and further determining the frequency offset on each path according to the time domain channel estimation value on each path. Therefore, in the embodiment of the invention, the frequency offset on each path can be estimated in the high-speed rail and multi-RRH environment, so that the accuracy of frequency offset estimation in the multi-RRH high-speed rail environment is improved.
Drawings
FIG. 1 is a flow chart of a method of frequency offset estimation according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method of frequency offset estimation according to an embodiment of the present invention;
fig. 3 is a schematic block diagram of a processing procedure of an LTE transmitting end/receiving end in the embodiment of the present invention;
FIG. 4 is a CRS time-frequency location diagram;
FIG. 5 is a schematic diagram of the processing procedure of the receiving end after obtaining the time domain resources on each path;
FIG. 6 is a diagram illustrating an apparatus for frequency offset estimation according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a first obtaining module in the frequency offset estimation apparatus according to the embodiment of the present invention;
fig. 8 is a diagram illustrating a second determining module in the frequency offset estimation apparatus according to the embodiment of the present invention;
FIG. 9 is a further schematic diagram of a frequency offset estimation apparatus according to an embodiment of the present invention;
fig. 10 is a schematic diagram of a tracking module in the frequency offset estimation apparatus according to the embodiment of the present invention;
FIG. 11 is a diagram illustrating an apparatus for frequency offset estimation according to an embodiment of the present invention;
FIG. 12 is a diagram illustrating a frequency offset estimation apparatus according to an embodiment of the present invention;
fig. 13 is a schematic diagram of a frequency offset estimation apparatus according to an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention will be made with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
As shown in fig. 1, the frequency offset estimation method according to the embodiment of the present invention is applied to a receiving end, and includes:
step 101, receiving time domain signals on each path sent by a transmitting terminal, and obtaining time frequency resources on each path according to the time domain signals on each path.
In the embodiment of the present invention, the transmission path of each RRH may be referred to as one path or one path. In a multi-RRH high-speed rail environment, the device has a plurality of paths. Here, for each path, the time domain signal on each path sent by the receiving end may be received, and the time frequency resource on each path may be obtained according to the time domain signal on each path.
Specifically, the time domain signals on each path sent by the transmitting end are received, and Fast Fourier Transform (FFT) is performed on the time domain signals on each path, respectively, to obtain the time frequency resources on each path.
And 102, respectively carrying out channel estimation on the time-frequency resources on each path to obtain a frequency domain channel estimation value on each path.
In this step, least-squares (LS) channel estimation is performed on the time-frequency resources on each path, respectively, to obtain frequency domain channel estimation values on each path.
And 103, determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path.
Here, a sequence of the frequency domain channel estimation values on the respective paths is subjected to Inverse Discrete Fourier Transform (IDFT) to determine time domain channel estimation values on the respective paths.
And step 104, determining the frequency offset on each path according to the time domain channel estimation value on each path.
In this step, for a first time domain channel estimation value and a second time domain channel estimation value in the time domain channel estimation values on the paths, a conjugate of the first time domain channel estimation value is calculated to obtain a value, and the value and the second time domain channel estimation value are multiplied to determine a frequency offset on the first path.
The first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
In the embodiment of the invention, the time-frequency resources on each path are obtained according to the time-domain signals on the multipath, and the channel estimation is respectively carried out on the time-frequency resources on each path to obtain the frequency-domain channel estimation value on each path. And then, determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path, and further determining the frequency offset on each path according to the time domain channel estimation value on each path. Therefore, in the embodiment of the invention, the frequency offset on each path can be estimated in the high-speed rail and multi-RRH environment, so that the accuracy of frequency offset estimation in the multi-RRH high-speed rail environment is improved.
As shown in fig. 2, the frequency offset estimation method according to the embodiment of the present invention includes:
step 201, obtaining time frequency resources on each path.
Step 202, performing Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path, respectively, to obtain time-domain signals on each path.
Step 203, sending the time domain signals on each path to a receiving end.
In the embodiment of the invention, the time-frequency resources on each path are obtained according to the time-domain signals on the multipath, and the channel estimation is respectively carried out on the time-frequency resources on each path to obtain the frequency-domain channel estimation value on each path. And then, determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path, and further determining the frequency offset on each path according to the time domain channel estimation value on each path. Therefore, in the embodiment of the invention, the frequency offset on each path can be estimated in the high-speed rail and multi-RRH environment, so that the accuracy of frequency offset estimation in the multi-RRH high-speed rail environment is improved.
The following embodiments are combined to describe a specific implementation process of the frequency offset estimation method of the present invention in detail.
Taking LTE (long term evolution ) as an example, as shown in fig. 3, a schematic block diagram of a processing procedure of an LTE transmitting end/receiving end is shown.
Suppose ak,lRepresents the time frequency resource, s, on the k subcarrier and the l symbol of the transmitting terminallAnd (t) represents the time domain signal at the t-th sampling point of the l-th symbol after the IFFT change at the transmitting end.
And at the transmitting end, acquiring time-frequency resources on each path, respectively carrying out fast Fourier inverse transformation on the time-frequency resources on each path to acquire time-domain signals on each path, and transmitting the time-domain signals on each path to the receiving end.
Suppose that under the 'multi-RRH high-speed rail environment', n RRHs exist, and the Doppler frequency shifts are respectively delta f1， Δf2，…，Δfn(ii) a The multipath delays are respectively delta t1，Δt2，…，Δtn(ii) a Relative power is respectively p1，p2，…， pn。
And for the receiving end, receiving the time domain signals on each path sent by the transmitting end, and obtaining the time frequency resources on each path according to the time domain signals on each path.
yl(t) represents the time domain signal at the tth sampling point of the ith symbol of the receiving end,p 1, 2., n, where n (t) represents the noise at time t.
rk,l＝FFT[yl(t)]It means the time-frequency resource on the kth sub-carrier and the l symbol after the receiving end is changed by the FFT.
In LTE, Cell-specific RS (CRS) is distributed discretely in time/frequency domain, and R is distributed0Representing CRS time-frequency location.
Fig. 5 is a schematic diagram of a processing procedure after the receiving end obtains time domain resources on each path. With reference to fig. 5, at the receiving end, LS channel estimation is performed on the time-frequency resources on each path, respectively, to obtain the frequency domain channel estimation value on each path.
According to rk,lAnd known pilot symbols ak,lAssuming that the noise influence is ignored, the frequency domain channel estimation value of the CRS position can be obtained through LS estimation:
according to the frequency domain sampling theorem, if the sequence length is M, the original time domain signal x (N) can be recovered from the frequency domain samples x (k) without distortion only if the number of frequency domain sampling points N > is M; otherwise, a time-domain aliasing phenomenon is generated. Generally, the resolvable multipath quantity is limited, and the maximum multipath delay is less than the CRS sampling point number on the frequency domain, so that the frequency domain sampling theorem is satisfied.
Frequency domain channel estimation value of each subcarrier on each symbolConstituent sequence HlBy IDFT, the time domain channel estimation value of each subcarrier can be recovered, and the time domain channel estimation value on the ith symbol and the pth path is expressed as
Taking the LTE system 20M bandwidth as an example, the FFT length is 2048, that is, 2048 subcarriers (1200 effective subcarriers, and the rest are virtual subcarriers) are total in the frequency domain. The CRS are equally spaced 6 subcarriers in the frequency domain, for a total of 200 CRS subcarriers. Since 2048/6 is not an integer, the 2048 subcarriers cannot be sampled in the frequency domain at equal intervals 6, i.e., the samples at equal intervals 6 are in fact non-uniformly sampled.
Suppose that a rectangular window is applied to 2048 subcarriers in the frequency domain, such as: 2048- >1944, then 1944/6 ═ 324 is an integer, i.e. IDFT length is 324; or 2048- >1536, then 1536/6 ═ 256, i.e., IDFT length 256. However, frequency domain plus rectangular windowing is equivalent to time domain convolution s inc functions, and can cause aliasing in time domain channel estimates, with smaller s inc function side lobes for "2048- > 1944" compared to both "2048- > 1944" and "2048- > 1536". Assuming that the IDFT length is selected from 324 or 256, it is recommended to select the IDFT length to take 324.
The time domain channel estimation of each symbol has the following relation:
the symbol represents the l + Δ t symbol and the time domain channel estimate value on the p path.
So, similarly, by different symbol positionsPerforming conjugate multiplication to obtain
Since Δ t is known, the result of conjugate multiplication C can be usedpThe phase of (a) is calculated to obtain the frequency deviation delta f of the p-th pathpThus, the purpose of estimating different frequency offset values from multiple RRHs (or multiple paths) is achieved.
On the basis of the above calculation of the Frequency offset on each path, the embodiment of the present invention may also use the Frequency offset to perform Automatic Frequency tracking (also called Automatic Frequency Control).
For automatic frequency tracking, only a single frequency offset can be tracked/corrected. Therefore, when there are multiple frequency offsets in a "multi-RRH high-speed rail environment", how to perform automatic frequency tracking needs to be considered. The frequency offset may cause Inter-Carrier Interference (ICI) in the OFDM system, and in the "multi-RRH high-speed rail environment", since the frequency offsets of all paths cannot be corrected, the ICI may inevitably exist.
However, the influence of ICI can be minimized by performing weighted averaging on the respective path frequency offsets, and this process can also prevent a rapid jump of the AFC tracking frequency offset Δ f.
Namely, determining a weighted average coefficient corresponding to each path, calculating a frequency offset weighted average value on each path according to the weighted average coefficient corresponding to each path and the frequency offset on each path, and performing automatic frequency tracking on the frequency offset weighted average value.
Calculating the weighted average of the frequency deviation on each path by using the following formula:
wherein,
where Δ f represents a frequency offset weighted average, P (Δ f)p) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
Or, in a specific application, a target frequency offset may be determined from the frequency offsets in the various paths according to a preset rule, and the target frequency offset may be subjected to automatic frequency tracking.
The preset rule may be any choice, or a fixed choice of the frequency offset on a certain path, and the like.
It should be noted that the method of the above embodiment can be applied not only to the LTE system, but also to all OFDM systems.
Therefore, the embodiment of the invention can accurately estimate the frequency deviation of each path in the multi-RRH high-speed rail environment, and can optimize the automatic frequency tracking performance by using the weighted average result of the frequency deviation of each path.
As shown in fig. 6, the frequency offset estimation apparatus according to the embodiment of the present invention includes:
a first obtaining module 601, configured to receive a time domain signal on each path sent by a transmitting end, and obtain a time-frequency resource on each path according to the time domain signal on each path; a second obtaining module 602, configured to perform channel estimation on the time-frequency resources on each path, respectively, to obtain frequency domain channel estimation values on each path; a first determining module 603, configured to determine, according to the frequency domain channel estimation value on each path, a time domain channel estimation value on each path; a second determining module 604, configured to determine, according to the time domain channel estimation value on each path, a frequency offset on each path.
As shown in fig. 7, the first obtaining module 601 includes:
a receiving submodule 6011, configured to receive time domain signals on each path sent by a transmitting end;
a transform submodule 6012, configured to perform fast fourier transform on the time domain signals on each path respectively, to obtain time frequency resources on each path.
The second obtaining module 602 is specifically configured to perform LS channel estimation on the time-frequency resources on each path, respectively, to obtain frequency-domain channel estimation values on each path.
The first determining module 603 is specifically configured to perform inverse discrete fourier transform on a sequence composed of the frequency domain channel estimation values on each path, and determine the time domain channel estimation values on each path.
As shown in fig. 8, the second determining module 604 includes: a calculating submodule 6041, configured to calculate a conjugate of a first time domain channel estimation value and a second time domain channel estimation value in the time domain channel estimation values on the paths, so as to obtain a value; a determining submodule 6042, configured to multiply the value with the second time domain channel estimation value, and determine a frequency offset on a first path; wherein the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
As shown in fig. 9, the apparatus further includes: a tracking module 605, configured to perform automatic frequency tracking on the frequency offset.
As shown in fig. 10, the tracking module 605 includes:
a determining submodule 6051 configured to determine a weighted average coefficient corresponding to each path; a calculating submodule 6052, configured to calculate a weighted average value of the frequency offset on each path according to the weighted average coefficient corresponding to each path and the frequency offset on each path; and a tracking sub-module 6053, configured to perform automatic frequency tracking on the frequency offset weighted average.
Specifically, the weighted average of the frequency offset in each path is calculated by using the following formula:
where Δ f represents a frequency offset weighted average, P (Δ f)p) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
Or, the tracking module 605 is specifically configured to determine a target frequency offset from the frequency offsets on the paths according to a preset rule, and perform automatic frequency tracking on the target frequency offset.
The working principle of the device according to the invention can be referred to the description of the method embodiment described above.
In the embodiment of the invention, the time-frequency resources on each path are obtained according to the time-domain signals on the multipath, and the channel estimation is respectively carried out on the time-frequency resources on each path to obtain the frequency-domain channel estimation value on each path. And then, determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path, and further determining the frequency offset on each path according to the time domain channel estimation value on each path. Therefore, in the embodiment of the invention, the frequency offset on each path can be estimated in the high-speed rail and multi-RRH environment, so that the accuracy of frequency offset estimation in the multi-RRH high-speed rail environment is improved.
As shown in fig. 11, the frequency offset estimation apparatus according to the embodiment of the present invention includes:
a first obtaining module 1101, configured to obtain time-frequency resources on each path; a second obtaining module 1102, configured to perform inverse fast fourier transform IFFT on the time-frequency resources on each path, respectively, to obtain time-domain signals on each path; a sending module 1103, configured to send the time domain signals on each path to a receiving end.
The working principle of the device according to the invention can be referred to the description of the method embodiment described above.
In the embodiment of the invention, the time-frequency resources on each path are obtained according to the time-domain signals on the multipath, and the channel estimation is respectively carried out on the time-frequency resources on each path to obtain the frequency-domain channel estimation value on each path. And then, determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path, and further determining the frequency offset on each path according to the time domain channel estimation value on each path. Therefore, in the embodiment of the invention, the frequency offset on each path can be estimated in the high-speed rail and multi-RRH environment, so that the accuracy of frequency offset estimation in the multi-RRH high-speed rail environment is improved.
As shown in fig. 12, the frequency offset estimation apparatus according to the embodiment of the present invention includes:
a processor 1200 for reading the program in the memory 1220 and executing the following processes: receiving, by a transceiver 1210, a time domain signal on each path sent by a transmitting end, and obtaining a time frequency resource on each path according to the time domain signal on each path; respectively carrying out channel estimation on the time-frequency resources on each path to obtain a frequency domain channel estimation value on each path; determining a time domain channel estimation value on each path according to the frequency domain channel estimation value on each path; determining the frequency deviation on each path according to the time domain channel estimation value on each path;
a transceiver 1210 for receiving and transmitting data under the control of the processor 1200.
In fig. 12, among other things, the bus architecture may include any number of interconnected buses and bridges, with one or more processors represented by processor 1200 and various circuits of memory represented by memory 1220 being linked together. The bus architecture may also link together various other circuits such as peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further herein. The bus interface provides an interface. The transceiver 1210 may be a plurality of elements, including a transmitter and a transceiver, providing a means for communicating with various other apparatus over a transmission medium. The processor 1200 is responsible for managing the bus architecture and general processing, and the memory 1220 may store data used by the processor 1200 in performing operations.
The processor 1200 is responsible for managing the bus architecture and general processing, and the memory 1220 may store data used by the processor 1200 in performing operations.
The processor 1200 is further configured to read the computer program and execute the following steps:
and respectively carrying out Fast Fourier Transform (FFT) on the time domain signals on each path to obtain time frequency resources on each path.
The processor 1200 is further configured to read the computer program and execute the following steps:
and respectively carrying out least square LS channel estimation on the time frequency resources on each path to obtain frequency domain channel estimation values on each path.
The processor 1200 is further configured to read the computer program and execute the following steps:
and performing Inverse Discrete Fourier Transform (IDFT) on the sequence consisting of the frequency domain channel estimation values on each path to determine the time domain channel estimation values on each path.
The processor 1200 is further configured to read the computer program and execute the following steps:
calculating the conjugate of the first time domain channel estimation value to obtain a value for the first time domain channel estimation value and the second time domain channel estimation value in the time domain channel estimation values on each path;
multiplying the value and the second time domain channel estimation value to determine the frequency offset on a first path;
wherein the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
The processor 1200 is further adapted to read the computer program and perform the step of performing an automatic frequency tracking of the frequency offset.
The processor 1200 is further configured to read the computer program and execute the following steps:
determining a weighted average coefficient corresponding to each path;
calculating the weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and carrying out automatic frequency tracking on the frequency deviation weighted average value.
The processor 1200 is further configured to read the computer program and execute the following steps:
calculating the weighted average of the frequency deviation on each path by using the following formula:
the time domain channel estimate of (c), n represents the total number of paths.
The processor 1200 is further configured to read the computer program and execute the following steps:
determining target frequency offset from the frequency offsets on the paths according to a preset rule;
and carrying out automatic frequency tracking on the target frequency offset.
As shown in fig. 13, the frequency offset estimation apparatus according to the embodiment of the present invention includes:
a processor 1300, for reading the program in the memory 1320, for executing the following processes: obtaining time-frequency resources on each path, performing Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path respectively to obtain time-domain signals on each path, and transmitting the time-domain signals on each path to a receiving end through a transceiver 1310;
a transceiver 1310 for receiving and transmitting data under the control of the processor 1300.
In fig. 13, among other things, the bus architecture may include any number of interconnected buses and bridges, with one or more processors represented by processor 1300 and various circuits of memory represented by memory 1320 being linked together. The bus architecture may also link together various other circuits such as peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further herein. The bus interface provides an interface. The transceiver 1310 may be a number of elements including a transmitter and a transceiver that provide a means for communicating with various other apparatus over a transmission medium. The processor 1300 is responsible for managing the bus architecture and general processing, and the memory 1320 may store data used by the processor 1300 in performing operations.
The processor 1300 is responsible for managing the bus architecture and general processing, and the memory 1320 may store data used by the processor 1300 in performing operations.
Furthermore, a computer-readable storage medium of an embodiment of the present invention stores a computer program executable by a processor to implement:
obtaining time-frequency resources on each path;
performing Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path respectively to obtain time-domain signals on each path;
and sending the time domain signals on each path to a receiving end.
Furthermore, a computer-readable storage medium of an embodiment of the present invention stores a computer program executable by a processor to implement:
receiving time domain signals on each path sent by a transmitting terminal, and obtaining time frequency resources on each path according to the time domain signals on each path;
respectively carrying out channel estimation on the time-frequency resources on each path to obtain frequency domain channel estimation values on each path;
determining a time domain channel estimation value on each path according to the frequency domain channel estimation value on each path;
and determining the frequency offset on each path according to the time domain channel estimation value on each path.
The receiving of the time domain signal on each path sent by the transmitting end and the obtaining of the time frequency resource on each path according to the time domain signal on each path include:
receiving time domain signals on each path sent by a transmitting terminal;
and respectively carrying out Fast Fourier Transform (FFT) on the time domain signals on each path to obtain time frequency resources on each path.
Wherein, the performing channel estimation on the time-frequency resources on each path respectively to obtain the frequency domain channel estimation value on each path includes:
and respectively carrying out least square LS channel estimation on the time frequency resources on each path to obtain frequency domain channel estimation values on each path.
Wherein, the determining the time domain channel estimation value on each path according to the frequency domain channel estimation value on each path includes:
and performing Inverse Discrete Fourier Transform (IDFT) on the sequence consisting of the frequency domain channel estimation values on each path to determine the time domain channel estimation values on each path.
Wherein, the determining the frequency offset on each path according to the time domain channel estimation value on each path includes:
calculating the conjugate of the first time domain channel estimation value to obtain a value for the first time domain channel estimation value and the second time domain channel estimation value in the time domain channel estimation values on each path;
multiplying the value and the second time domain channel estimation value to determine the frequency offset on a first path;
the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
Wherein the method further comprises:
and carrying out automatic frequency tracking on the frequency deviation.
Wherein the performing automatic frequency tracking on the frequency offset includes:
determining a weighted average coefficient corresponding to each path;
calculating the weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and carrying out automatic frequency tracking on the frequency deviation weighted average value.
Calculating a weighted average value of the frequency offset on each path according to the weighted average coefficient corresponding to each path and the frequency offset on each path, including:
calculating the weighted average of the frequency deviation on each path by using the following formula:
where Δ f represents a frequency offset weighted average, P (Δ f)p) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
Wherein the performing automatic frequency tracking on the frequency offset includes:
determining target frequency offset from the frequency offsets on the paths according to a preset rule;
and carrying out automatic frequency tracking on the target frequency offset.
In the several embodiments provided in the present application, it should be understood that the disclosed method and apparatus may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may be physically included alone, or two or more units may be integrated into one unit. The integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.
The integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) to execute some steps of the transceiving method according to various embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The foregoing is a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements should be construed as the protection scope of the present invention.

Claims (26)

1. A method of frequency offset estimation, comprising:
receiving time domain signals on each path sent by a transmitting terminal, and obtaining time frequency resources on each path according to the time domain signals on each path;
respectively carrying out channel estimation on the time-frequency resources on each path to obtain frequency domain channel estimation values on each path;
determining a time domain channel estimation value on each path according to the frequency domain channel estimation value on each path;
and determining the frequency offset on each path according to the time domain channel estimation value on each path.
2. The method of claim 1, wherein the receiving a time domain signal on each path sent by a transmitting end, and obtaining a time-frequency resource on each path according to the time domain signal on each path comprises:
receiving time domain signals on each path sent by a transmitting terminal;
and respectively carrying out Fast Fourier Transform (FFT) on the time domain signals on each path to obtain time frequency resources on each path.
3. The method of claim 1, wherein the performing channel estimation on the time-frequency resources on each path respectively to obtain the frequency-domain channel estimation value on each path comprises:
and respectively carrying out least square LS channel estimation on the time frequency resources on each path to obtain frequency domain channel estimation values on each path.
4. The method of claim 1, wherein the determining the time domain channel estimate on each path according to the frequency domain channel estimate on each path comprises:
and performing Inverse Discrete Fourier Transform (IDFT) on the sequence consisting of the frequency domain channel estimation values on each path to determine the time domain channel estimation values on each path.
5. The method of claim 1, wherein the determining the frequency offset for each path according to the time domain channel estimation value for each path comprises:
calculating the conjugate of the first time domain channel estimation value to obtain a value for the first time domain channel estimation value and the second time domain channel estimation value in the time domain channel estimation values on each path;
multiplying the value and the second time domain channel estimation value to determine the frequency offset on a first path;
and the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
6. The method of claim 1, further comprising:
and carrying out automatic frequency tracking on the frequency deviation.
7. The method of claim 6, wherein the automatic frequency tracking of the frequency offset comprises:
determining a weighted average coefficient corresponding to each path;
calculating a weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and carrying out automatic frequency tracking on the frequency deviation weighted average value.
8. The method of claim 7, wherein calculating the weighted average of the frequency offsets on each path according to the weighted average coefficient corresponding to each path and the frequency offset on each path comprises:
calculating the weighted average of the frequency deviation on each path by using the following formula:
Δf＝∑P(Δfp)·Δfp；
where, af represents a frequency offset weighted average,pP(Δfp) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
9. The method of claim 6, wherein the automatic frequency tracking of the frequency offset comprises:
determining target frequency offset from the frequency offsets on the paths according to a preset rule;
and carrying out automatic frequency tracking on the target frequency offset.
10. A method of frequency offset estimation, comprising:
obtaining time-frequency resources on each path;
performing Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path respectively to obtain time-domain signals on each path;
and sending the time domain signals on each path to a receiving end.
11. A frequency offset estimation apparatus, comprising: a transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor; it is characterized in that the preparation method is characterized in that,
the transceiver is used for receiving time domain signals on each path sent by the transmitting terminal;
the processor is used for reading the program in the memory and executing the following processes:
obtaining time-frequency resources on each path according to the time-domain signals on each path; respectively carrying out channel estimation on the time-frequency resources on each path to obtain a frequency domain channel estimation value on each path; determining a time domain channel estimation value on each path according to the frequency domain channel estimation value on each path; and determining the frequency offset on each path according to the time domain channel estimation value on each path.
12. The apparatus of claim 11, wherein the processor is further configured to read a program in the memory and perform the following: and respectively carrying out Fast Fourier Transform (FFT) on the time domain signals on each path to obtain time frequency resources on each path.
13. The apparatus of claim 11, wherein the processor is further configured to read a program in the memory and perform the following: and respectively carrying out least square LS channel estimation on the time frequency resources on each path to obtain frequency domain channel estimation values on each path.
14. The apparatus of claim 11, wherein the processor is further configured to read a program in the memory and perform the following: and performing Inverse Discrete Fourier Transform (IDFT) on the sequence consisting of the frequency domain channel estimation values on each path to determine the time domain channel estimation values on each path.
15. The apparatus of claim 11, wherein the processor is further configured to read a program in the memory and perform the following:
calculating the conjugate of the first time domain channel estimation value to obtain a value for the first time domain channel estimation value and the second time domain channel estimation value in the time domain channel estimation values on each path;
multiplying the value and the second time domain channel estimation value to determine the frequency offset on a first path;
wherein the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
16. The apparatus of claim 11, wherein the processor is further configured to read a program in the memory and perform the following:
and carrying out automatic frequency tracking on the frequency deviation.
17. The apparatus of claim 16, wherein the processor is further configured to read a program in the memory and perform the following:
determining a weighted average coefficient corresponding to each path;
calculating a weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and carrying out automatic frequency tracking on the frequency deviation weighted average value.
18. The apparatus of claim 17, wherein the processor is further configured to read a program in the memory and perform the following:
calculating the weighted average of the frequency deviation on each path by using the following formula:
Δf＝∑P(Δfp)·Δfp；
where, af represents a frequency offset weighted average,pP(Δfp) Represents a weighted average coefficient, Δ f, corresponding to each pathpDenotes the frequency offset on each path, p is 1,2, … n, the time domain channel estimation value on the ith path and the ith symbol are shown, and n represents the total number of paths.
19. The apparatus of claim 11, wherein the processor is further configured to read a program in the memory and perform the following:
determining target frequency offset from the frequency offsets on the paths according to a preset rule;
and carrying out automatic frequency tracking on the target frequency offset.
20. A frequency offset estimation apparatus, comprising: a transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor; it is characterized in that the preparation method is characterized in that,
the processor is used for reading the program in the memory and executing the following processes:
obtaining time-frequency resources on each path; performing Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path respectively to obtain time-domain signals on each path;
and the transceiver is used for transmitting the time domain signals on each path to a receiving end.
21. A frequency offset estimation apparatus, comprising:
the first acquisition module is used for receiving the time domain signals on each path sent by the transmitting terminal and acquiring the time frequency resources on each path according to the time domain signals on each path;
a second obtaining module, configured to perform channel estimation on the time-frequency resources on each path, respectively, to obtain frequency domain channel estimation values on each path;
a first determining module, configured to determine, according to the frequency domain channel estimation value on each path, a time domain channel estimation value on each path;
and a second determining module, configured to determine, according to the time domain channel estimation value on each path, a frequency offset on each path.
22. The apparatus of claim 21, wherein the second determining module comprises:
a calculating submodule, configured to calculate a conjugate of a first time domain channel estimation value and a second time domain channel estimation value among the time domain channel estimation values on the paths, so as to obtain a value;
the determining submodule is used for multiplying the numerical value and the second time domain channel estimation value to determine the frequency offset on a first path;
wherein the first time domain channel estimation value and the second time domain channel estimation value are time domain channel estimation values corresponding to different paths.
23. The apparatus of claim 21, further comprising:
and the tracking module is used for carrying out automatic frequency tracking on the frequency deviation.
24. The apparatus of claim 23, wherein the tracking module comprises:
the determining submodule is used for determining a weighted average coefficient corresponding to each path;
the calculating submodule is used for calculating the weighted average value of the frequency deviation on each path according to the weighted average coefficient corresponding to each path and the frequency deviation on each path;
and the tracking submodule is used for carrying out automatic frequency tracking on the frequency deviation weighted average value.
25. A frequency offset estimation apparatus, comprising:
the first acquisition module is used for acquiring time-frequency resources on each path;
a second obtaining module, configured to perform Inverse Fast Fourier Transform (IFFT) on the time-frequency resources on each path, respectively, to obtain time-domain signals on each path;
and the sending module is used for sending the time domain signals on each path to a receiving end.
26. A computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the steps in the method according to any one of claims 1 to 9; or
The computer program realizing the steps of the method as claimed in claim 10 when executed by a processor.
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