CN114598584B - Fine frequency offset estimation method and device in wireless communication system - Google Patents
Fine frequency offset estimation method and device in wireless communication system Download PDFInfo
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- 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
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- H04L27/2657—Carrier synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
Abstract
The disclosure relates to the technical field of wireless communication, and provides a fine frequency offset estimation method and device in a wireless communication system. The method comprises the following steps: receiving a data frame and positioning to a guard interval sequence of a long training sequence domain; intercepting a first test sequence with a first preset length from a preset sampling point of a guard interval sequence backward, wherein the guard interval sequence comprises a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is a sampling point between the middle sampling point and the ending sampling point; calculating a channel estimation value according to the first test sequence and the reference signal; intercepting a second test sequence with a second preset length from the last signal sampling point of the first test sequence; calculating a channel equalization value according to the channel estimation value and the second test sequence; and calculating a fine frequency offset estimation value according to the channel equalization value and the reference signal. The method and the device can improve the precision of fine frequency offset estimation of a wireless communication system, and the precision of the frequency offset estimation can reach about 10 Hz.
Description
Technical Field
The present disclosure relates to the field of wireless communication technologies, and in particular, to a method and an apparatus for estimating fine frequency offset in a wireless communication system.
Background
In the field of wireless communication, the superiority and inferiority of synchronization performance directly relate to the performance of the entire communication system (such as reliability of data transmission). Orthogonal Frequency Division Multiplexing (OFDM) is a high-speed transmission technique that can effectively combat interference between signal waveforms, which is one of the core techniques of fourth generation mobile communication systems. For OFDM systems, there are also implementation problems of synchronization (such as carrier synchronization and symbol synchronization) that are inevitable.
Symbol synchronization is crucial to OFDM systems, and errors in symbol timing position can cause inter-symbol crosstalk and inter-subcarrier crosstalk. In the prior art, symbol synchronization of general wireless WiFi signals (except for 802.11b protocol) is performed by performing cross-correlation calculation on two repeated Training sequences in a Long Training sequence field (L _ LTF) in the signal to obtain a phase difference between symbols, and then calculating a frequency offset value according to the phase and frequency. However, the correlation between L _ LTF symbols is weakened due to the influence of factors such as the channel condition of the wireless signal, and the accuracy of the frequency offset estimation is low.
Disclosure of Invention
In view of this, embodiments of the present disclosure provide a fine frequency offset estimation method and apparatus in a wireless communication system, an electronic device, and a computer-readable storage medium, so as to solve the problem in the prior art that correlation between L _ LTF symbols is weakened due to the influence of factors such as channel conditions of wireless signals, and thus accuracy of frequency offset estimation is low.
In a first aspect of the embodiments of the present disclosure, a method for estimating a fine frequency offset in a wireless communication system is provided, including:
receiving a data frame of a wireless transmission signal sent by a signal sending end, and positioning to a guard interval sequence of a long training sequence field of the data frame;
the method comprises the steps that a first test sequence with a first preset length is intercepted from a preset sampling point of a guard interval sequence, the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is a sampling point which is located between the middle sampling point and the ending sampling point and is not the middle sampling point or the ending sampling point;
calculating to obtain a channel estimation value according to the first test sequence and a preset reference signal;
intercepting a second test sequence with a second preset length from the last signal sampling point of the first test sequence;
calculating to obtain a channel equalization value according to the channel estimation value and the second test sequence;
and calculating to obtain a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal.
In a second aspect of the embodiments of the present disclosure, an apparatus for estimating a fine frequency offset in a wireless communication system is provided, including:
the data receiving module is configured to receive a data frame of a wireless transmission signal sent by a signal sending end and position the data frame to a guard interval sequence of a long training sequence field of the data frame;
the device comprises a first sequence intercepting module, a second sequence intercepting module and a third sequence intercepting module, wherein the first sequence intercepting module is configured to intercept a first test sequence with a first preset length from a preset sampling point of a guard interval sequence, the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is a sampling point which is located between the middle sampling point and the ending sampling point and is not the middle sampling point or the ending sampling point;
the channel estimation module is configured to calculate a channel estimation value according to the first test sequence and a preset reference signal;
a second sequence intercepting module configured to intercept a second test sequence of a second predetermined length from a last signal sampling point of the first test sequence;
the channel equalization module is configured to calculate a channel equalization value according to the channel estimation value and the second test sequence;
and the frequency offset estimation module is configured to calculate a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal.
In a third aspect of the embodiments of the present disclosure, an electronic device is provided, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the above method when executing the computer program.
In a fourth aspect of the embodiments of the present disclosure, a computer-readable storage medium is provided, which stores a computer program, which when executed by a processor, implements the steps of the above-mentioned method.
Compared with the prior art, the beneficial effects of the embodiment of the disclosure at least comprise: the method comprises the steps of positioning to a guard interval sequence of a long training sequence field of a data frame by receiving a data frame of a wireless transmission signal sent by a signal sending end; the method comprises the steps that a first test sequence with a first preset length is intercepted from a preset sampling point of a guard interval sequence, the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is a sampling point which is located between the middle sampling point and the ending sampling point and is not the middle sampling point or the ending sampling point; calculating to obtain a channel estimation value according to the first test sequence and a preset reference signal; intercepting a second test sequence with a second preset length from the last signal sampling point of the first test sequence; calculating to obtain a channel equalization value according to the channel estimation value and the second test sequence; calculating to obtain a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal; the method comprises the steps of carrying out channel estimation by using a first test sequence and a preset reference signal to obtain a channel estimation value, carrying out channel equalization calculation by using the channel estimation value and a second test sequence obtained by interception, well eliminating the influence of the channel on the signal phase under the condition that the channel has no instantaneous mutation, and simultaneously calculating a fine frequency offset estimation value of a signal receiving end receiving a data frame by using phase transformation caused by frequency offset, thereby not only enhancing the correlation between symbols of a long training sequence domain, but also improving the precision of fine frequency offset estimation, wherein the precision of the frequency offset estimation can reach about 10 Hz.
Drawings
To more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without inventive efforts.
FIG. 1 is a scenario diagram of an application scenario of an embodiment of the present disclosure;
fig. 2 is a flowchart illustrating a fine frequency offset estimation method in a wireless communication system according to an embodiment of the disclosure;
fig. 3 is a schematic structural diagram of a long training sequence field in a fine frequency offset estimation method in a wireless communication system according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a fine frequency offset estimation apparatus in a wireless communication system according to an embodiment of the present disclosure;
fig. 5 is a schematic structural diagram of an electronic device provided in an embodiment of the present disclosure.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the disclosed embodiments. However, it will be apparent to one skilled in the art that the present disclosure may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present disclosure with unnecessary detail.
A method and an apparatus for fine frequency offset estimation in a wireless communication system according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.
Fig. 1 is a scene schematic diagram of an application scenario of an embodiment of the present disclosure. The application scenario may include a signal transmitting end 101, a signal receiving end 102, and a wireless channel 103.
The signal sending end 101 generally refers to a sending device that sends out a signal (such as a wireless WiFi signal), for example, a wireless router, or a wireless network card with a function of switching between receiving and sending.
The signal receiving end 102 is generally a receiving device, such as a WLAN receiver (also referred to as a wireless network card), which can be used to receive the signal sent by the signal sending end 101.
The wireless channel 103 is a visual metaphor for a "connection path" between the signal transmitting end 101 and the signal receiving end 102 in wireless communication. For radio waves, which are transmitted from a signal transmitting end to a signal receiving end without a physical connection therebetween, there may be more than one propagation path, and in order to visually describe the operation between the signal transmitting end and the signal receiving end, it is conceivable that there is an invisible road connection therebetween, which is generally called a channel, and a wireless channel is a so-called wireless "frequency band.
In this embodiment, the signal receiving end 102 may receive a data frame of a wireless transmission signal sent by the signal sending end 101 through the wireless channel 103, and then, position the data frame to a guard interval sequence of a long training sequence field of the data frame; then, a first test sequence with a first preset length is intercepted backwards from a preset sampling point of a guard interval sequence, the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is a sampling point which is positioned between the middle sampling point and the ending sampling point and is not the middle sampling point or the ending sampling point; calculating to obtain a channel estimation value according to the first test sequence and a preset reference signal; then, a second test sequence with a second preset length is intercepted from the last signal sampling point of the first test sequence; then, according to the channel estimation value and the second test sequence, calculating to obtain a channel equalization value; and finally, calculating to obtain a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal, and well eliminating the influence of a wireless channel on the signal phase, thereby better enhancing the correlation between symbols of a long training sequence domain of the data frame of the wireless transmission signal, improving the accuracy of fine frequency offset estimation and ensuring that the data transmission of the wireless transmission communication is more reliable.
It should be noted that specific types of the signal sending end 101 and the signal receiving end 102 may be adjusted according to actual requirements of an application scenario, which is not limited in the embodiment of the present disclosure.
Fig. 2 is a flowchart illustrating a fine frequency offset estimation method in a wireless communication system according to an embodiment of the disclosure. The fine frequency offset estimation method in the wireless communication system of fig. 2 may be performed by the signal receiving end 102 of fig. 1. As shown in fig. 2, the method for estimating fine frequency offset in a wireless communication system includes:
step S201, receiving a data frame of a wireless transmission signal sent by a signal sending end, and positioning to a guard interval sequence of a long training sequence field of the data frame.
Referring to fig. 1, a signal receiving end 102 receives a data frame of a wireless transmission signal (e.g., a WIFI 802.11ag/n/ac/ax/be signal) sent by a signal sending end 101 through a wireless channel 103. The data frame structure of these wireless transmission signals typically includes a long training sequence field. Wherein, the Long Training sequence field refers to a Non-high throughput Long Training sequence field (Non-HT Long Training field, L _ LTF for short).
Fig. 3 shows a schematic structure of a long training sequence domain. As shown in fig. 3, the long training sequence field includes a guard interval sequence 301, a first training sequence 302, and a second training sequence 303.
Among them, the guard interval sequence (GI 2) usually has a plurality of signal sampling points. The first training sequence 302 (hereinafter referred to as "T1") and the second training sequence 303 (hereinafter referred to as "T2") are two repeated sequence fields in a long training sequence field, have the same sequence length, and generally include a plurality of signal sampling points. The number of signal samples of the guard interval sequence 301, the first training sequence 302 and the second training sequence 303 in the long training sequence domain is related to and proportional to the bandwidth. Specifically, when the bandwidth is 20M, the number of signal sampling points of the guard interval sequence 301 in the long training sequence domain is 32, and the number of sampling points of the first training sequence 302 and the number of sampling points of the second training sequence 303 are 64, respectively. When the bandwidth is 40M, the number of signal samples of the guard interval sequence 301 in the long training sequence domain is 64, and the number of samples of the first training sequence 302 and the number of samples of the second training sequence 303 are 128. When the bandwidth is 60M, the number of signal samples of the guard interval sequence 301 in the long training sequence domain is 128, and the number of samples of the first training sequence 302 and the number of samples of the second training sequence 303 are 256 respectively. It can be seen that, when the bandwidth is increased by N times, the number of sampling points of the guard interval sequence 301, the first training sequence 302 and the second training sequence 303 in the long training sequence field of the data frame of the wireless transmission signal is also increased by N times (where N is a non-zero positive number).
Step S202, a first test sequence with a first preset length is intercepted backwards from a preset sampling point of a guard interval sequence, the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is a sampling point which is located between the middle sampling point and the ending sampling point and is not the middle sampling point or the ending sampling point.
The first predetermined length is the same as the length of the first training sequence. For example, when the bandwidth is 20M, the length of the first training sequence is 64 signal samples, and the first predetermined length is 64 signal samples.
With continued reference to fig. 3, the guard interval sequence 301 includes a plurality of signal sampling points. For example, when the bandwidth is 20M, the guard interval sequence 301 includes 32 signal sampling points, which may be numbered as 1 st to 32 th signal sampling points in sequence, where the 1 st signal sampling point is a start sampling point, the 16 th signal sampling point is a middle sampling point, and the 32 th signal sampling point is an end sampling point. The preset sampling point is between 16 th sampling point and 32 th sampling point, namely any one of 17 th sampling point to 31 th sampling point.
As an example, it is assumed that in a wireless communication system with a bandwidth of 20M, a first test sequence with a first predetermined length is intercepted from a preset sampling point of a guard interval sequence, and specifically, a first test sequence with a length of 64 signal sampling points may be intercepted from a 17 th sampling point of the guard interval sequence. It is understood that the first test sequence herein includes the 17 th to 32 th signal sampling points in the guard interval sequence and the first 49 signal sampling points in the first training sequence.
Step S203, calculating to obtain a channel estimation value according to the first test sequence and a preset reference signal.
The predetermined reference signal refers to a long training sequence field value given in a wireless communication protocol (e.g., WiFi 802.11 ag/n/ac/ax/be) used in the wireless communication system.
Step S204, a second test sequence with a second preset length is intercepted from the last signal sampling point of the first test sequence.
The second predetermined length is the same as the length of the second training sequence. For example, at a bandwidth of 20M, the length of the second training sequence is 64 signal samples, and then the second predetermined length is 64 signal samples.
With reference to the example of step S202, if the first test sequence is a sequence including the 17 th to 32 th signal sampling points in the guard interval sequence and the first 49 signal sampling points in the first training sequence, 64 signal sampling points are intercepted from the 50 th signal sampling point of the first test sequence, and a second test sequence is obtained. That is, the second test sequence includes the 50 th to 64 th sampling points of the first training sequence, and the first 50 signal sampling points of the second training sequence.
And step S205, calculating to obtain a channel equalization value according to the channel estimation value and the second test sequence.
Channel equalization refers to an anti-fading measure taken to improve the transmission performance of a communication system in a fading channel. The method is mainly used for eliminating or weakening the problem of intersymbol interference caused by multipath time delay in broadband communication.
And step S206, calculating to obtain a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal.
The fine frequency offset estimation value is an estimation value of decimal frequency offset in frequency offset frequency deviation of a subcarrier. The frequency offset value of the decimal frequency offset is small and generally within the range of one subcarrier interval.
According to the technical scheme provided by the embodiment of the disclosure, channel estimation is performed by using the first test sequence and the preset reference signal to obtain a channel estimation value, and then the channel estimation value and the intercepted second test sequence are used for performing channel equalization calculation, so that the influence of the channel on the signal phase can be well eliminated under the condition that the channel has no instantaneous mutation, and meanwhile, the fine frequency offset estimation value of the data frame received by the signal receiving end can be calculated by utilizing phase transformation caused by frequency offset, so that the correlation between symbols of a long training sequence domain can be enhanced, the accuracy of fine frequency offset estimation can be improved, and the accuracy of frequency offset estimation can reach about 10 Hz.
In some embodiments, the step S203 includes:
performing fast Fourier transform calculation on the first test sequence to obtain a first conversion sequence;
and performing dot product calculation on the first conversion sequence and a preset reference signal to obtain a channel estimation value.
Fast Fourier Transform (FFT) is a method of rapidly calculating a Discrete Fourier Transform (DFT) of a sequence or an inverse thereof. Fourier analysis transforms the signal from the original domain (usually time or space) to a representation in the frequency domain or vice versa. The FFT quickly computes such a transform by decomposing the DFT matrix into products of sparse (mostly zero) factors.
In this embodiment, by performing FFT calculation on the first test sequence, a first transformed sequence (hereinafter referred to as "FFT _ t 1") having the same length as the first test sequence can be obtained. Then, the FFT _ t1 and the reference signal are subjected to dot product calculation to obtain a channel estimation value H.
Dot product, also known as inner product, quantity product, scalar product, dot product, refers to a binary operation that accepts two vectors on a real number R and returns a real-valued scalar. The method is a standard inner product of Euclidean space, a Cartesian coordinate system is introduced into the Euclidean space, and the inner product between vectors can be obtained by algebraic operation of vector coordinates or can be solved by introducing geometrical concepts such as lengths and angles of two vectors.
In some embodiments, the step S205 includes:
performing fast Fourier transform calculation on the second test sequence to obtain a second conversion sequence;
performing conjugate operation on the channel estimation value to obtain a conjugate value of the channel estimation value;
carrying out modulus operation on the channel estimation value to obtain a modulus value;
and calculating to obtain a channel equalization value according to the second conversion sequence, the conjugate value of the channel estimation value and the modulus value.
Wherein, according to the second conversion sequence, the conjugate value of the channel estimation value and the modulus value, calculating to obtain the channel equalization value, specifically including:
multiplying the second conversion sequence by the conjugate value of the channel estimation value to obtain a multiplication result;
and dividing the multiplication result by the square of the modulus value to obtain a channel equalization value.
As an example, the FFT calculation may be performed on the second test sequence to obtain a second transformed sequence. Then, the channel estimation value H may be substituted into a preset conjugate function y = conj (H) to calculate a conjugate value thereof; substituting the channel estimation value H into a preset modulus operation function y = abs (H), and calculating to obtain a modulus value; then calculating the product of the second conversion sequence and the conjugate value to obtain a multiplication result; and then, the quotient of the multiplication result and the square of the modulus value is obtained to obtain a channel equalization value.
Specifically, the channel equalization value is calculated as S = conj (h) FFT _ t2/((abs (h)) 2). Where S is the equalized result (i.e., the channel equalization value), conj () is the conjugate function, abs () is the modulo function, 2 represents the square, and FFT _ t2 represents the second conversion sequence.
In some embodiments, the step S206 includes:
performing conjugate operation on the reference signal to obtain a conjugate value of the reference signal;
calculating a phase difference value between the channel equalization value and a conjugate value of the reference signal;
calculating the average value of the phase difference values to obtain the average value of the phase differences,
and calculating to obtain a fine frequency offset estimation value of the data frame according to the phase difference mean value and the sequence length of the second test sequence.
Specifically, the conjugate value can be calculated by substituting the preset reference signal R into a preset conjugate function y = conj (R). Then according to the formula: p = S × conj (r), and calculates a phase difference P between the channel equalization value S and the conjugate value. Where P is the complex number of points of the second transform sequence. Then, the average value of the phase difference values P and the phase angle thereof are calculated to obtain the average value of the phase difference
. Finally, according to the formula: f =
And (2) pi t), and calculating to obtain a fine frequency offset estimation value f of the data frame. Where pi is the circumferential rate pi and t is the length of the second test sequence or the first test sequence (e.g., 64 consecutive sample signal points).
In some embodiments, referring to fig. 3, the long training sequence field of the data frame includes a guard interval sequence 301, a first training sequence 302, and a second training sequence 303, which are connected in sequence. The step S203 includes:
intercepting the last signal sampling point of the second training sequence forward to obtain an intercepting sequence, wherein the length of the intercepting sequence is the same as that of the guard interval sequence;
replacing a guard interval sequence in a long training sequence field of the data frame with an interception sequence to obtain an updated data frame;
and intercepting a first preset number of signal sampling points backwards from a first preset sampling point of a guard interval sequence of the updated data frame to obtain a first test sequence, wherein the first test sequence comprises a partial interception sequence and a partial first training sequence.
As an example, it is assumed that in a wireless communication system with a bandwidth of 20M, the guard interval sequence 301, the first training sequence 302, and the second training sequence 303 in the long training sequence domain of the data frame of the wireless transmission signal have 32, 64, and 64 signal sampling points, respectively. The signal sampling points of the guard interval sequences can be respectively numbered as 1 st to 32 th signal sampling points, then the signal sampling points of the first training sequence can be respectively numbered as 33 rd to 97 th signal sampling points, and then the signal sampling points of the second training sequence can be respectively numbered as 98 th to 162 th signal sampling points. First, the last signal sample (i.e. the 162 th signal sample) of the second training sequence may be truncated forward to the 130 th signal sample, and a total of 32 signal samples may be used as the truncation sequence. And then, replacing the guard interval sequence in the long training sequence domain of the data frame with an interception sequence to obtain an updated data frame. Then, a first preset sampling point (any one of 17 th to 31 th signal sampling points) of the guard interval sequence of the updated data frame is used for backward intercepting a first preset number (32 signal sampling points) of signal sampling points to obtain a first test sequence.
In some embodiments, calculating the channel estimation value according to the first test sequence and a preset reference signal includes:
a third preset number of signal sampling points are intercepted backwards from a second preset sampling point of a guard interval sequence of an updated data frame to obtain a third test sequence, wherein the first preset sampling point and the second preset sampling point are not overlapped, and the position difference between the first preset sampling point and the second preset sampling point is 1-3 sampling point positions;
calculating to obtain a first channel estimation value according to the first test sequence and a preset reference signal;
calculating to obtain a second channel estimation value according to the third test sequence and a preset reference signal;
and calculating the average value of the first channel estimation value and the second channel estimation value to obtain the channel estimation value.
With reference to the above example, if 32 signal sampling points are intercepted backward from the 17 th signal sampling point of the guard interval sequence of the updated data frame to obtain the first test sequence, a third predetermined number (32 signal sampling points) of signal sampling points may be intercepted backward from any one of the 18 th to 20 th signal sampling points to obtain a third test sequence, and then, the first channel estimation value is calculated according to the first test sequence and the preset reference signal, and the second channel estimation value is calculated according to the third test sequence and the preset reference signal, respectively; then, the average value of the first and second channel estimation values is calculated to obtain a channel estimation value (average value).
According to the technical scheme provided by the embodiment of the disclosure, a signal sampling point with the same length as a guard interval sequence is intercepted from the last signal sampling point of a second training sequence, an intercepted sequence is obtained, the guard interval sequence in an original data frame is replaced by the intercepted sequence, an updated data frame is obtained, and a first test sequence is intercepted from the updated data frame according to the method. In addition, the channel estimation value is calculated by intercepting the two test sequences, so that the accuracy of channel estimation can be improved, the channel estimation value is subsequently used for compensating the second test sequence, the influence of a wireless channel on the signal phase can be eliminated, and the result accuracy of subsequent fine frequency offset estimation can be further improved.
All the above optional technical solutions may be combined arbitrarily to form optional embodiments of the present application, and are not described herein again.
The following are embodiments of the disclosed apparatus that may be used to perform embodiments of the disclosed methods. For details not disclosed in the embodiments of the apparatus of the present disclosure, refer to the embodiments of the method of the present disclosure.
Fig. 4 is a schematic diagram of a fine frequency offset estimation apparatus in a wireless communication system according to an embodiment of the present disclosure. As shown in fig. 4, the fine frequency offset estimation apparatus in the wireless communication system includes:
a data receiving module 401 configured to receive a data frame of a wireless transmission signal sent by a signal sending end, and locate to a guard interval sequence of a long training sequence field of the data frame;
a first sequence intercepting module 402 configured to intercept a first test sequence of a first predetermined length backward from a preset sampling point of a guard interval sequence, the guard interval sequence including a plurality of signal sampling points, the plurality of signal sampling points including a start sampling point, an intermediate sampling point, and an end sampling point, the preset sampling point being a sampling point located between the intermediate sampling point and the end sampling point and not being the intermediate sampling point or the end sampling point;
a channel estimation module 403, configured to calculate a channel estimation value according to the first test sequence and a preset reference signal;
a second sequence truncation module 404 configured to truncate a second test sequence of a second predetermined length from a last signal sampling point of the first test sequence;
a channel equalization module 405 configured to calculate a channel equalization value according to the channel estimation value and the second test sequence;
and a frequency offset estimation module 406 configured to calculate a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal.
According to the technical scheme provided by the embodiment of the disclosure, a data receiving module 401 receives a data frame of a wireless transmission signal sent by a signal sending end and positions the data frame to a guard interval sequence of a long training sequence field of the data frame; the first sequence intercepting module 402 intercepts a first test sequence with a first preset length from a preset sampling point of a guard interval sequence backward, the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, an intermediate sampling point and an ending sampling point, and the preset sampling point is positioned between the intermediate sampling point and the ending sampling point and is not the intermediate sampling point or the sampling point at the end; the channel estimation module 403 calculates a channel estimation value according to the first test sequence and a preset reference signal; the second sequence intercepting module 404 intercepts a second test sequence with a second predetermined length from the last signal sampling point of the first test sequence; the channel equalization module 405 calculates a channel equalization value according to the channel estimation value and the second test sequence; the frequency offset estimation module 406 calculates a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal; the method comprises the steps of carrying out channel estimation by using a first test sequence and a preset reference signal to obtain a channel estimation value, carrying out channel equalization calculation by using the channel estimation value and a second test sequence obtained by interception, well eliminating the influence of the channel on the signal phase under the condition that the channel has no instantaneous mutation, and simultaneously calculating a fine frequency offset estimation value of a signal receiving end receiving a data frame by using phase transformation caused by frequency offset, thereby not only enhancing the correlation between symbols of a long training sequence domain, but also improving the precision of fine frequency offset estimation, wherein the precision of the frequency offset estimation can reach about 10 Hz.
In some embodiments, the channel estimation module 403 includes:
the first sequence transformation unit is configured to perform fast Fourier transformation calculation on the first test sequence to obtain a first transformation sequence;
and the dot product calculating unit is configured to perform dot product calculation on the first conversion sequence and a preset reference signal to obtain a channel estimation value.
In some embodiments, the channel equalization module 405 includes:
the second sequence transformation unit is configured to perform fast Fourier transformation calculation on the second test sequence to obtain a second transformation sequence;
the conjugate calculation unit is configured to perform conjugate operation on the channel estimation value to obtain a conjugate value of the channel estimation value;
the modulus taking unit is configured to perform modulus taking operation on the channel estimation value to obtain a modulus taking value;
and the equalization value calculating unit is configured to calculate a channel equalization value according to the second conversion sequence, the conjugate value of the channel estimation value and the modulus value.
In some embodiments, the equalization value calculating unit may be specifically configured to:
multiplying the second conversion sequence by the conjugate value of the channel estimation value to obtain a multiplication result;
and dividing the multiplication result by the square value of the modulus value to obtain a channel equalization value.
In some embodiments, the frequency offset estimation module 406 includes:
a conjugation unit configured to perform conjugation operation on the reference signal to obtain a conjugate value of the reference signal;
a phase difference calculation unit configured to calculate a phase difference value between the channel equalization value and a conjugate value of the reference signal;
an average value calculation unit configured to calculate an average value of the phase difference values, resulting in a phase difference average value,
and the frequency offset estimation unit is configured to calculate a fine frequency offset estimation value of the data frame according to the phase difference mean value and the sequence length of the second test sequence.
In some embodiments, the long training sequence field of the data frame includes a guard interval sequence, a first training sequence, and a second training sequence, which are sequentially connected. The first sequence intercepting module 402 includes:
the first interception unit is configured to intercept an interception sequence from the last signal sampling point of the second training sequence, wherein the length of the interception sequence is the same as that of the guard interval sequence;
the replacing unit is configured to replace a guard interval sequence in a long training sequence domain of the data frame with an intercepting sequence to obtain an updated data frame;
and the second interception unit is configured to intercept a first preset number of signal sampling points backwards from a first preset sampling point of the guard interval sequence of the updated data frame to obtain a first test sequence, and the first test sequence comprises a part of the interception sequence and a part of the first training sequence.
In some embodiments, the calculating, according to the first test sequence and a preset reference signal, a channel estimation value includes:
a third preset number of signal sampling points are intercepted backwards from a second preset sampling point of the guard interval sequence of the updated data frame to obtain a third test sequence, wherein the first preset sampling point and the second preset sampling point are not coincident, and the position difference between the first preset sampling point and the second preset sampling point is 1-3 sampling point positions;
calculating to obtain a first channel estimation value according to the first test sequence and a preset reference signal;
calculating to obtain a second channel estimation value according to the third test sequence and a preset reference signal;
and calculating the average value of the first channel estimation value and the second channel estimation value to obtain the channel estimation value.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure.
Fig. 5 is a schematic diagram of an electronic device 5 provided by the embodiment of the present disclosure. As shown in fig. 5, the electronic apparatus 5 of this embodiment includes: a processor 501, a memory 502 and a computer program 503 stored in the memory 502 and executable on the processor 501. The steps in the various method embodiments described above are implemented when the processor 501 executes the computer program 503. Alternatively, the processor 501 implements the functions of the respective modules/units in the above-described respective apparatus embodiments when executing the computer program 503.
The electronic device 5 may be an electronic device such as a desktop computer, a notebook, a palm computer, and a cloud server. The electronic device 5 may include, but is not limited to, a processor 501 and a memory 502. Those skilled in the art will appreciate that fig. 5 is merely an example of the electronic device 5, and does not constitute a limitation of the electronic device 5, and may include more or fewer components than shown, or different components.
The Processor 501 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like.
The storage 502 may be an internal storage unit of the electronic device 5, for example, a hard disk or a memory of the electronic device 5. The memory 502 may also be an external storage device of the electronic device 5, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like provided on the electronic device 5. The memory 502 may also include both internal and external storage units of the electronic device 5. The memory 502 is used for storing computer programs and other programs and data required by the electronic device.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned function distribution may be performed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules, so as to perform all or part of the functions described above. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit.
The integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, the present disclosure may implement all or part of the flow of the method in the above embodiments, and may also be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the computer program may implement the steps of the above methods and embodiments. The computer program may comprise computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying computer program code, recording medium, U.S. disk, removable hard disk, magnetic diskette, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier signal, telecommunications signal, software distribution medium, etc. It should be noted that the computer readable medium may contain suitable additions or additions that may be required in accordance with legislative and patent practices within the jurisdiction, for example, in some jurisdictions, computer readable media may not include electrical carrier signals or telecommunications signals in accordance with legislative and patent practices.
The above examples are only intended to illustrate the technical solutions of the present disclosure, not to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present disclosure, and they should be construed as being included in the scope of the present disclosure.
Claims (9)
1. A method for fine frequency offset estimation in a wireless communication system, comprising:
receiving a data frame of a wireless transmission signal sent by a signal sending end, and positioning to a guard interval sequence of a long training sequence field of the data frame;
intercepting a first test sequence with a first preset length from a preset sampling point of the guard interval sequence backwards, wherein the guard interval sequence comprises a plurality of signal sampling points, the plurality of signal sampling points comprise a starting sampling point, a middle sampling point and an ending sampling point, and the preset sampling point is positioned between the middle sampling point and the ending sampling point and is not the sampling point of the middle sampling point or the ending sampling point;
calculating to obtain a channel estimation value according to the first test sequence and a preset reference signal;
intercepting a second test sequence with a second preset length from the last signal sampling point of the first test sequence;
calculating to obtain a channel equalization value according to the channel estimation value and the second test sequence;
calculating to obtain a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal;
the long training sequence field of the data frame comprises a guard interval sequence, a first training sequence and a second training sequence which are connected in sequence;
intercepting a first test sequence with a first preset length from a preset sampling point of the guard interval sequence, wherein the first test sequence comprises:
intercepting forward from the last signal sampling point of the second training sequence to obtain an intercepted sequence, wherein the length of the intercepted sequence is the same as that of the guard interval sequence;
replacing the guard interval sequence in the long training sequence domain of the data frame with the interception sequence to obtain an updated data frame;
and intercepting a first preset number of signal sampling points backwards from a first preset sampling point of a guard interval sequence of the updated data frame to obtain a first test sequence, wherein the first test sequence comprises a part of the intercepted sequence and a part of the first training sequence.
2. The method of claim 1, wherein calculating the channel estimation value according to the first test sequence and a predetermined reference signal comprises:
performing fast Fourier transform calculation on the first test sequence to obtain a first conversion sequence;
and performing dot product calculation on the first conversion sequence and the preset reference signal to obtain a channel estimation value.
3. The method of claim 1, wherein calculating a channel equalization value according to the channel estimation value and the second test sequence comprises:
performing fast Fourier transform calculation on the second test sequence to obtain a second conversion sequence;
performing conjugate operation on the channel estimation value to obtain a conjugate value;
performing a modulus operation on the channel estimation value to obtain a modulus value;
and calculating to obtain a channel equalization value according to the second conversion sequence, the conjugate value and the modulus value.
4. The method of claim 3, wherein calculating a channel equalization value based on the second transformed sequence, the conjugate value, and the modulus value comprises:
multiplying the second conversion sequence and the conjugate value to obtain a multiplication result;
and dividing the multiplication result by the square value of the modulus value to obtain a channel equalization value.
5. The method of claim 1, wherein calculating the fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal comprises:
performing conjugate operation on the reference signal to obtain a conjugate function value;
calculating a phase difference value between the channel equalization value and the conjugate function value;
calculating the average value of the phase difference values to obtain the average value of the phase differences,
and calculating to obtain a fine frequency offset estimation value of the data frame according to the phase difference mean value and the sequence length of the second test sequence.
6. The method of claim 1, wherein calculating the channel estimation value according to the first test sequence and a predetermined reference signal comprises:
a third preset number of signal sampling points are intercepted backwards from a second preset sampling point of the guard interval sequence of the updated data frame to obtain a third test sequence, wherein the first preset sampling point is not overlapped with the second preset sampling point, and the position difference between the first preset sampling point and the second preset sampling point is 1-3 sampling point positions;
calculating to obtain a first channel estimation value according to the first test sequence and a preset reference signal;
calculating to obtain a second channel estimation value according to the third test sequence and a preset reference signal;
and calculating the mean value of the first channel estimation value and the second channel estimation value to obtain a channel estimation value.
7. An apparatus for fine frequency offset estimation in a wireless communication system, comprising:
the data receiving module is configured to receive a data frame of a wireless transmission signal sent by a signal sending end and position the data frame to a guard interval sequence of a long training sequence field of the data frame;
a first sequence intercepting module configured to intercept a first test sequence of a first predetermined length backward from a preset sampling point of the guard interval sequence, the guard interval sequence including a plurality of signal sampling points including a start sampling point, a middle sampling point, and an end sampling point, the preset sampling point being a sampling point located between the middle sampling point and the end sampling point and not being the middle sampling point or the end sampling point;
the channel estimation module is configured to calculate a channel estimation value according to the first test sequence and a preset reference signal;
a second sequence intercepting module configured to intercept a second test sequence of a second predetermined length from a last signal sampling point of the first test sequence;
the channel equalization module is configured to calculate a channel equalization value according to the channel estimation value and the second test sequence;
a frequency offset estimation module configured to calculate a fine frequency offset estimation value of the data frame according to the channel equalization value and the reference signal;
the long training sequence field of the data frame comprises a guard interval sequence, a first training sequence and a second training sequence which are connected in sequence;
intercepting a first test sequence with a first preset length from a preset sampling point of the guard interval sequence, wherein the first test sequence comprises:
intercepting forward from the last signal sampling point of the second training sequence to obtain an intercepted sequence, wherein the length of the intercepted sequence is the same as that of the guard interval sequence;
replacing the guard interval sequence in the long training sequence domain of the data frame with the interception sequence to obtain an updated data frame;
and intercepting a first preset number of signal sampling points backwards from a first preset sampling point of a guard interval sequence of the updated data frame to obtain a first test sequence, wherein the first test sequence comprises a part of the intercepted sequence and a part of the first training sequence.
8. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the steps of the method according to any of claims 1 to 6 when executing the computer program.
9. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 6.
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