CN114745240A - Method and device for determining frequency offset value of signal - Google Patents
Method and device for determining frequency offset value of signal Download PDFInfo
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Abstract
A method and a device for determining a frequency offset value of a signal are provided, the method comprises the following steps: receiving a plurality of received signals by adopting a plurality of antennas, wherein the plurality of received signals received by each antenna have respective arrival time and arrival angle; performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams, wherein the plurality of received signals on each beam have respective arrival time and belong to the same arrival angle interval; and carrying out frequency offset estimation on the received signal on each wave beam to obtain a frequency offset value of the received signal on each wave beam. The technical scheme is beneficial to quickly and accurately determining the frequency offset values of the received signals in different arrival angle directions.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a method and an apparatus for determining a frequency offset value of a signal.
Background
In the field of communications technology, when there is relative motion between a signal transmitting end (transmitter) and a signal receiving end (receiver), the frequency of an electromagnetic wave signal received by the receiver is different from the frequency of an electromagnetic wave signal transmitted by the transmitter, which is called doppler effect, wherein the difference between the frequency of the received signal and the frequency of the transmitted signal is called doppler shift or doppler frequency offset.
When the signal is transmitted to a moving receiver at only one angle of arrival (angle of incidence), then there is only one doppler shift; however, in the wireless channel transmission which is widely used at present, the propagation path between the transmitting end and the receiving end is often very complicated, and various obstacles such as mountains, trees, buildings, etc. are encountered. When a sine wave is transmitted to a moving receiver through a wireless channel with rich multipath components and receiving four directions of arrival angles, a doppler effect occurs due to relative motion between a transmitter and the receiver, and a plurality of doppler shifts are generated, so that the frequency spectrum of a received signal is broadened, which is called doppler spread (including frequency spectrum components with frequencies fc-fm to fc + fm, fc is the original frequency value of a signal transmitted by the transmitter, and fm is the maximum doppler frequency offset value). In the above case, the signal received by the receiver may be faded to different degrees. The frequency offset correction can be carried out on the signals by determining the frequency offset value of the received signals, and the Doppler spread spectrum is determined for application in a wider layer.
In the prior art, for a signal with only one incoming wave direction, since no doppler spread occurs (i.e. no set of multiple different doppler shifts occurs), the common techniques for determining the frequency offset value of the received signal are: using the receiving signals with a certain time interval, after compensating the phase influence of the corresponding transmitting signals, calculating the correlation value between the receiving signals pairwise, and estimating the signal frequency offset value by using the phase information of the correlation value and the time interval thereof. However, if the received signal arrives at the receiving end at multiple angles of arrival, it may take a long time for the received signal to perform frequency offset estimation, and some complex frequency offset estimation algorithms need to be used, which is time-consuming and tedious in calculation process and insufficient in accuracy.
Therefore, a method for determining frequency offset values of signals is needed, which is helpful to quickly and accurately determine the frequency offset values of received signals in a plurality of different directions of arrival angles.
Disclosure of Invention
The invention solves the technical problem of how to quickly and accurately determine the frequency offset values of received signals in a plurality of incoming wave directions with different arrival angles.
The embodiment of the invention provides a method for determining a frequency offset value of a signal, which comprises the following steps: receiving a plurality of received signals by adopting a plurality of antennas, wherein the plurality of received signals received by each antenna have respective arrival time and arrival angle; performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams, wherein the plurality of received signals on each beam have respective arrival time and belong to the same arrival angle interval; and carrying out frequency offset estimation on the received signal on each wave beam to obtain a frequency offset value of the received signal on each wave beam.
Optionally, the method further includes: and performing frequency offset correction on the received signal on each wave beam according to the frequency offset value of the received signal on each wave beam.
Optionally, performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams includes: and performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on all or part of beams.
Optionally, performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on partial beams includes: performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas, and calculating the signal-to-noise ratio average value and the energy average value of the plurality of received signals on each obtained beam; and selecting the wave beams with the average signal-to-noise ratio larger than a first preset threshold value or the average energy value larger than a second preset threshold value to obtain the receiving signals on the partial wave beams.
Optionally, performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams includes: and estimating the arrival angles of a plurality of received signals received by the plurality of antennas by adopting an arrival angle estimation algorithm to obtain a plurality of arrival angles, and aligning the peak directions of the beams of the plurality of received signals to the directions of the estimated arrival angles to obtain the received signals on the plurality of beams.
Optionally, the angle of arrival estimation algorithm is selected from: the Butterett Bartlett algorithm, the capone Capon algorithm, the multiple signal classification MUSIC algorithm.
Optionally, the performing frequency offset estimation on the received signal on each beam to obtain a frequency offset value of the received signal on each beam includes: for each beam, calculating correlation values of every two received signals corresponding to different sending moments in a plurality of received signals on the beam, and calculating an initial frequency offset value according to the correlation values; and determining the frequency offset value of the received signal on the beam according to the obtained plurality of initial frequency offset values.
Optionally, for each beam, the following formula is adopted to calculate a correlation value of each two of the multiple received signals on the beam, which corresponds to the received signals at different transmission time instants, and calculate an initial frequency offset value according to the correlation value:
R＝r(t0)×s*(t0)×r*(t1)×s(t1)；
wherein, fdFor indicating the initial frequency offset value; r is used to indicate a correlation value between two signals; angle () is used to indicate a phase angle function that computes complex numbers; r (t)0) For indicating transmission time t on a certain beam0The received signal of (a); r (t)1) For indicating transmission time t on a certain beam1The complex conjugate of the received signal of (a); s (t)0) For indicating r (t)0) Corresponding transmission signal s (t)0) The conjugate complex number of (a); s (t)1) Are respectively used for indicating r (t)1) A corresponding transmit signal; wherein, t1＞t0And satisfy
Optionally, determining the frequency offset value of the received signal on the beam according to the obtained multiple initial frequency offset values includes: taking the average value of the obtained initial frequency offset values as the frequency offset value of the received signal on the wave beam; alternatively, the median of the obtained plurality of initial frequency offset values is used as the frequency offset value of the received signal on the beam.
Optionally, after obtaining the frequency offset value of the received signal on each beam, the method further includes: and determining the Doppler spread spectrum according to the frequency offset value and the power average value of the received signals on each wave beam.
Optionally, the time domain minimum mean square error MMSE filtered channel estimation value is calculated according to the doppler spread spectrum.
Optionally, the following formula is adopted, and a channel estimation value after time domain minimum mean square error MMSE filtering is calculated according to the doppler spread spectrum:
Ht′mmse(l)＝RH′H×(RHH+σ2l)-1×HLS；
wherein Ht′mmse(l) A time domain MMSE filtered channel estimate indicative of an l-th OFDM symbol; rHHN for indicating time domain adjacencytfiltA first channel correlation matrix of OFDM symbols containing pilots with dimension Ntfilt×Ntfilt；RH′HFor indicating the l-th OFDM symbol and the nearest N to the OFDM symboltfiltA second channel correlation matrix of OFDM symbols containing pilot frequency with dimension of 1 × Ntfilt；HLSFor indicating the nearest N to the l-th OFDM symboltfiltMatrix of channel estimation values before time domain MMSE filtering of OFDM symbols containing pilot frequency, and dimension is NtfiltX 1; wherein N istfiltFor indicating the order of the time domain MMSE filter; sigma2For indicating HLSThe noise power of (c).
Optionally, the plurality of antennas satisfy one or more of the following: the plurality of antennas are arranged in an array; the arrangement direction of the plurality of antennas on the receiver is parallel to the movement direction of the receiver; the adjacent position spacing of the plurality of antennas is less than half of the carrier wavelength of the transmitted signal.
Optionally, the plurality of antennas are arranged in an array to satisfy one or more of the following: the plurality of antennas are arranged in a linear array; the antennas are arranged in a planar array; the antennas are arranged in a spherical array.
An embodiment of the present invention further provides a device for determining a frequency offset value of a signal, including: a signal receiving module, configured to receive multiple received signals by using multiple antennas, where the multiple received signals received by each antenna have respective arrival time and arrival angle; a beam decomposition module, configured to perform beam decomposition on multiple received signals received by the multiple antennas to obtain received signals on multiple beams, where the multiple received signals on each beam have respective arrival time and belong to the same arrival angle interval; and the frequency offset value determining module is used for carrying out frequency offset estimation on the received signal on each wave beam so as to obtain the frequency offset value of the received signal on each wave beam.
Embodiments of the present invention further provide a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor to perform the steps of the method for determining a frequency offset value of a signal.
The embodiment of the present invention further provides a terminal, which includes a memory and a processor, where the memory stores a computer program capable of running on the processor, and the processor executes the steps of the method for determining the frequency offset value of the signal when running the computer program.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, a plurality of antennas are adopted to receive a plurality of received signals, and the plurality of received signals received by each antenna have respective arrival time and arrival angle; performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams, wherein the plurality of received signals on each beam have respective arrival time and belong to the same arrival angle interval; and carrying out frequency offset estimation on the received signal on each wave beam to obtain a frequency offset value of the received signal on each wave beam. Compared with the prior art, the method that the phase information of the correlation values among the received signals with certain time intervals and the time intervals thereof are adopted to estimate the Doppler frequency offset value is only suitable for the signals in a single incoming wave direction, and when the received signals reach a receiving end at a plurality of arrival angles, the calculation process is time-consuming, tedious and insufficient in accuracy; the embodiment of the invention adopts the multiple antennas to respectively receive the signals in the multiple arrival angle directions, then carries out beam decomposition on the received signals, the decomposed received signals on each beam belong to the same arrival angle interval (namely, the arrival angle values of all the received signals on each beam are close), and then respectively calculates the frequency offset value of the received signals on each beam.
Further, after obtaining the frequency offset values of the received signals on the respective beams, the method further includes: and performing frequency offset correction on the received signal on each wave beam according to the frequency offset value of the received signal on each wave beam. In addition, a doppler spread spectrum is determined from the frequency offset value and the power average value of the received signal on each beam. In the embodiment of the present invention, after determining the frequency offset value of the received signal on each beam belonging to different arrival angle intervals, frequency offset correction, doppler spread spectrum determination, channel estimation calculation, and the like may be performed according to the requirements of the actual application scenario (for example, the channel estimation value after time domain minimum mean square error MMSE filtering is calculated according to the doppler spread spectrum).
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Fig. 1 is a flow chart of a method for determining a frequency offset value of a signal according to an embodiment of the present invention;
FIG. 2 is a flowchart of one embodiment of step S13 of FIG. 1;
fig. 3 is a flow chart of another method for determining a frequency offset value of a signal according to an embodiment of the present invention;
FIG. 4 is a flow chart of a method for determining a frequency offset value of a signal according to another embodiment of the present invention;
FIG. 5 is a diagram of a Doppler spread spectrum in an embodiment of the invention;
fig. 6 is a schematic structural diagram of a device for determining a frequency offset value of a signal according to an embodiment of the present invention.
Detailed Description
As mentioned above, in signal transmission, the relative motion between the transmitting end and the receiving end causes the doppler effect. When an electromagnetic wave signal arrives at a receiving end at a plurality of different arrival angles, a plurality of doppler shifts occur, and the spectrum of the received signal is broadened. The frequency offset correction can be carried out on the signals by determining the frequency offset value of the received signals, the Doppler spread spectrum is determined, and then the application in a wider layer is carried out.
In the prior art, for a signal with only one incoming wave direction, since no doppler spread occurs (i.e. no set of multiple different doppler shifts occurs), the common techniques for determining the frequency offset value of the received signal are: using the receiving signals with a certain time interval, after compensating the phase influence of the corresponding transmitting signals, calculating the correlation value between the receiving signals pairwise, and estimating the signal frequency offset value by using the phase information of the correlation value and the time interval thereof.
The inventor of the present invention has found through research that if a received signal arrives at multiple arrival angles, a longer time of frequency offset estimation may be required for the received signal, and some complex frequency offset estimation algorithms need to be used, so that the calculation process is time-consuming, tedious and insufficient in accuracy.
In the embodiment of the invention, a plurality of antennas are adopted to receive a plurality of received signals, and the plurality of received signals received by each antenna have respective arrival time and arrival angle; performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams, wherein the plurality of received signals on each beam have respective arrival time and belong to the same arrival angle interval; and carrying out frequency offset estimation on the received signal on each wave beam to obtain a frequency offset value of the received signal on each wave beam. Compared with the prior art, the method for estimating the Doppler frequency offset value according to the phase information of the correlation values between the received signals with a certain time interval and the time interval is usually adopted, the method is only suitable for the signals in a single incoming wave direction, and when the received signals reach at a plurality of arrival angles, the calculation process is time-consuming, tedious and insufficient in accuracy; the embodiment of the invention adopts the multiple antennas to respectively receive the signals in the multiple arrival angle directions, then carries out beam decomposition on the received signals, the decomposed received signals on each beam belong to the same arrival angle interval, and then respectively calculates the frequency offset value of the received signals on each beam.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, fig. 1 is a flowchart of a method for determining a frequency offset value of a signal according to an embodiment of the present invention. The method may include steps S11 through S13:
step S11: receiving a plurality of received signals by adopting a plurality of antennas, wherein the plurality of received signals received by each antenna have respective arrival time and arrival angle;
step S12: performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams, wherein the plurality of received signals on each beam have respective arrival time and belong to the same arrival angle interval;
step S13: and carrying out frequency offset estimation on the received signal on each wave beam to obtain a frequency offset value of the received signal on each wave beam.
It is understood that in a specific implementation, the method may be implemented by a software program running in a processor integrated within a chip or a chip module; alternatively, the method can be implemented in hardware or a combination of hardware and software.
In the specific implementation of step S11, the received signals may be electromagnetic wave signals transmitted by a base station, a vehicle-mounted terminal, a mobile phone, a computer, a tablet, etc. and reach a receiving end after being transmitted through a wireless channel, and specifically, due to the complicated path of the actual wireless channel, a transmitted signal may reach the receiving end in multiple directions of arrival after being transmitted through the wireless channel. The angle of arrival may refer to an angle between a wave ray and a certain direction (horizontal plane or normal to the horizontal plane), and may also be referred to as an incident angle. Specifically, the arrival angle of the received signal may be an included angle between an electromagnetic wave ray and a normal direction of the antenna array.
In a specific implementation, after the electromagnetic wave signal is sent out, since a propagation path between the transmitting end and the receiving end is often very complicated, the electromagnetic wave signal may encounter various obstacles such as mountains, trees, buildings, and the like, and the electromagnetic wave signal may be transmitted to the plurality of antennas through a wireless channel which has very rich multipath components and receives all directions of arrival angles, in this case, the plurality of received signals received by each antenna have respective arrival time and arrival angle. When there is relative motion between the transmitting end and the receiving end, a plurality of doppler shifts are generated due to the doppler effect, and the spectrum of the received signal is broadened.
In a specific implementation, when multiple antennas are used to receive the multiple received signals, the multiple antennas may be arranged in an array (including but not limited to a linear array, a planar array, and a spherical array). When the antennas are arranged in a linear array or a planar array, in order to avoid that the received signals with different arrival angles cannot be distinguished, the arrangement direction of the multiple antennas is parallel to the moving direction of the antenna array, and the position interval of adjacent antennas is less than half of the carrier wavelength of the transmitted signal. The moving direction of the antenna array may refer to a moving direction of a carrier of the antenna, and the carrier of the antenna may be a vehicle-mounted receiver, a radio, a mobile phone, or the like.
In a specific implementation of step S12, the performing beam decomposition on the multiple received signals received by the multiple antennas may be performing beam decomposition on the multiple received signals received by all or some of the multiple antennas within a preset time duration, and specifically, aligning peak directions of beams of the multiple received signals with respective directions of arrival angles obtained by estimation, so as to convert the received signals on the multiple antennas into received signals on multiple beams, where the received signals on each beam have respective arrival times and belong to the same arrival angle interval (that is, the arrival angles of the multiple received signals on each beam have similar values).
Further, performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams includes: and performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on all or part of beams.
In short, the orthogonal beam decomposition is to add all orthogonal beam directions together to cover all angles, so as to obtain received signals on all orthogonal beams. In a specific implementation, the specific method of the orthogonal beam decomposition may be a conventional method adopted in the prior art, and is not described herein again.
Further, performing orthogonal beam decomposition on the multiple received signals received by the multiple antennas to obtain received signals on partial beams includes: performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas, and calculating the signal-to-noise ratio average value and the energy average value of the plurality of received signals on each obtained beam; and selecting the wave beams with the average signal-to-noise ratio larger than a first preset threshold value or the average energy value larger than a second preset threshold value to obtain the receiving signals on the partial wave beams.
In a specific implementation, all orthogonal beam directions may be added together to cover all angles, so as to obtain received signals on all orthogonal beams, then calculate an average signal-to-noise ratio and an average energy value of the obtained multiple received signals on each beam, and then screen beams in which the average signal-to-noise ratio is greater than a first preset threshold or the average energy value is greater than a second preset threshold, so as to obtain received signals on the partial beams. Wherein the SIGNAL-to-NOISE RATIO (SNR) can be used to indicate the RATIO of SIGNAL to NOISE in the received SIGNAL, and the higher the SNR is, the more reliable the SIGNAL is.
Further, performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams includes: and estimating the arrival angles of a plurality of received signals received by the plurality of antennas by adopting an arrival angle estimation algorithm to obtain a plurality of arrival angles, and aligning the peak directions of the beams of the plurality of received signals to the directions of the estimated arrival angles to obtain the received signals on the plurality of beams.
In some non-limiting embodiments, the angle of arrival estimation algorithm may be selected from the buttlett algorithm, the capone Capon algorithm, the multi-signal classification MUSIC algorithm; other existing arrival angle estimation algorithms may also be selected, which is not limited in this embodiment of the present invention.
It should be noted that the above-described beam splitting method is only a non-limiting example, and in a specific implementation, the beam splitting may be performed on the multiple received signals received by the multiple antennas by using other suitable beam splitting methods, which is not described herein again.
In a specific implementation of step S13, a frequency offset estimation is performed on the received signal on each beam to obtain a frequency offset value of the received signal on each beam.
In a specific implementation, as described above, after performing beam decomposition on the multiple received signals received by the multiple antennas, the received signals on the multiple antennas are converted into received signals on multiple beams, and then frequency offset estimation is performed on the received signals on each beam. Since the multiple received signals on each beam obtained after decomposition belong to the same arrival angle interval (arrival angle values are close), the doppler spread is not serious, and therefore, only one frequency offset value can be estimated for the received signals on each beam.
In the embodiment of the invention, compared with the prior art that the method for estimating the Doppler frequency offset value by using the phase information of the correlation value between the received signals with a certain time interval and the time interval is often adopted, the method is only suitable for the signals in a single incoming wave direction, and when the received signals reach the receiving end at a plurality of arrival angles, the calculation process is time-consuming, tedious and insufficient in accuracy; the embodiment of the invention adopts the multiple antennas to respectively receive the signals in the multiple arrival angle directions, then carries out beam decomposition on the multiple received signals, the decomposed received signals on each beam belong to the same arrival angle interval, and then respectively estimates the frequency offset value of the received signal on each beam, thereby being beneficial to quickly and accurately determining the frequency offset values of the received signals in the multiple different arrival angle directions.
Referring to fig. 2, fig. 2 is a flowchart of a specific embodiment of step S13 in fig. 1. The performing of the frequency offset estimation on the received signal on each beam to obtain the frequency offset value of the received signal on each beam may include steps S21 to S22, which are described below.
In step S21, for each beam, a correlation value is calculated for each two of the plurality of received signals on the beam corresponding to the received signals at different transmission time instants, and an initial frequency offset value is calculated from the correlation values.
Wherein the correlation value is used for indicating the degree of correlation between the received signals at the different transmission time instants. The greater the correlation value, the higher the degree of correlation between the two received signals; the smaller the correlation, the lower the degree of correlation between the two received signals.
In step S22, a frequency offset value of the received signal on the beam is determined according to the obtained plurality of initial frequency offset values.
Further, for each beam, calculating a correlation value of each two of the plurality of received signals on the beam corresponding to the received signals at different transmission time instants using the following formula, and calculating an initial frequency offset value according to the correlation value:
R＝r(t0)×s*(t0)×r*(t1)×s(t1)；
wherein f isdFor indicating the initial frequency offset value; r is used to indicate a correlation value between two signals; angle () is used to indicate a phase angle function that computes complex numbers; r (t)0) For indicating transmission time t on a certain beam0The received signal of (a); r is*(t1) For indicating transmission time t on a certain beam1The complex conjugate of the received signal of (a); s (t)0) For indicating r (t)0) Corresponding transmission signal s (t)0) Is/are as followsA complex conjugate; s (t)1) Are respectively used for indicating r (t)1) A corresponding transmit signal; wherein, t1＞t0And satisfy
Further, in some non-limiting embodiments, for each beam, an average of the obtained plurality of initial frequency offset values may be used as the frequency offset value of the received signal on the beam; or taking the median of the obtained multiple initial frequency offset values as the frequency offset value of the received signal on the beam; and giving different weights to each initial frequency offset value obtained by calculation according to the signal-to-noise ratio or the energy extreme value of each received signal on the beam, and then performing weighting operation to determine the frequency offset value of the received signal on the beam. In a specific implementation, other suitable methods may also be used to determine the frequency offset value of the received signal on each beam, which is not limited in this embodiment of the present invention.
In the embodiment, please refer to the foregoing description and the step description in fig. 1 for further details regarding the steps S21 to S22, which are not repeated herein.
Referring to fig. 3, fig. 3 is a flowchart of another method for determining a frequency offset value of a signal according to an embodiment of the present invention. The method for determining the frequency offset value of the signal may include steps S31 to S35, which are described below.
In step S31, a plurality of antennas are used to receive a plurality of received signals, and each antenna receives a plurality of received signals having a respective arrival time and arrival angle.
In step S32, orthogonal beam decomposition is performed on the multiple received signals received by the multiple antennas to obtain received signals on all or part of beams, where the multiple received signals on each beam have respective arrival times and belong to the same arrival angle interval.
In step S33, for each beam, a correlation value is calculated for each two of the plurality of received signals on the beam corresponding to the received signals at different transmission time instants, and an initial frequency offset value is calculated from the correlation values.
In step S34, a frequency offset value of the received signal on the beam is determined according to the obtained plurality of initial frequency offset values.
In step S35, the received signal on each beam is subjected to frequency offset correction based on the frequency offset value of the received signal on each beam.
In a specific implementation, the frequency offset correction may adopt a conventional frequency offset correction method in the prior art, for example, the method one: time domain multiplication linear phase factor compensation is adopted; the second method comprises the following steps: and correcting the frequency deviation by adopting frequency domain convolution. After the corrected received signal is obtained, a pilot signal can be extracted therefrom, and channel estimation can be performed based on the pilot signal.
In the embodiment of the present invention, after the electromagnetic wave signal transmitted by the transmitting end is transmitted to the receiving end in motion through the wireless channel, the received signal in each direction of arrival angle may generate frequency offset, so that the original frequency spectrum of the received signal (the signal frequency spectrum when the transmitting end transmits) and the doppler frequency spectrum after frequency offset may be convolved with each other, that is, the time domain waveform of the original frequency spectrum is multiplied by the time domain waveform transform of the doppler frequency spectrum, thereby the signal is faded in the time domain. By adopting the technical scheme, the receiving signals on the plurality of antennas can be converted into the receiving signals on the plurality of wave beams, and the receiving signals on each wave beam belong to the same arrival angle interval (the arrival angle values are similar); then determining the frequency offset value of the received signal on each wave beam; and then, according to the frequency offset value of the received signal on each wave beam, carrying out frequency offset correction on the received signal on each wave beam, thereby being beneficial to enabling the frequency value of the received signal to be close to the original frequency value of the signal sent by the transmitting end and reducing the original information carried by the signal sent by the transmitting end as much as possible.
In the specific implementation, please refer to the foregoing description of steps 1 and 2 for more details regarding steps S31 to S35, which are not repeated herein.
Referring to fig. 4, fig. 4 is a flowchart of a method for determining a frequency offset value of a signal according to another embodiment of the present invention. The method for determining a frequency offset value of a signal may include steps S41 to S45, each of which is described below.
In step S41, a plurality of antennas are used to receive a plurality of received signals, and each antenna receives a plurality of received signals having a respective arrival time and arrival angle.
In step S42, the multiple received signals received by the multiple antennas are subjected to beam decomposition to obtain received signals on multiple beams, where the multiple received signals on each beam have respective arrival times and belong to the same arrival angle interval.
In step S43, a frequency offset estimation is performed on the received signal on each beam to obtain a frequency offset value of the received signal on each beam.
In step S44, a doppler spread spectrum is determined from the frequency offset value and the power average value of the received signal on each beam.
Referring to fig. 5, fig. 5 is a diagram illustrating a doppler spread spectrum according to an embodiment of the present invention. The doppler spread spectrum may be used to reflect the relationship between the frequency value of the received signal on each beam and the mean value of the power.
In the implementation, it is assumed that the transmitter transmits a signal with a frequency fcIf the above-mentioned doppler effect occurs due to relative motion, the spectrum of the received signal will be broadened and will include a frequency fc－fm～fc+fmIs known as the doppler spread spectrum.
In the Doppler spread spectrum, the abscissa is the value of the received signal frequency (f) on each beam, and the ordinate is the mean value of the received signal power (S) on each beamEz)，fcRepresenting the original frequency value of the electromagnetic wave signal emitted by the emitting terminal, fmAnd the maximum frequency deviation value generated after the Doppler frequency shift of the electromagnetic wave signal is represented. Wherein, for the received signal on each beam, there is a uniquely determined frequency offset value, and the maximum frequency offset value is the respective beamIs used to determine the maximum value of the frequency offset values.
With continued reference to fig. 4, in step S45, a time domain minimum mean square error, MMSE, filtered channel estimation value is calculated according to the doppler spread spectrum.
Further, the following formula is adopted to calculate the channel estimation value after the time domain Minimum Mean Square Error (MMSE) filtering according to the Doppler spread spectrum:
Ht′mmse(l)＝RH′H×(RHH+σ2l)-1×HLS；
wherein Ht′mmse(l) A time domain MMSE filtered channel estimate indicative of an l-th OFDM symbol; rHHN for indicating time domain adjacencytfiltA first channel correlation matrix of OFDM symbols containing pilots with dimension Ntilt×Ntfilt；RH′HFor indicating the l-th OFDM symbol and the nearest N to the OFDM symboltfiltA second channel correlation matrix of OFDM symbols containing pilot frequency with dimension of 1 × Ntfilt；HLsFor indicating the nearest N to the ith OFDM symboltfiltMatrix of channel estimation values before time domain MMSE filtering of OFDM symbols containing pilot frequency, and dimension is NtfiltX 1; wherein N istiltUsed for indicating the order of the time domain MMSE filter; sigma2For indicating HLSThe noise power of (c).
In specific implementation, a time domain correlation spectrum of a corresponding channel can be obtained by performing inverse fourier transform on the doppler spread spectrum; obtaining the first channel correlation matrix R according to the time domain correlation spectrum of the channelHHAnd a second channel correlation matrix RH′HEach element of (1); and/or performing frequency offset correction on the received signal on each wave beam according to the frequency offset value of the received signal on each wave beam to obtain a corrected signal; extracting OFDM symbols containing pilot frequency from the corrected signals, and then carrying out channel estimation according to the OFDM symbols containing pilot frequency to obtain a matrix H of channel estimation values before time domain MMSE filteringLS. Other suitable methods known in the art may also be used to determine the aforementioned matrices, the present inventionThe illustrative embodiments are not so limited.
In the embodiment of the present invention, after frequency offset values of received signals on each beam corresponding to different arrival angles are determined, a doppler spread spectrum may be determined, and then a channel estimation value after time domain minimum mean square error MMSE filtering may be calculated according to the needs of an actual application scenario, and then a Multiple-In Multiple-Out (MIMO) system is adopted to perform equalization processing.
The MIMO system uses a plurality of antennas at both the transmitting end and the receiving end to increase channel capacity, and forms a plurality of channels between transmission and reception. An obvious feature of MIMO systems is that they have very high spectral efficiency.
In the specific implementation, please refer to the foregoing description and the step descriptions in fig. 1 to fig. 3 for further details regarding the steps S41 to S45, which are not repeated herein.
Referring to fig. 6, fig. 6 is a schematic structural diagram of a device for determining a frequency offset value of a signal according to an embodiment of the present invention. The apparatus may include:
a signal receiving module 61, configured to receive multiple received signals by using multiple antennas, where the multiple received signals received by each antenna have respective arrival time and arrival angle;
a beam decomposition module 62, configured to perform beam decomposition on multiple received signals received by the multiple antennas to obtain received signals on multiple beams, where the multiple received signals on each beam have respective arrival time and belong to the same arrival angle interval;
a frequency offset value determining module 63, configured to perform frequency offset estimation on the received signal on each beam to obtain a frequency offset value of the received signal on each beam.
For the principle, specific implementation and beneficial effects of the apparatus for determining a frequency offset value of a signal, please refer to the foregoing and the related descriptions of the method for determining a frequency offset value of a signal shown in fig. 1 to 5, which are not described herein again.
In a specific implementation, the device for determining the frequency offset value of the signal may correspond to a chip having a function of determining the frequency offset value of the signal; or to a chip module having a function of determining a frequency offset value of a signal in a terminal, or to a terminal.
An embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor to perform the steps of the method for determining a frequency offset value of a signal. The computer-readable storage medium may include a non-volatile memory (non-volatile) or a non-transitory memory, and may further include an optical disc, a mechanical hard disk, a solid state hard disk, and the like.
Specifically, in the embodiment of the present invention, the processor may be a Central Processing Unit (CPU), and the processor may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
It will also be appreciated that the memory in the embodiments of the subject application can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. The nonvolatile memory may be a read-only memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically Erasable PROM (EEPROM), or a flash memory. Volatile memory can be Random Access Memory (RAM), which acts as external cache memory. By way of example and not limitation, many forms of Random Access Memory (RAM) are available, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (enhanced SDRAM), SDRAM (SLDRAM), synchlink DRAM (SLDRAM), and direct bus RAM (DR RAM).
The embodiment of the present invention further provides a terminal, which includes a memory and a processor, where the memory stores a computer program capable of running on the processor, and the processor executes the steps of the method for determining the frequency offset value of the signal when running the computer program. The terminal can include but is not limited to a mobile phone, a computer, a tablet computer and other terminal devices, and can also be a server, a cloud platform and the like.
The above embodiments may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, the above-described embodiments may be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. The procedures or functions according to the embodiments of the present application are wholly or partially generated when the computer instructions or the computer program are loaded or executed on a computer. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer program may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer program may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire or wirelessly.
In the several embodiments provided in the present application, it should be understood that the disclosed method, apparatus and system may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative; for example, the division of the unit is only a logic function division, and there may be another division manner in actual implementation; for example, various elements or components may be combined or may be integrated into another system, or some features may be omitted, or not implemented. The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may be separately and physically included, 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. For example, for each device or product applied to or integrated into a chip, each module/unit included in the device or product may be implemented by hardware such as a circuit, or at least a part of the module/unit may be implemented by a software program running on a processor integrated within the chip, and the rest (if any) part of the module/unit may be implemented by hardware such as a circuit; for each device or product applied to or integrated with the chip module, each module/unit included in the device or product may be implemented by using hardware such as a circuit, and different modules/units may be located in the same component (e.g., a chip, a circuit module, etc.) or different components of the chip module, or at least some of the modules/units may be implemented by using a software program running on a processor integrated within the chip module, and the rest (if any) of the modules/units may be implemented by using hardware such as a circuit; for each device and product applied to or integrated in the terminal, each module/unit included in the device and product may be implemented by hardware such as a circuit, different modules/units may be located in the same component (e.g., a chip, a circuit module, etc.) or different components in the terminal, or at least part of the modules/units may be implemented by a software program running on a processor integrated in the terminal, and the rest (if any) part of the modules/units may be implemented by hardware such as a circuit.
It should be understood that the term "and/or" herein is merely one type of association relationship that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" in this document indicates that the former and latter related objects are in an "or" relationship.
The "plurality" appearing in the embodiments of the present application means two or more.
The descriptions of the first, second, etc. appearing in the embodiments of the present application are only for illustrating and differentiating the objects, and do not represent the order or the particular limitation of the number of the devices in the embodiments of the present application, and do not constitute any limitation to the embodiments of the present application.
It should be noted that the sequence numbers of the steps in this embodiment do not represent a limitation on the execution sequence of the steps.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (17)
1. A method for determining a frequency offset value of a signal, comprising:
receiving a plurality of received signals by adopting a plurality of antennas, wherein the plurality of received signals received by each antenna have respective arrival time and arrival angle;
performing beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams, wherein the plurality of received signals on each beam have respective arrival time and belong to the same arrival angle interval;
and performing frequency offset estimation on the received signal on each wave beam to obtain a frequency offset value of the received signal on each wave beam.
2. The method of claim 1, further comprising:
and performing frequency offset correction on the received signal on each wave beam according to the frequency offset value of the received signal on each wave beam.
3. The method of claim 1, wherein performing beam decomposition on the plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams comprises:
and performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas to obtain received signals on all or part of beams.
4. The method of claim 3, wherein performing orthogonal beam decomposition on the plurality of received signals received by the plurality of antennas to obtain received signals on partial beams comprises:
performing orthogonal beam decomposition on a plurality of received signals received by the plurality of antennas, and calculating the signal-to-noise ratio average value and the energy average value of the plurality of received signals on each obtained beam;
and selecting the wave beams with the average signal-to-noise ratio larger than a first preset threshold value or the average energy value larger than a second preset threshold value to obtain the receiving signals on the partial wave beams.
5. The method of claim 1, wherein performing beam decomposition on the plurality of received signals received by the plurality of antennas to obtain received signals on a plurality of beams comprises:
and estimating the arrival angles of a plurality of received signals received by the plurality of antennas by adopting an arrival angle estimation algorithm to obtain a plurality of arrival angles, and aligning the peak directions of the beams of the plurality of received signals to the directions of the estimated arrival angles to obtain the received signals on the plurality of beams.
6. The method of claim 5, wherein said angle-of-arrival estimation algorithm is selected from the group consisting of:
the Butterett Bartlett algorithm, the capone Capon algorithm, the multiple signal classification MUSIC algorithm.
7. The method of claim 1, wherein performing frequency offset estimation on the received signal on each beam to obtain a frequency offset value of the received signal on each beam comprises:
for each wave beam, calculating the correlation value of each two received signals corresponding to different transmitting time moments in a plurality of received signals on the wave beam, and calculating an initial frequency offset value according to the correlation values;
and determining the frequency offset value of the received signal on the beam according to the obtained plurality of initial frequency offset values.
8. The method of claim 7, wherein for each beam, a correlation value is calculated for each two of the plurality of received signals on the beam corresponding to the received signals at different transmit times using the following formula, and wherein the initial frequency offset value is calculated based on the correlation values:
R＝r(t0)×s*(t0)×r*(t1)×s(t1)；
wherein f isdFor indicating the initial frequency offset value; r is used to indicate a correlation value between two signals; angle () is used to indicate a phase angle solving function of the complex number; r (t)0) For indicating transmission time t on a certain beam0The received signal of (1); r (t)1) For indicating transmission time t on a certain beam1The complex conjugate of the received signal of (a); s (t)0) For indicating r (t)0) Corresponding transmission signal s (t)0) The conjugate complex number of (a); s (t)1) Are respectively used for indicating r (t)1) A corresponding transmit signal; wherein, t1＞t0And satisfy
9. The method of claim 7, wherein determining the frequency offset value of the received signal on the beam based on the obtained plurality of initial frequency offset values comprises:
taking the average value of the obtained multiple initial frequency offset values as the frequency offset value of the received signal on the wave beam; alternatively, the first and second liquid crystal display panels may be,
and taking the median of the obtained plurality of initial frequency offset values as the frequency offset value of the received signal on the beam.
10. The method of claim 1, wherein after obtaining the frequency offset values for the received signals on the respective beams, the method further comprises:
and determining the Doppler spread spectrum according to the frequency offset value and the power average value of the received signals on each wave beam.
11. The method of claim 10, further comprising:
and calculating the channel estimation value after the MMSE filtering according to the Doppler spread spectrum.
12. The method of claim 11, wherein the time domain Minimum Mean Square Error (MMSE) filtered channel estimation value is calculated according to the Doppler spread spectrum by using the following formula:
Ht′mmse(l)＝RH′H×(RHH+σ2l)-1×HLS；
wherein Ht′mmse(l) A time domain MMSE filtered channel estimate indicative of an l-th OFDM symbol; rHHN for indicating time domain adjacencytfiltA first channel correlation matrix of OFDM symbols containing pilots with dimension Ntilt×Ntfilt；RH′HFor indicating the l-th OFDM symbol and the nearest N to the OFDM symboltfiltA second channel correlation matrix of OFDM symbols containing pilot frequency with dimension of 1 × Ntfilt；HLSFor indicating the nearest N to the ith OFDM symboltfiltMatrix of channel estimation values before time domain MMSE filtering containing pilot frequency OFDM symbols, with dimension of NtfiltX 1; wherein N istfiltFor indicating the order of the time domain MMSE filter; sigma2For indicating HLSThe noise power of (c).
13. The method of claim 1, wherein the plurality of antennas satisfy one or more of:
the plurality of antennas are arranged in an array;
the arrangement direction of the plurality of antennas on the receiver is parallel to the movement direction of the receiver;
the adjacent position spacing of the plurality of antennas is less than half of the carrier wavelength of the transmitted signal.
14. The method of claim 13, wherein the plurality of antennas are arranged in an array that satisfies one or more of:
the plurality of antennas are arranged in a linear array;
the plurality of antennas are arranged in a planar array;
the antennas are arranged in a spherical array.
15. An apparatus for determining a frequency offset value of a signal, comprising:
a signal receiving module, configured to receive multiple received signals by using multiple antennas, where the multiple received signals received by each antenna have respective arrival time and arrival angle;
a beam decomposition module, configured to perform beam decomposition on multiple received signals received by the multiple antennas to obtain received signals on multiple beams, where the multiple received signals on each beam have respective arrival time and belong to the same arrival angle interval;
and the frequency offset value determining module is used for carrying out frequency offset estimation on the received signal on each wave beam so as to obtain the frequency offset value of the received signal on each wave beam.
16. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method for determining a frequency offset value of a signal according to any one of claims 1 to 14.
17. A terminal comprising a memory and a processor, the memory having stored thereon a computer program operable on the processor, wherein the processor executes the computer program to perform the steps of the method for determining a frequency offset value of a signal according to any one of claims 1 to 14.
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