CN116388872B - Satellite laser communication signal frequency offset estimation method and device - Google Patents

Satellite laser communication signal frequency offset estimation method and device Download PDF

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CN116388872B
CN116388872B CN202310603933.9A CN202310603933A CN116388872B CN 116388872 B CN116388872 B CN 116388872B CN 202310603933 A CN202310603933 A CN 202310603933A CN 116388872 B CN116388872 B CN 116388872B
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frequency offset
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CN116388872A (en
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潘云强
王自川
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Beijing Rongwei Technology Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/118—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum specially adapted for satellite communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/616—Details of the electronic signal processing in coherent optical receivers
    • H04B10/6164—Estimation or correction of the frequency offset between the received optical signal and the optical local oscillator
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention provides a satellite laser communication signal frequency offset estimation method and device, which belong to the technical field of wireless communication, wherein the method comprises the steps of dividing satellite laser communication signals into a first preset number of sub-channels based on a first group of prototype filters to obtain first preset number of sub-channel signals, calculating the maximum integral power of each sub-channel signal and corresponding first frequency offset, and dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals; and calculating the maximum integral power of each sub-channel signal and the corresponding second frequency offset, if the maximum value of the first integral power is larger than the maximum value of the second integral power, determining the satellite laser communication signal frequency offset estimation as the first frequency offset, otherwise, determining the satellite laser communication signal frequency offset estimation as the second frequency offset, and effectively expanding the range of frequency offset estimation by the mode of twice frequency offset estimation and then determining the final frequency offset estimation.

Description

Satellite laser communication signal frequency offset estimation method and device
Technical Field
The invention relates to the technical field of wireless communication, in particular to a satellite laser communication signal frequency offset estimation method and device.
Background
In a coherent laser communication system, a transmitting end adopts a signal laser and an electro-optical modulator to complete optical signal modulation, and a receiving end mixes frequency with local oscillation laser and acquires an electric signal through a balance detector. In the homodyne coherent receiver, the local oscillation laser frequency needs to be consistent with the signal laser frequency; in a heterodyne coherent receiver, the difference between the local oscillator laser frequency and the signal laser frequency needs to be a fixed frequency. However, for lasers with output frequencies above 100THz (terahertz), the accuracy of the open loop frequency control can reach MHz levels even if one-half of the output frequency is achieved. On the other hand, the frequency of the output signal of the semiconductor laser can drift along with the working temperature, which can reach several GHz. Therefore, in a practical system, when the laser performs open loop control, a frequency offset of GHz order exists in the received signal. In the satellite laser communication scene, especially in the scenes of low-orbit satellite earth communication, low-orbit satellite machine communication, low-orbit satellite medium-high orbit satellite communication and the like, the low-orbit satellite has high moving speed, so that the received signal has large Doppler and Doppler change rate, the frequency offset of the received signal can reach GHz level, and the frequency change rate can reach MHz/s level. For example, in a low-orbit satellite laser communication scenario, the received signal frequency is shifted by 5GHz, and the frequency change rate is 30MHz/s.
In terrestrial optical fiber networks, high order quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM) such as 64QAM is commercially available, and higher order QAM (e.g., 512QAM, 1024 QAM) has been reported. At present, a frequency offset estimation method of 8PSK and 16APSK of a common Gao Jieheng envelope digital modulation mode can be expanded to higher-order MPSK signals. The method removes modulation information of signals by performing multiple times of frequency multiplication through MPSK, and then searches peak values through fast Fourier transform (fast Fourier transform, FFT) operation to obtain frequency offset. Such as 4 times the frequency of 8PSK signals, 8 times the frequency of 16APSK signals, and 24 times the frequency of 32 APSK.
However, after the frequency multiplication is finished, the frequency offset estimation range is reduced to 1/(2M) of the sampling rate, and the method is not suitable for satellite laser communication signals with large frequency offset.
Disclosure of Invention
The invention provides a satellite laser communication signal frequency offset estimation method and device, which are used for solving the defects that in the prior art, the frequency offset estimation range is narrow and the method and device are not suitable for large-frequency-offset satellite laser communication signal frequency offset estimation.
The invention provides a satellite laser communication signal frequency offset estimation method, which comprises the following steps:
dividing satellite laser communication signals into a first preset number of sub-channels based on a first group of prototype filters to obtain first preset number of sub-channel signals;
Respectively calculating first integral power of each sub-channel signal in the first preset number of sub-channel signals;
determining all maximum values in the first integral power and first frequency offsets corresponding to the maximum values of the first integral power;
dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals;
respectively calculating a second integral power of each sub-channel signal in the second preset number of sub-channel signals;
determining all the maximum values in the second integral power and second frequency deviations corresponding to the maximum values of the second integral power;
if the maximum value of the first integrated power is larger than the maximum value of the second integrated power, determining that the satellite laser communication signal frequency offset estimation is the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset estimation is the second frequency offset;
wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined magnitude of signal sampling rate.
According to the method for estimating the frequency offset of the satellite laser communication signal provided by the invention, the first integral power of each sub-channel signal in the first preset number of sub-channel signals is calculated respectively, and the method comprises the following steps:
Calculating the signal power of each sub-channel signal in the first preset number of sub-channel signals respectively;
and integrating each signal power to obtain a first integrated power of each sub-channel signal.
According to the method for estimating the frequency offset of the satellite laser communication signal provided by the invention, the signal power of each sub-channel signal in the first preset number of sub-channel signals is calculated respectively, and the method comprises the following steps:
determining a conjugate signal of each of the first preset number of sub-channel signals;
multiplying each sub-channel signal by the corresponding conjugate signal to obtain the signal power of each sub-channel signal.
According to the method for estimating the frequency offset of the satellite laser communication signal provided by the invention, the determining of the maximum value in all the first integral powers and the first frequency offset corresponding to the maximum value of the first integral power comprises the following steps:
determining the maximum value in all the first integral powers and a first sub-channel sequence number corresponding to the maximum value of the first integral power;
and calculating a first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number.
According to the method for estimating the frequency offset of the satellite laser communication signal provided by the invention, the calculating of the first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number comprises the following steps:
Calculating a first frequency offset of a sub-channel signal corresponding to the first sub-channel sequence number by using a first preset formula;
the first preset formula is as follows:
；
wherein ,representing a first frequency offset, ">Representing the number of the first sub-channel, the value range is +.>，/>Representing the sampling rate of the satellite laser communication signal, +.>Represents a first preset number, m=1/2/3 ….
According to the satellite laser communication signal frequency offset estimation method provided by the invention, the second group of prototype filters generate relative to the first group of prototype filtersIs offset from (a);
the dividing the satellite laser communication signal into a second preset number of sub-channels based on the second set of prototype filters to obtain a second preset number of sub-channel signals, including:
based on the second set of prototype filters, the satellite laser communication signal is divided into 2M+1 subchannels, resulting in 2M+1 subchannel signals.
According to the method for estimating the frequency offset of the satellite laser communication signal provided by the invention, the determining of the maximum value in all the second integral powers and the second frequency offset corresponding to the maximum value of the second integral power comprises the following steps:
determining the maximum value of all the second integrated powers and a second sub-channel sequence number corresponding to the maximum value of the second integrated power;
And calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number.
According to the method for estimating the frequency offset of the satellite laser communication signal provided by the invention, the calculating of the second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number comprises the following steps:
calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number by using a second preset formula;
the second preset formula is as follows:
；
wherein ,representing a second frequency offset>Represents the number of the second sub-channel and the value range is。
According to the method for estimating the frequency offset of the satellite laser communication signals, the satellite laser communication signals are divided into a first preset number of sub-channels based on the first group of prototype filters, so as to obtain the first preset number of sub-channel signals, and the method comprises the following steps:
dividing the satellite laser communication signals into a first preset number of sub-channels, and performing downsampling on the signals of each sub-channel;
filtering the signal of each downsampled subchannel based on a first set of prototype filters;
and performing inverse discrete Fourier transform on each filtered signal to obtain a first preset number of sub-channel signals.
The invention also provides a satellite laser communication signal frequency offset estimation device, which comprises:
the first dividing module is used for dividing the satellite laser communication signals into a first preset number of sub-channels based on the first group of prototype filters to obtain first preset number of sub-channel signals;
a first calculating module, configured to calculate a first integrated power of each of the first preset number of subchannel signals, respectively; determining all maximum values in the first integral power and first frequency offsets corresponding to the maximum values of the first integral power;
the second dividing module is used for dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals;
a second calculating module, configured to calculate a second integrated power of each of the sub-channel signals in the second preset number of sub-channel signals, respectively; determining all the maximum values in the second integral power and second frequency deviations corresponding to the maximum values of the second integral power;
the estimation module is used for determining that the satellite laser communication signal frequency offset is estimated to be the first frequency offset if the maximum value of the first integral power is larger than the maximum value of the second integral power, otherwise, determining that the satellite laser communication signal frequency offset is estimated to be the second frequency offset;
Wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined magnitude of signal sampling rate.
The invention also provides an electronic device, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the satellite laser communication signal frequency offset estimation method is realized by the processor when the program is executed.
The invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements a satellite laser communication signal frequency offset estimation method as described in any of the above.
The invention provides a satellite laser communication signal frequency offset estimation method and device, the method comprises the steps of dividing a satellite laser communication signal into a first preset number of sub-channels based on a first group of prototype filters, obtaining a first preset number of sub-channel signals, calculating the maximum integral power and the corresponding first frequency offset of each sub-channel signal in the first preset number of sub-channel signals, and dividing the satellite laser communication signal into a second preset number of sub-channels based on a second group of prototype filters, so as to obtain a second preset number of sub-channel signals; calculating the maximum integral power and the corresponding second frequency offset of each sub-channel signal in the second preset number of sub-channel signals, if the maximum value of the first integral power is larger than the maximum value of the second integral power, determining that the satellite laser communication signal frequency offset is estimated to be the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset is estimated to be the second frequency offset; the invention determines each frequency offset estimation by determining the maximum power mode, and the second prototype filter of the second frequency offset estimation is offset relative to the first prototype filter, thus improving the performance of the frequency offset estimation, effectively expanding the range of the frequency offset estimation and better realizing the frequency offset estimation of satellite laser communication signals with large frequency offset.
Drawings
In order to more clearly illustrate the invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic flow chart of a satellite laser communication signal frequency offset estimation method provided by an embodiment of the invention;
fig. 2 is a schematic diagram of dividing a satellite laser communication signal into a first preset number of subchannels according to an embodiment of the present invention;
fig. 3 is a schematic diagram of dividing a satellite laser communication signal into a second preset number of subchannels according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a signal processing flow provided in an embodiment of the present invention;
fig. 5 is a schematic diagram of channel division provided by an embodiment of the present invention;
fig. 6 is a schematic diagram illustrating frequency offset estimation comparison when the signal-to-noise ratio snr=7db of the ADC sampling signal provided by the embodiment of the invention;
fig. 7 is a schematic diagram of frequency offset estimation comparison when the signal-to-noise ratio snr= -3dB of the ADC sampling signal provided by the embodiment of the invention;
Fig. 8 is a schematic diagram of frequency offset estimation comparison when the signal-to-noise ratio snr= -10dB of the ADC sampling signal provided by the embodiment of the invention;
fig. 9 is a schematic structural diagram of a satellite laser communication signal frequency offset estimation device according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In laser communication, after the electric signal output by the balance detector passes through an electric channel, analog-to-Digital Converter (ADC) is used for completing Analog-to-digital conversion, and a large-scale field programmable gate array (Field Programmable Gate Array, FPGA) is used for completing demodulation and decoding of data. The electric channel completes the processing of filtering, amplifying and the like of the signal. When a received signal has larger frequency deviation, on one hand, the bandwidth of an electric channel can be exceeded, and the signal cannot be completely sampled by an ADC; on the other hand, large frequency offset and large frequency change rate increase difficulty in signal acquisition and tracking. In order to realize effective satellite laser communication, the problems of large frequency offset and large frequency change rate laser signal capturing and tracking in satellite laser communication need to be solved. Therefore, the method of the invention is adopted to realize the frequency offset estimation of the satellite laser communication signals with large frequency offset.
Fig. 1 is a flow chart of a satellite laser communication signal frequency offset estimation method according to an embodiment of the present invention.
As shown in fig. 1, the method for estimating frequency offset of satellite laser communication signals provided by the embodiment of the invention mainly comprises the following steps:
101. based on the first group of prototype filters, the satellite laser communication signals are divided into a first preset number of sub-channels, and the first preset number of sub-channel signals are obtained.
In a specific implementation process, two groups of prototype filters are designed first, namely a first group of prototype filters and a second group of prototype filters, and the second group of prototype filters generate offset relative to the first group of prototype filters, so that the frequency offset estimation performance is ensured to be improved during the second frequency offset estimation.
The received satellite laser communication signals are sampled by an ADC module, then based on a channelization technology, the satellite laser communication signals are divided into a first preset number of subchannels by utilizing polyphase filtering and inverse discrete Fourier transform (inverse discrete Fouriertransform, IDFT), wherein the first preset number of subchannels is 2M subchannels, and then the first preset number of subchannels are acquired, namely 2M subchannels are acquired, wherein M is 1/2/3 …. The sub-channel signal at this time is a complex signal, which is denoted as , wherein ,krepresenting the discrete sequence number or number of frequency offset estimates,kthe range of the value of (C) is 1/2/3 ….
Fig. 2 is a schematic diagram of dividing a satellite laser communication signal into a first preset number of subchannels according to an embodiment of the present invention. As shown in fig. 2, the QAM signal spectrum is of sinc spectrum type, and the maximum spectrum power is obtained at the center of the signal. The frequency interval between the maximum signal spectrum power and zero frequency is the frequency offset of the received signal. The division of the entire signal spectrum into sub-channels, for example, the division into 10 sub-channels in fig. 2, can clearly understand the division manner and principle of the satellite laser communication signals.
102. A first integrated power of each of the first preset number of sub-channel signals is calculated separately.
After obtaining 2M sub-channel signals, the signal power of each sub-channel signal in the 2M sub-channel signals is calculated as. Then each signal power is processedKPoint integration, a first integrated power of each sub-channel signal is obtained, wherein,Krepresenting the total number of frequency offset estimates.
Wherein, the first integral power is calculated as formula (1):
（1）；
wherein ,a first integrated power is indicated and,krepresenting the discrete sequence number or number of frequency offset estimates, KRepresenting the total number of frequency offset estimates.
The first integrated power of each sub-channel signal is calculated, respectively, to obtain 2M first integrated powers.
103. And determining the maximum value in all the first integral powers and the first frequency offset corresponding to the maximum value of the first integral power.
Comparing the magnitude relation of the 2M first integral powers, determining the maximum value of all the 2M first integral powers, and recording asDetermining the position of the maximum value of the first integral power to obtain a corresponding first frequency deviation, which is marked as +.>。
104. Based on the second set of prototype filters, the satellite laser communication signals are divided into a second preset number of sub-channels, and the second preset number of sub-channel signals are obtained.
The same principle as in step 101, the satellite laser communication signal is divided into a second preset number of sub-channels based on the second set of prototype filters, and the signal spectrum may be located between two sub-channels after the first channel division due to the randomness of the signal center frequency. FIG. 3 is a schematic diagram of the division of satellite laser communication signals into a second predetermined number of sub-channels according to an embodiment of the present invention, wherein as shown in FIG. 3, the power of the sub-channel signal at the center of the signal is reduced, and the frequency offset estimation performance is reduced at low signal-to-noise ratio, so that the second prototype filter set is compared with the first prototype filter set Thereby dividing the satellite laser communication signal into 2m+1 subchannels resulting in 2m+1 subchannels. Wherein the bandwidth of the middle 2M-1 sub-channel is +.>The sub-bandwidths of the channels on both sides are +.>。
105. A second integrated power is calculated for each of the second predetermined number of sub-channel signals.
The second integrated power of each of the 2m+1 sub-channel signals is calculated separately as in the calculation process of step 102. The specific process will not be explained in detail, and reference is made to step 102.
106. And determining the maximum value in all the second integral powers and the second frequency deviation corresponding to the maximum value of the second integral power.
Comparing the magnitude relation of the 2M+1 second integral powers, determining the maximum value of all the 2M+1 second integral powers, and marking asDetermining the position of the maximum value of the second integral power to obtain a corresponding second frequency deviation, which is marked as +.>。
107. And if the maximum value of the first integral power is larger than the maximum value of the second integral power, determining that the satellite laser communication signal frequency offset is estimated to be the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset is estimated to be the second frequency offset.
Through two frequency offset estimation, respectively obtain 、/> and />、/>Thus, a comparison is required> and />The size of (1)>＞/>Then the estimated frequency offset value is output as +.>Otherwise->≤/>Output estimated frequency offset value is +.>. Thus, the final frequency offset estimate is determined.
The satellite laser communication signal frequency offset estimation method provided by the embodiment comprises the steps of dividing a satellite laser communication signal into a first preset number of sub-channels based on a first group of prototype filters to obtain a first preset number of sub-channel signals, calculating the maximum integral power of each sub-channel signal in the first preset number of sub-channel signals and the corresponding first frequency offset, and dividing the satellite laser communication signal into a second preset number of sub-channels based on a second group of prototype filters to obtain a second preset number of sub-channel signals; calculating the maximum integral power and the corresponding second frequency offset of each sub-channel signal in the second preset number of sub-channel signals, if the maximum value of the first integral power is larger than the maximum value of the second integral power, determining that the satellite laser communication signal frequency offset is estimated to be the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset is estimated to be the second frequency offset; the invention determines each frequency offset estimation by determining the maximum power mode, and the second prototype filter of the second frequency offset estimation is offset relative to the first prototype filter, thus improving the performance of the frequency offset estimation, effectively expanding the range of the frequency offset estimation and better realizing the frequency offset estimation of satellite laser communication signals with large frequency offset.
Further, on the basis of the foregoing embodiment, in this embodiment, the calculating the first integrated power of each sub-channel signal in the first preset number of sub-channel signals includes: respectively calculating the signal power of each sub-channel signal in the first preset number of sub-channel signals; and integrating each signal power to obtain a first integrated power of each sub-channel signal.
Wherein calculating the signal power of each sub-channel signal in the first preset number of sub-channel signals respectively includes: determining the conjugate signal of each sub-channel signal in the first preset number of sub-channel signals, which is recorded asThe method comprises the steps of carrying out a first treatment on the surface of the And multiplying each sub-channel signal with the corresponding conjugate signal to obtain the signal power of each sub-channel signal.
Specifically, the signal power of each sub-channel signal is calculated as in formula (2):
（2）；
wherein ,representation->Is a conjugate signal of (a).
The signal power of each sub-channel signal can then be calculated by equation (2), and the first integrated power of each sub-channel signal can be calculated rapidly by equation (1) of the above embodiment.
Further, on the basis of the foregoing embodiment, determining the first frequency offset corresponding to the maximum value of the first integrated power and the maximum value of all the first integrated powers in this embodiment includes: determining the maximum value of all the first integral powers and a first sub-channel serial number corresponding to the maximum value of the first integral power; and calculating a first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number.
The calculating the first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number includes: calculating a first frequency offset of a sub-channel signal corresponding to the first sub-channel sequence number by using a first preset formula; a first preset formula such as formula (3):
（3）；
wherein ,representing a first frequency offset, ">Representing the number of the first sub-channel, the value range is +.>，/>Representing the sampling rate of the satellite laser communication signal, +.>Represents a first preset number, m=1/2/3 ….
Converting equation (3) to equation (4):
（4）；
wherein ,represents the first subchannel sequence number due to +.>The value of (2) is 1-2M, thus +.>The frequency offset estimation range of (a) is almost ± +.>And can distinguish the positive and negative of the frequency offset. Frequency offset estimationPrecision is->The frequency offset estimation result can be used as a frequency offset estimation result and fed back to the local oscillator laser at the front end to adjust the frequency offset of the received signal, as shown in fig. 4, which is a schematic diagram of the signal processing flow. The method comprises the steps of receiving satellite laser communication signals, performing coherent mixing, and detecting balance&And carrying out channel processing, carrying out frequency offset estimation based on channelization after ADC sampling processing, carrying out tuning control to realize frequency offset compensation after determining the frequency offset, and finally feeding back to the local oscillator laser at the front end. The frequency offset estimation range of the invention for all QAM modulated signals is-/ >The method is particularly suitable for satellite laser communication signals with large frequency offset and high-order QAM modulation. Meanwhile, the invention integrates the power of the sub-channel after the channelizing, searches the maximum value, and has good performance under the condition of low signal-to-noise ratio (SNR is less than 0 dB).
Further, based on the foregoing embodiment, determining the second frequency offset corresponding to the maximum value of the second integrated power and the maximum value of the second integrated power in this embodiment includes: determining the maximum value of all the second integral powers and the second sub-channel serial number corresponding to the maximum value of the second integral power; and calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number.
The calculating the second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number includes: calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number by using a second preset formula;
a second preset formula such as (5):
（5）；
wherein ,representing a second frequency offset>Represents the number of the second sub-channel and the value range is。
Converting equation (5) to equation (6):
（6）；
wherein ,the second sub-channel sequence number is represented, and similarly, the frequency offset estimation method of the embodiment can be seen through the formula (6) to distinguish the positive and negative of the frequency offset, has a wider frequency offset estimation range, and is particularly suitable for satellite laser communication signals with large frequency offset.
Further, based on the above embodiment, the dividing the satellite laser communication signal into the first preset number of sub-channels based on the first set of prototype filters in this embodiment, to obtain the first preset number of sub-channel signals includes: dividing satellite laser communication signals into a first preset number of sub-channels, and performing downsampling on signals of each sub-channel; filtering the signal of each downsampled subchannel based on the first set of prototype filters; and performing inverse discrete Fourier transform on each filtered signal to obtain a first preset number of sub-channel signals.
Fig. 5 is a schematic diagram of channel division provided in an embodiment of the present invention, specifically, as shown in fig. 5, the received satellite laser signal is first divided into 2M sub-channelsThen respectively performing M times downsampling on the signals of each sub-channel, and performing a first group of prototype filters E on the downsampled signals 0 (z 2 )、E 1 (z 2 )、…、E 2M-1 (z 2 ) Feeding inAnd performing line filtering, then performing IDFT operation to obtain information of each sub-channel, and outputting sub-channel signals: subchannel 1, subchannels 2, …, subchannel 2M.
In order to further verify the effect of the invention, the following simulation experiments are used for analysis and demonstration, and simulation parameters are as follows: ADC sampling rate 10GHz, symbol rate 1Gsps, frequency offset 3.5GHz, modulation system QPSK.
In this embodiment, 16 sub-channels are divided, that is, the number of IDFT points is 16, and 2048 point averaging is performed, so that 32768 sampling signals are required for completing one-time frequency offset estimation. The traditional frequency offset estimation algorithm based on FFT is compared with the invention in performance, wherein the number of FFT points is 1024, and the method performs incoherent accumulation for 32 times, and 32768 sampling signals are also needed for completing one-time frequency offset estimation. The frequency offset estimation performance at different signal-to-noise ratios is then compared separately.
Fig. 6 is a schematic diagram of frequency offset estimation comparison when the snr=7db of the ADC sampling signal provided by the embodiment of the invention, as shown in fig. 6, the ratio EsN 0=20db of the symbol energy to the noise power, that is, the snr=7db of the ADC sampling signal, and at this time, the peak value of the frequency offset estimation method based on FFT is obvious, and both the method and the method can effectively estimate the frequency offset, the method estimates the position of the sub-channel 14, and the conventional method estimates the position of the sub-channel 14.
Fig. 7 is a schematic diagram of frequency offset estimation comparison when the signal-to-noise ratio snr= -3dB of the ADC sampling signal provided by the embodiment of the invention, as shown in fig. 7, the ratio EsN 0=10 dB of symbol energy to noise power, that is, the signal-to-noise ratio snr= -3dB of the ADC sampling signal, where the frequency offset estimation method based on FFT cannot estimate the frequency offset, but the scheme of the invention can also effectively estimate the signal frequency offset.
Fig. 8 is a schematic diagram of frequency offset estimation comparison when the signal-to-noise ratio snr= -10dB of the ADC sampling signal provided by the embodiment of the invention, as shown in fig. 8, the ratio EsN 0=3 dB of symbol energy to noise power, that is, the signal-to-noise ratio snr= -10dB of the ADC sampling signal, where the frequency offset estimation method based on FFT cannot estimate the frequency offset, but the scheme of the invention can also effectively estimate the signal frequency offset.
The frequency offset estimation method has better frequency offset estimation effect, wide frequency offset estimation range and is also applicable under the condition of low signal to noise ratio.
Based on the same general inventive concept, the invention also protects a satellite laser communication signal frequency offset estimation device, and the satellite laser communication signal frequency offset estimation device provided by the invention is described below, and the satellite laser communication signal frequency offset estimation device described below and the satellite laser communication signal frequency offset estimation method described above can be referred to correspondingly.
Fig. 9 is a schematic structural diagram of a satellite laser communication signal frequency offset estimation device according to an embodiment of the present invention.
As shown in fig. 9, the satellite laser communication signal frequency offset estimation device provided by the invention includes:
the first dividing module 901 is configured to divide the satellite laser communication signal into a first preset number of sub-channels based on the first set of prototype filters, to obtain a first preset number of sub-channel signals;
A first calculating module 902, configured to calculate a first integrated power of each of a first preset number of sub-channel signals respectively; determining the maximum value in all the first integral powers and the first frequency offset corresponding to the maximum value of the first integral power;
the second dividing module 903 is configured to divide the satellite laser communication signal into a second preset number of sub-channels based on the second set of prototype filters, to obtain a second preset number of sub-channel signals;
a second calculating module 904, configured to calculate a second integrated power of each of a second preset number of sub-channel signals, respectively; determining the maximum value in all the second integral powers and the second frequency offset corresponding to the maximum value of the second integral power;
the estimation module 905 is configured to determine that the satellite laser communication signal frequency offset is estimated to be a first frequency offset if the maximum value of the first integrated power is greater than the maximum value of the second integrated power, and determine that the satellite laser communication signal frequency offset is estimated to be a second frequency offset if the maximum value of the first integrated power is greater than the maximum value of the second integrated power;
wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined amount of signal sampling rate.
Further, the first computing module 902 in this embodiment is specifically configured to:
Calculating the signal power of each sub-channel signal in the first preset number of sub-channel signals respectively;
and integrating each signal power to obtain a first integrated power of each sub-channel signal.
Further, the first computing module 902 in this embodiment is specifically configured to:
determining a conjugate signal of each of the first preset number of sub-channel signals;
multiplying each sub-channel signal by the corresponding conjugate signal to obtain the signal power of each sub-channel signal.
Further, the first computing module 902 in this embodiment is specifically configured to:
determining the maximum value in all the first integral powers and a first sub-channel sequence number corresponding to the maximum value of the first integral power;
and calculating a first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number.
Further, the first computing module 902 in this embodiment is specifically configured to:
calculating a first frequency offset of a sub-channel signal corresponding to the first sub-channel sequence number by using a first preset formula;
the first preset formula is as follows:
；
wherein ,representing a first frequency offset, ">Representing the number of the first sub-channel, the value range is +. >，/>Representing the sampling rate of the satellite laser communication signal, +.>Represents a first preset number, m=1/2/3 ….
Further, the second set of prototype filters in this implementation occurs with respect to the first set of prototype filtersIs offset from (a);
the second dividing module 903 is specifically configured to:
based on the second set of prototype filters, the satellite laser communication signal is divided into 2M+1 subchannels, resulting in 2M+1 subchannel signals.
Further, the second calculating module 904 in this embodiment is specifically configured to:
determining the maximum value of all the second integrated powers and a second sub-channel sequence number corresponding to the maximum value of the second integrated power;
and calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number.
Further, the second calculating module 904 in this embodiment is specifically configured to:
calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number by using a second preset formula;
the second preset formula is as follows:
；
wherein ,representing a second frequency offset>Represents the number of the second sub-channel and the value range is。
Further, the first dividing module 901 in this embodiment is specifically configured to:
dividing the satellite laser communication signals into a first preset number of sub-channels, and performing downsampling on the signals of each sub-channel;
Filtering the signal of each downsampled subchannel based on a first set of prototype filters;
and performing inverse discrete Fourier transform on each filtered signal to obtain a first preset number of sub-channel signals.
Fig. 10 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
As shown in fig. 10, the electronic device may include: a processor 1010, a communication interface (Communications Interface) 1020, a memory 1030, and a communication bus 1040, wherein the processor 1010, the communication interface 1020, and the memory 1030 communicate with each other via the communication bus 1040. Processor 1010 may invoke logic instructions in memory 1030 to perform a satellite laser communication signal frequency offset estimation method comprising: dividing satellite laser communication signals into a first preset number of sub-channels based on a first group of prototype filters to obtain first preset number of sub-channel signals; respectively calculating first integral power of each sub-channel signal in the first preset number of sub-channel signals; determining all maximum values in the first integral power and first frequency offsets corresponding to the maximum values of the first integral power; dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals; respectively calculating a second integral power of each sub-channel signal in the second preset number of sub-channel signals; determining all the maximum values in the second integral power and second frequency deviations corresponding to the maximum values of the second integral power; if the maximum value of the first integrated power is larger than the maximum value of the second integrated power, determining that the satellite laser communication signal frequency offset estimation is the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset estimation is the second frequency offset; wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined magnitude of signal sampling rate.
Further, the logic instructions in the memory 1030 described above may be implemented in the form of software functional units and stored in a computer readable storage medium when sold or used as a stand alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In yet another aspect, the present invention further provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, is implemented to perform the satellite laser communication signal frequency offset estimation method provided by the methods above, the method comprising: dividing satellite laser communication signals into a first preset number of sub-channels based on a first group of prototype filters to obtain first preset number of sub-channel signals; respectively calculating first integral power of each sub-channel signal in the first preset number of sub-channel signals; determining all maximum values in the first integral power and first frequency offsets corresponding to the maximum values of the first integral power; dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals; respectively calculating a second integral power of each sub-channel signal in the second preset number of sub-channel signals; determining all the maximum values in the second integral power and second frequency deviations corresponding to the maximum values of the second integral power; if the maximum value of the first integrated power is larger than the maximum value of the second integrated power, determining that the satellite laser communication signal frequency offset estimation is the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset estimation is the second frequency offset; wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined magnitude of signal sampling rate.
The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on this understanding, the foregoing technical solution may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method described in the respective embodiments or some parts of the embodiments.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The satellite laser communication signal frequency offset estimation method is characterized by comprising the following steps of:
dividing satellite laser communication signals into a first preset number of sub-channels based on a first group of prototype filters to obtain first preset number of sub-channel signals;
respectively calculating first integral power of each sub-channel signal in the first preset number of sub-channel signals;
determining all maximum values in the first integral power and first frequency offsets corresponding to the maximum values of the first integral power;
dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals;
Respectively calculating a second integral power of each sub-channel signal in the second preset number of sub-channel signals;
determining all the maximum values in the second integral power and second frequency deviations corresponding to the maximum values of the second integral power;
if the maximum value of the first integrated power is larger than the maximum value of the second integrated power, determining that the satellite laser communication signal frequency offset estimation is the first frequency offset, otherwise, determining that the satellite laser communication signal frequency offset estimation is the second frequency offset;
wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined magnitude of signal sampling rate.
2. The method of claim 1, wherein said separately calculating a first integrated power for each of said first predetermined number of sub-channel signals comprises:
calculating the signal power of each sub-channel signal in the first preset number of sub-channel signals respectively;
and integrating each signal power to obtain a first integrated power of each sub-channel signal.
3. The method of estimating frequency offset of satellite laser communication signals according to claim 2, wherein said calculating signal power of each of said first predetermined number of sub-channel signals, respectively, comprises:
Determining a conjugate signal of each of the first preset number of sub-channel signals;
multiplying each sub-channel signal by the corresponding conjugate signal to obtain the signal power of each sub-channel signal.
4. The method of claim 1, wherein determining the first frequency offset corresponding to the maximum value of all the first integrated powers and the maximum value of the first integrated power includes:
determining the maximum value in all the first integral powers and a first sub-channel sequence number corresponding to the maximum value of the first integral power;
and calculating a first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number.
5. The method for estimating frequency offset of satellite laser communication signal according to claim 4, wherein said calculating the first frequency offset of the sub-channel signal corresponding to the first sub-channel sequence number comprises:
calculating a first frequency offset of a sub-channel signal corresponding to the first sub-channel sequence number by using a first preset formula;
the first preset formula is as follows:
；
wherein ,representing a first frequency offset, ">Representing the number of the first sub-channel, the value range is +. >，/>Representing the sampling rate of the satellite laser communication signal, +.>Represents a first preset number, m=1/2/3 ….
6. The method of estimating frequency offset of a satellite laser communication signal according to claim 5, wherein said second set of prototype filters occurs with respect to said first set of prototype filtersIs offset from (a);
the dividing the satellite laser communication signal into a second preset number of sub-channels based on the second set of prototype filters to obtain a second preset number of sub-channel signals, including:
based on the second set of prototype filters, the satellite laser communication signal is divided into 2M+1 subchannels, resulting in 2M+1 subchannel signals.
7. The method of claim 6, wherein determining the second frequency offset corresponding to the maximum value of the second integrated power and the maximum value of the second integrated power includes:
determining the maximum value of all the second integrated powers and a second sub-channel sequence number corresponding to the maximum value of the second integrated power;
and calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number.
8. The method for estimating frequency offset of satellite laser communication signal according to claim 7, wherein said calculating the second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number comprises:
Calculating a second frequency offset of the sub-channel signal corresponding to the second sub-channel sequence number by using a second preset formula;
the second preset formula is as follows:
；
wherein ,representing a second frequency offset>Represents the number of the second sub-channel and the value range is。
9. The method for estimating frequency offset of satellite laser communication signals according to any one of claims 1 to 8, wherein dividing the satellite laser communication signals into a first preset number of sub-channels based on the first set of prototype filters to obtain the first preset number of sub-channel signals comprises:
dividing the satellite laser communication signals into a first preset number of sub-channels, and performing downsampling on the signals of each sub-channel;
filtering the signal of each downsampled subchannel based on a first set of prototype filters;
and performing inverse discrete Fourier transform on each filtered signal to obtain a first preset number of sub-channel signals.
10. A satellite laser communication signal frequency offset estimation device, comprising:
the first dividing module is used for dividing the satellite laser communication signals into a first preset number of sub-channels based on the first group of prototype filters to obtain first preset number of sub-channel signals;
A first calculating module, configured to calculate a first integrated power of each of the first preset number of subchannel signals, respectively; determining all maximum values in the first integral power and first frequency offsets corresponding to the maximum values of the first integral power;
the second dividing module is used for dividing the satellite laser communication signals into a second preset number of sub-channels based on a second group of prototype filters to obtain second preset number of sub-channel signals;
a second calculating module, configured to calculate a second integrated power of each of the sub-channel signals in the second preset number of sub-channel signals, respectively; determining all the maximum values in the second integral power and second frequency deviations corresponding to the maximum values of the second integral power;
the estimation module is used for determining that the satellite laser communication signal frequency offset is estimated to be the first frequency offset if the maximum value of the first integral power is larger than the maximum value of the second integral power, otherwise, determining that the satellite laser communication signal frequency offset is estimated to be the second frequency offset;
wherein the second set of prototype filters are offset from the first set of prototype filters by a predetermined magnitude of signal sampling rate.
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