CN113271152B - Frequency offset processing method and system for digital subcarrier multiplexing signal - Google Patents
Frequency offset processing method and system for digital subcarrier multiplexing signal Download PDFInfo
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Abstract
The invention discloses a frequency offset processing method and a frequency offset processing system for digital subcarrier multiplexing signals, which relate to the technical field of optical fiber communication, and the method comprises the following steps: setting a frequency deviation estimation range, selecting a plurality of test frequencies in the frequency deviation estimation range, testing frequency deviation compensation on the initial SCM signal by using each test frequency, independently calculating the signal average power of a low-frequency SCM signal in each frequency deviation compensation SCM signal, obtaining a frequency deviation estimation value according to the signal average power, and outputting a frequency deviation compensation SCM signal corresponding to the frequency deviation estimation value; the invention can estimate the frequency offset compensation before the dispersion compensation, has no influence on the transmission performance of the system and the complexity of the dispersion compensation, does not sacrifice the spectrum efficiency of the SCM system, and is transparent to the modulation format.
Description
Technical Field
The present invention relates to the field of optical fiber communication technologies, and in particular, to a frequency offset processing method and system for digital subcarrier multiplexing signals.
Background
Digital Signal Processing (DSP) has been widely used in coherent optical communication systems and can effectively compensate many types of linear impairments, such as Chromatic Dispersion (CD), frequency Offset (FO), polarization Mode Dispersion (PMD), etc., however, fiber nonlinear effects remain a determining factor limiting the transmission capacity of coherent optical communication systems.
The latest coherent optical communication system generally adopts a digital subcarrier multiplexing (SCM) technology, and compared with the conventional coherent optical communication system adopting a single carrier technology, the SCM system has better non-linearity resisting effect and higher flexibility.
The coherent optical communication system comprises a coherent transmitter and a coherent receiver, and frequency offset exists in a received SCM signal due to the fact that a coherent transmitter laser and a local oscillator laser of the coherent receiver are not locked to the frequency. The frequency offset estimation method in the traditional single-carrier coherent optical communication system mainly comprises a differential estimation method and a spectrum estimation method, but both the differential estimation method and the spectrum estimation method are frequency offset estimation technologies for the traditional single-carrier coherent transmission system, and when the frequency offset estimation technologies are used for carrying out frequency offset estimation, the frequency offset estimation needs to be carried out after dispersion compensation, but for the SCM system, the frequency offset compensation needs to be carried out before dispersion compensation, otherwise, the transmission performance of the system is deteriorated, and the complexity of the dispersion compensation is increased on the other hand.
Published under the number CN111585924 a: 2020-08-25, by conjugate multiplication processing of two packets of pilot information before and after, determining a frequency offset value between the two packets of pilot information before and after; and performing frequency offset compensation based on the frequency offset value, wherein the method can be deployed before dispersion compensation, but the method can sacrifice the frequency spectrum efficiency and reduce the sensitivity of a receiver.
Disclosure of Invention
The invention provides a frequency offset processing method and a system of digital subcarrier multiplexing signals, aiming at overcoming the defects that the transmission performance of the system is deteriorated when the differential estimation method and the spectrum estimation method in the prior art are used for carrying out frequency offset estimation after dispersion compensation and the defects that the sensitivity of a receiver is reduced by the frequency spectrum efficiency sacrifice generated when the frequency offset compensation problem is carried out after dispersion compensation in the prior art, and the technical scheme is as follows:
a frequency offset processing method of digital subcarrier multiplexing signals comprises the following steps:
s1, setting a frequency offset estimation range;
s2, selecting a plurality of test frequencies within a frequency deviation estimation range;
s3, testing frequency deviation compensation on the initial SCM signal received by the signal receiving end by using each testing frequency, and obtaining a corresponding frequency deviation compensation SCM signal after the initial SCM signal is subjected to frequency deviation compensation of the testing frequency;
s4, acquiring a low-frequency SCM signal in each frequency offset compensation SCM signal, and independently calculating the signal average power of each low-frequency SCM signal;
and S5, obtaining a frequency deviation estimation value according to the average power of each signal, and taking a frequency deviation compensation SCM signal corresponding to the frequency deviation estimation value as a frequency deviation processing result.
According to the technical scheme, firstly, a frequency deviation estimation range is determined according to the frequency deviation condition in an actual coherent optical communication system, then a plurality of test frequencies are selected from the frequency deviation estimation range, then each test frequency is used for compensating the frequency deviation for an initial SCM signal, a low-pass filter is used for filtering high-frequency subcarriers, finally, the average power of the signals obtained after filtering is calculated, and the magnitude of the frequency deviation value can be judged according to the average power corresponding to different test frequencies. The technical scheme can estimate the frequency offset compensation before the dispersion compensation, has no influence on the transmission performance of the system and the complexity of the dispersion compensation, does not sacrifice the spectrum efficiency of the SCM system, and is transparent to the modulation format.
Further, in step S1, the frequency offset estimation range is [ -mG, mG ], m is a real number, a value of m is determined according to a frequency offset condition in an actual coherent optical communication system, in step S2, the number of the test frequencies is N +1, an interval between two adjacent test frequencies is 2mG/N, and a vector set of the test frequencies is:
further, the step S3 of using each test frequency to test frequency offset compensation for the initial SCM signal received by the signal receiving end includes:
ignoring noise and other transmission impairment effects, only considering frequency offset, the initial SCM signal after the signal receiving end passes through the analog-to-digital converter is represented by the following formula:
Δ ν is frequency deviation between a transmitting end laser and a local oscillator laser, namely a frequency deviation value; a (n) is an SCM signal of a signal transmitting end; t is a unit of s Sampling time intervals for a signal receiving end, wherein n is a sequence number of symbols; performing frequency offset compensation according to the following formula:
Y(n)＝S(n)*exp(-j*2πnΔvT s )
substituting each test frequency into the formula, and performing frequency offset compensation on the initial SCM signal received by the signal receiving end by using each test frequency to obtain a frequency offset compensation SCM signal corresponding to each test frequency:
y i ＝S(n)*exp(-j*2πnF(i)T s )
the set of frequency offset compensated SCM signals is then:
Y＝[y 1 ,y 2 ,y 3 ,…,y i ]。
further, in step S4, the low-frequency SCM signal acquiring method includes: compensating each frequency offset for SCM signal y using a low pass filter i Filtering to filter the frequency offset compensation SCM signal y i The low-frequency SCM signal set obtained after filtering is as follows:
M＝[m 1 ,m 2 ,…,m i ]。
further, the signal average power in step S4 is calculated by using a power calculation formula of the discrete signal.
Further, the method for obtaining the frequency offset estimation value according to the average power of each signal in step S5 includes: determining a low frequency SCM signal m with a maximum signal average power i Said low frequency SCM signal m i The corresponding frequency offset before filtering is compensated for SCM signal to be y i Said frequency offset compensating SCM signal y i The corresponding test frequency is F (i) in the test frequency vector set F, the test frequency F (i) is a frequency deviation estimated value, and the frequency deviation compensates an SCM signal y i Is the result of the frequency offset processing.
A frequency offset processing system for a digital subcarrier multiplexed signal, the system being adapted to perform the method for frequency offset processing of the digital subcarrier multiplexed signal according to any of the above technical solutions, the system comprising: the device comprises a range selection unit, a test frequency selection unit, a frequency offset compensation calculation unit, a low-pass filter, a signal power calculation unit and a result processing unit;
the method comprises the steps of setting a frequency deviation estimation range by using a range selection unit, selecting a plurality of test frequencies by using a test frequency selection unit in the frequency deviation estimation range, testing frequency deviation compensation by using each test frequency for an initial SCM signal received by a signal receiving end by using a frequency deviation compensation calculation unit, obtaining a low-frequency SCM signal in the frequency deviation compensated SCM signal by using a low-pass filter, calculating the signal average power of the low-frequency SCM signal by using a signal power calculation unit, obtaining a frequency deviation estimation value by using a result processing unit according to the signal average power, and taking the frequency deviation compensated SCM signal corresponding to the frequency deviation estimation value as a frequency deviation processing result.
Furthermore, the frequency offset estimation range set by the range selection unit is [ -mG, mG ], m is a real number, and the value of m is determined according to the frequency offset condition in the actual coherent optical communication system; the number of the test frequencies selected by the test frequency selecting unit is N +1, the interval between two adjacent test frequencies is 2mG/N, and the vector set of the test frequencies is as follows:
further, the frequency offset compensation calculating unit uses each test frequency to test frequency offset compensation on an initial SCM signal received by the signal receiving end, where the initial SCM signal is represented by the following formula:
Δ ν is frequency deviation between a transmitting end laser and a local oscillator laser, namely a frequency deviation value; a (n) is a signal transmitting end SCM signal; t is a unit of s Sampling time intervals for a signal receiving end, wherein n is a sequence number of symbols;
the frequency offset compensation calculating unit performs frequency offset compensation according to the following formula:
Y(n)＝S(n)*exp(-j*2πnΔυT s )
the frequency deviation compensation calculating unit substitutes each test frequency into the formula, and the initial SCM signal received by the signal receiving end is subjected to frequency deviation compensation by using each test frequency, so that the frequency deviation compensation SCM signal corresponding to each test frequency can be obtained:
y i ＝S(n)*exp(-j*2πnF(i)T s )
the frequency offset compensation SCM signal set is as follows:
Y＝[y 1 ,y 2 ,y 3 ,…,y i ]。
further, the low-pass filter pairEach frequency offset compensated SCM signal y i Filtering to filter the frequency offset compensation SCM signal y i The low-frequency SCM signal set obtained after filtering is as follows:
M＝[m 1 ,m 2 ,…,m i ]
the signal power calculation unit calculates the low-frequency SCM signal by adopting a power calculation formula of the discrete signal to obtain signal average power;
the result processing unit determines a low frequency SCM signal m with the largest signal average power i And looking up the low frequency SCM signal m i Corresponding pre-filtering frequency offset compensation SCM signal y i Said frequency offset compensating SCM signal y i The corresponding test frequency is F (i) in the test frequency vector set F, the test frequency F (i) is a frequency deviation estimated value, and the frequency deviation compensates the SCM signal y i Is the result of the frequency offset processing.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
the technical scheme of the invention comprises the steps of firstly determining a frequency deviation estimation range according to the frequency deviation condition in an actual coherent optical communication system, then selecting a plurality of test frequencies from the frequency deviation estimation range, then compensating the frequency deviation for an initial SCM signal by using each test frequency, filtering a high-frequency subcarrier by using a low-pass filter, finally calculating the average power of the signal obtained after filtering, and judging the magnitude of the frequency deviation value according to the average power corresponding to different test frequencies. The technical scheme can estimate the frequency offset compensation before the dispersion compensation, has no influence on the transmission performance of the system and the complexity of the dispersion compensation, does not sacrifice the spectrum efficiency of the SCM system, and is transparent to the modulation format.
Drawings
FIG. 1 is a flowchart of the steps of example 1;
FIG. 2 is a frequency spectrum diagram of SCM signals at a transmitting end and a receiving end;
FIG. 3 is a graph of test frequency versus corresponding signal average power;
FIG. 4 is a diagram of a relationship between a set frequency offset and an estimated frequency offset;
fig. 5 is a system architecture diagram of embodiment 2.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
the technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
In this embodiment, an initial SCM signal with a baud rate of 64Gbaud is used, each subcarrier adopts a dual-polarization 16-order quadrature amplitude modulation (DP-16 QAM) format, the number of subcarriers is 4, and a roll-off coefficient of a root-raised cosine shaping filter at a transmitting end is 0.1, so that a bandwidth of each subcarrier is 64G/4 × (1 + 0.1) =17.6GHz. In the transmission process, a preset frequency offset of 1.5GHz and additive white gaussian noise are introduced, and fig. 2 is a frequency spectrum diagram of SCM signals of a transmitting end and a receiving end, wherein the sampling rate is 80G/s. The implementation steps of the method are shown in figure 1, and the method comprises the following detailed steps:
s1, setting a frequency offset estimation range;
the frequency offset estimation range is [ -mG, mG ].
m is a real number, and a value of m is determined according to a frequency offset condition in an actual coherent optical communication system, in this embodiment, a frequency estimation range is: [ -2.5G Hz,2.5G Hz ].
In other embodiments, the frequency offset estimation range calculation method may also use the baud rate of the initial SCM signal divided by 2 and then divided by 4.
S2, selecting a plurality of test frequencies within a frequency deviation estimation range;
the number of the test frequencies is N +1, the interval between two adjacent test frequencies is 2mG/N, and the vector set of the test frequencies is as follows:
in this example, the number of test frequencies was set to be N +1=21, and the set of test frequencies was F = [ -2.5GHz, -2.5g Hz +5g Hz/20, …,2.5G Hz ]
The specific number of the test frequencies is determined according to the precision of the frequency deviation estimation value required by practical application, and the more the number of the test frequencies is, the greater the calculation complexity and the calculation resource overhead are, and the higher the precision of the frequency deviation estimation value is.
S3, testing frequency offset compensation on the initial SCM signal received by the signal receiving end by using each testing frequency, and obtaining a corresponding frequency offset compensation SCM signal after the initial SCM signal is subjected to frequency offset compensation of one testing frequency;
the testing frequency offset compensation of the initial SCM signal received by the signal receiving end by using each testing frequency comprises the following steps:
ignoring noise and other transmission impairment effects, only considering frequency offset, the initial SCM signal after the signal receiving end passes through the analog-to-digital converter is represented by the following formula:
Δ ν is frequency deviation between a transmitting end laser and a local oscillator laser, namely a frequency deviation value; a (n) is a signal transmitting end SCM signal; t is s Sampling time intervals for a signal receiving end, wherein n is a sequence number of symbols; performing frequency offset compensation according to the following formula:
Y(n)＝S(n)*exp(-j*2πnΔυT s )
substituting each test frequency into the formula, and performing frequency offset compensation on the initial SCM signal received by the signal receiving end by using each test frequency to obtain a frequency offset compensation SCM signal:
y i ＝S(n)*exp(-j*2πnF(i)T s )
the set of frequency offset compensated SCM signals is then:
Y＝[y 1 ,y 2 ,y 3 ,…,y i ]。
s4, acquiring a low-frequency SCM signal in each frequency offset compensation SCM signal, and independently calculating the signal average power of each low-frequency SCM signal;
the low-frequency SCM signal acquisition method comprises the following steps: compensating each frequency offset for SCM signal y using a low pass filter i Filtering is carried outRemoving the frequency offset compensated SCM signal y i The low-frequency SCM signal set obtained after filtering is as follows:
M＝[m 1 ,m 2 ,…,m i ]。
in this embodiment, the low-pass filter is a rectangular filter, and the rectangular filter is used to compensate the frequency offset for the SCM signal y i In the frequency range of [ -17.6GHz,17.6GHz]The information in the signal is extracted, and the average power of the signal is calculated by adopting a power calculation formula of a discrete signal.
Calculating each signal M within M i The test frequency is plotted against the corresponding signal average power as shown in fig. 3.
And S5, obtaining a frequency deviation estimation value according to the average power of each signal, and taking a frequency deviation compensation SCM signal corresponding to the frequency deviation estimation value as a frequency deviation processing result.
The method for obtaining the frequency offset estimation value according to the average power of each signal comprises the following steps: determining a low frequency SCM signal m with a maximum signal average power i Said low frequency SCM signal m i The corresponding frequency offset before filtering is compensated for SCM signal to be y i Said frequency offset compensating SCM signal y i The corresponding test frequency is F (i) in the test frequency vector set F, and the test frequency F (i) is the frequency offset estimation value.
In this embodiment, the test frequency corresponding to the highest point of the test frequency and the corresponding signal average power curve in fig. 3 is 1.5GHz, that is, the frequency offset estimation value is 1.5GHz.
In an actual coherent optical communication system, in addition to the frequency offset processing described in this embodiment, linear impairment compensation is also required, where the linear impairment compensation includes dispersion compensation, and the frequency offset processing is performed before dispersion compensation.
In order to evaluate the accuracy of the frequency offset estimation of the present invention, fig. 4 is a scatter plot of the set frequency offset and the estimated frequency offset, which shows that the present invention can achieve very high frequency offset estimation accuracy under different set frequency offsets.
Example 2
The embodiment discloses a frequency offset processing system of digital subcarrier multiplexing signals, which comprises: the device comprises a range selection unit, a test frequency selection unit, a frequency offset compensation calculation unit, a low-pass filter, a signal power calculation unit and a result processing unit;
the method comprises the steps of setting a frequency deviation estimation range by using a range selection unit, selecting a plurality of test frequencies by using a test frequency selection unit in the frequency deviation estimation range, testing frequency deviation compensation by using each test frequency for an initial SCM signal received by a signal receiving end by using a frequency deviation compensation calculation unit, obtaining a low-frequency SCM signal in the frequency deviation compensated SCM signal by using a low-pass filter, calculating the signal average power of the low-frequency SCM signal by using a signal power calculation unit, obtaining a frequency deviation estimation value by using a result processing unit according to the signal average power, and taking the frequency deviation compensated SCM signal corresponding to the frequency deviation estimation value as a frequency deviation processing result.
The frequency deviation estimation range set by the range selection unit is [ -mG, mG ], m is a real number, and the value of m is determined according to the frequency deviation condition in the actual coherent optical communication system; the number of the test frequencies selected by the test frequency selecting unit is N +1, the interval between two adjacent test frequencies is 2mG/N, and the vector set of the test frequencies is as follows:
the frequency offset compensation calculating unit uses each test frequency to test frequency offset compensation on an initial SCM signal received by a signal receiving end, wherein the initial SCM signal is represented by the following formula:
Δ ν is a frequency deviation between a transmitting end laser and a local oscillator laser, namely a frequency deviation value; a (n) is a signal transmitting end SCM signal; t is s Sampling time intervals for a signal receiving end, wherein n is a sequence number of symbols;
the frequency offset compensation calculating unit performs frequency offset compensation according to the following formula:
Y(n)＝S(n)*exp(-j*2πnΔυT s )
the frequency deviation compensation calculating unit substitutes each test frequency into the formula, and the initial SCM signal received by the signal receiving end is subjected to frequency deviation compensation by using each test frequency, so that the frequency deviation compensation SCM signal corresponding to each test frequency can be obtained:
y i ＝S(n)*exp(-j*2πnF(i)T s )
the frequency offset compensation SCM signal set is as follows:
Y＝[y 1 ,y 2 ,y 3 ,…,y i ]。
the low pass filter compensates the SCM signal y for each frequency offset i Filtering to filter the frequency offset compensation SCM signal y i The low-frequency SCM signal set obtained after filtering is as follows:
M＝[m 1 ,m 2 ,…,m i ]
the signal power calculation unit calculates the low-frequency SCM signal by adopting a power calculation formula of the discrete signal to obtain signal average power;
the result processing unit determines a low frequency SCM signal m with the largest signal average power i And looking up the low frequency SCM signal m i Corresponding pre-filtering frequency offset compensation SCM signal y i Said frequency offset compensating SCM signal y i The corresponding test frequency is F (i) in the test frequency vector set F, the test frequency F (i) is a frequency deviation estimated value, and the frequency deviation compensates the SCM signal y i As a result of frequency offset processing
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (5)
1. A frequency offset processing method of digital subcarrier multiplexing signals is used for processing the frequency offset of initial digital subcarrier multiplexing signals received by a receiving end of a coherent optical communication system, the digital subcarrier multiplexing signals are called SCM signals, and the method is characterized by comprising the following steps:
s1, setting a frequency offset estimation range;
s2, selecting a plurality of test frequencies within a frequency deviation estimation range;
the frequency offset estimation range is [ -mG, mG ], m is a real number, a numerical value of m is determined according to a frequency offset condition in an actual coherent optical communication system, the number of the test frequencies is N +1, the interval between two adjacent test frequencies is 2mG/N, and a vector set of the test frequencies is as follows:
s3, testing frequency offset compensation on the initial SCM signal received by the signal receiving end by using each testing frequency, and obtaining a corresponding frequency offset compensation SCM signal after the initial SCM signal is subjected to frequency offset compensation of one testing frequency;
the initial SCM signal test frequency offset compensation comprises the following steps:
ignoring noise and other transmission impairment effects, only considering frequency offset, the initial SCM signal after the signal receiving end passes through the analog-to-digital converter is represented by the following formula:
Δ ν is frequency deviation between a transmitting end laser and a local oscillator laser, namely a frequency deviation value; a (n) is a signal transmitting end SCM signal; t is s Sampling time intervals for a signal receiving end, wherein n is the sequence number of symbols; performing frequency offset compensation according to the following formula:
Y(n)＝S(n)*exp(-j*2πnΔυT s )
substituting each test frequency into the formula, and performing frequency offset compensation on the initial SCM signal received by the signal receiving end by using each test frequency to obtain a frequency offset compensation SCM signal corresponding to each test frequency:
y i ＝S(n)*exp(-j*2πnF(i)T s )
the set of frequency offset compensated SCM signals is then:
Y＝[y 1 ,y 2 ,y 3 ,…,y i ]；
s4, acquiring a low-frequency SCM signal in each frequency offset compensation SCM signal, and independently calculating the signal average power of each low-frequency SCM signal; the signal average power is calculated by adopting a power calculation formula of a discrete signal;
the low-frequency SCM signal acquisition method comprises the following steps: compensating each frequency offset for SCM signal y using a low pass filter i Filtering to filter the frequency offset compensation SCM signal y i The low-frequency SCM signal set obtained after filtering is as follows:
M＝[m 1 ,m 2 ,…,m i ]；
s5, obtaining a frequency deviation estimation value according to the average power of each signal, and taking a frequency deviation compensation SCM signal corresponding to the frequency deviation estimation value as a frequency deviation processing result; the method for obtaining the frequency offset estimation value according to the average power of each signal comprises the following steps: determining a low frequency SCM signal m with a maximum signal average power i Said low frequency SCM signal m i The corresponding frequency offset before filtering is compensated for SCM signal to be y i Said frequency offset compensating SCM signal y i The corresponding test frequency is F (i) in the test frequency vector set F, the test frequency F (i) is a frequency deviation estimated value, and the frequency deviation compensates the SCM signal y i Is the result of the frequency offset processing.
2. A system for frequency offset processing of a digital subcarrier multiplexed signal, the system being configured to perform the method for frequency offset processing of a digital subcarrier multiplexed signal of claim 1, the system comprising: the device comprises a range selection unit, a test frequency selection unit, a frequency offset compensation calculation unit, a low-pass filter, a signal power calculation unit and a result processing unit;
the method comprises the steps of setting a frequency deviation estimation range by using a range selection unit, selecting a plurality of test frequencies by using a test frequency selection unit in the frequency deviation estimation range, testing frequency deviation compensation by using each test frequency for an initial SCM signal received by a signal receiving end by using a frequency deviation compensation calculation unit, obtaining a low-frequency SCM signal in the frequency deviation compensated SCM signal by using a low-pass filter, calculating the signal average power of the low-frequency SCM signal by using a signal power calculation unit, obtaining a frequency deviation estimation value by using a result processing unit according to the signal average power, and taking the frequency deviation compensated SCM signal corresponding to the frequency deviation estimation value as a frequency deviation processing result.
3. The system of claim 2, wherein the range selection unit sets the frequency offset estimation range as [ -mG, mG ], m is a real number, and determines the value of m according to the frequency offset condition in the actual coherent optical communication system; the number of the test frequencies selected by the test frequency selecting unit is N +1, the interval between two adjacent test frequencies is 2mG/N, and the vector set of the test frequencies is as follows:
4. the system of claim 3, wherein the frequency offset compensation calculating unit uses each test frequency to test frequency offset compensation for an initial SCM signal received by the signal receiving end, the initial SCM signal being represented by the following equation:
Δ ν is frequency deviation between a transmitting end laser and a local oscillator laser, namely a frequency deviation value; a (n) is a signal transmitting end SCM signal; t is s Sampling time intervals for a signal receiving end, wherein n is a sequence number of symbols;
the frequency offset compensation calculating unit performs frequency offset compensation according to the following formula:
Y(n)＝S(n)*exp(-j*2πnΔυT s )
the frequency deviation compensation calculating unit substitutes each test frequency into the formula, and the initial SCM signal received by the signal receiving end is subjected to frequency deviation compensation by using each test frequency, so that the frequency deviation compensation SCM signal corresponding to each test frequency can be obtained:
y i ＝S(n)*exp(-j*2πnF(i)T s )
the frequency offset compensation SCM signal set is as follows:
Y＝[y 1 ,y 2 ,y 3 ,…,y i ]。
5. the system of claim 4, wherein the low pass filter compensates each frequency offset for the SCM signal y i Filtering to filter the frequency offset compensation SCM signal y i The low-frequency SCM signal set obtained after filtering is as follows:
M＝[m 1 ,m 2 ,…,m i ]
the signal power calculation unit calculates the low-frequency SCM signal by adopting a power calculation formula of the discrete signal to obtain signal average power;
the result processing unit determines a low frequency SCM signal m with the largest signal average power i And looking up the low frequency SCM signal m i Corresponding pre-filtering frequency offset compensation SCM signal y i Said frequency offset compensating SCM signal y i The corresponding test frequency is F (i) in the test frequency vector set F, the test frequency F (i) is a frequency deviation estimated value, and the frequency deviation compensates the SCM signal y i Is the result of the frequency offset processing.
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| CN101499991A (en) * | 2009-03-17 | 2009-08-05 | 广东工业大学 | MIMO-OFDM system carrier frequency bias and sampling offset combined estimation method under IQ unbalance |
| CN102820932A (en) * | 2012-08-10 | 2012-12-12 | 武汉邮电科学研究院 | Frequency deviation self-adaptive precise compensation system and frequency deviation self-adaptive precise compensation method in coherence optical communication |
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