CN114826854B - FBMC synchronization improvement method and device based on estimation compensation mode - Google Patents
FBMC synchronization improvement method and device based on estimation compensation mode Download PDFInfo
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Abstract
The invention discloses an FBMC synchronization improvement method and device based on an estimation compensation mode, wherein the method comprises the steps of receiving a training sequence, carrying out cross correlation with a local sequence to obtain a cross correlation value, and obtaining an energy average value through calculation; constructing a synchronization measurement function through the cross-correlation value and the energy average value, and acquiring a timing synchronization point through maximum likelihood synchronization estimation; performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence; performing decimal frequency offset estimation on the synchronous training sequence to obtain a frequency offset estimation value; and continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met and synchronization is completed.
Description
Technical Field
The invention relates to an FBMC synchronization improvement method and device based on an estimation compensation mode, and belongs to the technical field of FBMC system synchronization algorithms.
Background
According to the proposal of the new application scene and the performance index of 5G, proper modulation waveforms need to be selected to meet the requirements of future communication systems. Around the application requirements, the industry has proposed a variety of multi-carrier techniques, such as:
universal filtered multi-carrier (UFMC), universal filtered multi-carrier (GFDM), and filter bank multi-carrier (FBMC) techniques, where FBMC techniques are considered the most likely alternative to OFDM being 5G modulated waves.
Compared with OFDM, FBMC uses a pulse shaping filter with good design, so that the out-of-band attenuation is fast and has good robustness to synchronization errors; through a well designed filter, all subcarriers do not need to be strictly orthogonal, a CP does not need to be added, and the system has higher flexibility and spectrum utilization rate; and flexible frequency band bandwidth design can utilize scattered spectrum resources, and the characteristics make the FBMC technology a research hotspot for next-generation mobile communication.
In the FBMC system, each subcarrier only overlaps with an adjacent subcarrier, and non-adjacent subcarriers will not overlap, so that the FBMC system adopts an offset positive amplitude modulation (OQAM) mode to ensure orthogonality between adjacent subcarriers, but only ensures real number domain orthogonality of the system, and there is inherent imaginary interference in complex number domain, which results in that the channel estimation and timing synchronization method with good design in the existing OFDM system cannot be directly used in the FBMC system. Channel synchronization and channel estimation are important components of the receiver-side demodulator, and have a direct impact on the performance of the system. The system needs to demodulate the received data at the receiving end, and firstly needs to determine the initial position of the received signal to ensure the alignment of the initial points of IFFT and FFT, and the receiving end needs to perform timing synchronization to achieve the purpose of correct demodulation. In order to demodulate the correct channel parameters, it is also necessary to design a channel estimation algorithm with good performance. The research and design of channel estimation and channel synchronization algorithms are the primary problems solved by the FBMC system, and the quality of the channel synchronization and estimation algorithms have a critical influence on the application of the system. Since FBMC is strictly orthogonal only in the real number domain, which means that there is imaginary interference on each subcarrier, a well designed channel estimation method in OFDM system cannot be applied to FBMC system. Moreover, the FBMC system does not use CP, which causes the system to be sensitive to timing errors, and it becomes important to design a timing synchronization algorithm with more excellent synchronization performance.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide an FBMC synchronization improvement method and device based on an estimation and compensation mode, which can enable an FBMC system to have a better timing synchronization effect under the condition of carrier frequency offset in the environment of low signal to noise ratio or high signal to noise ratio.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
in a first aspect, the present invention provides an FBMC synchronization improvement method based on an estimation compensation mode, including:
receiving a training sequence, performing cross-correlation with a local sequence to obtain a cross-correlation value, and calculating to obtain an energy average value;
constructing a synchronization measurement function through the cross-correlation value and the energy average value, and acquiring a timing synchronization point through maximum likelihood synchronization estimation;
performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence;
performing decimal frequency offset estimation on the synchronous training sequence to obtain a frequency offset estimation value;
and continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing the synchronization.
Further, the step of performing cross-correlation between the received training sequence and the local sequence to obtain a cross-correlation value, and obtaining an energy average value by calculating includes:
the system receives a training sequence r (n) and a local sequence s (n) to carry out cross correlation to obtain a cross correlation function c (d), and an energy average value p (d) is obtained, and the formula is as follows:
wherein N is the number of sampling points in one symbol period, d is the starting point of the training sequence r (N) used for correlation, p=qn is the interval, q is a positive integer, and L BD The filter cut-off length for the undisturbed BD part of the sync training sequence.
Further, the constructing a synchronization metric function through the cross-correlation value and the energy average value, and obtaining a timing synchronization point through maximum likelihood synchronization estimation includes:
from c (d) and p (d), a synchronization metric function is obtained
Local sequence and method for the production thereofThe strongest correlation point of training sequence is timing synchronization point d c The maximum likelihood synchronization estimation is adopted to obtain:
wherein ,
τ m for maximum multipath delay +.>
Representing an upward rounding.
Further, the performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence includes:
through the obtained timing synchronization point d c The training sequence is compensated in timing and compensated by using normalized frequency offset epsilon, and the expression of the synchronous training sequence is obtained as follows:
wherein epsilon=Δf/F is normalized frequency offset, Δf is frequency offset, F is subcarrier spacing, d' is timing offset, o (n) is mean 0, and variance is
Additive white gaussian noise of (c).
Further, the step of performing decimal frequency offset estimation on the synchronous training sequence to obtain an estimated value of the frequency offset includes:
and performing decimal frequency offset estimation on the repeated synchronous training symbols which are completely consistent in the BD section by utilizing the symbol structure of the synchronous training sequence r' (n), and defining a measure for frequency offset estimation:
wherein ,r'* (n+d) represents the conjugated sequence of r' (n+d), wherein P=qN is the interval, N is the sampling point number in one symbol period, and q is in the value range of [1, Q]Q is the number of repeated samples of the synchronization training sequence r ' (n), which is a positive integer, and r ' (n+p+d) =r ' (n+d) is given due to the redundancy characteristic of the synchronization training symbol, and the carry-over metric function is obtained:
the frequency offset estimate may be expressed as:
wherein, the angle { Z } is the angle value of the complex number Z, and the value range is [ -pi, pi]Therefore, the range of the normalized frequency offset value is
Because the positive integer K is less than or equal to N, the positive integer K is equal to the positive integer K only when critical sampling is performed, wherein the value range of q is [1, Q]Therefore, when k=n and q=1, the normalized frequency offset estimation range is maximized to be [ -0.5,0.5]But the smaller the q value is, the larger the frequency offset estimation range is, but the larger the corresponding frequency offset estimation error is; conversely, the larger the q value is, the smaller the frequency offset estimation range is, but the smaller the corresponding frequency offset estimation error is, when the signal to noise ratio and the sampling coefficient are fixed, the frequency offset estimation error and +_>
And in direct proportion.
Further, the step of continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing the synchronization includes:
using the obtained frequency offset estimation value
Is in alignment withThe step training sequence r' (n) continues to carry out frequency offset compensation to obtain
When the frequency offset estimates the range epsilon range (q m ) And frequency offset estimation value epsilon m The following conditions are satisfied:
ε m ∈ε range (q m ),ε m ∈ε range (q m+1 ),ε m+1 ∈ε range (q m+1 ),ε m *ε m >0
wherein the q value is 1 to 4, the m initial value is 1, and the frequency offset compensation step is continued;
otherwise, the frequency offset estimation range and the estimation precision meet the system requirements, and the synchronization is completed.
Further, the method further comprises the following steps: fine synchronization is performed by utilizing a least square algorithm, and a synchronization starting point is obtained as follows:
d＝argmax[2|M(d)|-B(d)]
wherein ：
in a second aspect, the present invention provides an FBMC synchronization improvement apparatus based on an estimation compensation method, including:
the computing unit is used for receiving the training sequence, carrying out cross correlation with the local sequence to obtain a cross correlation value, and obtaining an energy average value through computing;
the timing synchronization point acquisition unit is used for constructing a synchronization measurement function through the cross correlation value and the energy average value and acquiring a timing synchronization point through maximum likelihood synchronization estimation;
the synchronous training sequence acquisition unit is used for carrying out timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence;
the frequency offset estimation value acquisition unit is used for carrying out decimal frequency offset estimation on the synchronous training sequence to acquire a frequency offset estimation value;
and the synchronization unit is used for continuously performing frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing synchronization.
In a third aspect, the present invention provides an FBMC synchronization improvement apparatus based on an estimation and compensation method, including a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is operative according to the instructions to perform the steps of the method according to any one of the preceding claims.
A computer-readable storage medium having stored thereon a computer program, the advantageous effects achieved by the present invention compared to the prior art are:
the invention provides an FBMC synchronization improvement method and device based on an estimation compensation mode, which carry out coarse timing synchronization by adopting cross correlation by utilizing the characteristic of ZC sequence delay correlation; after coarse timing synchronization compensation, carrier frequency offset estimation is carried out by adopting autocorrelation, and the estimated frequency offset is subjected to sequence compensation; then, carrying out frequency offset estimation on the compensated sequence again by utilizing a self-adaptive recursion estimation algorithm until the system requirement is met; finally, the compensated sequence is utilized again, and the noise influence is considered to carry out fine symbol timing synchronization; the invention can make the FBMC system have better timing synchronization effect under the condition of carrier frequency offset through estimation and compensation, no matter in the environment of low signal-to-noise ratio or high signal-to-noise ratio.
Drawings
FIG. 1 is a flow chart provided by an embodiment of the present invention;
FIG. 2 is a diagram of a synchronous training symbol structure provided in an embodiment of the invention;
FIG. 3 is a graph of frequency offset estimation error versus q value provided by an embodiment of the invention;
FIG. 4 is a table of simulation parameters provided by an embodiment of the invention;
fig. 5 is a timing accuracy simulation result diagram provided in an embodiment of the invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
Example 1
The embodiment introduces an FBMC synchronization improvement method based on an estimation compensation mode, which includes:
receiving a training sequence, performing cross-correlation with a local sequence to obtain a cross-correlation value, and calculating to obtain an energy average value;
constructing a synchronization measurement function through the cross-correlation value and the energy average value, and acquiring a timing synchronization point through maximum likelihood synchronization estimation;
performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence;
performing decimal frequency offset estimation on the synchronous training sequence to obtain a frequency offset estimation value;
and continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing the synchronization.
As shown in fig. 1, the application process of the FBMC synchronization improvement method based on the estimation and compensation method provided in this embodiment specifically involves the following steps:
step 1: coarse timing synchronization is performed by adopting cross correlation based on the characteristic of ZC sequence delay correlation;
(21) The system knows that the received synchronous training sequence r (n) and the local sequence s (n) are subjected to cross correlation to obtain a cross correlation function c (d), and an energy average value p (d) is obtained.
Wherein N is within one symbol periodThe number of sampling points, d is the starting point of the synchronous training sequence r (n) used for correlation, P=qN is interval, q is positive integer, L BD The filter cut-off length for the undisturbed BD part of the sync training sequence.
(22) From c (d) and p (d), a synchronization metric function is obtained
The highest correlation point between the local sequence and the synchronous training sequence is the timing synchronization point d c . The method comprises the following steps of obtaining through maximum likelihood synchronous estimation:
wherein 
τ m For maximum multipath delay +.>
Representing an upward rounding.
Step 2: after coarse timing synchronization compensation, carrying out carrier frequency offset estimation by adopting autocorrelation, and carrying out sequence compensation on the estimated frequency offset;
through the obtained timing synchronization point d c The synchronous training sequence is compensated in timing and compensated by normalized frequency offset epsilon, and the expression of the obtained signal is
Wherein epsilon=Δf/F is normalized frequency offset, Δf is frequency offset, F is subcarrier spacing, d' is timing offset, o (n) is mean 0, and variance is
Additive white gaussian noise of (c).
Step 3: carrying out frequency offset estimation on the compensated sequence again by utilizing a self-adaptive recursion estimation algorithm until the system requirement is met;
and performing decimal frequency offset estimation on the repeated training symbols which are completely consistent in the BD section by utilizing the symbol structure of the synchronous training sequence r' (n), and defining a measure for frequency offset estimation:
r' * (n+d) represents the conjugate sequence of r' (n+d), the metric function uses all synchronous training symbols in BD segment shown in fig. 2, and has higher reliability, wherein P=qN is interval, N is sampling point number in one symbol period, and q has a value range of [1, Q]Q is the number of repeated samples of the synchronous training sequence r' (n), which is a positive integer. Due to the redundancy property of the sync training symbols, r '(n+p+d) =r' (n+d), the carry-over metric function is available:
the frequency offset estimate may be expressed as:
wherein { Z } is the angle value of complex number Z, and the value range is [ -pi, pi]Therefore, the range of the normalized frequency offset value is
Because the positive integer K is less than or equal to N, the positive integer K is equal to the positive integer K only when critical sampling is performed, wherein the value range of q is [1, Q]Therefore, when k=n and q=1, the normalized frequency offset estimation range is maximized to be [ -0.5,0.5]. So when K is unchanged, the size of the frequency offset estimation range decreases with an increase in q value, and the smaller the frequency offset estimation range is, the worse the timing accuracy is. As shown in the relation diagram of the frequency offset estimation error and q value in fig. 3, when q value is smaller, the corresponding frequency offset estimation error is larger;conversely, the larger the q value, the smaller the corresponding frequency offset estimation error. When the signal-to-noise ratio and the sampling coefficient are fixed, the frequency offset estimation error is +.>
And in direct proportion.
Using the obtained frequency offset estimation value
Frequency offset compensation is continuously carried out on the synchronous training sequence r (n) to obtain +.>
When the frequency offset estimates the range epsilon range (q m ) And frequency offset estimation value epsilon m The following conditions are satisfied:
ε m ∈ε range (q m ),ε m ∈ε range (q m+1 ),ε m+1 ∈ε range (q m+1 ),ε m *ε m >0
where q is 1 to 4 and m is 1 initially. Repeating step 4;
otherwise, the balance of the frequency offset estimation range and the estimation precision is achieved, the system requirement is met, and the next step is carried out.
Step 4: and finally, performing fine symbol timing synchronization by using the compensated sequence.
To take noise effects into account and to use a least squares algorithm for fine synchronization, where this is for ease of presentation. The synchronization training sequence r '(n) after the last estimated compensation is denoted by r (n), i.e., let r (n) =r' (n).
The specific algorithm is as follows:
from the formula
It is known that the data can be further simplified into the range where the data is not disturbed:
if the noise is large, o (n+qN+d) o in that equation * This term (n+d) cannot be ignored and will then affect the accuracy of the timing synchronization estimate. Fine synchronization estimation is performed by solving for the minimum of the following formulas:
wherein 
Order the
B (d), the formula is written +.>
If a minimum is to be obtained, when the cosine term is 1, the equation becomes:
B(d)-2|M(d)|
the synchronization starting point position is: d=argmax [2|M (d) | -B (d) ].
Example 2
The present embodiment provides an FBMC synchronization improvement device based on an estimation compensation mode, including:
the computing unit is used for receiving the training sequence, carrying out cross correlation with the local sequence to obtain a cross correlation value, and obtaining an energy average value through computing;
the timing synchronization point acquisition unit is used for constructing a synchronization measurement function through the cross correlation value and the energy average value and acquiring a timing synchronization point through maximum likelihood synchronization estimation;
the synchronous training sequence acquisition unit is used for carrying out timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence;
the frequency offset estimation value acquisition unit is used for carrying out decimal frequency offset estimation on the synchronous training sequence to acquire a frequency offset estimation value;
and the synchronization unit is used for continuously performing frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing synchronization.
Example 3
The embodiment provides an FBMC synchronization improvement device based on an estimation compensation mode, which comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is operative according to the instructions to perform the steps of the method according to any one of embodiment 1.
Example 4
The present embodiment provides a computer-readable storage medium having stored thereon a computer program characterized in that: the program when executed by a processor implements the steps of the method of any of embodiment 1.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.
Claims (4)
1. An FBMC synchronization improvement method based on an estimation compensation mode, comprising:
receiving a training sequence, performing cross-correlation with a local sequence to obtain a cross-correlation value, and calculating to obtain an energy average value;
constructing a synchronization measurement function through the cross-correlation value and the energy average value, and acquiring a timing synchronization point through maximum likelihood synchronization estimation;
performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence;
performing decimal frequency offset estimation on the synchronous training sequence to obtain a frequency offset estimation value;
continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing synchronization;
the receiving training sequence and the local sequence are subjected to cross-correlation to obtain a cross-correlation value, and an energy average value is obtained through calculation, and the method comprises the following steps:
the system receives a training sequence r (n) and a local sequence s (n) to carry out cross correlation to obtain a cross correlation function c (d), and an energy average value p (d) is obtained, and the formula is as follows:
wherein N is the number of sampling points in one symbol period, d is the starting point of the training sequence r (N) used for correlation, p=qn is the interval, q is a positive integer, and L BD Filter cut-off length for undisturbed BD parts of the synchronization training sequence;
the step of constructing a synchronization metric function through the cross-correlation value and the energy average value and obtaining a timing synchronization point through maximum likelihood synchronization estimation comprises the following steps:
from c (d) and p (d), a synchronization metric function is obtained
The strongest correlation point between the local sequence and the training sequence is the timing synchronization point d c The maximum likelihood synchronization estimation is adopted to obtain:
wherein ,
τ m for maximum multipath delay +.>
Represents rounding up;
the step of performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence comprises the following steps:
through the obtained timing synchronization point d c The training sequence is compensated in timing and compensated by using normalized frequency offset epsilon, and the expression of the synchronous training sequence is obtained as follows:
wherein epsilon=Δf/F is normalized frequency offset, Δf is frequency offset, F is subcarrier spacing, d' is timing offset, o (n) is mean 0, and variance is
Additive white gaussian noise of (2);
the step of performing decimal frequency offset estimation on the synchronous training sequence to obtain the frequency offset estimation value comprises the following steps:
and performing decimal frequency offset estimation on the repeated synchronous training symbols which are completely consistent in the BD section by utilizing the symbol structure of the synchronous training sequence r' (n), and defining a measure for frequency offset estimation:
wherein ,r'* (n+d) represents the conjugated sequence of r' (n+d), wherein P=qN is the interval, N is the sampling point number in one symbol period, and q is in the value range of [1, Q]Q is the number of repeated samplings of the synchronous training sequence r ' (n), is a positive integer, and r ' (n+P+d) =r ' (n+d) is brought into the metric function due to the redundancy characteristic of the synchronous training symbolsThe method can obtain:
the frequency offset estimate may be expressed as:
wherein, the angle { Z } is the angle value of the complex number Z, and the value range is [ -pi, pi]Therefore, the range of the normalized frequency offset value is
Because the positive integer K is less than or equal to N, the positive integer K is equal to the positive integer K only when critical sampling is performed, wherein the value range of q is [1, Q]Therefore, when k=n and q=1, the normalized frequency offset estimation range is maximized to be [ -0.5,0.5]But the smaller the q value is, the larger the frequency offset estimation range is, but the larger the corresponding frequency offset estimation error is; conversely, the larger the q value is, the smaller the frequency offset estimation range is, but the smaller the corresponding frequency offset estimation error is, when the signal to noise ratio and the sampling coefficient are fixed, the frequency offset estimation error and +_>
Proportional relation;
and continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing the synchronization, wherein the method comprises the following steps:
using the obtained frequency offset estimation value
Continuously performing frequency offset compensation on the synchronous training sequence r' (n) to obtain
When the frequency offset estimates the range epsilon range (q m ) And frequency offset estimation value epsilon m The following conditions are satisfied:
ε m ∈ε range (q m ),ε m ∈ε range (q m+1 ),ε m+1 ∈ε range (q m+1 ),ε m *ε m >0
wherein the q value is 1 to 4, the m initial value is 1, and the frequency offset compensation step is continued;
otherwise, the frequency offset estimation range and the estimation precision meet the system requirements, and the synchronization is completed;
further comprises: fine synchronization is performed by utilizing a least square algorithm, and a synchronization starting point is obtained as follows:
d＝argmax[2|M(d)|-B(d)]
wherein ：
2. an FBMC synchronization improving apparatus based on an estimation compensation method, comprising:
the computing unit is used for receiving the training sequence, carrying out cross correlation with the local sequence to obtain a cross correlation value, and obtaining an energy average value through computing;
the timing synchronization point acquisition unit is used for constructing a synchronization measurement function through the cross correlation value and the energy average value and acquiring a timing synchronization point through maximum likelihood synchronization estimation;
the synchronous training sequence acquisition unit is used for carrying out timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence;
the frequency offset estimation value acquisition unit is used for carrying out decimal frequency offset estimation on the synchronous training sequence to acquire a frequency offset estimation value;
the synchronization unit is used for continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing synchronization;
wherein: the receiving training sequence and the local sequence are subjected to cross-correlation to obtain a cross-correlation value, and an energy average value is obtained through calculation, and the method comprises the following steps:
the system receives a training sequence r (n) and a local sequence s (n) to carry out cross correlation to obtain a cross correlation function c (d), and an energy average value p (d) is obtained, and the formula is as follows:
wherein N is the number of sampling points in one symbol period, d is the starting point of the training sequence r (N) used for correlation, p=qn is the interval, q is a positive integer, and L BD Filter cut-off length for undisturbed BD parts of the synchronization training sequence;
the step of constructing a synchronization metric function through the cross-correlation value and the energy average value and obtaining a timing synchronization point through maximum likelihood synchronization estimation comprises the following steps:
from c (d) and p (d), a synchronization metric function is obtained
The strongest correlation point between the local sequence and the training sequence is the timing synchronization point d c The maximum likelihood synchronization estimation is adopted to obtain:
wherein ,
τ m for maximum multipath delay +.>
Represents rounding up;
the step of performing timing compensation on the training sequence through the timing synchronization point to obtain a synchronous training sequence comprises the following steps:
through the obtained timing synchronization point d c The training sequence is compensated in timing and compensated by using normalized frequency offset epsilon, and the expression of the synchronous training sequence is obtained as follows:
wherein epsilon=Δf/F is normalized frequency offset, Δf is frequency offset, F is subcarrier spacing, d' is timing offset, o (n) is mean 0, and variance is
Additive white gaussian noise of (2);
the step of performing decimal frequency offset estimation on the synchronous training sequence to obtain the frequency offset estimation value comprises the following steps:
and performing decimal frequency offset estimation on the repeated synchronous training symbols which are completely consistent in the BD section by utilizing the symbol structure of the synchronous training sequence r' (n), and defining a measure for frequency offset estimation:
wherein ,r'* (n+d) represents the conjugated sequence of r' (n+d), wherein P=qN is the interval, N is the sampling point number in one symbol period, and q is in the value range of [1, Q]Q is the number of repeated samples of the synchronization training sequence r ' (n), which is a positive integer, and r ' (n+p+d) =r ' (n+d) is given due to the redundancy characteristic of the synchronization training symbol, and the carry-over metric function is obtained:
the frequency offset estimate may be expressed as:
wherein, the angle { Z } is the angle value of the complex number Z, and the value range is [ -pi, pi]Therefore, the range of the normalized frequency offset value is
Because the positive integer K is less than or equal to N, the positive integer K is equal to the positive integer K only when critical sampling is performed, wherein the value range of q is [1, Q]Therefore, when k=n and q=1, the normalized frequency offset estimation range is maximized to be [ -0.5,0.5]But the smaller the q value is, the larger the frequency offset estimation range is, but the larger the corresponding frequency offset estimation error is; conversely, the larger the q value is, the smaller the frequency offset estimation range is, but the smaller the corresponding frequency offset estimation error is, when the signal to noise ratio and the sampling coefficient are fixed, the frequency offset estimation error and +_>
Proportional relation;
and continuing to perform frequency offset compensation on the synchronous training sequence by using the frequency offset estimation value until the system requirement is met, and completing the synchronization, wherein the method comprises the following steps:
using the obtained frequency offset estimation value
Continuously performing frequency offset compensation on the synchronous training sequence r' (n) to obtain
When the frequency offset estimates the range epsilon range (q m ) And frequency offset estimation value epsilon m The following conditions are satisfied:
ε m ∈ε range (q m ),ε m ∈ε range (q m+1 ),ε m+1 ∈ε range (q m+1 ),ε m *ε m >0
wherein the q value is 1 to 4, the m initial value is 1, and the frequency offset compensation step is continued;
otherwise, the frequency offset estimation range and the estimation precision meet the system requirements, and the synchronization is completed;
further comprises: fine synchronization is performed by utilizing a least square algorithm, and a synchronization starting point is obtained as follows:
d＝argmax[2|M(d)|-B(d)]
wherein ：
3. an FBMC synchronization improving device based on an estimation compensation mode is characterized in that: comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is operative according to the instructions to perform the steps of the method of claim 1.
4. A computer-readable storage medium having stored thereon a computer program, characterized by: which when executed by a processor carries out the steps of the method of claim 1.
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