CN116016084A - Frequency offset tracking correction device and method - Google Patents
Frequency offset tracking correction device and method Download PDFInfo
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Abstract
The invention discloses a frequency offset tracking correction device and a method, wherein the device comprises the following steps: the system comprises a signal source, a training sequence extraction module, a first frequency offset estimation module, a first frequency offset correction module, a segmentation module, a second frequency offset estimation module and a second frequency offset correction module which are sequentially connected, wherein the second frequency offset correction module is provided with two output ends, one end of the second frequency offset correction module is connected with the segmentation module, the other end of the second frequency offset correction module is a signal output end, a corrected user data signal sequence is output, the training sequence is subjected to frequency offset estimation through the first frequency offset estimation module and the first frequency offset correction module to obtain a frequency offset estimation value, the user data signal sequence is subjected to frequency offset correction through the frequency offset estimation value, the corrected user data signal sequence is uniformly segmented to obtain unit signal sequences, and the frequency offset estimation value output by each unit signal sequence carries out frequency offset estimation and tracking on the residual user data signal, so that the user data signal is subjected to multiple frequency offset estimation and tracking, and the frequency offset tracking efficiency and accuracy are improved.
Description
Technical Field
The invention relates to a wireless communication system, in particular to a device and a method for tracking and correcting frequency offset of crystal oscillator.
Background
The crystal oscillator is an indispensable structure in a communication system, and provides counting and beats for signal transmission, and affects carrier frequency of wireless communication, and due to the working characteristics of the crystal oscillator, frequency offset cannot be avoided in signal transmission. Another method is blind detection, i.e. according to the characteristics of the modulated signal, such as QPSK modulation, then performing a fourth-order operation on the received signal will result in a single-tone sequence, and performing a spectral analysis on the sequence to obtain a frequency offset value, which will be referred to as method two.
The first advantage of the method is that the method is simple and has high estimation accuracy, but the disadvantage is that too many training sequences are inserted, which affects the efficiency of information transmission of the system, and less insertion affects the estimation accuracy. The second method has the advantages of high transmission efficiency, but has limitation, and if the modulation mode is a higher-order modulation mode, the accuracy of the method is also greatly reduced.
Because of the defects of the two modes, a frequency offset tracking correction device with high estimation accuracy and high precision and unrestricted use scenes is needed.
Disclosure of Invention
The invention aims to provide a frequency offset tracking correction device aiming at the defects that the frequency offset tracking correction in the prior art cannot have high accuracy and high precision and the use scene is limited.
The purpose of the invention is realized in the following way:
a frequency offset tracking correction apparatus comprising: the system comprises a signal source, a training sequence extraction module, a first frequency offset estimation module, a first frequency offset correction module, a segmentation module, a second frequency offset estimation module and a second frequency offset correction module which are sequentially connected, wherein the second frequency offset correction module comprises two signal output ports, one signal output port is connected with the segmentation module, and the other signal output port is a signal sequence output port after frequency offset tracking and correction.
Preferably, the baseband signal from the signal includes a training sequence and a user data signal.
Preferably, the first frequency offset estimation module divides the phase sequence into two segments according to the phase sequence obtained by the frequency offset to obtain a phase difference caused by the frequency offset, calculates the average value of the phase difference, and outputs the first frequency offset estimation value
Preferably, the segmentation module uniformly segments the user data signals, the segmented user data signals are marked as a segment 1, a segment 2 and a segment 3 … … segment m, and the user data signals output by the segmentation module are marked as a segment i, wherein i is more than or equal to 1 and less than or equal to m.
Preferably, the length of the segment i output by the segmentation module is 1-2 times of the length of the training sequence.
Preferably, the second frequency offset correction module performs frequency offset correction on the remaining user data signal sequences in the segmentation module.
The invention also discloses a frequency offset tracking correction method, which comprises the following steps:
step S1, a signal source transmits a baseband signal with a training sequence and a user data signal;
step S2, extracting the training sequence from the baseband signal;
s3, performing frequency offset estimation on the training sequence to obtain a first frequency offset estimation value;
s4, correcting the user data signal according to the first frequency offset estimation value to obtain a corrected user data signal;
step S5, uniformly segmenting the corrected user data signal, and marking the user data signal as segment 1, segment 2 and segment 3 … … segment m;
s6, extracting a segment i from the segments 1-m, wherein i is more than or equal to 1 and less than or equal to m, and modulating the segment i to obtain a segment i' with a pseudo training sequence;
s7, obtaining a frequency offset estimation value of the segmented i sequence according to the segmented i sequence and the segmented i' sequence, and marking the frequency offset estimation value as a second frequency offset estimation value;
s8, carrying out frequency offset correction on signals formed by the segments (i+1) to m according to the second frequency offset estimation value;
step S9, after the signals formed by the segments (i+1) to m are subjected to frequency offset correction, i=i+1 is given, and the process returns to step S6 until i=m, so as to finish receiving the baseband signals.
Preferably, in the step 6, the modulation scheme is QPSK.
Based on the technical scheme, the invention has the following characteristics:
firstly, user data are subjected to segmentation processing to obtain unit user data signal sequences, each unit signal sequence carries out frequency offset estimation and then outputs a frequency offset estimation value, and the rest user data signal sequences are subjected to frequency offset correction, so that the frequency offset estimation and tracking times are improved, and further the frequency offset tracking precision is improved.
Secondly, the generation of the pseudo training sequence gets rid of the problem that the frequency offset estimation can be carried out only by depending on the transmission training sequence, and excessive training sequences do not need to be inserted, so that the frequency offset tracking precision is ensured, and meanwhile, the efficiency of the system for transmitting information is improved.
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FIG. 1 is a schematic diagram of a frequency offset tracking and correcting device according to the present invention;
FIG. 2 is a time slot format of signal data sent by a baseband according to the present invention;
fig. 3 is a schematic diagram of frequency offset tracking correction after user data signal segmentation according to the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
The invention aims to provide a frequency offset tracking correction device and a frequency offset tracking correction method, which are used for solving the problems of low system transmission efficiency and low system transmission precision in the prior art. For further disclosure of the present invention, the present invention will now be further described with reference to the accompanying drawings.
Referring to fig. 1, the frequency offset tracking correction device includes a signal source 1, a training sequence extraction module 2, a first frequency offset estimation module 3, a first frequency offset correction module 4, a segmentation module 5, a pseudo training sequence generation module 6, a second frequency offset estimation module 7, and a second frequency offset correction module 8, which are sequentially connected, wherein the second frequency offset correction module 8 includes two signal output ends, one signal output end is connected with the segmentation module 5, and the other signal output end outputs a user data signal after frequency offset tracking correction.
The signal source 1 outputs a baseband signal, and the baseband signal is r (N), n=0, 1,2 … … N-1, N is a natural number according to the time slotThe format can be divided into a training sequence and a user data signal, the training sequence extracting module 2 extracts the training sequence from the baseband signal r (n), and the training sequence is denoted as r p (n) the length of which is denoted as M P Wherein r is p (n)＝r(n)，n＝0,1,2……M P -1。
The first frequency offset estimation module 3 receives the training sequence r according to the first frequency offset estimation module p (n) performing frequency offset estimation, specifically, firstly obtaining a phase sequence caused by frequency offset, namely alpha (n),
α(n)＝r p (n)×conj(c(n))，n＝0,1,2……M P -1, wherein conj (°) represents taking the conjugate, c (n) is the local sequence, i.e. the training sequence in the baseband signal;
dividing the phase sequence alpha (n) into two sections to obtain the phase difference caused by the frequency offset, which is marked as delta (n),
delta (n) =alpha (n+τ) ×conj (α (n)), n=0, 1,2 … … τ -1, where
The average value theta of the phase difference delta (n) is calculated, the accuracy of estimation is improved,
finally, a first frequency offset estimation value f is calculated est ，
f s For the symbol rate, at which the sender transmits and the receiver receives, this is relevant to the specific physical layer scheme, which is not particularly constrained by the present invention for purposes of general description.
The first frequency offset correction module 4 is used for correcting the first frequency offset estimated value f according to the first frequency offset estimated value f rst Correcting the received user data signal sequence to obtain r f (n)，
The segmentation module 5 segments the corrected user data signal, each segment having a length of the training sequence length M P The signal sequence of the segment i is output by the segment module, wherein i is more than or equal to 1 and less than or equal to m.
The pseudo-training sequence generating module 6 receives the signal sequence of segment i, denoted r i f (n)，
r i f (n)＝r f (i×M p +n)，n＝0,1,…,M i
The pseudo training sequence corresponding to the signal sequence of segment i is denoted as c i (n), by r i f (n) conversion to c i (n) can be implemented by a modulation mode, and the modulation mode adopted by the selected embodiment of the invention is QPSK, and specifically, the modulation process is as follows:
wherein n=0, 1, …, M i Real (·) represents the real part and imag (·) represents the imaginary part.
The second frequency offset estimation module 7 receives the pseudo training sequence c i And (n) processing, wherein the processing mode is the same as that of the first frequency offset estimation module, a pseudo training sequence corresponding to the signal sequence of the section i is obtained and marked as a section i', and the frequency offset estimation value of the section i is obtained according to the training sequence of the section i and marked as a second frequency offset estimation value.
The second frequency offset correction module 8 corrects the remaining segment sequences of the user data signal sequence according to the received second frequency offset estimation value, and as can be seen from fig. 3, the remaining user data signal sequence refers to the signal sequence formed from the i+1th segment to the m-th segment.
After that, the second frequency offset estimation module 8 continues to perform frequency offset estimation and correction on the segment i+1 after the segment i, i=i+1 is given, the signal sequence of the segment i enters the pseudo training sequence generation module 6 to obtain a pseudo training sequence corresponding to the segment i, the second frequency offset estimation module 7 processes the pseudo training sequence corresponding to the segment i, the second frequency offset correction module 8 is passed until i=m, the frequency offset estimation and correction on the segment m are completed, the output signal sequence is the signal sequence after m+1 times of frequency offset estimation and correction, the signal sequence after frequency offset correction can be output without continuously inserting the training sequence, the frequency offset correction frequency is increased in the middle, and the frequency offset estimation precision is further improved.
In addition, the signal sequence processed by the frequency offset tracking correction device carries out frequency offset tracking and correction on the original signal sequence through the generated pseudo training sequence, thereby eliminating the situation that the frequency offset estimation and tracking can be carried out only by depending on the sent training sequence, and greatly improving the application range of the frequency offset tracking correction device.
As another embodiment of the invention, the invention also discloses a frequency offset tracking correction method, which comprises the following steps:
step S1, a signal source 1 transmits a baseband signal with a training sequence and a user data signal;
step S2, a training sequence extracting module 2 extracts a training sequence from the baseband signal;
step S3, the first frequency offset estimation module 3 carries out frequency offset estimation on the training sequence to obtain a first frequency offset estimation value;
step S4, the first frequency offset correction module 4 corrects the user data signal according to the first frequency offset estimation value to obtain a corrected user data signal;
step S5, the segmentation module 5 uniformly segments the corrected user data signal, and marks the user data signal as a segment 1, a segment 2 and a segment 3 … … segment m;
s6, a pseudo training sequence generating module 6 extracts a segment i from the segments 1-m, wherein i is more than or equal to 1 and less than or equal to m, and the segment i is modulated to obtain a segment i' with a pseudo training sequence, wherein the modulation mode can be QPSK or other modulation modes;
s7, a second frequency offset estimation module 7 obtains a frequency offset estimation value of the segmented i sequence according to the segmented i sequence and the segmented i' sequence, and marks the frequency offset estimation value as a second frequency offset estimation value;
s8, a second frequency offset correction module 8 carries out frequency offset correction on signals formed by the segments (i+1) to m according to a second frequency offset estimation value;
step S9, after the signals formed by the segments (i+1) to m are subjected to frequency offset correction, i=i+1 is given, the step S6 is returned until i=m, the frequency offset estimation and tracking of the signal sequence of the segment m are completed, and the second frequency offset correction module 8 outputs the user data signal sequence subjected to m+1 times of frequency offset estimation and correction.
It should be noted that, in this embodiment, the formula processing manner in each module is the same as that in the first embodiment, and detailed description thereof is omitted.
In summary, the present invention provides a device for tracking and correcting frequency offset, which performs segmentation processing on user data signal sequences, and performs frequency offset estimation and correction on remaining user data signals by using a frequency offset estimation value of each segment of signal sequence, so that a user output signal sequence is subjected to multiple frequency offset estimation and correction, and efficiency and accuracy of user data signal transmission are improved. Meanwhile, the frequency offset correction and tracking of the user data signal can be realized without depending on transmitting a plurality of training sequences, and the application range of the frequency offset tracking correction device is enlarged.
The above embodiments are provided for illustrating the present invention and not for limiting the present invention, and various changes and modifications may be made by one skilled in the relevant art without departing from the spirit and scope of the present invention, and thus all equivalent technical solutions should be defined by the claims.
Claims (8)
1. A frequency offset tracking correction apparatus, comprising: the system comprises a signal source, a training sequence extraction module, a first frequency offset estimation module, a first frequency offset correction module, a segmentation module, a second frequency offset estimation module and a second frequency offset correction module which are sequentially connected, wherein the second frequency offset correction module comprises two signal output ports, one signal output port is connected with the segmentation module, and the other signal output port is a signal sequence output port after frequency offset tracking and correction.
2. The apparatus of claim 1 wherein the baseband signal from which the signal is derived comprises a training sequence and a user data signal.
3. The apparatus of claim 1, wherein the first frequency offset estimation module divides the phase sequence equally into two segments according to the phase sequence obtained by the frequency offset, obtains a phase difference caused by the frequency offset, calculates an average value of the phase difference, and outputs the first frequency offset estimation value.
4. The apparatus of claim 1 wherein the segmentation module uniformly segments the user data signal, the segmented user data signal is denoted as segment 1, segment 2, segment 3 … …, and the user data signal output by the segmentation module is denoted as segment i, wherein 1.ltoreq.i.ltoreq.m.
5. The apparatus of claim 4, wherein the length of the segment i output by the segmentation module is 1-2 times the length of the training sequence.
6. The apparatus of claim 1, wherein the second frequency offset correction module performs frequency offset correction on the remaining user data signal sequences in the segmentation module.
7. The frequency offset tracking correction method is characterized by comprising the following steps of:
step S1, a signal source transmits a baseband signal with a training sequence and a user data signal;
step S2, extracting the training sequence from the baseband signal;
s3, performing frequency offset estimation on the training sequence to obtain a first frequency offset estimation value;
s4, correcting the user data signal according to the first frequency offset estimation value to obtain a corrected user data signal;
step S5, uniformly segmenting the corrected user data signal, and marking the user data signal as segment 1, segment 2 and segment 3 … … segment m;
s6, extracting a segment i from the segments 1-m, wherein i is more than or equal to 1 and less than or equal to m, and modulating the segment i to obtain a segment i with a pseudo training sequence ， ；
Step S7, according to the segment i sequence and the segment i ， The sequence is used for obtaining a frequency offset estimation value of the segmented i sequence and marking the frequency offset estimation value as a second frequency offset estimation value;
s8, carrying out frequency offset correction on signals formed by the segments (i+1) to m according to the second frequency offset estimation value;
step S9, after the signals formed by the segments (i+1) to m are subjected to frequency offset correction, i=i+1 is given, and the process returns to step S6 until i=m, so as to finish receiving the baseband signals.
8. The method of correcting frequency offset tracking according to claim 7, wherein in the step 6, the modulation scheme is QPSK.
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