CN116192588A - Method and device for synchronizing signals of large frequency offset resistant single carrier system under multipath channel - Google Patents

Method and device for synchronizing signals of large frequency offset resistant single carrier system under multipath channel Download PDF

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CN116192588A
CN116192588A CN202211342829.0A CN202211342829A CN116192588A CN 116192588 A CN116192588 A CN 116192588A CN 202211342829 A CN202211342829 A CN 202211342829A CN 116192588 A CN116192588 A CN 116192588A
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frequency offset
sequence
module
correlation
synchronization
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马文峰
姚远翔
王聪
田辉
赵几航
吴霞
郝向宇
史涵意
于琼
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Army Engineering University of PLA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H04L27/266—Fine or fractional frequency offset determination and synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03178—Arrangements involving sequence estimation techniques
    • H04L25/03305—Joint sequence estimation and interference removal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H04L27/2659—Coarse or integer frequency offset determination and synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset
    • 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

Abstract

The invention provides a method and a device for synchronizing signals of a single carrier system resistant to large frequency offset under a multipath channel, wherein the method comprises the following steps: step one, a timing synchronization module calculates an input signal and outputs a correct timing position of a data frame; and step two, the carrier synchronization module processes the signals according to the correct timing position to obtain frequency offset and outputs corrected signals. The invention adopts a new synchronization sequence and timing measurement method based on ZC sequence, and has more obvious correlation peak at correct timing moment, which can effectively inhibit the influence of side peak on correct discrimination under multipath channel and low signal-to-noise ratio, and improve synchronization performance. Meanwhile, the invention also provides a signal synchronization device of the anti-large frequency offset single carrier system under the multipath channel, which has higher synchronization success rate and lower peak-to-average ratio under the multipath channel.

Description

Method and device for synchronizing signals of large frequency offset resistant single carrier system under multipath channel
Technical Field
The invention relates to a method and a device for synchronizing signals of a single carrier system resistant to large frequency offset under a multipath channel, and belongs to the technical field of path allocation.
Background
The single Carrier frequency domain equalization (SC-FDE) technique is another technique that is also widely used to combat multipath fading. The SC-FDE technology is through single carrier modulation, the channel is not required to be divided into a plurality of sub-carriers, and the problem that the peak-to-average ratio (Peak to Average Power Ratio, PAPR) of a transmitting signal in the OFDM technology is too high is avoided, so that the performance requirement on a radio frequency amplifier is low, and the method is widely applied to communication systems such as Wi-Fi, 4G, 5G and the like; inter-carrier interference (Inter-Carrier Interference, ICI) and Inter-symbol interference (Inter-Symbol Interference, ISI) are introduced in the communication system due to any synchronization error, thereby reducing the performance of the single carrier communication system; synchronization is thus an important step that the communication system must perform.
At present, a synchronization algorithm based on a training sequence is mostly adopted in a practical system, because the algorithm is flexible and changeable in a preamble structure, and the preamble can be constructed by adopting sequences with different characteristics. Moreover, the algorithm can utilize different related processing modes aiming at different structures, and can be improved from various angles to continuously improve the synchronous estimation performance. The synchronization method proposed at the present stage mainly comprises 3 methods of delay autocorrelation, symmetrical autocorrelation and local sequence cross correlation.
Among them, the most classical method is the Shi Mide mole-Cox (Schmidl-Cox, SC) algorithm based on delayed autocorrelation proposed by Schmidl and Cox, which is based on a training symbol structure of [ a, a ], and determines the starting point by calculating correlation peaks of two identical parts before and after; but its timing measurement function has a plateau around the correct timing point that leads to blurring of the frame start point, increasing the error of the estimation. Minn proposes an improved timing algorithm based on the training symbol structure of [ A, A, -A, -A ], the biggest advantage of this approach is that the peak plateau is reduced at the timing instant; however, a plurality of larger peaks are easy to appear at wrong moments, which brings difficulty to the selection of decision threshold. Park then devised a new conjugate symmetric training symbol that produced a clearer timing metric at the correct starting point than Schmidl and Minn, but still had small side lobes. Zadoff-chu (ZC) sequence is a synchronization sequence with good characteristics such as constant amplitude and zero auto-correlation, and based on this, malik proposes a synchronization method using a special preamble consisting of two conjugated ZC sequences and performing cross-correlation using a local sequence. Fang, jian and Fan, respectively, propose different algorithms to improve the synchronization performance, but the performance under multipath fading channels needs to be improved. The Yang provides a timing synchronization method based on local sequence cross correlation, a rapid timing search window and double threshold decision, so that the false alarm probability and the capture loss probability are effectively reduced, and the synchronization performance is better under a multipath channel; but its algorithm has two side peaks beside the timing measure.
However, in the prior art, aiming at a wireless communication system, particularly a single carrier communication system, when a signal has a larger carrier frequency offset under the influence of a multipath channel, the correct starting position of a signal frame cannot be obtained, and the carrier frequency offset caused by interference such as multipath effect and the like on the signal is corrected, so that the synchronization performance is affected.
Disclosure of Invention
The invention provides a signal synchronization method and device of a single carrier system resistant to large frequency offset under a multipath channel, which aims at a wireless communication system, particularly a single carrier communication system, and obtains the correct starting position of a signal frame and corrects carrier frequency offset brought by interference such as multipath effect and the like to the signal when the signal has larger carrier frequency offset under the influence of the multipath channel, thereby improving the synchronization performance.
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 a method for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel, comprising the following steps:
step one: and calculating an input signal with a novel synchronization sequence based on the ZC sequence, judging by adopting a double-threshold method, and outputting the correct timing position of the data frame.
Step two: and respectively carrying out coarse frequency offset correction processing on the signals according to the correct timing positions, correcting the fine frequency offset to obtain frequency offset, and outputting corrected signals.
Further, in the first step, an input signal with a novel synchronization sequence based on a ZC sequence is calculated, and is discriminated by a double-threshold method, and a correct timing position of an output data frame is outputted, including the following steps:
splicing a synchronous sequence into a data sequence, wherein the synchronous sequence is positioned in front of the data sequence; the synchronization sequence is generated based on the ZC sequence; the expression of the ZC sequence is:
Figure BDA0003917016260000031
wherein: j represents a complex number; r is the sequence root index; n is the length of ZC sequence; n represents each sample point; if the two roots are mutually quality, the generated two sequence correlation peaks are almost zero, a new training sequence structure [ A, B, C, D ] is designed]The method comprises the steps of carrying out a first treatment on the surface of the The training sequence consists of 1 symbol with length N, wherein A is a symbol with length N/4 and root index r a Is a ZC sequence of (2);
Figure BDA0003917016260000032
since the inverse fast fourier transform does not change the nature of the CAZAC sequence, a can be constructed directly using a or a sequence generated by N/4 point IFFT of a;
b is a sequence symmetrical to a and conjugated, representing a conjugate;
B(n)＝A*(N/4-n)
c is a length N, and the root index is r c Wherein r is a ZC sequence of (2) c And r a Mutual quality;
and D is a sequence symmetrical to C and conjugated, representing a conjugation;
D(n)＝C*(N/4-n)
the transmitting end splices the synchronous sequence into the data to be transmitted;
after receiving the signal, the receiving end calculates the received signal and the locally stored synchronous sequence to find out the maximum value;
the metric function is defined as follows according to the proposed structure of the preamble symbol:
Figure BDA0003917016260000041
Figure BDA0003917016260000042
Figure BDA0003917016260000043
wherein: p (d) is the correlation between the received sequence y and the local sequence H, y * () Represents conjugation; r (d) is the modulus of the received samples, used for normalization; h (k) is a local synchronization sequence; k represents each sample point.
Adopting a double-threshold method, adopting different thresholds according to the fading suffered by the correlation value, and finding out a sample point when the measurement function is maximum, namely the correct timing moment of the data frame start;
the current sample point is d, firstly, the measurement in a sliding window with the length of 100 sample points before a decision point is averaged to obtain a value Ma, and the average value Ma is multiplied by a coefficient g to obtain a dynamic threshold Th 1 The method comprises the steps of carrying out a first treatment on the surface of the Then average the measurement values in the sliding window of 100 sample points after the decision point to obtain Mb, and multiplying the average Mb by the coefficient g to obtain the dynamic threshold Th 2 The method comprises the steps of carrying out a first treatment on the surface of the The coefficient g can be adjusted according to different channels; at the same time, the measurement value of the current sample is larger than the dynamic threshold T 1 And T 2 When the sample is considered to be the correct timing position;
Figure BDA0003917016260000044
namely, the correct timing moment;
Figure BDA0003917016260000045
Figure BDA0003917016260000046
Figure BDA0003917016260000051
further, in the second step, coarse frequency offset correction processing is performed on the signals according to the correct timing positions, fine frequency offset correction is performed to obtain frequency offset, corrected signals are output, and the method comprises the following steps:
determining different attempted frequency offsets according to the frequency offset range and the attempted times to be corrected, and generating local sequences of M different frequency offsets; register for later comparison;
synchronizing the received signal with the local sequences of M different frequency offsets for cross-correlation; finding out the maximum value in M.N correlation results, wherein the corresponding coarse frequency deviation is the coarse frequency deviation which is considered to be correct;
correcting the received signal by using the found coarse frequency offset;
the received signals are subjected to correlation and summation, and the precise frequency offset is calculated after the angles are calculated;
and correcting the received signal by using the found fine frequency offset.
Further, determining different attempted frequency offsets according to the frequency offset range and the number of attempted times to be corrected, generating local sequences of M different frequency offsets, including:
generating different local sequences according to the attempted coarse frequency offset; the coarse frequency offset correction adopts a frequency offset trial method; and determining different attempted frequency offsets according to the frequency offset range and the attempted times which need to be corrected, and generating M different local sequences.
Further, correcting the received signal using the found coarse frequency offset, including:
the coarse frequency offset is fHz, the original local sequence is p (n), the frequency offset is 0, and the local sequence corresponding to the coarse frequency offset is
p f (n)＝p(n)·exp(j2πnf/fs)
Where fs is the sampling frequency, j represents complex numbers, and n represents each sample point.
Further, the received signals are subjected to correlation, summation and angle calculation to calculate the precise frequency offset, and the method comprises the following steps:
at the time of obtaining the synchronization position n s And coarse frequency offset f co Then, according to the synchronous position, carrying out cross-correlation on the synchronous sequence r (n) and the local synchronous sequence y (n), and eliminating the influence of the coarse frequency offset phase; correlated phase result C f The method comprises the step of obtaining the precise frequency offset f through calculation, wherein the precise frequency offset f comprises frequency offset information fo ；
Figure BDA0003917016260000061
Figure BDA0003917016260000062
Wherein N represents the length of the synchronization sequence, i represents each sample point, N s Representing the correct timing position, angle () represents the angle, conj () represents the conjugate, since angle (C) f ) Is strictly defined as [ -pi, +pi]In the range, the range in which the fine frequency offset can be detected is only related to the length N of the synchronization sequence;
correcting the received signal using the found fine frequency offset, comprising:
obtaining the fine frequency offset f fo Then, the data is subjected to fine frequency offset correction, and the initial position of the data frame and the corrected data are output
Figure BDA0003917016260000063
And (3) completing synchronization:
Figure BDA0003917016260000064
in a second aspect, the present invention provides a signal synchronization device of a single carrier system with large frequency offset resistance under multipath channel, comprising:
symbol timing synchronization module: the method is used for calculating an input signal with a novel synchronous sequence based on the ZC sequence, judging by adopting a double-threshold method and outputting a correct timing position of a data frame;
carrier frequency synchronization module: and the device is used for respectively carrying out coarse frequency offset correction processing on the signals according to the correct timing positions, correcting the fine frequency offset to obtain frequency offset and outputting corrected signals.
Further, the symbol timing synchronization module includes:
and a registering module: and the system is used for determining different attempted frequency offsets according to the frequency offset range and the attempted times which need to be corrected, and the generated M different local sequences are stored in a register module so as to be called when the coarse frequency offset is corrected.
And a sliding correlation module: the sliding window length is the length of the synchronous sequence, the real part and the imaginary part are calculated separately during the correlation, and the real part and the imaginary part are added and subtracted after being multiplied respectively to obtain the value after the correlation.
Threshold calculation module: for calculating a threshold value based on the set threshold value.
And a comparison module: the sliding correlation module is used for comparing the correlation value calculated by the sliding correlation module with the threshold value calculated by the threshold calculation module all the time, and when the correlation value is larger than the threshold value, the point is considered to be the true data frame starting point.
The signal received by the receiving end is firstly divided into a real part and an imaginary part, the real part and the imaginary part enter the sliding correlation module, the sum of correlation values in the sliding window corresponding to each point is output, and the values are output to the comparison module. And outputting the signal to a threshold calculation module, and calculating the noise value in the window corresponding to each point by the threshold calculation module and outputting the noise value to a comparison module. And the comparison module compares the correlation value corresponding to each point with a threshold value, and when the correlation value is larger than the threshold value, the position index of the point is output to the carrier frequency synchronization module at the later stage.
Further, the carrier frequency synchronization module includes:
coarse frequency offset register module: and the method is used for determining different attempted frequency offsets according to the frequency offset range and the attempted times which need to be corrected, and generating local sequences of M different frequency offsets. Is registered in a register for later comparison.
And a coarse frequency offset correlation module: the method is used for simultaneously carrying out correlation processing on the received signal and the local sequences of M different frequency offsets, wherein the frequency offset of the local sequence used by the maximum value of the correlation is considered to be the correct coarse frequency offset.
And a coarse frequency offset correction module: for correcting the received signal using the found coarse frequency offset.
The fine frequency deviation calculation module: the method is used for calculating the precise frequency offset of the received signals after the angles are calculated through correlation and summation.
And a fine frequency deviation correction module: and the method is used for correcting the received signal by using the found fine frequency offset.
Carrier frequency synchronization module: the device is used for outputting corrected signals after passing through the coarse frequency offset registering module, the coarse frequency offset correlation module, the coarse frequency offset correction module, the fine frequency offset calculation module and the fine frequency offset correction module.
In a third aspect, the present invention provides a signal synchronization device of a single carrier system with large frequency offset resistance under a multipath channel, which comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention adopts a new synchronization sequence and timing measurement method based on ZC sequence, and has more obvious correlation peak at correct timing moment, which can effectively inhibit the influence of side peak on correct discrimination under multipath channel and low signal-to-noise ratio, and improve synchronization performance.
2. The invention provides a method for judging the dynamic threshold value, which has better synchronization effect in a low signal-to-noise ratio environment.
3. Since the frequency offset can be detected in a range which is only related to the length N of the synchronization sequence, the longer the synchronization sequence is, the larger the frequency offset can be corrected, but the longer the synchronization sequence is, the data volume which can be transmitted by the signal is reduced. Therefore, the invention provides a coarse frequency offset test method, the coarse frequency offset correction is carried out by the test method, the frequency offset is corrected to a range where the fine frequency offset can be calculated, and the range of the frequency offset which can be corrected is greatly improved when the fine frequency offset correction is carried out.
4. Compared with the existing multi-carrier technology, the invention has lower peak-to-average ratio, reduces power loss and improves the efficiency of the amplifier.
Drawings
FIG. 1 is a flow chart of a method for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel;
fig. 2 is a symbol timing flow chart of the symbol timing synchronization module for the input signal in the signal synchronization method of the anti-large frequency offset single carrier system under the multipath channel.
Fig. 3 is a flow chart of carrier frequency synchronization module to input signal carrier frequency synchronization in the method for synchronizing signals of anti-large frequency offset single carrier system under multipath channel.
Fig. 4 is a partial block diagram of a sliding correlation calculation processing section of an input signal by a symbol timing synchronization module in a signal synchronization method of a large frequency offset resistant single carrier system under a multipath channel.
Fig. 5 is a partial block diagram of a carrier frequency synchronization module for performing coarse frequency offset synchronization on an input signal in a signal synchronization method of a large frequency offset resistant single carrier system under a multipath channel.
Fig. 6 is a partial block diagram of a carrier frequency synchronization module for performing fine frequency offset synchronization on an input signal in a signal synchronization method of a large frequency offset resistant single carrier system under a multipath channel.
Fig. 7 is a comparison of synchronization performance of the signal synchronization method of the anti-large frequency offset single carrier system under the multipath channel and the extended pedestrian channel (Extended Pedestrian A, EPA) model multipath channel under the 3GPP standard of the existing common synchronization method.
Fig. 8 is a comparison of synchronization performance of the signal synchronization method of the anti-large frequency offset single carrier system under the multipath channel and the multipath channel of the extended typical urban channel (Extended Typical Urban, ETU) model under the 3GPP standard of the existing common synchronization method.
Fig. 9 is a comparison of synchronization performance of the signal synchronization method of the anti-large frequency offset single carrier system under the multipath channel and the extended vehicle channel (Extended Vehicular A, EVA) model multipath channel under the 3GPP standard of the existing common synchronization method.
Fig. 10 is a diagram showing the comparison of PAPR of different modulation modes under the conditions of 256 points long and 64 points cyclic prefix in a signal synchronization method of a large frequency offset resistant single carrier system under a multipath channel and a common OFDM system.
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.
Embodiment one:
the embodiment provides a signal synchronization method of a large frequency offset resistant single carrier system under a multipath channel, which comprises the following steps:
step one: the timing synchronization module calculates the input signal and outputs the correct timing position of the data frame.
Step two: and the carrier synchronization module processes the signals according to the correct timing position to obtain frequency offset and outputs corrected signals.
The first step of the timing synchronization module calculates an input signal and outputs a correct timing position of a data frame, and the first step of the timing synchronization module comprises the following steps:
and (1) splicing the synchronous sequence into the data sequence, wherein the synchronous sequence is positioned before the data sequence. The synchronization sequence is generated based on the ZC sequence. The expression of the ZC sequence is:
Figure BDA0003917016260000101
wherein: r is a sequence root index (root index); n is the length of ZC sequence. Two roots, if mutually homogeneous, produce two sequence correlation peaks of almost zero, so a new training sequence structure [ A, B, C, D ] is designed herein using these properties]. The training sequence consists of 1 symbol with length N, wherein A is a symbol with length N/4 and root index r a Is a ZC sequence of (c).
Figure BDA0003917016260000102
Since the inverse fast fourier transform (Inverse Fast Fourier Transform, IFFT) does not change the nature of the CAZAC sequence, a can be constructed directly using a or the sequence generated by the N/4-point IFFT of a.
B is a sequence symmetrical and conjugated to A.
B(n)＝A*(N/4-n)
C is a length N, and the root index is r c Wherein r is a ZC sequence of (2) c And r a Mutually good quality.
Figure BDA0003917016260000111
And D is a sequence symmetrical and conjugated to C.
D(n)＝C*(N/4-n)
The sender concatenates the synchronization sequence into the data to be transmitted.
And (2) after receiving the signal, the receiving end calculates the received signal and the locally stored synchronization sequence to find out the maximum value.
The metric function is defined as follows according to the proposed structure of the preamble symbol:
Figure BDA0003917016260000112
Figure BDA0003917016260000113
Figure BDA0003917016260000114
wherein: p (d) is the correlation between the received sequence y and the local sequence H; r (d) is the modulus of the received samples and is used for normalization.
And (3) adopting a double-threshold method, adopting different thresholds according to the fading suffered by the correlation value, and finding out the sample point when the measurement function is maximum, namely the correct timing moment of the data frame start.
Taking the current sample point as d, firstly taking the average value of the metrics in a sliding window with the length of 100 sample points before a decision point to obtain a value Ma, and multiplying the average value Ma by a coefficient g to obtain a dynamic threshold Th 1 . Then average the measurement values in the sliding window of 100 sample points after the decision point to obtain Mb, and multiplying the average Mb by the coefficient g to obtain the dynamic threshold Th 2 . The coefficient g can be adjusted according to the channel. At the same time, the measurement value of the current sample is larger than the dynamic threshold T 1 And T 2 When the sample is considered to be the correct timing position.
Figure BDA0003917016260000121
I.e. the correct timing instant.
Figure BDA0003917016260000122
Figure BDA0003917016260000123
Figure BDA0003917016260000124
The carrier synchronization module in the second step processes the signal according to the correct timing bit value to obtain a frequency offset, and outputs a corrected signal, and the method comprises the following steps:
step (1), generating different local sequences according to the attempted coarse frequency offset. The coarse frequency offset correction adopts a frequency offset try method. And determining different attempted frequency offsets according to the frequency offset range and the attempted times which need to be corrected, and generating M different local sequences.
Assuming that the coarse frequency offset is fHz, the original local sequence is p (n) (the local sequence with the frequency offset of 0), the local sequence corresponding to the coarse frequency offset is
p f (n)＝p(n)·exp(j2πnf/fs)
Where fs is the sampling frequency.
And (2) synchronizing the received signals with the local sequences of M different frequency offsets by a correlation module in the carrier synchronization module. And finding out the maximum value in M.N correlation results, wherein the corresponding coarse frequency deviation is the coarse frequency deviation which is considered to be correct.
Step (3), in obtaining the synchronization position n s And coarse frequency offset f co And then, according to the synchronous position, carrying out cross-correlation on the synchronous sequence r (n) and the local synchronous sequence y (n), and simultaneously eliminating the influence of the coarse frequency offset phase. The related phase result contains frequency offset information, and the frequency offset result can be obtained through calculation.
Figure BDA0003917016260000125
Figure BDA0003917016260000126
Where N represents the sync sequence length and angle () represents the angle. Due to angle (C) f ) Is strictly defined as [ -pi, +pi]Within the range, the range over which the fine frequency offset can be detected is only dependent on the synchronization sequence length N.
After the precise frequency offset is obtained, the precise frequency offset correction is carried out on the data, and the initial position of the data frame and the corrected data are output to complete synchronization.
Figure BDA0003917016260000131
Embodiment two:
the embodiment provides a signal synchronization device of a single carrier system resistant to large frequency offset under a multipath channel, which can be used for realizing the method described in the first embodiment and comprises a symbol timing synchronization module and a carrier frequency synchronization module.
The sub-modules included in the symbol timing synchronization module are a registering module, a sliding correlation module, a threshold calculation module and a comparison module in sequence according to the sequence of connection. The functions of the respective modules are as follows:
the register module is used for determining different attempted frequency offsets according to the frequency offset range and the attempted times to be corrected, and M generated different local sequences are stored in the register module so as to be conveniently called when the coarse frequency offset is corrected.
And the sliding correlation module performs sliding correlation on the received data signal and the local synchronous sequence, wherein the sliding window length is the synchronous sequence length, real parts and imaginary parts are calculated separately during correlation, and the real parts and the imaginary parts are added and subtracted after multiplication respectively to obtain a value after correlation.
And the threshold calculating module is used for calculating a threshold value according to the set threshold value.
And the comparison module is used for always comparing the correlation value calculated by the sliding correlation module with the threshold value calculated by the threshold calculation module, and when the correlation value is larger than the threshold value, the point is considered to be the true data frame starting point.
The signal received by the receiving end is firstly divided into a real part and an imaginary part, the real part and the imaginary part enter the sliding correlation module, the sum of correlation values in the sliding window corresponding to each point is output, and the values are output to the comparison module. And outputting the signal to a threshold calculation module, and calculating the noise value in the window corresponding to each point by the threshold calculation module and outputting the noise value to a comparison module. And the comparison module compares the correlation value corresponding to each point with a threshold value, and when the correlation value is larger than the threshold value, the position index of the point is output to the carrier frequency synchronization module at the later stage.
The carrier frequency synchronization module comprises a sub-module, a coarse frequency offset register module, a coarse frequency offset correlation module, a coarse frequency offset correction module, a fine frequency offset calculation module and a fine frequency offset correction module which are sequentially connected in sequence. The functions of the respective modules are as follows:
the coarse frequency offset register module determines different attempted frequency offsets according to the frequency offset range and the attempted times which need to be corrected, and generates local sequences of M different frequency offsets. Is registered in a register for later comparison.
And the coarse frequency offset correlation module is used for simultaneously carrying out correlation processing on the received signal and the local sequences of M different frequency offsets, wherein the frequency offset of the local sequence used by the maximum value of correlation is considered to be the correct coarse frequency offset.
And the coarse frequency offset correction module corrects the received signal by using the found coarse frequency offset.
And the fine frequency offset calculation module calculates the fine frequency offset of the received signals after calculating the angles through correlation and summation.
And the fine frequency offset correction module corrects the received signal by using the found fine frequency offset.
The carrier frequency synchronization module outputs corrected signals after passing through the coarse frequency offset registering module, the coarse frequency offset correlation module, the coarse frequency offset correction module, the fine frequency offset calculation module and the fine frequency offset correction module.
Compared with the prior art, the invention adopts a new synchronization sequence and timing measurement method based on ZC sequence, and has more obvious correlation peak at correct timing moment, which can effectively inhibit the influence of side peak on correct discrimination under multipath channel and low signal-to-noise ratio, and improve synchronization performance. And a dynamic threshold judging method is provided, so that the method has a better synchronization effect in a low signal-to-noise ratio environment. Since the frequency offset can be detected in a range which is only related to the length N of the synchronization sequence, the longer the synchronization sequence is, the larger the frequency offset can be corrected, but the longer the synchronization sequence is, the data volume which can be transmitted by the signal is reduced. Therefore, the invention provides a coarse frequency offset test method, the coarse frequency offset correction is carried out by the test method, the frequency offset is corrected to a range where the fine frequency offset can be calculated, and the range of the frequency offset which can be corrected is greatly improved when the fine frequency offset correction is carried out. Meanwhile, compared with the existing multi-carrier technology, the invention has lower peak-to-average ratio, reduces power loss and improves the efficiency of the amplifier.
Embodiment III:
the embodiment of the invention provides a signal synchronization device of a single carrier system resistant to large frequency offset under a multipath channel, which comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of the first aspect.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
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 (10)

1. A signal synchronization method of a large frequency offset resistant single carrier system under a multipath channel is characterized by comprising the following steps:
calculating an input signal with a novel synchronization sequence based on the ZC sequence, judging by adopting a double-threshold method, and outputting a correct timing position of a data frame;
and respectively carrying out coarse frequency offset correction processing on the signals according to the correct timing positions, correcting the fine frequency offset to obtain frequency offset, and outputting corrected signals.
2. The method for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel according to claim 1, wherein in the first step, an input signal with a novel synchronization sequence based on a ZC sequence is calculated, discrimination is performed by adopting a double threshold method, and a correct timing position of an output data frame is outputted, comprising the following steps:
splicing a synchronous sequence into a data sequence, wherein the synchronous sequence is positioned in front of the data sequence; the synchronization sequence is generated based on the ZC sequence; the expression of the ZC sequence is:
Figure FDA0003917016250000011
wherein: j represents a complex number; r is the sequence root index; n is the length of ZC sequence; n represents each sample point; if the two roots are mutually quality, the generated two sequence correlation peaks are almost zero, a new training sequence structure [ A, B, C, D ] is designed]The method comprises the steps of carrying out a first treatment on the surface of the The training sequence consists of 1 symbol with length N, wherein A is a symbol with length N/4 and root index r a Is a ZC sequence of (2);
Figure FDA0003917016250000012
since the inverse fast fourier transform does not change the nature of the CAZAC sequence, a can be constructed directly using a or a sequence generated by N/4 point IFFT of a;
b is a sequence symmetrical to a and conjugated, representing a conjugate;
B(n)＝A*(N/4-n)
c is a length N, and the root index is r c Wherein r is a ZC sequence of (2) c And r a Mutual quality;
Figure FDA0003917016250000021
and D is a sequence symmetrical to C and conjugated, representing a conjugation;
D(n)＝C*(N/4-n)
the transmitting end splices the synchronous sequence into the data to be transmitted;
after receiving the signal, the receiving end calculates the received signal and the locally stored synchronous sequence to find out the maximum value;
the metric function is defined as follows according to the proposed structure of the preamble symbol:
Figure FDA0003917016250000022
Figure FDA0003917016250000023
Figure FDA0003917016250000024
wherein: p (d) is the correlation between the received sequence y and the local sequence H, y * () Represents conjugation; r (d) is the modulus of the received samples, used for normalization; h (k) is a local synchronization sequence; k represents each sample point;
adopting a double-threshold method, adopting different thresholds according to the fading suffered by the correlation value, and finding out a sample point when the measurement function is maximum, namely the correct timing moment of the data frame start;
the current sample point is d, firstly, the measurement in a sliding window with the length of 100 sample points before a decision point is averaged to obtain a value Ma, and the average value Ma is multiplied by a coefficient g to obtain a dynamic threshold Th 1 The method comprises the steps of carrying out a first treatment on the surface of the Then average the measurement values in the sliding window of 100 sample points after the decision point to obtain Mb, and multiplying the average Mb by the coefficient g to obtain the dynamic threshold Th 2 The method comprises the steps of carrying out a first treatment on the surface of the The coefficient g can be adjusted according to different channels; at the same time, the measurement value of the current sample is larger than the dynamic threshold T 1 And T 2 When the sample is considered to be the correct timing position;
Figure FDA0003917016250000025
i.e. correct timingTime;
Figure FDA0003917016250000026
Figure FDA0003917016250000031
Figure FDA0003917016250000032
3. the method for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel according to claim 1, wherein in the second step, coarse frequency offset correction processing is performed on the signals according to correct timing positions, fine frequency offset correction is performed to obtain frequency offset, and corrected signals are output, and the method comprises the following steps:
determining different attempted frequency offsets according to the frequency offset range and the attempted times to be corrected, and generating local sequences of M different frequency offsets; register for later comparison;
synchronizing the received signal with the local sequences of M different frequency offsets for cross-correlation; finding out the maximum value in M.N correlation results, wherein the corresponding coarse frequency deviation is the coarse frequency deviation which is considered to be correct;
correcting the received signal by using the found coarse frequency offset;
the received signals are subjected to correlation and summation, and the precise frequency offset is calculated after the angles are calculated;
and correcting the received signal by using the found fine frequency offset.
4. The method for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel according to claim 3, wherein determining different attempted frequency offsets according to the frequency offset range to be corrected and the number of attempted times, generating local sequences of M different frequency offsets, comprises:
generating different local sequences according to the attempted coarse frequency offset; the coarse frequency offset correction adopts a frequency offset trial method; and determining different attempted frequency offsets according to the frequency offset range and the attempted times which need to be corrected, and generating M different local sequences.
5. The method for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel as claimed in claim 3, wherein the correcting the received signals by using the found coarse frequency offset comprises:
the coarse frequency offset is fHz, the original local sequence is p (n), the frequency offset is 0, and the local sequence corresponding to the coarse frequency offset is
p f (n)＝p(n)·exp(j2πnf/fs)
Where fs is the sampling frequency, j represents complex numbers, and n represents each sample point.
6. The method for synchronizing signals of a single carrier system with large frequency offset resistance under multipath channel as claimed in claim 5, wherein the calculating the fine frequency offset of the received signals after the correlation, summation and angle calculation comprises the following steps:
at the time of obtaining the synchronization position n s And coarse frequency offset f co Then, according to the synchronous position, carrying out cross-correlation on the synchronous sequence r (n) and the local synchronous sequence y (n), and eliminating the influence of the coarse frequency offset phase; correlated phase result C f The method comprises the step of obtaining the precise frequency offset f through calculation, wherein the precise frequency offset f comprises frequency offset information fo ；
Figure FDA0003917016250000041
Figure FDA0003917016250000042
/>
Wherein N represents the length of the synchronization sequence, i represents each sample point, N s Representing the correct timing position, angle () represents the angle, conj () representsConjugation is taken due to angle (C) f ) Is strictly defined as [ -pi, +pi]In the range, the range in which the fine frequency offset can be detected is only related to the length N of the synchronization sequence;
correcting the received signal using the found fine frequency offset, comprising:
obtaining the fine frequency offset f fo Then, the data is subjected to fine frequency offset correction, and the initial position of the data frame and the corrected data are output
Figure FDA0003917016250000043
And (3) completing synchronization:
Figure FDA0003917016250000044
7. a signal synchronization device of a single carrier system resistant to large frequency offset under a multipath channel, comprising:
symbol timing synchronization module: the method is used for calculating an input signal with a novel synchronous sequence based on the ZC sequence, judging by adopting a double-threshold method and outputting a correct timing position of a data frame;
carrier frequency synchronization module: and the device is used for respectively carrying out coarse frequency offset correction processing on the signals according to the correct timing positions, correcting the fine frequency offset to obtain frequency offset and outputting corrected signals.
8. The apparatus for synchronizing signals of a single carrier system with large frequency offset resistance under a multipath channel as claimed in claim 7, wherein said symbol timing synchronization module comprises:
and a registering module: the system is used for determining different attempted frequency offsets according to the frequency offset range and the attempted times to be corrected, and M generated different local sequences are stored in a register module so as to be conveniently called when the coarse frequency offset is corrected;
and a sliding correlation module: the sliding window length is the length of the synchronous sequence, the real part and the imaginary part are calculated separately during the correlation, and the real part and the imaginary part are added and subtracted after being multiplied respectively to obtain a value after the correlation;
threshold calculation module: for calculating a threshold value based on the set threshold value;
and a comparison module: the sliding correlation module is used for calculating a sliding correlation value according to the data frame starting point of the data frame, and the sliding correlation module is used for calculating a sliding correlation value according to the data frame starting point;
the signal received by the receiving end is firstly divided into a real part and an imaginary part, the real part and the imaginary part enter a sliding correlation module, the sum of correlation values in a sliding window corresponding to each point is output, and the values are output to a comparison module; outputting the signal to a threshold calculation module, calculating the noise value in the window corresponding to each point by the threshold calculation module, and outputting the noise value to a comparison module; and the comparison module compares the correlation value corresponding to each point with a threshold value, and when the correlation value is larger than the threshold value, the position index of the point is output to the carrier frequency synchronization module at the later stage.
9. The apparatus for synchronizing signals of a single carrier system against large frequency offset in a multipath channel as claimed in claim 7, wherein said carrier frequency synchronizing module comprises:
coarse frequency offset register module: the method comprises the steps of determining different attempted frequency offsets according to a frequency offset range and the number of attempted times which need to be corrected, and generating local sequences of M different frequency offsets; register for later comparison;
and a coarse frequency offset correlation module: the method comprises the steps of performing correlation processing on a received signal and local sequences of M different frequency offsets at the same time, wherein the frequency offset of the local sequence used by the maximum value of correlation is considered to be the correct coarse frequency offset;
and a coarse frequency offset correction module: the method comprises the steps of correcting received signals by using the found coarse frequency offset;
the fine frequency deviation calculation module: the method comprises the steps of obtaining an angle of a received signal, and calculating a precise frequency offset of the received signal through correlation and summation;
and a fine frequency deviation correction module: the method comprises the steps of correcting received signals by using the found precise frequency offset;
carrier frequency synchronization module: the device is used for outputting corrected signals after passing through the coarse frequency offset registering module, the coarse frequency offset correlation module, the coarse frequency offset correction module, the fine frequency offset calculation module and the fine frequency offset correction module.
10. The signal synchronization device of the large frequency offset resistant single carrier system under the multipath channel is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor being operative according to the instructions to perform the steps of the method according to any one of claims 1 to 6.
CN202211342829.0A 2022-10-31 2022-10-31 Method and device for synchronizing signals of large frequency offset resistant single carrier system under multipath channel Pending CN116192588A (en)

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