CN116232828A - OFDM timing synchronization method based on improved CAZAC sequence - Google Patents

OFDM timing synchronization method based on improved CAZAC sequence Download PDF

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CN116232828A
CN116232828A CN202211542649.7A CN202211542649A CN116232828A CN 116232828 A CN116232828 A CN 116232828A CN 202211542649 A CN202211542649 A CN 202211542649A CN 116232828 A CN116232828 A CN 116232828A
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sequence
frequency offset
ofdm
timing synchronization
estimation
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范新革
杜俭业
鲍永亮
郭成龙
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Aerospace Science and Industry Shenzhen Group Co Ltd
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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
    • 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
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2662—Symbol synchronisation
    • H04L27/2663—Coarse synchronisation, e.g. by correlation
    • 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
    • H04L27/2662—Symbol synchronisation
    • H04L27/2665—Fine synchronisation, e.g. by positioning the FFT window
    • 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
    • H04L27/2668—Details of algorithms
    • H04L27/2673—Details of algorithms characterised by synchronisation parameters
    • H04L27/2676—Blind, i.e. without using known symbols
    • H04L27/2678—Blind, i.e. without using known symbols using cyclostationarities, e.g. cyclic prefix or postfix
    • 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
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    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention discloses an OFDM timing synchronization method based on an improved CAZAC sequence, which relates to the technical field of OFDM synchronization and comprises the following steps: constructing a preamble sequence T based on the CAZAC sequence, wherein the length of the preamble sequence T occupies one OFDM symbol length, the lengths of four parts are equally divided, a cyclic prefix CP is added in the preamble sequence T to insert the preamble sequence T into a frame structure, and the preamble sequence T is used as a transmission signal of a transmitter to be transmitted to a receiver; performing cross correlation on the sequence C and the sequences A and D in a receiver to obtain a correlation peak value of timing synchronization, and completing OFDM timing synchronization; then, frequency offset estimation is carried out by using the sequence C and the sequence D to obtain a rough estimation value of the fractional frequency offset, and fine estimation of the fractional frequency offset is carried out by using the repeatability of the cyclic prefix; and finally, carrying out integer frequency offset estimation by utilizing the cyclic shift characteristics of the first two parts of the sequence to finish carrier synchronization of the OFDM symbols.

Description

OFDM timing synchronization method based on improved CAZAC sequence
Technical Field
The invention relates to the technical field of OFDM synchronization, in particular to an OFDM timing synchronization method based on an improved CAZAC sequence.
Background
OFDM is a multi-carrier transmission technology, the synchronous algorithm is relatively mature, the common synchronous algorithm is of a data auxiliary type and a non-data auxiliary type, wherein the non-data auxiliary type algorithm is a blind synchronous algorithm, and the algorithm has the advantages of no additional cost and high bandwidth utilization rate; the data auxiliary algorithm is to insert additional information into the transmitted symbols for synchronization, and has low calculation complexity and optimal performance.
The most classical algorithm is timing and frequency offset synchronization by the Schmidl design using a preamble sequence occupying two OFDM symbol lengths. Minn et al propose a new training queue structure, the algorithm produces a sharper timing correlation peak and higher synchronization accuracy. In addition, in the design of the preamble sequence, because the CAZAC sequence has good auto-correlation and cross-correlation properties, the method is adopted by a plurality of researchers, and the researchers add weighting factors into the CAZAC sequence to design different preamble sequences so as to improve the accuracy of OFDM synchronization.
Specifically, in the classical Schmidl algorithm, there is a plateau in the timing metric function, resulting in a deviation in the timing start position. Although the algorithm proposed by Minn et al can produce sharper peaks, the algorithm is greatly affected by the signal-to-noise ratio, and the timing synchronization accuracy can be affected in environments with low signal-to-noise ratios. The algorithm for synchronizing by using the CAZAC sequence includes a Fang algorithm, a Jian algorithm and a Shao algorithm, and the algorithms have good performance under multipath channels, but extra weighted sequences are needed when the receiving end performs synchronization, so that the computational complexity is increased additionally.
A new algorithm is urgently needed to solve the problem that OFDM technology itself is sensitive to frequency offset and has high timing synchronization requirements.
Disclosure of Invention
The invention aims at: a time-frequency synchronization scheme based on the CAZAC sequence is provided, a new preamble sequence is designed, and a new OFDM symbol timing and frequency offset synchronization algorithm is provided, so that the stability and accuracy of OFDM system synchronization are improved.
The technical scheme of the invention is as follows: there is provided an OFDM timing synchronization method based on an improved CAZAC sequence, the method comprising:
constructing a preamble sequence T= [ A B C D ] based on the CAZAC sequence, wherein the length of the preamble sequence T occupies one OFDM symbol length, the lengths of four parts of the sequence A, the sequence B, the sequence C and the sequence D are divided equally, a cyclic prefix CP is added in the preamble sequence T, and the cyclic prefix CP is inserted into a frame structure and is used as a transmission signal of an OFDM system transmitter to be transmitted to an OFDM system receiver;
after the preamble sequence T is sent to an OFDM system receiver, the sequence C is used for carrying out cross correlation with the sequence A and the sequence D respectively to obtain a correlation peak value of timing synchronization, and OFDM timing synchronization is completed; then, frequency offset estimation is carried out by using the sequence C and the sequence D to obtain a rough estimation value of the fractional frequency offset, and fine estimation of the fractional frequency offset is carried out by using the repeatability of the cyclic prefix; finally, the cyclic shift characteristics of the first two parts of the sequence are utilized to carry out integral frequency offset estimation, so as to complete carrier synchronization of OFDM symbols;
wherein, the sequence B is conjugate symmetrical with the sequence A, the sequence C is the inverse of the interval of the sequence B, and the sequence D is the same as the sequence C.
In any of the above embodiments, further, the sequence a is represented as:
Figure BDA0003978415280000021
the sequence B is expressed as:
Figure BDA0003978415280000031
the sequence C is expressed as:
C(k)＝(-1) k B * (k) Where r is a positive integer and N represents the total number of subcarriers.
In any of the above solutions, further, the timing synchronization includes:
the timing synchronization metric function of the preamble sequence T is defined as:
Figure BDA0003978415280000032
wherein:
Figure BDA0003978415280000033
Figure BDA0003978415280000034
start position θ=argmax at which timing synchronization is obtained d (M(d))。
In any of the above solutions, further, carrier synchronization includes: fractional frequency offset coarse estimation, fractional frequency offset fine estimation, and integer frequency offset estimation.
In any of the above technical solutions, further, the fractional frequency offset rough estimation is:
Figure BDA0003978415280000035
wherein P is ε1 Can be determined by the correct start position of the training sequence
Figure BDA0003978415280000036
Obtaining:
Figure BDA0003978415280000037
in any of the above technical solutions, further, the fractional frequency offset fine estimation is:
Figure BDA0003978415280000038
wherein I can be obtained from the cyclic prefix portion of the constructed synchronization preamble sequence:
Figure BDA0003978415280000042
in any one of the above technical solutions, further, the sequence received by the method has an integer multiplying power offset, which is calculated by the sequence a and the sequence B, and the decision function is expressed as:
Figure BDA0003978415280000043
/>
Figure BDA0003978415280000044
wherein A is * (k+g) is the conjugate sequence of the known CAZAC sequence A (k), and is cyclically shifted by g units, F (g) will generate a sharp peak reflecting the integer frequency offset due to the good autocorrelation properties of the CAZAC sequence, and the final normalized frequency offset is
Figure BDA0003978415280000045
The beneficial effects of the invention are as follows:
in the technical scheme of the invention, the preamble sequence T is constructed based on the CAZAC sequence, and the length is only one OFDM symbol, so that the transmission efficiency can be improved; the constructed leader sequence has simple structural construction mode and can be obtained by simply converting the CAZAC sequence;
in the preferred implementation mode of the invention, all the synchronization processes are completed under the time domain condition, and frequency domain conversion is not needed, so that the synchronization efficiency can be effectively improved; the leader sequence of the invention has good auto-correlation and cross-correlation properties, and the sequences superior to the sequences of other authors in the prior art can be obviously seen from simulation comparison results.
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The advantages of the foregoing and additional aspects of the invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic flow diagram of an OFDM timing synchronization method based on a modified CAZAC sequence according to one embodiment of the invention;
fig. 2 is a diagram of a preamble sequence structure of an OFDM timing synchronization method based on a modified CAZAC sequence according to an embodiment of the present invention;
fig. 3 is a cyclic structure diagram of a preamble sequence of an OFDM timing synchronization method based on a modified CAZAC sequence according to an embodiment of the present invention;
FIG. 4 is a simulated contrast diagram of an OFDM timing synchronization method based on a modified CAZAC sequence according to one embodiment of the invention;
FIG. 5 is a timing metric function MSE performance comparison for an OFDM timing synchronization method based on a modified CAZAC sequence according to one embodiment of the invention;
FIG. 6 is a fractional frequency offset estimation function MSE performance comparison for an improved CAZAC sequence based OFDM timing synchronization method according to one embodiment of the present invention;
fig. 7 is a total frequency offset estimated MSE performance comparison for an OFDM timing synchronization method based on a modified CAZAC sequence in accordance with one embodiment of the invention.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. It should be noted that, without conflict, embodiments of the present invention and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those described herein, and the scope of the invention is therefore not limited to the specific embodiments disclosed below.
The complete OFDM system is divided into a transmitter and a receiver, and the OFDM symbol after IFFT processing in the transmitter can be expressed as:
Figure BDA0003978415280000051
wherein N represents the total number of subcarriers, N cp Represents a cyclic prefix, N u The number of effective subcarriers is represented, X (k) represents a data symbol transmitted on the kth subcarrier, and j is an imaginary unit.
The receiver receives the signal sent by the transmitter, and considering the general model of the OFDM system, there is delay and phase distortion in the received signal, so the signal received by the receiver can be expressed as:
Figure BDA0003978415280000061
Figure BDA0003978415280000062
where θ represents the timing offset of the symbol, ε is the frequency offset normalized by the subcarrier, w (n) represents zero-mean complex Gaussian white noise, h (m) is the impulse response of the channel transfer function, h (m) can also be represented by h (n), and L is the maximum delay of the time-domain channel samples. r (n) is the OFDM symbol received by the receiver, and y (n) is the OFDM symbol received by the receiver in the absence of clock errors and frequency offsets.
As shown in fig. 1, the present embodiment provides an OFDM timing synchronization method based on an improved CAZAC sequence, which includes:
as shown in fig. 2, a preamble sequence t= [ ab C D ] is constructed based on CAZAC sequence, wherein A, B, C, D becomes the first, second, third, and fourth portions in order.
Wherein the sequence is
Figure BDA0003978415280000063
Sequence->
Figure BDA0003978415280000064
The sequence B and the sequence A keep conjugate symmetry; sequence C (k) = (-1) k B * (k) Sequence C is the inverse of the interval of sequence B; sequence D (k) =c (k), sequence D being identical to sequence C; r is a positive integer.
As shown in fig. 3, a cyclic prefix CP is added to the preamble sequence T, and inserted into a frame structure, and transmitted as a transmission signal of the OFDM system transmitter to the OFDM system receiver.
Compared with the traditional PN sequence, the CAZAC sequence has good auto-correlation and cross-correlation properties, and can greatly improve the timing and frequency offset estimation precision under Gaussian channels and multipath fading channels. The CAZAC sequence properties can be described as:
Figure BDA0003978415280000071
‖μ(k)‖＝C，
the CAZAC sequence can then be expressed as:
μ(k)＝exp(jπrk 2 /N 1 ),k＝0,1,...,(N-1)，
where r=1, n 1 ＝N/2。
The preamble sequence T constructed in the embodiment occupies one OFDM symbol length, the structure is divided into four parts, and the lengths of each part are equally divided.
After the preamble sequence T is sent to a receiver, the preamble sequence T is multiplied by window movement of 1/4 OFDM symbol length, and then the correlation peak value of timing synchronization is obtained by performing cross correlation on the preamble sequence T and the preamble sequence A and the preamble sequence D respectively by utilizing the preamble sequence C, so that the timing synchronization starting position is obtained, and the OFDM timing synchronization is completed, wherein the specific steps are as follows:
the timing synchronization metric function of the preamble sequence T is defined as:
Figure BDA0003978415280000072
wherein:
Figure BDA0003978415280000073
Figure BDA0003978415280000074
start position θ=argmax at which timing synchronization is obtained d (M(d))。
As shown in fig. 4, in this embodiment, simulation is performed on eight timing synchronization metric functions under a gaussian channel, which includes a technical solution provided in the same kind of paper, and the Proposed Method is an improved algorithm provided in this embodiment, it can be seen that, due to a platform effect existing in the Schmidl scheme in which the cyclic prefix exists, the improved Method has a sharper peak value, and the side lobe effect is smaller, so that higher synchronization accuracy can be obtained. The Minn and Wang algorithms have two adjacent correlation peaks, so that the starting position of timing synchronization is difficult to judge, and the improved algorithm is close to the Shao algorithm, but has smaller side lobes and is easier to acquire the accurate starting position of timing synchronization.
After the OFDM timing synchronization is completed, carrier synchronization is performed, where the carrier synchronization is divided into fractional frequency offset estimation and integer frequency offset estimation, and in this embodiment, the fractional frequency offset estimation is performed by dividing the fractional frequency offset estimation into coarse estimation and fine estimation, and the fractional frequency offset estimation is completed in the time domain by using the repeatability of the sequence C and the sequence D as follows:
Figure BDA0003978415280000081
wherein P is ε1 Can be determined by the correct start position of the training sequence
Figure BDA0003978415280000082
Obtaining:
Figure BDA0003978415280000083
at this time, decimal frequency bias
Figure BDA0003978415280000084
The estimated range of (1) is [ -1,1]After fractional frequency offset coarse estimation, fractional frequency offset is utilized
Figure BDA0003978415280000085
Compensating the received signal, and the residual decimal frequency offset is less than +/-0.5.
Since the cyclic prefix is a replica of the latter part of the sequence, the fractional frequency offset estimation can be refined by the cyclic prefix, and the fractional frequency offset estimation function is:
Figure BDA0003978415280000086
Figure BDA0003978415280000087
where I may be obtained from the Cyclic Prefix (CP) portion of the constructed synchronization preamble sequence.
When there is an integer frequency offset in the received sequence, first, the received signal is compensated by using the estimated decimal frequency offset estimation value, and only the integer frequency offset exists in the compensated received signal, and the CAZAC can be expressed as follows under the AWGN channel:
Figure BDA0003978415280000091
wherein ε is i Representing integer frequency offset, it can be seen from the above that the CAZAC sequence is cyclically shifted left by ε when integer frequency offset is present i Units of. That is, when there is an integer multiple frequency offset, the preamble sequence A is cyclically shifted left by ε i /4 units. Because the sequence B and the sequence A are conjugate symmetrical, when the integral frequency offset exists, the sequence B circularly shifts epsilon to the right i /4 units. The integer multiple frequency offset sequence A and the sequence B are calculated to complete carrier synchronization, and the decision function can be expressed as:
Figure BDA0003978415280000092
Figure BDA0003978415280000093
wherein A is * (k+g) is a known conjugated sequence of CAZAC sequence A (k), and is cyclically shifted by g units. Since CAZAC sequences have good autocorrelation properties, F (g) will produce a sharp peak that reflects an integer multiple frequency offset. Final normalized frequency offset of
Figure BDA0003978415280000094
And the estimation range may be up to N times the OFDM subcarrier spacing.
And outputting the carrier synchronization result as an OFDM symbol time-frequency synchronization result.
In another embodiment of the present invention, the improved algorithm provided by the present invention is simulated with prior art methods. All algorithm schemes are tested under an AWGN channel, the parameter settings of all algorithm schemes are consistent, and the parameter settings are as follows: FFT point number 256, cp length 64, normalized frequency offset 10.3. Each algorithm was simulated 5000 times and the results averaged.
The performance of the timing metric function can be observed through the Mean Square Error (MSE) of the timing metric, as shown in fig. 5, the algorithm provided by the invention is close to the Shao algorithm in timing performance, is obviously superior to the Fang algorithm and the Schmidl algorithm at low signal-to-noise ratio, and has excellent symbol timing performance.
As shown in FIG. 6, the decimal frequency offset performance of the algorithm provided by the invention is superior to the VandeBeek algorithm and the JianghuaWei algorithm and is inferior to the Moose algorithm.
As shown in FIG. 7, the algorithm provided by the invention has higher precision and smaller frequency offset error and has obviously better synchronization performance than the Ren algorithm and the Schmidl algorithm at a low signal-to-noise ratio through MSE curves.
In summary, the present invention provides an OFDM timing synchronization method based on an improved CAZAC sequence, including: and constructing a preamble sequence T= [ A B C D ] based on the CAZAC sequence, wherein the length of the preamble sequence T occupies one OFDM symbol length, the lengths of four parts of the sequence A, the sequence B, the sequence C and the sequence D are divided equally, a cyclic prefix CP is added in the preamble sequence T, and the cyclic prefix CP is inserted into a frame structure and is used as a transmission signal of an OFDM system transmitter to be transmitted to an OFDM system receiver.
After the preamble sequence T is sent to an OFDM system receiver, the sequence C is used for carrying out cross correlation with the sequence A and the sequence D respectively to obtain a correlation peak value of timing synchronization, and OFDM timing synchronization is completed; then, frequency offset estimation is carried out by using the sequence C and the sequence D to obtain a rough estimation value of the fractional frequency offset, and fine estimation of the fractional frequency offset is carried out by using the repeatability of the cyclic prefix; and finally, carrying out integer frequency offset estimation by utilizing the cyclic shift characteristics of the first two parts of the sequence to finish carrier synchronization of the OFDM symbols.
The steps in the invention can be sequentially adjusted, combined and deleted according to actual requirements.
Although the invention has been disclosed in detail with reference to the accompanying drawings, it is to be understood that such description is merely illustrative and is not intended to limit the application of the invention. The scope of the invention is defined by the appended claims and may include various modifications, alterations and equivalents of the invention without departing from the scope and spirit of the invention.

Claims (7)

1. An OFDM timing synchronization method based on an improved CAZAC sequence, the method comprising:
constructing a preamble sequence T= [ A B C D ] based on a CAZAC sequence, wherein the length of the preamble sequence T occupies one OFDM symbol length, the lengths of four parts of a sequence A, a sequence B, a sequence C and a sequence D are divided equally, a cyclic prefix CP is added in the preamble sequence T, and the cyclic prefix CP is inserted into a frame structure and is used as a transmission signal of an OFDM system transmitter to be transmitted to an OFDM system receiver;
after the preamble sequence T is sent to the OFDM system receiver, the correlation peak value of timing synchronization is obtained by respectively carrying out cross correlation on the preamble sequence T and the sequence A and the sequence D by utilizing the sequence C, and the OFDM timing synchronization is completed; then, frequency offset estimation is carried out by using the sequence C and the sequence D to obtain a rough estimation value of the fractional frequency offset, and fine estimation of the fractional frequency offset is carried out by using the repeatability of the cyclic prefix; finally, the cyclic shift characteristics of the first two parts of the sequence are utilized to carry out integral frequency offset estimation, so as to complete carrier synchronization of OFDM symbols;
wherein, the sequence B is conjugate symmetrical with the sequence A, the sequence C is the inverse of the interval of the sequence B, and the sequence D is the same as the sequence C.
2. The improved CAZAC sequence-based OFDM timing synchronization method of claim 1, wherein the sequence a is expressed as:
Figure FDA0003978415270000011
the sequence B is expressed as:
Figure FDA0003978415270000012
the sequence C is expressed as:
C(k)＝(-1) k B * (k)，
where r is a positive integer and N represents the total number of subcarriers.
3. The improved CAZAC sequence based OFDM timing synchronization method of claim 1, wherein the timing synchronization comprises:
the timing synchronization metric function of the preamble sequence T is defined as:
Figure FDA0003978415270000021
wherein:
Figure FDA0003978415270000022
Figure FDA0003978415270000023
start position θ=argmax at which timing synchronization is obtained d (M(d))。
4. The improved CAZAC sequence based OFDM timing synchronization method of claim 1, wherein the carrier synchronization comprises: fractional frequency offset coarse estimation, fractional frequency offset fine estimation, and integer frequency offset estimation.
5. The improved CAZAC sequence based OFDM timing synchronization method of claim 4, wherein the fractional frequency offset coarse estimate is:
Figure FDA0003978415270000024
wherein P is ε1 Can be determined by the correct start position of the training sequence
Figure FDA0003978415270000025
Obtaining: />
Figure FDA0003978415270000026
6. The improved CAZAC sequence based OFDM timing synchronization method of claim 4, wherein the fractional frequency offset fine estimate is:
Figure FDA0003978415270000027
wherein I can be obtained from the cyclic prefix portion of the constructed synchronization preamble sequence:
Figure FDA0003978415270000031
7. the improved CAZAC sequence-based OFDM timing synchronization method of claim 1, wherein the sequence received by the method has an integer multiple offset, calculated from sequence a and sequence B, and the decision function is expressed as:
Figure FDA0003978415270000032
Figure FDA0003978415270000033
wherein A is * (k+g) is the conjugate sequence of the known CAZAC sequence A (k), and is cyclically shifted by g units, F (g) will generate a sharp peak reflecting the integer multiple frequency offset due to the good autocorrelation properties of the CAZAC sequence, and the final normalized frequency offset is
Figure FDA0003978415270000034
/>
CN202211542649.7A 2022-12-02 2022-12-02 OFDM timing synchronization method based on improved CAZAC sequence Pending CN116232828A (en)

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