A timing advance and carrier frequency offset joint estimation method based on conjugate symmetric ZC sequence

Abstract

The application discloses a method for jointly estimating timing advance and frequency offset based on conjugate symmetric ZC sequences, and relates to the technical field of wireless communication, and comprises the following steps: inputting a preamble sequence extracted from a demodulated received signal; correlating two ZC sequences in the preamble sequence with local ZC sequences respectively and obtaining peak values of correlation result amplitudes; iteratively performing decimal multiple frequency offset compensation estimation to obtain a decimal multiple frequency offset estimation value and a compensated preamble sequence; performing timing advance estimation and integer multiple frequency offset estimation to obtain a timing advance estimation value and an integer multiple frequency offset estimation value; combining the decimal multiple and integer multiple frequency offset estimation values to obtain a frequency offset estimation value; ending timing advance and frequency offset estimation, and outputting the estimation values of the timing advance and the frequency offset. The application eliminates the negative influence of the decimal multiple frequency offset on the ZC sequence by iteratively compensating and estimating the decimal multiple frequency offset, and realizes high-performance joint estimation of timing advance and frequency offset which is robust to frequency shift and noise based on the structure of the conjugate symmetric ZC sequence, and is suitable for non-ground network communication scenarios with large Doppler frequency shift and low received signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and more specifically, to a joint estimation method for timing advance and carrier frequency offset based on conjugate symmetric ZC sequences. Background Technology

[0002] With the rapid development of mobile communication technology, terrestrial mobile communication systems have gradually become more complete, especially with the widespread adoption of 5G technology, which has significantly improved the coverage and transmission speed of terrestrial networks. However, as communication demands continue to grow, users' requirements for communication quality and service coverage are also increasing, particularly in remote areas, mountainous regions, oceans, and airspace where terrestrial networks are difficult to cover. To meet these demands, non-terrestrial networks (NTNs), such as low Earth orbit (LEO) satellites and high-altitude platform systems, are gradually becoming key technologies for solving this problem as an important supplement to terrestrial networks. NTNs can provide extensive global coverage, especially in remote areas and disaster emergency situations, providing users with efficient and reliable communication services. In NTNs, random access is the first step in establishing communication between user equipment (UE) and satellites or base stations, ensuring a reliable initial connection in various complex environments (such as remote areas, at sea, and in the air). Timing advance estimation and frequency offset estimation play crucial roles in the random access process of NTNs. They not only ensure signal synchronization between the UE and the base station or satellite but also improve the access success rate, reduce interference and errors, thereby improving the efficiency of random access. However, timing advance and frequency offset estimation in NTNs face challenges such as high dynamism, Doppler frequency shift, long propagation delay, low signal-to-noise ratio, and multipath effects. Effectively addressing these challenges requires more advanced algorithms and more efficient estimation methods to ensure that NTNs can provide reliable and efficient communication services in complex and dynamic environments. Summary of the Invention

[0003] This invention addresses the problems of timing advance estimation and carrier frequency offset estimation based on random access preamble sequences in non-terrestrial networks. Based on conjugate symmetric ZC sequences, an iterative joint estimation method for timing advance and carrier frequency offset is proposed. This scheme is robust in environments with large frequency offsets and low received signal-to-noise ratios, and is suitable for non-terrestrial network communication systems with Doppler frequency shifts and low received power.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A joint estimation method for timing advance and carrier frequency offset based on conjugate symmetric ZC sequences includes the following steps:

[0006] S1: Input the preamble sequence extracted from the demodulated received signal;

[0007] S2: Receive the two ZC sequences in the preamble sequence and perform cross-correlation operations with the local ZC sequence respectively, and obtain the peak values ​​of the two cross-correlation results respectively;

[0008] S3: Perform fractional frequency offset compensation and estimation to obtain the received preamble sequence after fractional frequency offset estimation and compensation;

[0009] S4: Perform timing advance and integer multiple frequency offset estimation to obtain the timing advance estimate and integer multiple frequency offset estimate;

[0010] S5: Based on the frequency offset estimates of fractional and integer multiples, obtain the final carrier frequency offset estimate;

[0011] S6: Timing advance and carrier frequency offset estimation ends, output the estimated values ​​of timing advance and carrier frequency offset.

[0012] Preferably, the preamble sequences sent and received in step S1 are specifically as follows:

[0013] S1.1: The transmitted random access preamble sequence is a conjugate symmetric Zadoff-Chu sequence (hereinafter referred to as the ZC sequence), which is composed of two ZC sequences concatenated in the time domain. The first and second ZC sequences are represented as follows:

[0014]

[0015] Where N is the length of the ZC sequence, and u and v are the root indices of the two ZC sequences, respectively. Under the condition that u = Nv, the ZC sequence... u (n) and ZC v (n) satisfies the conjugate relation, that is

[0016] S1.2: The transmitted preamble sequence passes through an additive white Gaussian noise (AWGN) channel. The first and second ZC sequences of the received preamble sequence y(n) are respectively represented as follows:

[0017]

[0018] Where ε is the frequency offset normalized to the subcarrier spacing, τ is the propagation delay, and w(n) is a frequency response function with a mean of 0 and a variance of 0. AWGN.

[0019] Preferably, in step S2, cross-correlation operations are performed on the two ZC sequences in the received preamble sequence and the local ZC sequence respectively, and the peak values ​​of the two cross-correlation results are obtained respectively, specifically as follows:

[0020] S2.1: Receive the two ZC sequences y1(n) and y2(n) of the preamble sequence y(n) and the local ZC sequence ZC respectively. u(n), ZC v (n) performs cross - correlation operation, which can be expressed as

[0021]

[0022] where \(l = 0,1,\cdots,N - 1\) is the cyclic shift value of the local ZC sequence, and \((\cdot) N represents the modulo operator with divisor \(N\);

[0023] S2.2: Perform peak search on the amplitudes of the cross - correlation results \(C1(l)\) and \(C2(l)\), and the peaks are respectively represented as \(p1\) and \(p2\). Specifically

[0024] p i =\(\max|C i (l)|\), \(i = 1,2\).

[0025] Preferably, in step S3, fractional - frequency offset compensation and estimation are performed iteratively. Specifically

[0026] S3.1: Initialize the parameters in the iterative process: the current iteration number \(m = 1\); \(y c (n)=y t (n)=y(n), y c (n) is the received signal for which compensation is attempted, and \(y t (n) is the received signal for which compensation is effective; the current fractional - frequency offset \(\varepsilon t = 0.5\), the current estimated value of the fractional - frequency offset P is the maximum mean value of the amplitudes of the cross - correlation results of two received ZC sequences in the iterative process, and \(P1\), \(P2\) are respectively the means of the amplitudes of the cross - correlation results in the current iteration and the previous iteration;

[0027] S3.2: Update the parameters, \(m=m + 1\),

[0028] S3.3: Calculate the cross - correlation results of two ZC sequences of \(y c (n)\), update the two amplitude peaks \(p1\) and \(p2\), and update

[0029] S3.4: If \(P1>P\), update \(\varepsilon t =\(\varepsilon t / 2\), \(y t (n)=y c (n)\), \(P = P1\), or \(P1,P2<P\), update \(\varepsilon t =-\(\varepsilon t \); otherwise, update \(\varepsilon t =\(\varepsilon t / 2\);

[0030] S3.5: If m≤M, return to step S3.2; otherwise, end the iteration and output the received signal y after fractional-fold frequency offset compensation. t (n) and fractional frequency offset estimation results

[0031] Preferably, in step S4, timing advance and integer multiple frequency offset estimation are performed, specifically as follows:

[0032] S4.1: The received signal y after fractional-fold frequency offset compensation t Perform cross-correlation on the two ZC sequences of (n) and analyze their magnitudes |C i (l)|, i=1,2, perform a peak search to obtain peak indices l1 and l2 respectively, specifically as follows:

[0033]

[0034] S4.2: Obtain the timing advance estimate based on peak indices l1 and l2. and integer multiples of frequency offset estimates Specifically

[0035]

[0036] Preferably, in step S5, the estimation value is based on the fractional octave frequency offset. and integer multiples of frequency offset estimates Obtain the final carrier frequency offset estimate Specifically:

[0037] Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0039] Figure 2 A schematic diagram comparing the timing advance estimation (MSE) of different algorithms provided in the embodiments.

[0040] Figure 3 This is a schematic diagram comparing the mean carrier frequency offset estimation values ​​of different algorithms provided in the embodiment.

[0041] Figure 4 A schematic diagram comparing the carrier frequency offset estimation (MSE) of different algorithms provided in the embodiments. Detailed Implementation

[0042] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0043] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0044] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0045] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] Example 1

[0047] This example provides a joint estimation method for timing advance and carrier frequency offset based on conjugate symmetric ZC sequences, such as... Figure 1 As shown, it includes the following steps:

[0048] S1: Input the preamble sequence extracted from the demodulated received signal;

[0049] S2: Receive the two ZC sequences in the preamble sequence and perform cross-correlation operations with the local ZC sequence respectively, and obtain the peak values ​​of the two cross-correlation results respectively;

[0050] S3: Perform fractional frequency offset compensation and estimation to obtain the received preamble sequence after fractional frequency offset estimation and compensation;

[0051] S4: Perform timing advance and integer multiple frequency offset estimation to obtain the timing advance estimate and integer multiple frequency offset estimate;

[0052] S5: Based on the frequency offset estimates of fractional and integer multiples, obtain the final carrier frequency offset estimate;

[0053] S6: Timing advance and carrier frequency offset estimation ends, output the estimated values ​​of timing advance and carrier frequency offset.

[0054] Example 2

[0055] This embodiment, based on Embodiment 1, continues to disclose the following content:

[0056] The preamble sequences sent and received in step S1 are as follows:

[0057] S1.1: The transmitted random access preamble sequence is a conjugate symmetric Zadoff-Chu sequence (hereinafter referred to as the ZC sequence), which is composed of two ZC sequences concatenated in the time domain. The first and second ZC sequences are represented as follows:

[0058]

[0059] Where N is the length of the ZC sequence, and u and v are the root indices of the two ZC sequences, respectively. Under the condition that u = Nv, the ZC sequence... u (n) and ZC v (n) satisfies the conjugate relation, that is

[0060] S1.2: The transmitted preamble sequence passes through an additive white Gaussian noise (AWGN) channel. The first and second ZC sequences of the received preamble sequence y(n) are respectively represented as follows:

[0061]

[0062] Where ε is the frequency offset normalized to the subcarrier spacing, τ is the propagation delay, and w(n) is a frequency response function with a mean of 0 and a variance of 0. AWGN.

[0063] In step S2, the two received ZC sequences y1(n) and y2(n) in the preamble sequence y(n) are cross-correlated with the local ZC sequence to obtain the peak values ​​of the two cross-correlation results, specifically:

[0064] S2.1: Receive the two ZC sequences y1(n) and y2(n) of the preamble sequence y(n) and the local ZC sequence ZC respectively. u (n),ZC v (n) performing cross-correlation can be represented as

[0065]

[0066] Where l = 0, 1, ..., N-1 are the cyclic shift values ​​of the local ZC sequence, (·) N The modulo operator is used to divide by N.

[0067] S2.2: Perform peak search on the amplitudes of the cross-correlation results C1(l) and C2(l), where the peak values ​​are denoted as p1 and p2, respectively.

[0068] p i =max|C i (l)|, i=1,2.

[0069] Step S3 iteratively performs fractional octave frequency offset compensation and estimation, specifically as follows:

[0070] S3.1: Initialize the parameters during the iteration process: current iteration number m = 1; y c (n)=y t (n) = y(n), y c (n) is the received signal that attempts to compensate, y t (n) is the effectively compensated received signal; the current fractional frequency offset ε to be compensated is... t =0.5, current fractional frequency offset estimate P is the maximum mean of the peak amplitudes of the cross-correlation results of the two received ZC sequences during the iteration process, and P1 and P2 are the mean of the peak amplitudes of the two cross-correlation results in the current iteration and the previous iteration, respectively.

[0071] S3.2: Update the parameter, m = m + 1,

[0072] S3.3: Calculate y c The cross - correlation result of two ZC sequences of (n), update two amplitude peaks p1 and p2, update

[0073] S3.4: If P1 > P, update ε t = ε t / 2, y t (n) = y c (n), P = P1, or P1, P2 < P, update ε t = - ε t ; Otherwise, update ε t = ε t / 2;

[0074] S3.5: If m ≤ M, return to step S3.2; Otherwise, end the iteration and output the received signal y t (n) after fractional frequency offset compensation and the fractional frequency offset estimation result

[0075] In step S4, timing advance and integer frequency offset estimation are performed, specifically:

[0076] S4.1: Perform cross - correlation operations on two ZC sequences of the received signal y t (n) after fractional frequency offset compensation respectively, perform peak search on their amplitudes |C i (l)|, i = 1, 2, and obtain peak indices l1 and l2 respectively, specifically

[0077]

[0078] S4.2: Obtain the timing advance estimation value and the integer frequency offset estimation value Specifically

[0079]

[0080] In step S5, based on the fractional frequency offset estimation value and the integer frequency offset estimation value obtain the final carrier frequency offset estimation value Specifically:

[0081]

[0082] Example 3 (Timing Advance MSE)

[0083] Based on Embodiments 1 and 2, this embodiment provides the following specific embodiments:

[0084] The simulation parameters are set as follows: the simulation channel is set to AWGN channel, the signal-to-noise ratio (hereinafter referred to as SNR) ranges from -20dB to -12dB, the normalized frequency offset ranges from -15 to 15, the maximum delay difference is 0.7ms, and the number of Monte Carlo simulations is 10,000.

[0085] Regarding the performance estimation before timing, the mean square error (MSE) of the timing advance estimation results is used as the metric. The improved joint estimation method for timing advance and carrier frequency offset based on conjugate symmetric ZC sequences (ECSZC), the timing advance and frequency offset estimation method based on constant envelope zero autocorrelation sequences (CAZCA, C. Yang, L. Wang, C. Peng, S. Zhang, Y. Cui and C. Ma, "A Robust Time-Frequency Synchronization Method for Underwater Acoustic OFDM Communication Systems," IEEE Access, vol. 12, pp. 21908-21920, 2024.), and the timing advance and frequency offset estimation method based on ZC conjugate symmetric sequences (CSZC, T.A. Khan and X. Lin, "Random Access Preamble Design for 3GPP Non-terrestrial Networks," in Proc. IEEE Globecom) proposed in this invention are compared. This paper compares three algorithms: the timing advance estimation method based on symmetric Zadoff-Chu sequences (hereinafter referred to as TAE-SZC, G.Cui, Y.He, P.Li and W.Wang, "Enhanced Timing Advanced Estimation With Symmetric Zadoff-Chu Sequences for Satellite Systems," IEEE Commun. Lett., vol.19, no.5, pp.747-750, May 2015). The lower the timing advance estimation MSE, the better the performance of the timing advance estimation method. Specifically, the following is a comparison: Figure 2As shown, the MSE of all timing estimation algorithms decreases with increasing SNR. Under all SNR conditions, the timing estimation MSE of the ECSZC of this invention is lower than that of the other three methods. When SNR ≥ -15dB, the timing estimation performance of the ECSZC of this invention is improved by at least 1dB compared to the other three existing methods.

[0086] The above examples illustrate that the ECSZC proposed in this invention has superior estimation performance compared to the other three methods, and can still achieve accurate timing advance estimation in AWGN channels with large frequency offset and low signal-to-noise ratio.

[0087] Example 4 (Carrier Frequency Offset Estimated Average Value)

[0088] Based on Embodiments 1 and 2, this embodiment provides the following specific embodiments:

[0089] The simulation parameters are set as follows: the simulation channel is set to AWGN channel, the SNR is 20dB, the normalized frequency offset range is -15 to 15, and the number of Monte Carlo simulations is 10,000.

[0090] Regarding the carrier frequency offset estimation range, the average carrier frequency offset estimation value is used as the evaluation standard. The ECSZC proposed in this invention is compared with CAZAC, CSZC, and the frequency offset estimation method based on repeating sequence structure (hereinafter referred to as RS, H. Minn, V. K. Hargava and K. Letaief, "A robust timing and frequency synchronization for OFDM systems," IEEE Trans on Wireless Commun., vol. 2, no. 4, pp. 822-839, Jul. 2003.). Under the premise that the average carrier frequency offset estimation value curve changes in accordance with the ideal curve, the larger the average carrier frequency offset estimation value, the larger the carrier frequency offset estimation range, as detailed below: Figure 3 As shown, the average carrier frequency offset estimation curves of CAZAC, CSZC, and the ECSZC proposed in this invention coincide with the ideal curve, while the average carrier frequency offset estimation of RS only varies between -2 and 2. Specifically, when the normalized carrier frequency offset range is -2 to 2, the average carrier frequency offset estimation curve of RS follows the same trend as the ideal curve; otherwise, when it exceeds the range of -2 to 2, its average carrier frequency offset estimation curve deviates from the ideal curve, therefore its effective carrier frequency offset estimation range is -2 to 2. Within the normalized frequency offset range of -15 to 15, the average carrier frequency offset estimation curves of CAZAC, CSZC, and the ECSZC proposed in this invention all show the same trend as the ideal curve.

[0091] The above examples illustrate that the ECSZC of the present invention has a large carrier frequency offset estimation range and is applicable to communication scenarios with large frequency offsets.

[0092] Example 5 (Carrier Frequency Offset Estimation, MSE)

[0093] Based on Embodiments 1 and 2, this embodiment provides the following specific embodiments:

[0094] The simulation parameters are set as follows: the simulation channel is set to AWGN channel, the SNR range is -20dB to -12dB, the normalized frequency offset range is -15 to 15, and the number of Monte Carlo simulations is 10,000.

[0095] Regarding carrier frequency offset estimation performance, the carrier frequency offset estimation MSE is used as the evaluation standard. The ECSZC proposed in this invention is compared with CAZAC, CSZC, and RS, as follows: Figure 4 As shown, with the increase of SNR, RS fails to estimate because its normalized frequency offset range exceeds its effective estimation range, and its carrier frequency offset estimation MSE does not change significantly and remains at a high level. The carrier frequency offset estimation MSE of the other three methods decreases with the increase of SNR. Except for RS, which fails to estimate, the MSE of ECSZC of this invention is smaller than that of CAZAC and CSZC under all signal-to-noise ratio conditions, and its MSE is less than 10 when SNR ≥ -14dB. -2 .

[0096] The above examples illustrate that, in AWGN channels with large frequency offset and low signal-to-noise ratio, the ECSZC proposed in this invention has excellent carrier frequency offset estimation performance, and can still achieve high-precision estimation even under low SNR conditions.

[0097] The same or similar labels correspond to the same or similar parts;

[0098] The positional relationships depicted in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0099] Obviously, the above examples of the present invention are merely illustrative of the invention and are not intended to limit the implementation of the invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A joint estimation method for timing advance and carrier frequency offset based on conjugate symmetric ZC sequences, characterized in that, Includes the following steps: S1: Input the preamble sequence extracted from the demodulated received signal, wherein the preamble sequence is formed by concatenating two conjugate symmetric Zadoff-Chu sequences (ZC sequences) in the time domain; S2: Receive the two ZC sequences in the preamble sequence and perform cross-correlation operations with the local ZC sequence respectively, and obtain the peak values ​​of the two cross-correlation results respectively; S3: Iteratively perform fractional frequency offset compensation and estimation on the two received ZC sequences. By updating the frequency offset to be compensated and verifying the effectiveness of the compensation in a cyclic iterative manner, the received preamble sequence after fractional frequency offset estimation and compensation is obtained. S4: Based on the compensated preamble sequence, perform cross-correlation between the two received ZC sequences and the local ZC sequence to obtain the peak index, and calculate the timing advance estimate and integer multiple frequency offset estimate based on the peak index; S5: Based on the frequency offset estimates of fractional and integer multiples, obtain the final carrier frequency offset estimate; S6: Timing advance and carrier frequency offset estimation ends, outputting the estimated values ​​of timing advance and carrier frequency offset.

2. The method for jointly estimating timing advance and carrier frequency offset based on conjugate symmetric ZC sequences according to claim 1, characterized in that, The preamble sequences sent and received in step S1 are as follows: S1.1: The transmitted random access preamble sequence consists of two concatenated conjugate Zadoff-Chu sequences (ZC sequences) in the time domain. The first and second ZC sequences are represented as follows: Where N is the length of the ZC sequence, and u and v are the root indices of the two ZC sequences, respectively. Under the condition that u = Nv, the ZC sequence... u (n) and ZC v (n) satisfies the conjugate relation, that is S1.2: The transmitted preamble sequence passes through an additive white Gaussian noise (AWGN) channel. The first and second ZC sequences of the received preamble sequence y(n) are respectively represented as follows: Where ε is the frequency offset normalized to the subcarrier spacing, τ is the propagation delay, and w(n) is a frequency response function with a mean of 0 and a variance of 0. AWGN.

3. The method for jointly estimating timing advance and carrier frequency offset based on conjugate symmetric ZC sequences according to claim 1, characterized in that, In step S2, cross-correlation operations are performed on the two ZC sequences in the received preamble sequence and the local ZC sequence, and the peak values ​​of the two cross-correlation results are obtained respectively. Specifically: S2.1: Receive the two ZC sequences y1(n) and y2(n) of the preamble sequence y(n) and the local ZC sequence ZC respectively. u (n),ZC v (n) performing cross-correlation can be represented as Where l = 0, 1, ..., N-1 are the cyclic shift values ​​of the local ZC sequence, and N is the length of the ZC sequence, (·) N The modulo operator is used to divide by N. S2.2: Perform peak search on the amplitudes of the cross-correlation results C1(l) and C2(l), where the peak values ​​are denoted as p1 and p2, respectively. p i =max|C i (l)|,i=1,2。 4. The method for jointly estimating timing advance and carrier frequency offset based on conjugate symmetric ZC sequences according to claim 1, characterized in that, Step S3 iteratively performs fractional-harmonic frequency offset compensation and estimation on the two received ZC sequences, specifically as follows: S3.1: Initialize the parameters during the iteration process: current iteration number m = 1; y c (n)=y t (n) = y(n), y c (n) is the received signal that attempts to compensate, y t (n) is the effectively compensated received signal; the current fractional frequency offset ε to be compensated is... t =0.5, current fractional frequency offset estimate Where p1 and p2 are the peak values ​​of the cross-correlation results between the two received ZC sequences and the local ZC sequence, respectively, P is the maximum mean of the peak values ​​of the cross-correlation results of the two received ZC sequences during the iteration process, and P1 and P2 are the mean values ​​of the peak values ​​of the two cross-correlation results in the current iteration and the previous iteration, respectively. S3.2: Update parameters, m = m + 1, Where ε is the frequency offset normalized to the subcarrier spacing, and N is the length of the ZC sequence; S3.3: Calculate y c The cross-correlation results of the two ZC sequences of (n) with the local ZC sequence are used to update the two amplitude peaks p1 and p2, and update... S3.4: If P1 > P, update ε t =ε t / 2,y t (n)=y c (n), P = P1, If both P1 and P2 are less than P, update ε. t =-ε t Otherwise, update ε t =ε t / 2; S3.5: If m≤M, return to step S3.2; otherwise, end the iteration and output the received signal y after fractional-fold frequency offset compensation. t (n) and fractional frequency offset estimation results 5. The method for jointly estimating timing advance and carrier frequency offset based on conjugate symmetric ZC sequences according to claim 1, characterized in that, In step S4, cross-correlation operations are performed on the two received ZC sequences with the local ZC sequence to obtain the peak index. Based on the peak index, the timing advance estimate and the integer multiple frequency offset estimate are calculated, specifically as follows: S4.1: The received signal y after fractional-fold frequency offset compensation t Perform cross-correlation on the two ZC sequences of (n) and analyze their magnitudes |C i (l)|, i=1,2, perform a peak search to obtain peak indices l1 and l2 respectively, specifically as follows: S4.2: Obtain the timing advance estimate based on peak indices l1 and l2. and integer multiples of frequency offset estimates Specifically Where N is the length of the ZC sequence.

6. The method for jointly estimating timing advance and carrier frequency offset based on conjugate symmetric ZC sequences according to claim 1, characterized in that, In step S5, the estimated value is based on the fractional octave frequency offset. and integer multiples of frequency offset estimates Obtain the final carrier frequency offset estimate Specifically:

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