Coarse frequency offset and primary synchronization signal joint detection method for non-ground network system

Abstract

The invention provides a non-ground network system coarse frequency offset and primary synchronization signal joint detection method, and belongs to the technical field of 5G non-ground network communication. The method comprises the following steps: receiving a signal to obtain a to-be-detected sampling point sequence; performing uniform time division extraction to obtain n paths of parallel data; carrying out frequency domain equalization, and converting the data into a frequency domain by adopting 50% overlapping block processing; performing frequency domain equalization operation to obtain a time domain cross-correlation sequence of each block; discarding the first half part of the sequence and retaining the second half part of the sequence, and cascading and splicing the second half part of the sequence of the n blocks of one path of data into a correlation value sequence group to obtain n paths of parallel cross-correlation sequence groups; the sequence is converted into a single-path cross-correlation sequence through parallel-serial conversion; and detecting the peak value of the single-path cross-correlation sequence, completing the detection of a main synchronization signal, and obtaining the position of a synchronization point and a coarse frequency offset value. According to the invention, PSS detection and coarse frequency offset estimation can be realized with extremely low complexity in a 5G non-ground network system.

Description

Technical Field

[0001] The present invention relates to the field of 5G non-terrestrial network communication technology, and in particular to a method for jointly detecting a coarse frequency deviation and a primary synchronization signal (PSS) of a non-terrestrial network (NTN) system, which is suitable for scenarios such as high-speed moving trains, high-speed drones, and satellite communications. Background Art

[0002] Synchronization plays a vital role in wireless communication. Only with accurate system synchronization can the entire communication system work properly. PSS detection is an important synchronization process in 5G communication. Its detection performance and complexity will affect the performance of the entire system. However, in 5G non-terrestrial networks, there are multipath fading channel effects, especially in ultra-high noise environments and severe Doppler frequency deviations. Accurate detection of PSS is extremely challenging.

[0003] Currently, the commonly used PSS detection algorithm is the sliding cross-correlation algorithm. This algorithm uses the good correlation characteristics of the PSS sequence to use the local PSS sequence for cross-correlation, derives the cross-correlation sequence, and detects the PSS by detecting the correlation peak to complete the synchronization of the entire system. However, under the influence of large Doppler frequency deviation and low signal-to-noise ratio in 5G non-terrestrial network systems, to ensure the detection accuracy of traditional algorithms, multi-channel parallel detection is required, which leads to a rapid increase in the complexity of the entire system, consumes too many logic resources, and cannot be deployed on various types of hardware platforms. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a method for joint detection of coarse frequency deviation and primary synchronization signal of non-terrestrial network system. The present invention can effectively improve the estimation accuracy of channel signal-to-noise ratio in an environment with ultra-low signal-to-noise ratio, multipath deep fading and large Doppler frequency deviation, thereby greatly reducing the complexity under the premise of ensuring detection performance, and completing the estimation of coarse frequency deviation while completing PSS detection.

[0005] The technical solution adopted by the present invention is:

[0006] A method for jointly detecting a coarse frequency deviation and a primary synchronization signal of a non-terrestrial network system comprises the following steps:

[0007] S1: The terminal receives the signal and performs analog-to-digital conversion, and obtains the sampling point sequence to be detected through anti-aliasing filtering and downsampling;

[0008] S2: Evenly extract the sampling point sequence to be detected in time division, complete the serial-to-parallel conversion, and obtain n parallel data, each of which has a different delay;

[0009] S3: Perform frequency domain equalization on each data channel, and adopt 50% overlapping block processing, so that each data channel is converted into n blocks, and after the blocks are converted into the frequency domain by fast Fourier transform;

[0010] S4: Based on the equivalence of time domain cross-correlation and frequency domain dot product operations, frequency domain equalization operation is performed on each block of data, and the time domain cross-correlation sequence of each block is obtained by inverse Fourier transform. There is a time delay relationship between the time domain cross-correlation sequences of n blocks of each data channel;

[0011] S5: For each block of time domain mutual correlation sequence, discard the first half of the sequence and retain the second half of the sequence, then concatenate the second half of the sequences of n blocks of 1-way data into a correlation value sequence group to obtain an n-way parallel mutual correlation sequence group;

[0012] S6: converting the n-way parallel cross-correlation sequence group into a single-way cross-correlation sequence by parallel-to-serial conversion according to different delays;

[0013] S7: Detect the peak value of the single-channel cross-correlation sequence, complete the main synchronization signal detection, and obtain the synchronization point position and the coarse frequency deviation value.

[0014] Furthermore, in step S2, the sequence of sampling points to be detected is uniformly time-divided and extracted in the following manner:

[0015]

[0016] Among them, y(m) is the sampling point sequence to be detected, m is the point in the sequence, and y n (k) is the nth data after serial-to-parallel conversion.

[0017] Furthermore, in step S3, the specific method of using 50% overlapping block processing is:

[0018] For each data channel, a data block is first taken according to the length of the fast Fourier transform window. The length of each subsequent data block is the length of the fast Fourier transform window, but the starting point of the data block is the center point of the previous data block, and 50% overlapping blocks are completed in sequence.

[0019] Furthermore, the specific method of step S4 is:

[0020] Frequency domain equalization is performed based on the equivalence of cross-correlation operation and frequency domain point multiplication operation. The cross-correlation sequence is calculated by inverse fast Fourier transform after frequency domain point multiplication. At the same time, multiple groups of frequency domain main synchronization signal sequences with preset frequency offsets are detected in parallel to obtain a series of parallel segmented correlation value sequence groups. The calculation formula is as follows:

[0021] Y n,b (k) = FFT[y n,b (k)]

[0022]

[0023] Among them, y n,b (k) is the b-th block of data in the n-th path, Y n,b (k) is y n,b (k) is the frequency domain sequence, is the p-th type primary synchronization signal sequence with a preset frequency offset of f, p = 0, 1, 2, for The frequency domain sequence, c n,b,f,p (k) is a segmented correlation value sequence of the b-th block data of the n-th channel to the p-th type primary synchronization signal sequence with a preset frequency offset of f. FFT is a fast Fourier transform, and IFFT is an inverse fast Fourier transform.

[0024] Furthermore, the correlation value sequence group in step S5 is:

[0025]

[0026] in, c b,n,f,p The second half of the sequence (k), C n,f,p (k) is the parallel correlation value sequence group after splicing.

[0027] Further, in step S6, the single-path cross-correlation sequence after parallel-to-serial conversion is:

[0028] C f,p (k)=[C 1,f,p (0),C 2,θ,ω (0),…,C n,θ,ω (0),C 1,f,p (1),C 2,f,p (1),…,C n,f,p (1),…,C n,f,p (k)]

[0029] Among them, C f,p (k) is the single-path cross-correlation sequence after parallel-to-serial conversion.

[0030] Furthermore, the specific method of step S7 is:

[0031] By using the single-path cross-correlation sequence C f,p (k) Perform parallel peak value threshold detection to obtain the synchronization point position and the size of the coarse frequency deviation.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. The present invention can effectively improve the estimation accuracy of the channel signal-to-noise ratio in an environment with ultra-low signal-to-noise ratio, multipath deep fading and large Doppler frequency deviation, thereby greatly reducing the complexity while ensuring the detection performance.

[0034] 2. The present invention can complete the estimation of coarse frequency offset while completing PSS detection.

[0035] 3. The present invention is designed based on the multipath fading channel and large Doppler frequency deviation scenarios of 5G non-terrestrial networks, which solves the problem of high complexity of traditional algorithms in 5G non-terrestrial network scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0037] Figure 1 It is a schematic diagram of the principle of the present invention. DETAILED DESCRIPTION

[0038] In order to explain the present invention more clearly, the present invention is further described below in conjunction with embodiments and drawings. It should be understood by those skilled in the art that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0039] A method for jointly detecting a coarse frequency deviation and a primary synchronization signal in a non-terrestrial network system, such as Figure 1 As shown, the following steps are included:

[0040] S1: The terminal samples and digitizes the baseband received signal through ADC. In order to reduce the complexity of the subsequent digital signal processing algorithm and the chip area, the sampled signal is filtered through an anti-aliasing filter to suppress high-frequency signal interference. After downsampling, a low sampling rate sequence to be detected is obtained and cached.

[0041] This method first performs aliasing filtering on the original sampling points sampled by the ADC, and obtains the information of the entire SSB block through anti-aliasing filtering. At the same time, when designing the anti-aliasing filter bandwidth, a protection interval of ±400KHz is added compared to the SSB bandwidth to prevent SSB information loss due to large Doppler frequency deviation. Downsampling after anti-aliasing filtering will not cause aliasing of subcarriers and thus affect system performance. The downsampling multiple determines the complexity of the subsequent frequency domain equalization algorithm. Downsampling without affecting performance can significantly reduce the complexity of the system.

[0042] S2: In order to further reduce the complexity of the cross-correlation operation and maintain a high synchronization time resolution, the sequence to be detected is uniformly time-divided by the serial-to-parallel conversion module to extract the input sequence and convert it into n-way parallel data sequences. The data delays between the n-way data sequences are different. The time synchronization resolution can be improved later by detecting the maximum value after the n-way cross-correlation operation.

[0043] The downsampled data is then sent to the serial-to-parallel conversion module to divide the sequence of sampling points to be detected into n data paths in the following manner. The serial-to-parallel conversion module evenly extracts the sampling points to be detected in time division in the following manner:

[0044]

[0045] Among them, y(m) is the sampling point sequence to be detected, y n (k) is the nth data after serial-to-parallel conversion.

[0046] S3: Each channel of data is frequency-domain equalized and processed in blocks with 50% overlap. After the blocks are divided, the data is converted to the frequency domain through fast Fourier transform. The specific method is as follows:

[0047] For each data channel, a data block is first taken according to the length of the fast Fourier transform window. The length of each subsequent data block is the length of the fast Fourier transform window, but the starting point of the data block is the center point of the previous data block. 50% overlapping blocks are completed in sequence, and the blocked data is transformed into the frequency domain by fast Fourier transform.

[0048] S4: Based on the equivalence of time domain cross-correlation and frequency domain dot multiplication operations, each block data is subjected to frequency domain equalization operation, and the time domain cross-correlation sequence value is obtained through inverse Fourier transform. There is a time delay relationship between the n cross-correlation sequences. The specific method is:

[0049] Frequency domain equalization is performed based on the equivalence of cross-correlation operation and frequency domain point multiplication operation. The correlation value sequence is calculated by inverse fast Fourier transform after frequency domain point multiplication. At the same time, multiple groups of frequency domain PSS sequences with preset frequency offsets are detected in parallel to obtain a series of parallel segmented correlation value sequence groups. The calculation formula is as follows:

[0050] Y n,b (k) = FFT[y n,b (k)]

[0051]

[0052] Among them, y n,b (k) is the b-th block of data in the n-th path, Y n,b (k) is y n,b (k) is the frequency domain sequence, is the p-th (p=0,1,2) type PSS sequence with a preset frequency offset of f, for The frequency domain sequence, c n,b,f,p (k) is the segmented correlation value sequence of the b-th block data of the n-th channel to the p-th type PSS sequence with f preset frequency offset, FFT is fast Fourier transform, and IFFT is inverse fast Fourier transform.

[0053] S5: The first half of the correlation value sequence obtained by frequency domain block processing is affected by the aliasing error of circular convolution, so the first half of the mutual correlation sequence is discarded, and only the mutual correlation value output in the second half is retained. The mutual correlation sequence data blocks output from each of the n channels are cascaded and spliced ​​to obtain a continuous mutual correlation sequence output.

[0054] For c n,b,f,p (k) Since the second half of the 50% overlapping blocks is valid data, it is necessary to discard the first half of the sequence after each IFFT and keep the second half and splice them in sequence to obtain the correlation value sequence. The formula is as follows:

[0055]

[0056] in, is the first half of the sequence, is the second half of the sequence, C n,f,p (k) is the parallel correlation value sequence group after splicing.

[0057] S6: The n-channel parallel cross-correlation sequences are converted into a single-channel cross-correlation sequence by using a time-division multiplexing parallel-to-serial conversion module according to different delays. The time synchronization resolution of the single-channel cross-correlation sequence is improved compared with each channel sequence in the n channels.

[0058] The concatenated parallel correlation value sequence group is converted into a single-channel correlation value sequence group through parallel-to-serial conversion. The formula is as follows:

[0059] C f,p (k)=[C 1,f,p (0),C 2,θ,ω (0),…,C n,θ,ω (0),C 1,f,p (1),C 2,f,p (1),…,C n,f,p (1),…,C n,f,p (k)]

[0060] Among them, C f,p (k) is the sequence group after the parallel-to-serial conversion modules are combined. f,p (k) The correlation value sequence group performs parallel peak value threshold detection to obtain the synchronization point position and the size of the coarse frequency deviation.

[0061] S7: Detect the peak value of the single-channel cross-correlation sequence, complete the main synchronization signal detection, and obtain the synchronization point position and the coarse frequency deviation value.

[0062] Finally, through C f,p (k) The correlation value sequence group performs parallel peak value threshold detection to obtain the synchronization point position and the size of the coarse frequency deviation.

[0063] Based on the correlation between the cross-correlation operation and the frequency domain dot multiplication operation, the present invention adopts the overlapping frequency domain equalization method to perform core PSS detection, and performs multi-path parallel detection for extremely low signal-to-noise ratio and large Doppler frequency deviation scenarios in non-terrestrial network systems. The present invention is designed based on a 5G non-terrestrial network system and is suitable for all 5G non-terrestrial network systems. It can realize PSS detection and coarse frequency deviation estimation with extremely low complexity in a 5G non-terrestrial network system, and solves the problem that the traditional sliding cross-correlation algorithm is too complex in extremely low signal-to-noise ratio and large Doppler frequency deviation scenarios in a 5G non-terrestrial network system.

[0064] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system, characterized in that: The following steps are involved: S1: The terminal receives the signal and performs analog-to-digital conversion, and obtains the sampling point sequence to be detected through anti-aliasing filtering and downsampling; S2: Evenly extract the sampling point sequence to be detected in time division, complete the serial-to-parallel conversion, and obtain n parallel data, each of which has a different delay; S3: Perform frequency domain equalization on each data channel, and adopt 50% overlapping block processing, so that each data channel is converted into n blocks, and after the blocks are converted into the frequency domain by fast Fourier transform; S4: Based on the equivalence of time domain cross-correlation and frequency domain dot product operations, frequency domain equalization operation is performed on each block of data, and the time domain cross-correlation sequence of each block is obtained by inverse Fourier transform. There is a time delay relationship between the time domain cross-correlation sequences of n blocks of each data channel; S5: For each block of time domain mutual correlation sequence, discard the first half of the sequence and retain the second half of the sequence, then concatenate the second half of the sequences of n blocks of 1-way data into a correlation value sequence group to obtain an n-way parallel mutual correlation sequence group; S6: converting the n-way parallel cross-correlation sequence group into a single-way cross-correlation sequence by parallel-to-serial conversion according to different delays; S7: Detect the peak value of the single-channel cross-correlation sequence, complete the main synchronization signal detection, and obtain the synchronization point position and the coarse frequency deviation value.

2. A method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system according to claim 1, characterized in that: In step S2, the sequence of sampling points to be detected is uniformly time-divided and extracted in the following manner: Among them, y(m) is the sampling point sequence to be detected, m is the point in the sequence, and y n (k) is the nth data after serial-to-parallel conversion.

3. A method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system according to claim 1, characterized in that: In step S3, the specific method of using 50% overlapping block processing is: For each data channel, a data block is first taken according to the length of the fast Fourier transform window. The length of each subsequent data block is the length of the fast Fourier transform window, but the starting point of the data block is the center point of the previous data block, and 50% overlapping blocks are completed in sequence.

4. The method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system according to claim 1, characterized in that: The specific method of step S4 is: Frequency domain equalization is performed based on the equivalence of cross-correlation operation and frequency domain point multiplication operation. The cross-correlation sequence is calculated by inverse fast Fourier transform after frequency domain point multiplication. At the same time, multiple groups of frequency domain main synchronization signal sequences with preset frequency offsets are detected in parallel to obtain a series of parallel segmented correlation value sequence groups. The calculation formula is as follows: Y n,b (k)=FFT[y n,b (k)] Among them, y n,b (k) is the b-th block of data in the n-th path, Y n,b (k) is y n,b (k) is the frequency domain sequence, is the p-th type primary synchronization signal sequence with a preset frequency offset of f, p = 0, 1, 2, for The frequency domain sequence, c n,b,f,p (k) is a segmented correlation value sequence of the b-th block data of the n-th channel to the p-th type primary synchronization signal sequence with a preset frequency offset of f. FFT is a fast Fourier transform, and IFFT is an inverse fast Fourier transform.

5. A method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system according to claim 4, characterized in that: The correlation value sequence group in step S5 is: in, c b,n,f,p The second half of the sequence (k), C n,f,p (k) is the parallel correlation value sequence group after splicing.

6. A method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system according to claim 5, characterized in that: In step S6, the single-path cross-correlation sequence after parallel-to-serial conversion is: C f，p (k)=[C 1，f，p (0),C 2,θ，ω (0),…,C n，θ，ω (0),C 1，f， p(1), C 2，f，p (1),…,C n，f，p (1),…,C n，f，p (k)] Among them, C f，p (k) is the single-path cross-correlation sequence after parallel-to-serial conversion.

7. A method for joint detection of coarse frequency deviation and primary synchronization signal of a non-terrestrial network system according to claim 6, characterized in that: The specific method of step S7 is: By using the single-path cross-correlation sequence C f，p (k) Perform parallel peak value threshold detection to obtain the synchronization point position and the size of the coarse frequency deviation.

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