Signal Synchronization Method, Apparatus, Device, Medium and Product

Abstract

The present application provides a signal synchronization method, apparatus, device, medium and product. The method includes: performing preset coarse synchronization processing on a received signal to determine a coarse synchronization result corresponding to the received signal; based on the coarse synchronization result, performing preset fine synchronization processing on the received signal after the coarse synchronization processing by using a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result; the PSS and the SSS belong to the same synchronization signal block SSB time slot; the number of the first sub-signal segments is the same as the number of the second sub-signal segments; performing signal synchronization compensation on the received signal after the fine synchronization processing according to the fine synchronization result to complete signal synchronization. The method of the present application can effectively utilize the local characteristics of the synchronization signal through the correlation relationship characteristics between the first sub-signal segment of the PSS and the second sub-signal segment of the secondary synchronization signal SSS, and improve the synchronization accuracy in a low signal-to-noise ratio scenario.

Description

Technical Field

[0001] This application relates to the technical field of non-terrestrial network communication, and in particular, to a signal synchronization method, apparatus, device, medium, and product. Background Art

[0002] Currently, NTN (Non-Terrestrial Networks) can be used to provide wide-area coverage, enhance the capabilities of terrestrial networks, or provide communication services in areas with insufficient terrestrial infrastructure.

[0003] In the scenario of non-terrestrial networks such as satellite communication, the high-speed movement state of the transmitting end will generate a large Doppler frequency offset. During the signal reception process, generally, the receiving end will compensate for the Doppler frequency offset. However, if the signal-to-noise ratio is low, it will affect the accuracy of the Doppler frequency offset compensation value, thereby affecting the accuracy of signal synchronization.

[0004] Therefore, in the scenario of low signal-to-noise ratio, it is necessary to optimize the accuracy of signal synchronization. Summary of the Invention

[0005] This application provides a signal synchronization method, apparatus, device, medium, and product, which is used to optimize the accuracy of signal synchronization in the scenario of low signal-to-noise ratio.

[0006] The first aspect of this application provides a signal synchronization method, including:

[0007] Performing a preset coarse synchronization process on the received signal to determine the corresponding coarse synchronization result of the received signal;

[0008] Based on the coarse synchronization result, performing a preset fine synchronization process on the received signal after the coarse synchronization process by using a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result; the PSS and the SSS belong to the same synchronization signal block SSB time slot; the number of the first sub-signal segments is the same as the number of the second sub-signal segments;

[0009] Performing signal synchronization compensation on the received signal after the fine synchronization process according to the fine synchronization result to complete signal synchronization.

[0010] Further, in the method as described above, the performing a preset coarse synchronization process on the received signal to determine the corresponding coarse synchronization result of the received signal includes:

[0011] Compensating the received signal according to each preset frequency offset to generate a corresponding compensated received signal;

[0012] Input each of the compensated received signals, the PSS, and the SSS into a first preset correlation operation algorithm to determine corresponding correlation operation results based on the first preset correlation operation algorithm;

[0013] If the maximum value among all the correlation operation results is greater than a preset threshold, then determine the preset frequency offset corresponding to the maximum value and the corresponding time offset as the coarse synchronization result.

[0014] Further, in the method as described above, perform a preset fine synchronization process on the received signal after coarse synchronization processing based on a first sub-signal segment of the pre-stored primary synchronization signal PSS and a second sub-signal segment of the pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result, including:

[0015] Determine a first correlation relationship feature between each third sub-signal segment and the corresponding first sub-signal segment; the third sub-signal segment is obtained by dividing the received signal after coarse synchronization processing; the number of the third sub-signal segments is the same as the number of the first sub-signal segment and the second sub-signal segment;

[0016] Determine a second correlation relationship feature between each of the third sub-signal segments and the corresponding second sub-signal segment;

[0017] Determine the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features;

[0018] Determine the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment.

[0019] Further, in the method as described above, the coarse synchronization result includes a coarse synchronization time offset;

[0020] The determining the first correlation relationship feature between the third sub-signal segment and the corresponding first sub-signal segment includes:

[0021] Determine a plurality of candidate time offsets; the candidate time offsets are based on the coarse synchronization time offset;

[0022] Input the candidate time offsets, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment into a second preset correlation operation algorithm to generate the first correlation relationship feature corresponding to the candidate time offset based on the second preset correlation operation algorithm.

[0023] Further, in the method as described above, the determining the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features includes:

[0024] For each candidate time offset, calculate the sum between each corresponding first correlation relationship feature and each corresponding second correlation relationship feature;

[0025] Determine the candidate time offset corresponding to the maximum value of each of the sums as the moment of fine timing synchronization.

[0026] Further, in the method as described above, the determining the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment includes:

[0027] Determine the third correlation relationship characteristics between each of the third sub-signal segments and the corresponding second sub-signal segments;

[0028] Input each of the third correlation relationship characteristics into a third preset correlation operation algorithm to determine the fourth correlation relationship characteristics between each of the third correlation relationship characteristics based on the third preset correlation operation algorithm;

[0029] Determine the fifth correlation relationship characteristics between the second correlation relationship characteristics and the first correlation relationship characteristics;

[0030] Determine the frequency offset of the fine timing synchronization according to the fourth correlation relationship characteristics and the fifth correlation relationship characteristics.

[0031] Further, in the method as described above, the determining the fifth correlation relationship characteristics between the second correlation relationship characteristics and the first correlation relationship characteristics includes:

[0032] Input the second correlation relationship characteristics and the first correlation relationship characteristics in the same inverse fast Fourier transform (IFFT) point number region into a fourth preset correlation operation algorithm to generate the corresponding fifth correlation relationship characteristics.

[0033] Further, in the method as described above, the determining the frequency offset of the fine timing synchronization according to the fourth correlation relationship characteristics and the fifth correlation relationship characteristics includes:

[0034] Perform phase conversion processing on the fourth correlation relationship characteristics to generate the corresponding first phase parameter;

[0035] Perform phase conversion processing on the fifth correlation relationship characteristics to generate the corresponding intermediate phase parameter;

[0036] Perform averaging processing on the intermediate phase parameter to generate the corresponding second phase parameter;

[0037] Perform weighted summation on the first phase parameter and the second phase parameter to generate the frequency offset of the fine timing synchronization.

[0038] The second aspect of the present application provides a signal synchronization device, including:

[0039] A coarse synchronization module for performing a preset coarse synchronization process on the received signal to determine the coarse synchronization result corresponding to the received signal;

[0040] A fine synchronization module, which is used to perform preset fine synchronization processing on the received signal after coarse synchronization processing based on a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS, and generate a corresponding fine synchronization result; the PSS and the SSS belong to the same synchronization signal block SSB time slot; the number of the first sub-signal segments is the same as the number of the second sub-signal segments;

[0041] A signal synchronization module, which is used to perform signal synchronization compensation on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

[0042] Further, for the device as described above, the coarse synchronization module is specifically used for:

[0043] Compensate the received signal according to each preset frequency offset to generate a corresponding compensated received signal; input each of the compensated received signals, the PSS, and the SSS into a first preset correlation operation algorithm to determine a corresponding correlation operation result based on the first preset correlation operation algorithm; if the maximum value among all the correlation operation results is greater than a preset threshold value, then determine the preset frequency offset corresponding to the maximum value and the corresponding time offset as the coarse synchronization result.

[0044] Further, for the device as described above, when the fine synchronization module performs preset fine synchronization processing on the received signal after coarse synchronization processing based on a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result, it is specifically used for:

[0045] Determine a first correlation relationship feature between each third sub-signal segment and the corresponding first sub-signal segment; the third sub-signal segment is obtained by dividing the received signal after coarse synchronization processing; the number of the third sub-signal segments is the same as the number of the first sub-signal segments and the second sub-signal segments; determine a second correlation relationship feature between each third sub-signal segment and the corresponding second sub-signal segment; determine the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features; determine the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment.

[0046] Further, for the device as described above, the coarse synchronization result includes a coarse synchronization time offset;

[0047] When the fine synchronization module determines the first correlation relationship feature between the third sub-signal segment and the corresponding first sub-signal segment, it is specifically used for:

[0048] Determine multiple candidate time offsets; the candidate time offsets are based on the coarse synchronization time offset; input the candidate time offsets, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment into a second preset correlation operation algorithm to generate the first correlation relationship feature corresponding to the candidate time offset based on the second preset correlation operation algorithm.

[0049] Further, for the device as described above, when the fine synchronization module determines the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features, it is specifically configured to:

[0050] For each candidate time offset, calculate the sum between each corresponding first correlation relationship feature and each corresponding second correlation relationship feature; determine the candidate time offset corresponding to the maximum value of each of the sums as the moment of fine timing synchronization.

[0051] Further, for the device as described above, when the fine synchronization module determines the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment, it is specifically configured to:

[0052] Determine the third correlation relationship feature between each of the third sub-signal segments and the corresponding second sub-signal segment; input each of the third correlation relationship features into a third preset correlation operation algorithm to determine the fourth correlation relationship feature between each of the third correlation relationship features based on the third preset correlation operation algorithm; determine the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature; determine the frequency offset of the fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature.

[0053] Further, for the device as described above, when the fine synchronization module determines the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature, it is specifically configured to:

[0054] Input the second correlation relationship feature and the first correlation relationship feature in the point region of the same inverse fast Fourier transform (IFFT) into a fourth preset correlation operation algorithm to generate the corresponding fifth correlation relationship feature.

[0055] Further, for the device as described above, when the fine synchronization module determines the frequency offset of the fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature, it is specifically configured to:

[0056] Perform phase conversion processing on the fourth correlation relationship feature to generate a corresponding first phase parameter; perform phase conversion processing on the fifth correlation relationship feature to generate a corresponding intermediate phase parameter; perform averaging processing on the intermediate phase parameter to generate a corresponding second phase parameter; perform weighted summation on the first phase parameter and the second phase parameter to generate the frequency offset of the fine timing synchronization.

[0057] A third aspect of the present application provides a communication device, including: a memory and a processor;

[0058] The memory stores computer-executable instructions;

[0059] The processor executes the computer-executable instructions stored in the memory to implement the signal synchronization method according to any one of the first aspects.

[0060] A fourth aspect of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, they are used to implement the signal synchronization method according to any one of the first aspects.

[0061] A fifth aspect of the present application provides a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the signal synchronization method according to any one of the first aspects.

[0062] A signal synchronization method, device, equipment, medium and product provided by the present application, the method includes: performing a preset coarse synchronization process on a received signal to determine a coarse synchronization result corresponding to the received signal; based on the coarse synchronization result, performing a preset fine synchronization process on the received signal after the coarse synchronization process based on a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result; the PSS and the SSS belong to the same synchronization signal block SSB time slot; the number of the first sub-signal segments is the same as the number of the second sub-signal segments; performing signal synchronization compensation on the received signal after the fine synchronization process according to the fine synchronization result to complete signal synchronization. The signal synchronization method of the present application can effectively utilize the local characteristics of the synchronization signal through the correlation relationship characteristics between the first sub-signal segment of the PSS, the second sub-signal segment of the secondary synchronization signal SSS and the received signal, and improve the synchronization accuracy in a low signal-to-noise ratio scenario. Description of the Drawings

[0063] The drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0064] Figure 1 It is a schematic diagram of an application scenario of the signal synchronization method provided by the present application;

[0065] Figure 2 It is a flowchart of the signal synchronization method provided by the present application Figure 1 ;

[0066] Figure 3 It is a flowchart of the signal synchronization method provided by the present application Figure 2 ;

[0067] Figure 4a Schematic diagram of half frame provided for this application;

[0068] Figure 4b Schematic diagram of frame structure provided for this application;

[0069] Figure 4c Schematic diagram of time slot structure provided for this application;

[0070] Figure 4d Schematic diagram of SSB time slot provided for this application;

[0071] Figure 4e Schematic diagram of Data time slot provided for this application;

[0072] Figure 5a Schematic diagram of data symbol transmission process provided for this application;

[0073] Figure 5b Schematic diagram of amplitude-frequency response of transmit filter provided for this application;

[0074] Figure 5c Schematic diagram of signal processing process at receiving end provided for this application;

[0075] Figure 5d Schematic diagram of amplitude-frequency response of receive filter;

[0076] Figure 5e Schematic diagram of decoding process provided for this application;

[0077] Figure 6 Schematic diagram of capture probability curve provided for this application;

[0078] Figure 7 Schematic diagram of frequency offset estimation error curve provided for this application

[0079] Figure 8 Schematic diagram of bit error rate curve provided for this application;

[0080] Figure 9 Schematic diagram of structure of signal synchronization device provided for this application;

[0081] Figure 10 Schematic diagram of structure of communication device provided for this application.

[0082] Through the above-mentioned drawings, specific embodiments of this application have been shown, and there will be more detailed descriptions hereinafter. These drawings and written descriptions are not intended to limit the scope of the concept of this application in any way, but to illustrate the concept of this application to those skilled in the art by referring to specific embodiments. Detailed implementation manners

[0083] Exemplary embodiments will be described in detail herein, and examples thereof are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0084] Technical term explanation:

[0085] The Secondary Synchronization Signal (SSS) is one of the key signals in a communication network and is used for signal synchronization by a receiving device.

[0086] The Primary Synchronization Signal (PSS) is one of the key signals in a communication network and is used for signal synchronization by a receiving device, mainly for downlink frame synchronization.

[0087] The Synchronization Signal and PBCH block (SSB) is a key component in a communication network and is used to implement functions such as cell search, timing and frequency synchronization, location and mobility management, and access and measurement.

[0088] The technical solution of the present application will be described in detail below with specific embodiments. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0089] To clearly understand the technical solution of the present application, the conceptual process of the technical solution will be introduced in detail first. In the scenario of non-terrestrial networks such as satellite communication, due to the high-speed movement and frequent handovers of satellites relative to the ground, the large time delay of the link and the instability of the channel are more prominent compared to the terrestrial communication scenario. The relatively high-speed movement between the satellite and terrestrial communication devices such as terminals will generate a large Doppler frequency shift, thus seriously affecting the reception and processing of signals.

[0090] In the related art, for the Doppler frequency shift caused by satellite motion, corresponding compensation is performed at the transmitting end or the receiving end to reduce the influence of the Doppler effect on the decoding of the received signal. Since it is difficult to perform compensation at the transmitting end, the main compensation means are basically concentrated at the receiving end. In the frequency offset compensation of the related art, the ability to correct the Doppler frequency offset is weak, especially in scenarios with a low signal-to-noise ratio. Due to the high-speed relative motion between the satellite and the terminal, the Doppler effect will occur, resulting in a shift in the carrier frequency of the received signal. Currently, the receiving terminal usually relies on the PSS signal and the SSS signal for frequency offset estimation. Using only the PSS signal or only the SSS signal for frequency offset estimation may not fully utilize all available synchronization signal information, resulting in problems such as an insufficient frequency offset estimation range and a large residual frequency offset, thereby affecting the decoding performance. In addition, since the PSS signal and the SSS signal sequences are both short, performing the overall cross-correlation using only the PSS and SSS in the same SSB time slot is very susceptible to interference from random noise and distortion under low signal-to-noise conditions, which may also lead to problems such as an insufficient frequency offset estimation range and a large residual frequency offset.

[0091] At the same time, the frequency offset compensation in the related art needs to rely on ephemeris information. The satellite needs to send ephemeris information to the ground terminal, and then the ground terminal performs pre-compensation for the Doppler frequency deviation based on the obtained information and then performs frequency offset estimation and correction. This process needs to rely on ephemeris information to correct a large Doppler frequency offset, which will make the design of the actual system very complex.

[0092] In addition, the frequency offset compensation in the related art is sensitive to the time synchronization deviation of the system. Using only the PSS signal or the SSS signal for fine frequency offset estimation requires a high time synchronization performance of the system. If the synchronization performance of the system is not good, it may lead to a decrease in the reception quality of the PSS signal, thereby affecting the accuracy of the fine frequency offset estimation. In addition, the time synchronization deviations in different SSB time slots may be different, which will also bring large errors and interference to the cross-correlation operation results of the PSS or SSS in different SSB time slots, thus deteriorating the frequency offset estimation performance.

[0093] Therefore, in scenarios with a low signal-to-noise ratio, it is necessary to optimize the accuracy of signal synchronization.

[0094] Therefore, aiming at the problem that in the prior art, in scenarios with a low signal-to-noise ratio, it is necessary to optimize the accuracy of signal synchronization, the inventor found in the research that based on the first sub-signal segment of the PSS, the second sub-signal segment of the secondary synchronization signal SSS, and the correlation relationship characteristics of the received signal, the local characteristics of the synchronization signal can be effectively utilized to improve the accuracy of synchronization under low signal-to-noise conditions.

[0095] Specifically, the signal synchronization process is as follows:

[0096] Perform preset coarse synchronization processing on the received signal to determine the coarse synchronization result corresponding to the received signal.

[0097] Based on the coarse synchronization result, the received signal after the coarse synchronization processing is subjected to preset fine synchronization processing based on the first sub-signal segment of the pre-stored primary synchronization signal PSS and the second sub-signal segment of the pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result. PSS and SSS belong to the same synchronization signal block SSB time slot. The number of the first sub-signal segments is the same as the number of the second sub-signal segments.

[0098] Signal synchronization compensation is performed on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

[0099] The signal synchronization method of the present application can effectively utilize the local characteristics of the synchronization signal through the correlation characteristics between the first sub-signal segment of the PSS, the second sub-signal segment of the auxiliary synchronization signal SSS, and the received signal, thereby improving the synchronization accuracy in low signal-to-noise ratio scenarios.

[0100] Based on the above creative findings, the inventor proposed the technical solution of the present application.

[0101] The following describes the application scenarios of the signal synchronization method provided in the embodiments of the present application. Figure 1 As shown, the figure exemplarily shows a receiving end device 1 and a sending end device 2. The receiving end device 1 and the sending end device 2 are communication devices in a non-terrestrial network, such as satellite network devices, gateways, user terminals, etc.

[0102] Exemplarily, in this embodiment, the sending end device 2 is a satellite network device, and the receiving end device 1 is a user terminal.

[0103] The sending device 2 transmits a signal to the receiving device 1, that is, ① transmits a signal to the receiving end, and the receiving device 1 provides feedback on the reception of the initial data packet, that is, ① transmits a feedback message. At this time, the receiving device 1 performs the following process:

[0104] ②Perform preset coarse synchronization processing on the received signal to determine the coarse synchronization result corresponding to the received signal.

[0105] ③ Based on the coarse synchronization result, the received signal after the coarse synchronization processing is subjected to preset fine synchronization processing based on the first sub-signal segment of the pre-stored main synchronization signal PSS and the second sub-signal segment of the pre-stored secondary synchronization signal SSS to generate the corresponding fine synchronization result.

[0106] ④ Perform signal synchronization compensation on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

[0107] Other subsequent processes for data reception can be carried out after signal synchronization, which are not limited in this embodiment.

[0108] The embodiments of the present application will be introduced below with reference to the accompanying drawings of the specification.

[0109] Figure 2 It is a flowchart of the signal synchronization method provided by the present application Figure 1 , such as Figure 2 shown, the execution subject of the embodiment of the present application is a signal synchronization device, and this signal synchronization device can be integrated in a communication device, such as a user terminal. Then, the signal synchronization method provided in this embodiment includes the following steps:

[0110] Step S101, perform a preset rough synchronization process on the received signal to determine the rough synchronization result corresponding to the received signal.

[0111] In some embodiments, the preset rough synchronization process can adopt common rough synchronization processing methods, such as only using the PSS signal for rough synchronization, or other preset rough synchronization processing methods, such as combining the PSS signal and the SSS signal to perform a correlation operation with the received signal and perform summation and normalization operations to complete rough synchronization.

[0112] The rough synchronization result includes the rough synchronization frequency offset, the rough timing synchronization position or the so-called rough synchronization time offset, and subsequent fine synchronization processing can be performed based on the rough synchronization time offset and the rough synchronization frequency offset.

[0113] Step S102, based on the rough synchronization result, perform a preset fine synchronization process on the received signal after rough synchronization processing by using the first sub-signal segment of the pre-stored primary synchronization signal PSS and the second sub-signal segment of the pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result. The PSS and the SSS belong to the same synchronization signal block SSB time slot. The number of the first sub-signal segments is the same as the number of the second sub-signal segments.

[0114] In this embodiment, fine synchronization processing is performed based on the rough synchronization result. For example, the synchronization position of fine synchronization can be searched in a relatively small window before and after the rough timing synchronization position, and the frequency offset of fine synchronization can be found in a relatively small frequency offset range before and after the rough synchronization frequency offset.

[0115] The first sub-signal segment is a sub-signal segment generated after dividing the primary synchronization signal PSS, and the second sub-signal segment is a sub-signal segment generated after dividing the secondary synchronization signal SSS. Among them, the number of the first sub-signal segments is the same as the number of the second sub-signal segments, which is convenient for subsequent preset fine synchronization processing of the received signal after rough synchronization processing by using the first sub-signal segment of the pre-stored primary synchronization signal PSS and the second sub-signal segment of the pre-stored secondary synchronization signal SSS. For example, fine synchronization processing can be performed through the correlation relationship characteristics among the first sub-signal segment, the second sub-signal segment, and the received signal.

[0116] Step S103: Perform signal synchronization compensation on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

[0117] In this embodiment, based on the fine synchronization result such as fine synchronization time offset and fine synchronization frequency offset, corresponding signal synchronization compensation is performed on the received signal to complete signal synchronization. After signal synchronization is completed, subsequent signal reception-related processing can be performed, such as channel estimation, channel equalization, soft demodulation, deinterleaving, channel decoding, and other processes.

[0118] A signal synchronization method provided by an embodiment of the present application includes: performing preset coarse synchronization processing on a received signal to determine a corresponding coarse synchronization result of the received signal. Based on the coarse synchronization result, performing preset fine synchronization processing on the received signal after coarse synchronization processing based on a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result. PSS and SSS belong to the same synchronization signal block SSB time slot. The number of the first sub-signal segments is the same as the number of the second sub-signal segments. Perform signal synchronization compensation on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

[0119] The signal synchronization method of the present application can effectively utilize the local characteristics of the synchronization signal through the correlation relationship characteristics between the first sub-signal segment of PSS and the second sub-signal segment of the secondary synchronization signal SSS, and improve the synchronization accuracy in low signal-to-noise ratio scenarios.

[0120] Figure 3 It is a flowchart of the signal synchronization method provided by the present application Figure 2 , such as Figure 3 shown, the signal synchronization method provided in this embodiment is a further refinement based on the signal synchronization method provided in the previous embodiment of the present application. The signal synchronization method provided in this embodiment includes the following steps.

[0121] Step S201: Compensate the received signal according to each preset frequency offset to generate a corresponding compensated received signal.

[0122] In this embodiment, the preset frequency offset can be set according to frequency offset segments. For example, the preset frequency band can be divided into multiple small segments, and the starting frequency offset or the ending frequency offset of each small segment can be set as the preset frequency offset.

[0123] Exemplarily, assume that the preset frequency band is -60KHz to 60KHz, which can be divided into multiple small segments every 10KHz, i.e., -60KHz to -51KHz, -50KHz to -41KHz, etc. The preset frequency offset can be -60 kHz, -50 kHz, -40 kHz, -30kHz, -20 kHz, -10 kHz, 0 kHz, 10 kHz, 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz.

[0124] Step S202: Input each compensated received signal, PSS, and SSS into a first preset correlation operation algorithm to determine the corresponding correlation operation result based on the first preset correlation operation algorithm.

[0125] In this embodiment, the first preset correlation operation algorithm is as follows:

[0126]

[0127] Where S PSS * (k) and S SSS * (k) represent the time-domain waveforms of the local PSS synchronization signal and the local SSS synchronization signal pre-stored at the receiving end, such as the user terminal. P n (Δ) represents the sum of the results after performing correlation operations on S PSS * (k) and S SSS * (k) with the received signal sequences r n (k + Δ) and r n (K + k + Δ) respectively (the subscript n represents the nth group of frequency offset compensation). Δ represents the time offset of the received signal, and the denominator represents the energy of the corresponding part of the received signal, which is used to normalize the result of the correlation operation. k represents the moment, and K represents the maximum moment.

[0128] Find the maximum value of each Pn sequence. If the maximum value is greater than the preset threshold, it is considered that the PSS signal has arrived. That is: , where Th is the preset threshold.

[0129] At this time, the frequency offset corresponding to the maximum value is the result of the coarse synchronization frequency offset estimation, and the time offset Δ corresponding to the maximum value is the detected offset of the initial symbol timing synchronization. Optionally, in order to reduce the influence of the multipath channel, window summation processing can be performed on the correlation values, and then the maximum value is obtained.

[0130] Step S203: If the maximum value among all the correlation operation results is greater than the preset threshold, determine the preset frequency offset corresponding to the maximum value and the corresponding time offset as the coarse synchronization result.

[0131] In this embodiment, the preset threshold value can be set accordingly according to actual applications, and this embodiment does not limit this. At the same time, as described in the foregoing S202, if the maximum value among all relevant operation results is greater than the preset threshold value, the preset frequency offset corresponding to the maximum value is the result of the coarse synchronization frequency offset estimation, and the time offset corresponding to the maximum value is the detected offset of the initial symbol timing synchronization. Therefore, the preset frequency offset corresponding to the maximum value and the corresponding time offset can be determined as the coarse synchronization result.

[0132] Compared with the related art where only the PSS signal is used for coarse synchronization, the method of this embodiment combines the PSS signal and the SSS signal to perform a correlation operation with the received signal and perform summation and normalization operations for coarse time-frequency synchronization, thereby effectively improving the accuracy of coarse timing synchronization and increasing the range and accuracy of coarse frequency offset estimation.

[0133] The coarse frequency offset estimation of the method of this embodiment adopts the method of frequency offset sub-region estimation and compensation, which greatly increases the range of coarse frequency offset estimation and can effectively get rid of the dependence on the ephemeris file for most Doppler frequency deviation estimations. In the complex communication environment of non-terrestrial networks, by performing sub-region compensation processing on the frequency offset according to the numerical value, this method can more accurately estimate and compensate the frequency deviation, thereby improving the performance of the communication system. The basic idea of sub-region estimation is to divide the Doppler frequency deviation into multiple intervals according to the numerical value, and then perform frequency pre-compensation on the received signal according to the starting frequency deviation of each interval, so as to obtain multiple groups of received signals after different pre-compensations. Thereafter, the Doppler frequency offset is judged to be in which interval by judging the peak value of the sliding correlation operation between the PSS signal and the SSS signal and the signals after different frequency deviation pre-compensations. The advantage of this is that it can increase the range of coarse frequency deviation estimation, reduce the difficulty of fine frequency offset estimation, and improve the accuracy and robustness of the estimation.

[0134] Step S204, based on the coarse synchronization result, perform a preset fine synchronization process on the received signal after coarse synchronization processing based on the first sub-signal segment of the pre-stored primary synchronization signal PSS and the second sub-signal segment of the pre-stored secondary synchronization signal SSS, and generate a corresponding fine synchronization result.

[0135] In this embodiment, since the coarse timing synchronization has completed a relatively accurate timing window, during fine timing synchronization, relevant searches are only performed within a relatively small window before and after the coarse timing synchronization position.

[0136] Optionally, in this embodiment, S204 can be specifically as follows:

[0137] Determine the first correlation relationship feature between each third sub-signal segment and the corresponding first sub-signal segment. The third sub-signal segment is obtained by dividing the received signal after rough synchronization processing. The number of third sub-signal segments is the same as the number of first sub-signal segments and second sub-signal segments. Among them, the third sub-signal segment can be obtained by dividing some received signals with frequency offset compensation performed in advance during the rough synchronization process, or by dividing the received signals corresponding to the rough synchronization frequency offset in the rough synchronization result.

[0138] Determine the second correlation relationship feature between each third sub-signal segment and the corresponding second sub-signal segment.

[0139] Determine the timing of fine timing synchronization according to each first correlation relationship feature and each second correlation relationship feature.

[0140] Determine the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment.

[0141] In this embodiment, there is a one-to-one correspondence between the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment. Exemplarily, the primary synchronization signal PSS is divided into 10 first sub-signal segments, the secondary synchronization signal SSS is divided into 10 second sub-signal segments, and the received signal is divided into 10 third sub-signal segments, where the first first sub-signal segment, the first second sub-signal segment, and the first third sub-signal segment correspond. Optionally, the lengths of the first first sub-signal segment, the first second sub-signal segment, and the first third sub-signal segment are the same.

[0142] Optionally, in this embodiment, the rough synchronization result includes the rough synchronization time offset. The process of determining the first correlation relationship feature between the third sub-signal segment and the corresponding first sub-signal segment can be specifically as follows:

[0143] Determine multiple candidate time offsets. The candidate time offsets are based on the rough synchronization time offset.

[0144] Input the candidate time offsets, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment into the second preset correlation operation algorithm to generate the first correlation relationship feature corresponding to the candidate time offsets based on the second preset correlation operation algorithm.

[0145] In this embodiment, since the rough timing synchronization has completed a relatively accurate timing window, during the fine timing synchronization, the correlation search is only performed within a small window before and after the rough timing synchronization position. The above candidate time offsets are the time offsets selected within a small window before and after the rough timing synchronization position.

[0146] In this embodiment, the second preset correlation operation algorithm changes accordingly according to the number of segments of the first sub-signal segment. If the number of segments is two, the second preset correlation operation algorithm is specifically as follows:

[0147]

[0148]

[0149] Among them, Abs1(k) is the first correlation relationship feature between the first sub-signal and the third sub-signal segment of the first segment, Abs3(k) is the first correlation relationship feature between the first sub-signal and the third sub-signal segment of the second segment, N S represents the number of points of IFFT (Inverse Fast Fourier Transform), r(k) is the third sub-signal segment, k is the candidate timing offset, and other parameters are the same as those in the foregoing algorithm.

[0150] Correspondingly, the method for determining the second correlation relationship feature between each third sub-signal segment and the corresponding second sub-signal segment is similar to the method for determining the first correlation relationship feature, and can also be calculated by using a preset correlation operation algorithm. The specific algorithm is as follows:

[0151]

[0152]

[0153] Among them, Abs2(k) is the second correlation relationship feature between the second sub-signal and the third sub-signal segment of the first segment, Abs4(k) is the second correlation relationship feature between the second sub-signal and the third sub-signal segment of the second segment, 1024 is the number of points of IFFT, and 72 is the length of the cyclic prefix (CP, Cyclic Prefix). The number of points of IFFT and the length of CP can be changed according to actual applications. 2 means performing cross-correlation every other symbol, and other parameters are the same as those in the foregoing algorithm.

[0154] If the number of segments of the above-mentioned preset correlation operation algorithm and the second preset correlation operation algorithm is 3 segments, it includes three algorithms; if the number of segments is n segments, it includes n algorithms. This embodiment only exemplarily describes the situation in the 2-segment scenario.

[0155] Optionally, in this embodiment, the process of determining the timing synchronization moment according to each first correlation relationship feature and each second correlation relationship feature can be specifically as follows:

[0156] For each candidate timing offset, calculate the sum between each corresponding first correlation relationship feature and each corresponding second correlation relationship feature.

[0157] Determine the candidate timing offset corresponding to the maximum value of each sum as the timing synchronization moment.

[0158] In this embodiment, calculating the sum between each corresponding first correlation relationship feature and each corresponding second correlation relationship feature can be expressed as the following expression:

[0159]

[0160] When Abs(k) reaches the maximum value, the corresponding candidate timing offset is the moment of precise timing synchronization.

[0161] Optionally, in this embodiment, the process of determining the frequency offset of precise timing synchronization based on the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment may be specifically as follows:

[0162] Determine the third correlation relationship features between each third sub-signal segment and the corresponding second sub-signal segment.

[0163] Input each third correlation relationship feature into a third preset correlation operation algorithm to determine the fourth correlation relationship features between each third correlation relationship feature based on the third preset correlation operation algorithm.

[0164] Determine the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature.

[0165] Determine the frequency offset of precise timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature.

[0166] In this embodiment, the third preset correlation operation algorithm is specifically as follows:

[0167]

[0168] Among them, P ’ SSS represents the fourth correlation relationship feature, and other parameters are the same as those in the foregoing algorithm.

[0169] Optionally, in this embodiment, the process of determining the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature may be specifically as follows:

[0170] Input the second correlation relationship feature and the first correlation relationship feature in the same inverse fast Fourier transform (IFFT) point number region into a fourth preset correlation operation algorithm to generate the corresponding fifth correlation relationship feature.

[0171] In this embodiment, if the second correlation relationship feature corresponds to two sub-signal segments, the fourth preset correlation operation algorithm may be specifically as follows:

[0172]

[0173]

[0174] Among them, P1 is the fifth correlation relationship feature of the point number region corresponding to the first segment, P2 is the fifth correlation relationship feature of the point number region corresponding to the second segment, and other parameters are the same as those in the foregoing algorithm.

[0175] Optionally, in this embodiment, determining the frequency offset of precise timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature includes:

[0176] Performing a phase transformation process on the fourth correlation relationship feature to generate a corresponding first phase parameter.

[0177] Performing a phase transformation process on the fifth correlation relationship feature to generate a corresponding intermediate phase parameter.

[0178] Performing an averaging process on the intermediate phase parameter to generate a corresponding second phase parameter.

[0179] Performing a weighted summation on the first phase parameter and the second phase parameter to generate the frequency offset of precise timing synchronization.

[0180] In this embodiment, the first phase parameter , where P can be the fourth correlation relationship feature or a feature obtained by omitting some data from the fourth correlation relationship feature. The second phase parameter is . The frequency offset of precise timing synchronization is , where α is a weight factor between 0 and 1. Optimizing this weight factor will affect the effect of precise frequency offset estimation, and it can be continuously optimized according to actual applications to obtain the optimal value.

[0181] The specific calculation process is as follows:

[0182] Assume that there is a carrier frequency deviation of Δf between the transmitter and the receiver. Without considering noise, the received signal can be expressed in the following form:

[0183]

[0184] where T S represents the sampling interval, N S represents the number of points of IFFT, S(k) is the transmitted signal, and j represents the imaginary symbol. Substituting into the third preset correlation operation algorithm, we can obtain:

[0185]

[0186] where S SSS (k) represents the time-domain waveform of the SSS synchronization signal transmitted by the transmitter, and other parameters are the same as those in the foregoing algorithm.

[0187] Assume that α(k) = S SSS (k)*S SSS *(k). Here, α(k) is a real number, then:

[0188]

[0189] Analyze The operation result, expand the summation terms, and then perform cross multiplication. Then the corresponding terms and The result of multiplication is a real number, denoted as . While the results of cross multiplication of other terms are complex random variables, and there are a total of terms. Let each term be expressed as . Then the above formula can be expressed as:

[0190]

[0191]

[0192] The latter term is the result of superposition of a large number of complex random variables and can be considered as a Gaussian random variable. Then only consider the former term

[0193]

[0194] Introduce the phase parameter , then the estimation of the frequency deviation based on the autocorrelation of the SSS signal before and after is:

[0195]

[0196] After that, we divide the PSS signal and the SSS signal into two identical signal sequences before and after respectively, and then perform cross-correlation operations on the first half of the PSS signal and the first half of the SSS signal, and on the second half of the PSS signal and the second half of the SSS signal, to obtain the aforementioned P1 and P2.

[0197] After some mathematical transformations, we can further obtain the following expressions:

[0198]

[0199]

[0200] where S PSS (k) represents the time-domain waveform of the PSS synchronization signal sent by the transmitter, and other parameters are the same as those of the aforementioned algorithm.

[0201] After organizing the above two formulas, we can obtain:

[0202]

[0203]

[0204] Introduce the principal value of the phase parameter , and the estimated value of the frequency deviation based on the cross-correlation of the first half and the second half of the PSS signal and the SSS signal can be obtained as:

[0205]

[0206] Combined with and and the weight factor α, the final fine-timed synchronous frequency offset can be obtained.

[0207] In the fine synchronization stage of the method of this embodiment, the first estimation of the frequency deviation is performed by using the mutual relationship characteristics between all sub-segments of the segmented PSS signal and all corresponding sub-segments of the segmented SSS signal, and then the second estimation of the frequency deviation is performed by using the similarity characteristics between all sub-segments of the segmented SSS signal and the received signal and the mutual relationship characteristics of the corresponding sub-segments. By multiplying the results of the two estimations by different dynamic weight factors and then adding them together, the final fine synchronization estimated frequency offset is obtained. Note that the sum of the two weight factors is 1, and optimizing the values of these two weight factors will effectively increase the accuracy of the fine frequency offset estimation.

[0208] Step S205: Perform signal synchronization compensation on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

[0209] In this embodiment, after signal synchronization, the subsequent process of receiving and processing the signal can continue.

[0210] The subsequent process can be as follows:

[0211] First, perform FFT (Fast Fourier Transform) on the OFDM (Orthogonal Frequency Division Multiplexing) symbol where the DMRS (Demodulation Reference Signal) is placed. Extract the received signal at the pilot position in the frequency domain, and combined with the DMRS reference signal, perform frequency domain LS (Least Squares) estimation to obtain the estimated channel gain as H LS (k) = Y(k) / P(k).

[0212] where P(k) is the frequency domain sequence of the DMRS. After channel estimation, in order to further reduce the influence of channel estimation noise and improve the accuracy of channel estimation, first estimate the frequency domain response of the guard band sub-carriers by means of extrapolation to obtain the channel frequency domain response H ’ LS (k) of the entire frequency band. Then, convert it to the time domain through IFFT, and the following expression can be obtained:

[0213]

[0214] For the obtained channel time-domain impulse response, the influence of noise is reduced by windowing, that is, only the head and tail parts of the obtained time-domain response are taken, and the middle part is set to zero (the middle part can be considered as noise). Then, the windowed channel time-domain response is subjected to FFT transformation to the frequency domain to obtain the frequency-domain response. Finally, the channel is smoothed in the frequency domain to obtain the channel estimation value H(k) for channel equalization. The average window length is 5 (configurable), and the optimized smoothing method in this embodiment is as follows:

[0215]

[0216] The noise power can be estimated from the channel responses before and after smoothing. The specific method for estimating the noise power is as follows:

[0217]

[0218] MMSE equalization algorithm is used for channel equalization. According to the algorithm theory of MMSE, we can obtain the equalization coefficients as follows:

[0219]

[0220] After that, further MMSE equalization compensation is performed on the signal, and the equalized signal is as follows:

[0221]

[0222] Soft information is extracted from the equalized signal according to the characteristics of QPSK (Quadrature Phase Shift Keying) modulation:

[0223]

[0224]

[0225] The soft demodulated information is first deinterleaved. Since under the harsh conditions of low signal-to-noise ratio and multipath, soft information is prone to misjudgment, and statistically, the probability that the soft information of two bits is misjudged simultaneously becomes smaller. Therefore, in this embodiment, the average of two adjacent deinterleaved soft information is taken, which can improve the reliability of the soft information. That is:

[0226] ,

[0227] where LLR’(n) is the soft information after despreading.

[0228] Turbo decoding is performed according to the soft information extracted from the equalized signal.

[0229] The soft information extracted during channel equalization is divided into soft information of information bits Sum check bit soft , the check bit information is further divided into check information 1, and check information 2, y 2p .

[0230] Component decoder 1 utilizes the soft information of information bits and check information 1, , to extract extrinsic information L 12 e . After interleaving the extrinsic information, it serves as the prior information for component decoder 2.

[0231] Component decoder 2 utilizes the interleaved information bit information, check information 2, y 2p , and the extrinsic information provided by decoder 1 as prior information to calculate the posterior probability information L(u n ) and extrinsic information L 21 e . The extrinsic information calculated by component decoder 2 is deinterleaved and provided as prior information to component decoder 1 for the next iteration.

[0232] Through the above iterative processing, the decoding performance is greatly improved.

[0233] The method of this embodiment first divides the PSS signal and SSS signal in the same SSB time slot into multiple sub - segments respectively, and combines the mutual relationship characteristics between each sub - segment of the PSS signal and the corresponding sub - segment of the SSS signal, the mutual relationship characteristics between each sub - segment of the PSS signal, the mutual relationship characteristics between each sub - segment of the SSS signal, and the similarity characteristics between all sub - segment signals and the received signal, effectively increasing the characteristics and identifiability of the synchronization signal, and improving the time - frequency synchronization performance under low signal - to - noise ratio and large Doppler frequency offset conditions.

[0234] The method of this embodiment only uses the PSS signal and SSS signal in one SSB time slot for synchronization. Compared with many related technologies that use the PSS signal and SSS signal in different SSB time slots for overall cross - correlation synchronization, it effectively reduces the processing delay and complexity of the frequency offset estimation algorithm, ensuring the real - time nature of signal reception.

[0235] Ideally, the phases of each sub - segment of the segmented synchronization signal should be continuous and regularly changing. Under low signal - to - noise ratio conditions, the influence of noise may disrupt the continuity and regularity of the phase change of some data sub - segment sequences. Therefore, segmenting the synchronization signal and combining the mutual relationship characteristics between all sub - segment signals and the similarity characteristics between all sub - segment signals and the received signal to estimate the frequency offset can effectively utilize the local characteristics of the synchronization signal and improve the frequency offset estimation accuracy under low signal - to - noise ratio conditions.

[0236] To facilitate the understanding of the signal synchronization method of this embodiment, the following will be combined with Figures 4a to 5e for further description.

[0237] During the signal reception process, in order to overcome the problems such as large Doppler frequency offset caused by the high-speed moving state of the transmitting end and signal crosstalk in the case of low signal-to-noise ratio, the main purpose of this application is to achieve high-precision time-frequency synchronization under large Doppler frequency offset and low signal-to-noise ratio conditions.

[0238] The process of the embodiment of this application (the algorithms involved are the same as those of the foregoing embodiments) specifically includes:

[0239] S1: Design a radio frame, and adopt the frame structure of the 5G NTN protocol downlink channel.

[0240] S2: Data symbol transmission processing flow.

[0241] S3: Receiver signal processing flow.

[0242] In step S1, when designing a radio frame and adopting the frame structure of the 5G NTN downlink channel, the specific steps include:

[0243] S11: Design a radio frame, which has 2 half-frames with a duration of 10 ms. The half-frame structure is as Figure 4a shown, including half-frame 1 and half-frame 2. The radio frame is as Figure 4b shown. One half-frame has 10 time slots, each time slot is 0.5 ms, and each time slot has 14 OFDM symbols. Among them, the first OFDM symbol has a CP length of 88 samples (at a sampling rate of 30.72 M), and the subsequent 13 OFDM symbols have a CP length of 72 samples (at a sampling rate of 30.72 M). Among them, the first time slot of the half-frame carries the PSS and SSS synchronization sequences, which is called the SSB time slot, and the subsequent 9 time slots only carry data and DMRS (demodulation reference signal), which is called the Data time slot.

[0244] S12: Design the SSB time slot structure. As Figure 4cAs shown in the figure, the OFDM symbols with indices 0 to 3 are data symbols (the OFDM symbol with index 2 inserts DMRS), and as a coded code block, after modulation, they are sequentially mapped to the corresponding subcarriers. The OFDM symbols with indices 4 to 7 are synchronization symbols and PBCH (Physical Broadcast Channel Symbol) symbols (4 is the PSS symbol, 6 is the SSS symbol, 5 / 7 are PBCH symbols). The OFDM symbols with indices 8 to 10 are data symbols (the OFDM symbol with index 8 inserts DMRS), and they are a coded code block. The OFDM symbols with indices 11 to 13 are data symbols (the OFDM symbol with index 11 inserts DMRS), and they are a coded code block. In the DMRS insertion method, the data symbols occupy the middle 612 subcarriers, and the PSS and SSS occupy the middle 127 subcarriers.

[0245] As Figure 4d and Figure 4e shown, the SSB time slot has 3 code blocks: [0, 1, 2, 3], [8, 9, 10], [11, 12, 13], and the DATA time slot has 4 code blocks: [0, 1, 2, 3], [4, 5, 6, 7], [8, 9, 10], [11, 12, 13].

[0246] In step S2, the data symbol transmission process is as Figure 5a shown, and the specific steps include:

[0247] S21: To improve transmission reliability, the source bits are spread by a factor of 2.

[0248] S22: The Turbo channel coding uses a Turbo code with a code rate of 1 / 3, which can ensure very strong error correction ability.

[0249] S23: Interleaving: Each modulation method has two interleaving lengths (QPSK and 16QAM (Quadrature Amplitude Modulation)), which support coded code blocks with lengths of 4 OFDM symbols and 3 OFDM symbols respectively.

[0250] S24: The modulation methods used are QPSK and 16QAM modulation methods.

[0251] S25: Carrier mapping: Map the data subcarriers to the middle 612 subcarriers.

[0252] S26: Adding Pilots, PSS, and SSS: Place 306 pilots at the pilot subcarrier positions. The pilot symbols can refer to the 5G (Fifth Generation Mobile Communication Technology) protocol, and the symbols obtained by QPSK modulating a random sequence are used as pilots. Pilots are used for channel estimation and tracking the phase rotation caused by residual frequency offset.

[0253] S27: IFFT: Perform a 1024-point IFFT transformation.

[0254] S28: Adding CP and Frame Assembly: For the data after IFFT transformation, place 88 or 72 points at the end in front of the data samples to form an OFDM symbol.

[0255] S29: Oversampling, Filtering: Perform twice oversampling, and control the cut-off frequency of the low-pass filter at about 10M. As Figure 5b shows the amplitude-frequency response of the transmit filter, where the horizontal axis is frequency and the vertical axis is amplitude.

[0256] In step S3, the receiver signal processing, as Figure 5c is the schematic diagram of the receiver signal processing flow, and the specific steps include:

[0257] S31: After receiving filtering, at this time it is the IQ data at the oversampling stage. The amplitude-frequency response of the filter is as Figure 5d shown, where the horizontal axis is frequency and the vertical axis is amplitude. By filtering, out-of-band noise can be filtered to improve the receiving performance.

[0258] S32: Coarse Synchronization includes Coarse Timing Synchronization and Coarse Frequency Offset Estimation and Compensation: During coarse synchronization, since large frequency offset will affect the relevant performance of synchronization and lead to synchronization failure, therefore, first, the frequency offset of different segments is used to pre-compensate the received signal for frequency offset, and then the signals after frequency offset pre-compensation are respectively correlated with the local PSS sequence and SSS sequence and then summed. The moment corresponding to the maximum correlation peak exceeding the threshold is the coarse timing synchronization position, and the frequency offset corresponding to the maximum peak is the coarse frequency offset estimation. The range of frequency offset segmentation is set to -60KHz~60KHz, and the step is 10KHz.

[0259] The following derivation gives the coarse timing estimation metric. The transmitted signal is represented as s(t), the received signal is r(t) (to reduce the processing complexity, the signals after 2-fold decimation in coarse timing synchronization are used for correlation operations), and w(t) is the additive white Gaussian noise. Then the received signal at the terminal can be expressed in the following form:

[0260]

[0261] At time k, the received signal is sampled, and the following expression for the received signal can be obtained:

[0262]

[0263] After compensating the received signal for different frequency offsets, the following expression can be obtained:

[0264]

[0265] where Δf n takes -60 kHz, -50 kHz, -40 kHz, -30 kHz, -20 kHz, -10 kHz, 0 kHz, 10 kHz, 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz respectively.

[0266] Symbol rough timing and rough frequency offset estimation can be obtained by performing correlation operations between the locally saved PSS synchronization signal and SSS synchronization signal and the received signal, as follows:

[0267]

[0268] S PSS *(k) and S SSS *(k) represent the time-domain waveforms of the locally saved PSS synchronization signal and locally saved SSS synchronization signal at the receiver. P n (Δ) represents the sum of the results after performing correlation operations between S PSS *(k ) and S SSS *(k ) and the received signal sequence r n (k + Δ) and r n (k + K + Δ) respectively (the subscript n represents the nth group of frequency offset compensation). Δ represents the offset of the received signal, and the denominator represents the energy of the corresponding part of the received signal, which is used to normalize the result of the correlation operation. Find the highest peak of each P n sequence, and then compare the magnitudes of these values. When the maximum value exceeds a certain threshold, it is considered that the PSS signal has arrived. That is:

[0269]

[0270] At the same time, the frequency offset corresponding to the maximum value is the result of the rough frequency offset estimation, and the offset Δ corresponding to the maximum value is the detected offset of the initial symbol timing synchronization. It should be noted that in order to reduce the influence of the multipath channel, windowed summation processing can be performed on the correlation values, and then the maximum value can be found.

[0271] S33: Fine synchronization includes fine timing synchronization and fine frequency offset estimation and compensation: Fine timing synchronization and fine frequency offset estimation are performed using the PSS sequence and the SSS sequence. Since coarse timing synchronization has already completed a relatively accurate timing window, during fine timing synchronization, correlation searches are only performed within a relatively small window before and after the coarse timing synchronization position. Specifically, let

[0272]

[0273]

[0274]

[0275]

[0276] Summing the above four expressions, we can obtain the following mathematical expression:

[0277]

[0278] When Abs(k) takes the maximum value, the corresponding moment is the moment of fine timing synchronization.

[0279] Assume that there is a carrier frequency deviation of Δf between the transmitter and the receiver. Without considering noise, the received signal can be expressed in the following form:

[0280]

[0281] where, T S represents the sampling interval, and N S represents the number of points of the IFFT. Substituting into the following formula, we can obtain the following expression:

[0282]

[0283]

[0284] Assume that α(k) = S SSS (k)*S SSS *(k), where α(k) is a real number, then

[0285]

[0286] Analyze the operation result, expand the summation term, and then perform cross multiplication. Then the result of multiplying the corresponding terms and is a real number, denoted as . And the results of cross multiplying other terms are a complex random variable, with a total of terms. Let each term be expressed as Then the above formula can be expressed as:

[0287]

[0288]

[0289] The latter term is the result of the superposition of a large number of complex random variables and can be regarded as a Gaussian random variable. Then only consider the former term

[0290]

[0291] Introduce the phase parameter , then the estimation of the frequency deviation based on the autocorrelation of the SSS signal before and after is:

[0292]

[0293] After that, we divide the PSS signal and the SSS signal into two identical signal sequences (two sub-segments of the same length) before and after respectively, and then perform cross-correlation operations on the first half of the PSS signal and the first half of the SSS signal, and perform cross-correlation operations on the second half of the PSS signal and the second half of the SSS signal, to obtain the following two operation results:

[0294]

[0295]

[0296] Through some mathematical transformations, we can further obtain the following expressions:

[0297]

[0298]

[0299] After arranging the above two formulas, we can get

[0300]

[0301]

[0302] Introduce the principal value phase parameter , and the estimated value of the frequency deviation based on the cross-correlation of the first half and the second half of the PSS signal and the SSS signal respectively can be obtained as:

[0303]

[0304] Combining and , we can obtain the final estimated value of the frequency deviation as:

[0305]

[0306] Here, α is a weight factor between 0 and 1. Optimizing this weight factor will affect the effect of fine frequency offset estimation.

[0307] S34: Data subframe FFT and channel estimation: First, perform FFT on the OFDM symbol where the DMRS signal is placed. Then, extract the received signal at the pilot position in the frequency domain, and perform frequency-domain LS estimation in combination with the DMRS reference signal to obtain the estimated channel gain as H LS (k) = Y(k) / P(k). Where P(k) is the frequency-domain sequence of the DMRS. After channel estimation, in order to further reduce the influence of channel estimation noise and improve the accuracy of channel estimation, first estimate the frequency-domain response of the guard band subcarriers by means of extrapolation to obtain the channel frequency-domain response H LS (k) of the entire frequency band. Then, convert it to the time domain through IFFT to obtain the following expression:

[0308]

[0309] For the obtained channel time-domain impulse response, reduce the influence of noise by windowing, that is, only take the head and tail parts of the obtained time-domain response, and set the middle part to zero (the middle part can be considered as noise). Then perform FFT transformation on the windowed channel time-domain response to the frequency domain to obtain the frequency-domain response, and finally perform smoothing processing on the channel in the frequency domain to obtain the channel estimation value H(k) for channel equalization. The average window length is 5 (configurable), and the specific smoothing method is as follows:

[0310]

[0311] The noise power can be estimated through the channel responses before and after smoothing, and the specific method is as follows:

[0312]

[0313] S35: Channel equalization uses the MMSE equalization algorithm. According to the algorithm theory of MMSE, we can obtain the equalization coefficient as follows:

[0314]

[0315] After that, further perform MMSE equalization compensation on the signal, and the equalized signal is as follows:

[0316]

[0317] S36: Soft demodulation: Extract soft information from the equalized signal according to the characteristics of QPSK modulation:

[0318]

[0319]

[0320] S37: Deinterleaving: The information obtained from soft demodulation is first deinterleaved. Under harsh conditions of low signal-to-noise ratio and multipath, soft information is prone to misjudgment. Statistically, the probability that the soft information of two adjacent bits is in error simultaneously becomes smaller. Therefore, the average of two adjacent deinterleaved soft information bits is calculated, which can improve the reliability of the soft information. That is:

[0321]

[0322] where LLR’(n) is the soft information after despreading.

[0323] S38: Channel decoding: Turbo decoding is performed based on the soft information extracted from the equalized signal.

[0324] As Figure 5e shown, the soft information extracted during channel equalization is divided into information-bit soft information and parity-bit soft information . The parity-bit soft information is further divided into parity information 1, and parity information 2, y 2p .

[0325] Component decoder 1, i.e., DEC1 in the figure, uses the information-bit soft information and parity information 1, , to extract extrinsic information L 12 e . After interleaving, the extrinsic information is used as the prior information for component decoder 2.

[0326] Component decoder 2 uses the interleaved information-bit information, parity information 2, y 2p , and the extrinsic information provided by decoder 1 as prior information to calculate the posterior probability information L(u n ) and extrinsic information L 21 e . The extrinsic information calculated by component decoder 2, i.e., DEC2 in the figure, is deinterleaved and used as prior information for component decoder 1 for the next iteration.

[0327] After the above iterative processing, the decoding performance is greatly improved, and the final result u k is generated.

[0328] To more clearly explain the embodiments of the present application, specific examples of the present application in practical applications are provided below.

[0329] Regarding the simulation results:

[0330] The channel adopts the TDL (Tapped Delay Line) channel specified by 3GPP (3rd Generation Partnership Project). Since the TDL-A channel is a Rayleigh multipath channel and is the most severe, the TDL-A is selected as the simulation channel in this simulation scheme. The maximum Doppler frequency offset is set to 52KHz, the frequency offset change rate is 750Hz / s, and the SNR (Signal to Noise Ratio) is set to vary dynamically from -8dB to 4dB.

[0331] The specific results are as Figures 6 to 8 shown. Figure 6 shows the relationship between the acquisition probability of a signal processing system and the signal-to-noise ratio. The x-axis is the SNR and the y-axis is the acquisition probability. Figure 7 shows the trend of the average estimated frequency offset error varying with the signal-to-noise ratio. The x-axis is the SNR and the y-axis is the frequency offset estimation error. Figure 8 shows the relationship between the bit error rate and the signal-to-noise ratio. The x-axis is the SNR and the y-axis is the bit error rate (BER, Bit Error Ratio).

[0332] Figure 9 is a schematic structural diagram of the signal synchronization device provided by this application. As Figure 9 shown, in this embodiment, the signal synchronization device 300 can be set in a communication device. The signal synchronization device 300 includes:

[0333] A coarse synchronization module 301, configured to perform a preset coarse synchronization process on the received signal to determine the coarse synchronization result corresponding to the received signal.

[0334] A fine synchronization module 302, configured to perform a preset fine synchronization process on the received signal after coarse synchronization based on the first sub-signal segment of the pre-stored primary synchronization signal PSS and the second sub-signal segment of the pre-stored secondary synchronization signal SSS, and generate a corresponding fine synchronization result. The PSS and SSS belong to the same synchronization signal block SSB time slot. The number of the first sub-signal segments is the same as the number of the second sub-signal segments.

[0335] A signal synchronization module 303, configured to perform signal synchronization compensation on the received signal after fine synchronization according to the fine synchronization result to complete signal synchronization.

[0336] The signal synchronization device provided in this embodiment can execute Figure 2 the technical solution of the method embodiment shown, and its implementation principle and technical effect are similar to those of Figure 2 the method embodiment shown, and will not be elaborated here one by one.

[0337] Based on the signal synchronization device provided in the previous embodiment, the signal synchronization device provided in this application further refines the signal synchronization device. The signal synchronization device 300 includes:

[0338] Optionally, in this embodiment, the coarse synchronization module 301 is specifically configured to:

[0339] Compensate the received signal according to each preset frequency offset to generate a corresponding compensated received signal. Input each compensated received signal, PSS, and SSS into a first preset correlation operation algorithm to determine a corresponding correlation operation result based on the first preset correlation operation algorithm. If the maximum value among all the correlation operation results is greater than a preset threshold, then determine the preset frequency offset corresponding to the maximum value and the corresponding time offset as the coarse synchronization result.

[0340] Optionally, in this embodiment, when the fine synchronization module 302 performs a preset fine synchronization process on the received signal after coarse synchronization processing based on a first sub-signal segment of the pre-stored primary synchronization signal PSS and a second sub-signal segment of the pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result, it is specifically configured to:

[0341] Determine a first correlation relationship feature between each third sub-signal segment and the corresponding first sub-signal segment. The third sub-signal segment is obtained by dividing the received signal after coarse synchronization processing. The number of third sub-signal segments is the same as the number of first sub-signal segments and the number of second sub-signal segments. Determine a second correlation relationship feature between each third sub-signal segment and the corresponding second sub-signal segment. Determine the moment of fine timing synchronization according to each first correlation relationship feature and each second correlation relationship feature. Determine the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment.

[0342] Optionally, in this embodiment, the coarse synchronization result includes a coarse synchronization time offset.

[0343] When the fine synchronization module 302 determines the first correlation relationship feature between the third sub-signal segment and the corresponding first sub-signal segment, it is specifically configured to:

[0344] Determine a plurality of candidate time offsets. The candidate time offsets are based on the coarse synchronization time offset. Input the candidate time offsets, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment into a second preset correlation operation algorithm to generate a first correlation relationship feature corresponding to the candidate time offset based on the second preset correlation operation algorithm.

[0345] Optionally, in this embodiment, when the fine synchronization module 302 determines the moment of fine timing synchronization according to each first correlation relationship feature and each second correlation relationship feature, it is specifically configured to:

[0346] For each candidate time offset, calculate the sum between each corresponding first correlation relationship feature and each corresponding second correlation relationship feature. Determine the candidate time offset corresponding to the maximum value of each sum as the moment of fine timing synchronization.

[0347] Optionally, in this embodiment, when the fine synchronization module 302 determines the frequency offset of fine timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment, it is specifically configured to:

[0348] Determine the third correlation relationship feature between each third sub-signal segment and the corresponding second sub-signal segment. Input each third correlation relationship feature into a third preset correlation operation algorithm to determine the fourth correlation relationship feature between each third correlation relationship feature based on the third preset correlation operation algorithm. Determine the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature. Determine the frequency offset of fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature.

[0349] Optionally, in this embodiment, when the fine synchronization module 302 determines the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature, it is specifically configured to:

[0350] Input the second correlation relationship feature and the first correlation relationship feature in the same inverse fast Fourier transform (IFFT) point number region into a fourth preset correlation operation algorithm to generate the corresponding fifth correlation relationship feature.

[0351] Optionally, in this embodiment, when the fine synchronization module 302 determines the frequency offset of fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature, it is specifically configured to:

[0352] Perform phase conversion processing on the fourth correlation relationship feature to generate the corresponding first phase parameter. Perform phase conversion processing on the fifth correlation relationship feature to generate the corresponding intermediate phase parameter. Perform an averaging process on the intermediate phase parameter to generate the corresponding second phase parameter. Perform a weighted sum on the first phase parameter and the second phase parameter to generate the frequency offset of fine timing synchronization.

[0353] The signal synchronization device provided in this embodiment can execute Figures 2 - 8 the technical solution of the method embodiment shown, and its implementation principle and technical effect are similar to those of Figures 2 - 8 the method embodiment shown, and will not be elaborated here one by one.

[0354] According to the embodiments of the present application, the present application also provides a communication device, a computer-readable storage medium, and a computer program product.

[0355] As Figure 10 shown, Figure 10It is a schematic structural diagram of a communication device provided by this application. The communication device is intended for various forms of devices with communication functions, such as workbenches, mobile phones, vehicle-mounted terminals, and other suitable computers. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of this application described and / or claimed herein.

[0356] As Figure 10 shown, the communication device includes: a processor 401 and a memory 402. Each component is interconnected using different buses and can be installed on a common motherboard or installed in other ways as needed. The processor can process instructions executed within the communication device.

[0357] The memory 402 is the non-transitory computer-readable storage medium provided by this application. Among them, the memory stores instructions executable by at least one processor, so that at least one processor executes the signal synchronization method provided by this application. The non-transitory computer-readable storage medium of this application stores computer instructions, and the computer instructions are used to cause the computer to execute the signal synchronization method provided by this application.

[0358] As a non-transitory computer-readable storage medium, the memory 402 can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the signal synchronization method in the embodiments of this application (for example, Figure 9 shown coarse synchronization module 301, fine synchronization module 302, and signal synchronization module 303). The processor 401 executes various functional applications and data processing of the communication device by running the non-transitory software programs, instructions, and modules stored in the memory 402, that is, implements the signal synchronization method in the above method embodiments.

[0359] At the same time, this embodiment also provides a computer-readable storage medium, and computer-executable instructions are stored in the computer-readable storage medium. When the computer-executable instructions are executed by the processor, they are used to implement the signal synchronization method of the above embodiment.

[0360] This embodiment also provides a computer product. When the instructions in the computer product are executed by the processor of the communication device, the communication device can execute the signal synchronization method of the above embodiment.

[0361] Those skilled in the art will easily think of other implementation schemes of the embodiments of this application after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptive changes of the embodiments of this application, and these variations, uses, or adaptive changes follow the general principles of the embodiments of this application and include well-known common knowledge or conventional technical means in the technical field not disclosed in the embodiments of this application.

[0362] It should be understood that the embodiments of the present application are not limited to the exact structures that have been described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the embodiments of the present application is only limited by the appended claims.

Claims

1. A signal synchronization method, characterized in that, Including: Performing preset coarse synchronization processing on the received signal to determine the coarse synchronization result corresponding to the received signal; Based on the coarse synchronization result, performing preset fine synchronization processing on the received signal after coarse synchronization processing by using a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result; the PSS and the SSS belong to the same synchronization signal block SSB time slot; the number of the first sub-signal segments is the same as the number of the second sub-signal segments; Performing signal synchronization compensation on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization; The performing preset fine synchronization processing on the received signal after coarse synchronization processing by using a first sub-signal segment of a pre-stored primary synchronization signal PSS and a second sub-signal segment of a pre-stored secondary synchronization signal SSS to generate a corresponding fine synchronization result includes: Determining a first correlation relationship feature between each third sub-signal segment and the corresponding first sub-signal segment; the third sub-signal segment is obtained by dividing the received signal after coarse synchronization processing; the number of the third sub-signal segments is the same as the number of the first sub-signal segments and the number of the second sub-signal segments; Determining a second correlation relationship feature between each of the third sub-signal segments and the corresponding second sub-signal segment; Determining the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features; Determining a third correlation relationship feature between each of the third sub-signal segments and the corresponding second sub-signal segment; Inputting each of the third correlation relationship features into a third preset correlation operation algorithm to determine a fourth correlation relationship feature between each of the third correlation relationship features based on the third preset correlation operation algorithm; Determining a fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature; Determining the frequency offset of the fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature.

2. The method according to claim 1, wherein The performing preset coarse synchronization processing on the received signal to determine the coarse synchronization result corresponding to the received signal includes: Compensating the received signal according to each preset frequency offset to generate a corresponding compensated received signal; Inputting each of the compensated received signals, the PSS, and the SSS into a first preset correlation operation algorithm to determine a corresponding correlation operation result based on the first preset correlation operation algorithm; If the maximum value among all the correlation operation results is greater than a preset threshold value, determining the preset frequency offset corresponding to the maximum value and the corresponding time offset as the coarse synchronization result.

3. The method according to claim 1, wherein The coarse synchronization result includes a coarse synchronization time offset; The determining the first correlation relationship feature between the third sub-signal segment and the corresponding first sub-signal segment includes: Determining a plurality of candidate time offsets; the candidate time offsets are based on the coarse synchronization time offset; Inputting the candidate time offsets, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment into a second preset correlation operation algorithm to generate the first correlation relationship feature corresponding to the candidate time offsets based on the second preset correlation operation algorithm.

4. The method according to claim 3, wherein The determining the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features includes: For each candidate time offset, calculate the sum between each corresponding first correlation relationship feature and each corresponding second correlation relationship feature; Determine the candidate time offset corresponding to the maximum value of each of the sums as the moment of fine timing synchronization.

5. The method according to claim 1, wherein The determining of the fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature includes: Input the second correlation relationship feature and the first correlation relationship feature in the same inverse fast Fourier transform (IFFT) point number region into a fourth preset correlation operation algorithm to generate a corresponding fifth correlation relationship feature.

6. The method according to claim 1, wherein The determining of the frequency offset of the fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature includes: Perform a phase transformation process on the fourth correlation relationship feature to generate a corresponding first phase parameter; Perform a phase transformation process on the fifth correlation relationship feature to generate a corresponding intermediate phase parameter; Perform an averaging process on the intermediate phase parameter to generate a corresponding second phase parameter; Perform a weighted summation on the first phase parameter and the second phase parameter to generate the frequency offset of the fine timing synchronization.

7. A signal synchronization device, characterized in that, It includes: A coarse synchronization module, configured to perform a preset coarse synchronization process on a received signal to determine a coarse synchronization result corresponding to the received signal; A fine synchronization module, configured to, based on the coarse synchronization result, perform a preset fine synchronization process on the received signal after the coarse synchronization process based on a first sub-signal segment of a pre-stored primary synchronization signal (PSS) and a second sub-signal segment of a pre-stored secondary synchronization signal (SSS) to generate a corresponding fine synchronization result; the PSS and the SSS belong to the same synchronization signal block (SSB) time slot; the number of the first sub-signal segments is the same as the number of the second sub-signal segments; A signal synchronization module, configured to perform signal synchronization compensation on the received signal after the fine synchronization process according to the fine synchronization result to complete signal synchronization; The fine synchronization module is specifically configured to determine a first correlation relationship feature between each third sub-signal segment and a corresponding first sub-signal segment; the third sub-signal segments are obtained by dividing the received signal after the coarse synchronization process; the number of the third sub-signal segments is the same as the number of the first sub-signal segments and the second sub-signal segments; determine a second correlation relationship feature between each third sub-signal segment and a corresponding second sub-signal segment; determine the moment of fine timing synchronization according to each of the first correlation relationship features and each of the second correlation relationship features; determine a third correlation relationship feature between each third sub-signal segment and a corresponding second sub-signal segment; Input each of the third correlation relationship features into a third preset correlation operation algorithm to determine a fourth correlation relationship feature between each of the third correlation relationship features based on the third preset correlation operation algorithm; Determine a fifth correlation relationship feature between the second correlation relationship feature and the first correlation relationship feature; determine the frequency offset of the fine timing synchronization according to the fourth correlation relationship feature and the fifth correlation relationship feature.

8. A communication device, characterized in that, It includes: A memory and a processor; The memory stores computer execution instructions; The processor executes the computer execution instructions stored in the memory to implement the signal synchronization method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the signal synchronization method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the signal synchronization method according to any one of claims 1 to 6.

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