Signal synchronization method, device, equipment, medium and product

Abstract

The invention provides a signal synchronization method and device, equipment, a medium and a product, and the method comprises the steps: carrying out the preset coarse synchronization processing of a received signal, and determining a coarse synchronization result corresponding to the received signal; on the basis of the coarse synchronization result, performing preset fine synchronization processing on the receiving 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 generating 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 that of the second sub-signal segments; and performing signal synchronization compensation on the receiving signal after the fine synchronization processing according to the fine synchronization result so as to complete signal synchronization. According to the method provided by the invention, the local features of the synchronization signal can be effectively utilized through the correlation features among the first sub-signal segment of the PSS, the second sub-signal segment of the secondary synchronization signal SSS and the received signal, and the synchronization precision in a low signal-to-noise ratio scene is improved.

Description

Technical Field

[0001] The present application relates to the field of non-terrestrial network communication technology, and in particular to a signal synchronization method, device, equipment, 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 where terrestrial infrastructure is insufficient.

[0003] In non-terrestrial networks such as satellite communications, the high-speed movement of the transmitter will produce a large Doppler frequency offset. During the signal reception process, the receiver generally compensates 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 scenarios with low signal-to-noise ratio, it is necessary to optimize the accuracy of signal synchronization. Summary of the invention

[0005] The present application provides a signal synchronization method, apparatus, device, medium and product for optimizing the accuracy of signal synchronization in a scenario with a low signal-to-noise ratio.

[0006] The first aspect of the present application provides a signal synchronization method, comprising:

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

[0008] Based on the coarse synchronization result, a preset fine synchronization process is performed on the received signal after the coarse synchronization process 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; 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] Signal synchronization compensation is performed on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

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

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

[0012] 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;

[0013] If the maximum value among all the related operation results is greater than the preset threshold value, the preset frequency deviation and the corresponding time offset corresponding to the maximum value are determined as the coarse synchronization result.

[0014] Further, in the method as described above, the step of performing a preset fine synchronization process on the received signal after the coarse synchronization process 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 includes:

[0015] Determine a first correlation feature between each third sub-signal segment and the corresponding first sub-signal segment; the third sub-signal segments are obtained by dividing the received signal after the 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;

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

[0017] Determine a precise timing synchronization moment according to each of the first correlation characteristics and each of the second correlation characteristics;

[0018] A frequency deviation for precise timing synchronization is determined based on 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 of a first correlation 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] The candidate time offset, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment are input 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] Furthermore, in the above method, the step of determining the precise timing synchronization moment according to each of the first correlation characteristics and each of the second correlation characteristics comprises:

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

[0025] The candidate time offset corresponding to the maximum value of each of the sums is determined as the moment of precise timing synchronization.

[0026] Further, in the above method, the step of determining the frequency deviation for precise timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment includes:

[0027] Determining a third correlation feature between each of the third sub-signal segments and the corresponding second sub-signal segment;

[0028] Inputting each of the third correlation features into a third preset correlation operation algorithm to determine a fourth correlation feature between each of the third correlation features based on the third preset correlation operation algorithm;

[0029] determining a fifth correlation feature between the second correlation feature and the first correlation feature;

[0030] The frequency offset of the precise timing synchronization is determined according to the fourth correlation feature and the fifth correlation feature.

[0031] Further, in the above method, the determining of the fifth correlation feature between the second correlation feature and the first correlation feature comprises:

[0032] The second correlation feature and the first correlation feature of the same inverse fast Fourier transform IFFT point area are input into the fourth preset correlation operation algorithm to generate a corresponding fifth correlation feature.

[0033] Further, in the above method, the determining the frequency deviation of the precise timing synchronization according to the fourth correlation feature and the fifth correlation feature includes:

[0034] Performing phase conversion processing on the fourth correlation feature to generate a corresponding first phase parameter;

[0035] Performing phase conversion processing on the fifth correlation feature to generate a corresponding intermediate phase parameter;

[0036] Performing an averaging process on the intermediate phase parameters to generate corresponding second phase parameters;

[0037] A weighted sum is performed on the first phase parameter and the second phase parameter to generate a frequency deviation for precise timing synchronization.

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

[0039] A coarse synchronization module, used to perform a preset coarse synchronization process on a received signal and determine a coarse synchronization result corresponding to the received signal;

[0040] A fine synchronization module, configured to perform preset fine synchronization processing on the received signal after the 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 on the basis of the coarse synchronization result, 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] The signal synchronization module 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, in the above device, the coarse synchronization module is specifically used for:

[0043] The received signal is compensated according to each preset frequency deviation to generate a corresponding compensated received signal; each of the compensated received signals, the PSS and the SSS is input 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, the preset frequency deviation corresponding to the maximum value and the corresponding time offset are determined as the coarse synchronization result.

[0044] Further, in the above-mentioned device, the fine synchronization module performs preset fine synchronization processing on the received signal after the 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 to generate a corresponding fine synchronization result, specifically for:

[0045] Determine a first correlation characteristic between each third sub-signal segment and the corresponding first sub-signal segment; the third sub-signal segments are 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 characteristic between each third sub-signal segment and the corresponding second sub-signal segment; determine the moment of precise timing synchronization according to each first correlation characteristic and each second correlation characteristic; determine the frequency deviation of precise timing synchronization according to the first sub-signal segment, the second sub-signal segment and the third sub-signal segment.

[0046] Further, in the above device, the coarse synchronization result includes a coarse synchronization time deviation;

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

[0048] Determine multiple candidate time offsets; the candidate time offset is based on the coarse synchronization time offset; input the candidate time offset, 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, in the above-mentioned device, when the precise synchronization module determines the precise timing synchronization moment according to each of the first correlation characteristics and each of the second correlation characteristics, it is specifically used to:

[0050] For each candidate time offset, the sum of each corresponding first correlation feature and each corresponding second correlation feature is calculated; and the candidate time offset corresponding to the maximum value of each sum is determined as the moment of precise timing synchronization.

[0051] Further, in the above-mentioned device, when the fine synchronization module determines the frequency deviation of the fine timing synchronization according to the first sub-signal segment, the second sub-signal segment and the third sub-signal segment, it is specifically used to:

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

[0053] Further, in the above-mentioned device, when determining the fifth correlation feature between the second correlation feature and the first correlation feature, the fine synchronization module is specifically used to:

[0054] The second correlation feature and the first correlation feature of the same inverse fast Fourier transform IFFT point area are input into the fourth preset correlation operation algorithm to generate a corresponding fifth correlation feature.

[0055] Further, in the above-mentioned device, when the fine synchronization module determines the frequency deviation of the fine timing synchronization according to the fourth correlation feature and the fifth correlation feature, it is specifically used to:

[0056] The fourth correlation feature is subjected to phase transformation processing to generate a corresponding first phase parameter; the fifth correlation feature is subjected to phase transformation processing to generate a corresponding intermediate phase parameter; the intermediate phase parameter is averaged to generate a corresponding second phase parameter; the first phase parameter and the second phase parameter are weightedly summed to generate the frequency deviation for precise 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 as described in any one of the first aspects.

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

[0061] A fifth aspect of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the signal synchronization method described in any one of the first aspects.

[0062] The present application provides a signal synchronization method, device, equipment, medium and product, the method comprising: 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 the 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 auxiliary 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; and performing signal synchronization compensation on the received signal after the fine synchronization processing 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 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, and improve the synchronization accuracy in low signal-to-noise ratio scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0064] Figure 1 A schematic diagram of an application scenario of the signal synchronization method provided in this application;

[0065] Figure 2 Schematic diagram of the signal synchronization method provided in this application Figure 1 ;

[0066] Figure 3 Schematic diagram of the signal synchronization method provided in this application Figure 2 ;

[0067] Figure 4a A half-frame schematic diagram provided for this application;

[0068] Figure 4b A schematic diagram of the frame structure provided for this application;

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

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

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

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

[0073] Figure 5b A schematic diagram of the amplitude-frequency response of the transmit filter provided in this application;

[0074] Figure 5c A schematic diagram of the signal processing flow at the receiving end provided for this application;

[0075] Figure 5d is a schematic diagram of the amplitude-frequency response of the receiving filter;

[0076] Figure 5e A schematic diagram of the decoding process provided for this application;

[0077] Figure 6 A schematic diagram of the 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 the bit error rate curve provided for this application;

[0080] Fig. 9 A schematic diagram of the structure of the signal synchronization device provided by this application;

[0081] Fig.10 A schematic diagram of the structure of the communication device provided in this application.

[0082] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0083] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices 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 the communication network and is used for signal synchronization of the receiving device.

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

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

[0088] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments 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 in conjunction with the accompanying drawings.

[0089] In order to clearly understand the technical solution of the present application, the conception process of the technical solution is first introduced in detail. In non-terrestrial networks such as satellite communications, due to the high-speed movement and frequent switching of satellites relative to the ground, the large link delay and channel instability are more prominent than in terrestrial communication scenarios. The relative high-speed movement between satellites and terrestrial communication equipment such as terminals will produce a large Doppler frequency shift, which will seriously affect the reception and processing of signals.

[0090] In the related art, for the Doppler frequency shift caused by satellite movement, corresponding compensation is performed at the transmitting end or the receiving end to reduce the impact of the Doppler effect on the decoding of the received signal. Due to the difficulty of 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 correction ability of the Doppler frequency offset is weak, especially in the scenario with low signal-to-noise ratio. Due to the high-speed relative motion between the satellite and the terminal, the Doppler effect will occur, causing the carrier frequency of the received signal to shift. At present, the receiving terminal usually relies on PSS signals and SSS signals for frequency offset estimation. Using only PSS signals or only SSS signals for frequency offset estimation may not make full use of all available synchronization signal information, resulting in insufficient frequency offset estimation range and large residual frequency offset, thereby affecting the decoding performance. In addition, since both the PSS signal and the SSS signal sequences are short, using only the PSS and SSS in the same SSB time slot for overall cross-correlation is very susceptible to random noise interference and distortion under low signal-to-noise ratio conditions, and may also cause the problem of insufficient frequency offset estimation range and large residual frequency offset.

[0091] At the same time, the frequency offset compensation of related technologies needs to rely on ephemeris information. The satellite needs to send ephemeris information to the ground terminal, and then the ground terminal pre-compensates the Doppler frequency deviation based on the information obtained before estimating and correcting the frequency offset. This process needs to rely on ephemeris information to correct the Doppler frequency deviation, which will make the design of the actual system very complicated.

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

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

[0094] Therefore, in order to solve the problem in the prior art of optimizing the accuracy of signal synchronization in scenarios with low signal-to-noise ratio, the inventors have discovered through research that the local characteristics of the synchronization signal can be effectively utilized based on the correlation characteristics of 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 under low signal-to-noise ratio 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] After the signal synchronization, other subsequent processes of data reception may be performed, which are not limited in this embodiment.

[0108] The embodiments of the present application are introduced below in conjunction with the drawings in the specification.

[0109] Figure 2 Schematic diagram of the signal synchronization method provided in this application Figure 1 ,like Figure 2 As shown, the execution subject of the embodiment of the present application is a signal synchronization device, which can be integrated in a communication device, such as a user terminal. The signal synchronization method provided in this embodiment includes the following steps:

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

[0111] In some embodiments, the preset coarse synchronization processing may adopt a commonly used coarse synchronization processing method, such as using only the PSS signal for coarse synchronization, or may adopt other preset coarse synchronization processing methods, such as combining the PSS signal and the SSS signal to perform correlation operations with the received signal and perform summation and normalization operations to complete coarse synchronization.

[0112] The coarse synchronization result includes a coarse synchronization frequency deviation and a coarse timing synchronization position or a coarse synchronization time deviation. Subsequent fine synchronization processing can be performed based on the coarse synchronization time deviation and the coarse synchronization frequency deviation.

[0113] Step S102, 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, and a corresponding fine synchronization result is generated. 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.

[0114] In this embodiment, fine synchronization processing is performed based on the coarse synchronization result. For example, the fine synchronization position can be searched in a smaller window before and after the coarse timing synchronization position, and the fine synchronization frequency deviation can be searched in a smaller frequency deviation range before and after the coarse synchronization frequency deviation.

[0115] The first sub-signal segment is a sub-signal segment generated by dividing the primary synchronization signal PSS, and the second sub-signal segment is a sub-signal segment generated by dividing the secondary synchronization signal SSS. The number of the first sub-signal segments is the same as the number of the second sub-signal segments, which facilitates the subsequent preset fine synchronization processing of the received signal after the coarse synchronization processing based on the pre-stored first sub-signal segment of the primary synchronization signal PSS and the pre-stored second sub-signal segment of the secondary synchronization signal SSS. For example, the fine synchronization processing can be performed through the correlation characteristics between the first sub-signal segment, the second sub-signal segment, and the received signal.

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

[0117] In this embodiment, based on the fine synchronization results such as fine synchronization time offset and fine synchronization frequency offset, the received signal is compensated for the corresponding signal synchronization to complete the signal synchronization. After completing the signal synchronization, 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 coarse synchronization result corresponding to the received signal. Based on the coarse synchronization result, a preset fine synchronization processing is performed on the received signal after the 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 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. Signal synchronization compensation is performed on the received signal after the 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 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.

[0120] Figure 3 Schematic diagram of the signal synchronization method provided in this application Figure 2 ,like Figure 3 As shown, the signal synchronization method provided in this embodiment is further refined on the basis of the signal synchronization method provided in the previous embodiment of the present application, and the signal synchronization method provided in this embodiment includes the following steps.

[0121] Step S201, compensating a received signal according to each preset frequency offset to generate a corresponding compensated received signal.

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

[0123] For example, assuming that the preset frequency band is -60KHz~60KHz, it can be divided into multiple small segments every 10KHz, that is, -60KHz~-51KHz, -50KHz~-41KHz, etc. The preset frequency deviation 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 a 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] Among them, S PSS * (k) and S SSS * (k) represents the time domain waveform of the local PSS synchronization signal and the local SSS synchronization signal pre-stored by the receiving end such as the user terminal, P n (Δ) represents S PSS * (k) and S SSS * (k) and the received signal sequence r n (k+Δ) and r n (K+k+Δ) is the sum of the results of the correlation operations (the subscript n represents the nth group of frequency offset compensation), Δ represents the time offset of the received signal, the denominator represents the energy of the corresponding part of the received signal, and is used to normalize the results of the correlation operation, k represents the time, and K represents the maximum time.

[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 value.

[0129] At this time, the frequency offset corresponding to the maximum value is the result of the rough synchronization frequency offset estimation, and the time offset Δ corresponding to the maximum value is the offset of the detected initial symbol timing synchronization. Optionally, in order to reduce the impact of the multipath channel, the correlation values ​​can be windowed and summed, and then the maximum value is calculated.

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

[0131] In this embodiment, the preset threshold value can be set accordingly according to the actual application, and this embodiment does not limit this. At the same time, as in the aforementioned S202, if the maximum value among all the 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 offset of the detected 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 that only uses the PSS signal for coarse synchronization, the method of this embodiment combines the PSS signal and the SSS signal to perform correlation operations with the received signal and perform summation and normalization operations to perform coarse time and frequency synchronization, thereby effectively improving the accuracy of coarse timing synchronization and increasing the range and accuracy of coarse frequency offset estimation.

[0133] The rough frequency deviation estimation of the method of this embodiment adopts the method of frequency deviation regional estimation and compensation, which greatly increases the scope of rough frequency deviation estimation and can effectively get rid of the dependence of Doppler frequency deviation estimation on ephemeris files. In the complex communication environment of non-ground network, by performing interval compensation processing on the frequency deviation according to the numerical value, the method can more accurately estimate and compensate for the frequency deviation, thereby improving the performance of the communication system. The basic idea of ​​interval 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-compensation. Thereafter, the peak value of the sliding correlation operation between the PSS signal and the SSS signal and the signal after pre-compensation with different frequency deviations is used to determine in which interval the Doppler frequency deviation is located. The advantage of this is that the scope of rough frequency deviation estimation can be increased, the difficulty of precise frequency deviation estimation can be reduced, and the accuracy and robustness of the estimation can be improved.

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

[0135] In this embodiment, since the coarse timing synchronization has completed a relatively accurate timing window, during the fine timing synchronization, the correlation search is only performed in a smaller window before and after the coarse timing synchronization position.

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

[0137] Determine a first correlation 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 the coarse 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. The third sub-signal segment may be obtained by dividing certain received signals that have been pre-compensated for frequency offset during the coarse synchronization process, or by dividing the received signal corresponding to the coarse synchronization frequency offset in the coarse synchronization result.

[0138] A second correlation characteristic between each third sub-signal segment and the corresponding second sub-signal segment is determined.

[0139] The precise timing synchronization moment is determined according to each first correlation feature and each second correlation feature.

[0140] A frequency deviation for precise timing synchronization is determined based on 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, wherein the first first sub-signal segment, the first second sub-signal segment, and the first third sub-signal segment correspond to each other. Optionally, the first first sub-signal segment, the first second sub-signal segment, and the first third sub-signal segment have the same length.

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

[0143] A plurality of candidate timing offsets are determined, wherein the candidate timing offsets are based on the coarse synchronization timing offset.

[0144] The candidate time offset, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment are input 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.

[0145] In this embodiment, since the coarse timing synchronization has completed a relatively accurate timing window, during the fine timing synchronization, the correlation search is only performed in a smaller window before and after the coarse timing synchronization position. The candidate time offset is the time offset selected in the smaller window before and after the coarse timing synchronization position.

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

[0147]

[0148]

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

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

[0151]

[0152]

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

[0154] The above-mentioned preset related operation algorithm and the second preset related operation algorithm include three algorithms if the number of segments is 3, and include n algorithms if the number of segments is n. This embodiment only exemplarily describes the situation under the 2-segment scenario.

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

[0156] For each candidate time offset, the sum of each corresponding first correlation feature and each corresponding second correlation feature is calculated.

[0157] The candidate time offset corresponding to the maximum value of each sum is determined as the time for precise timing synchronization.

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

[0159]

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

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

[0162] A third correlation feature between each third sub-signal segment and the corresponding second sub-signal segment is determined.

[0163] The third correlation features are input into a third preset correlation operation algorithm to determine a fourth correlation feature between the third correlation features based on the third preset correlation operation algorithm.

[0164] A fifth correlation feature between the second correlation feature and the first correlation feature is determined.

[0165] The frequency offset for precise timing synchronization is determined based on the fourth correlation feature and the fifth correlation 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 feature, and other parameters are the same as in the above algorithm.

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

[0170] The second correlation feature and the first correlation feature of the same inverse fast Fourier transform IFFT point area are input into the fourth preset correlation operation algorithm to generate a corresponding fifth correlation feature.

[0171] In this embodiment, if the second correlation 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 feature of the point area corresponding to the first segment, P2 is the fifth correlation feature of the point area corresponding to the second segment, and other parameters are the same as those of the aforementioned algorithm.

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

[0176] Perform phase conversion processing on the fourth correlation feature to generate a corresponding first phase parameter.

[0177] The fifth correlation feature is subjected to phase conversion processing to generate a corresponding intermediate phase parameter.

[0178] The intermediate phase parameters are averaged to generate corresponding second phase parameters.

[0179] A weighted sum is performed on the first phase parameter and the second phase parameter to generate a frequency deviation for precise timing synchronization.

[0180] In this embodiment, the first phase parameter , where P can be the fourth correlation feature, or it can be the feature of the fourth correlation feature omitting some data. The second phase parameter is The frequency deviation for precise timing synchronization is , where α is a weight factor between 0 and 1. The optimization of this weight factor will affect the effect of precise frequency deviation 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] Assuming that there is a carrier frequency deviation of Δf between the transmitter and the receiver, without considering noise, the received signal can be expressed as follows:

[0183]

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

[0185]

[0186] Among them, S SSS (k) represents the time domain waveform of the SSS synchronization signal sent by the transmitter, and other parameters are the same as those of the above algorithm.

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

[0188]

[0189] analyze The result of the operation is to expand the summation term and then perform cross multiplication. Then the corresponding term and The result of the multiplication is a real number, let The result of cross-multiplication of other terms is a complex random variable, with a total of Items, let each item be expressed as . Then the above formula can be expressed as:

[0190]

[0191]

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

[0193]

[0194] Introducing phase parameters , then the frequency deviation based on the autocorrelation of the SSS signal before and after is estimated as:

[0195]

[0196] After that, we divide the PSS signal and the SSS signal into two identical signal sequences, and then perform cross-correlation operation on the first half of the PSS signal and the first half of the SSS signal, and perform cross-correlation operation 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 expression:

[0198]

[0199]

[0200] Among them, 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 above algorithm.

[0201] By rearranging the above two equations, we can obtain:

[0202]

[0203]

[0204] Introducing the phase main value parameter , the frequency deviation estimation value 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] Combination and And the weight factor α, the final frequency deviation for precise timing synchronization can be obtained.

[0207] In the fine synchronization stage, the method of this embodiment uses the mutual relationship characteristics of all sub-segments of the segmented PSS signal and all sub-segments corresponding to the segmented SSS signal to make a first estimate of the frequency deviation, and then uses the similar characteristics of all sub-segments of the segmented SSS signal and the received signal and the mutual relationship characteristics of the corresponding sub-segments to make a second estimate of the frequency deviation, and the final fine synchronization estimated frequency deviation is obtained by multiplying the two estimation results by different dynamic weight factors and then adding them. Note that the sum of the two weight factors is 1, and optimizing the values ​​of the two weight factors will effectively increase the accuracy of the fine frequency deviation estimation.

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

[0209] In this embodiment, after the signal is synchronized, 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 Divisition Multiplexing) symbol where the DMRS (Demodulation Reference Signal) is placed. The received signal at the pilot position is extracted in the frequency domain, and the frequency domain LS (Least Squares) estimation is performed in combination with the DMRS reference signal to obtain the estimated channel gain H LS (k) = Y(k) / P(k).

[0212] Where P(k) is the frequency domain sequence of DMRS. After channel estimation, in order to further reduce the impact of channel estimation noise and improve the accuracy of channel estimation, the frequency domain response of the protection sideband subcarrier is first estimated by extrapolation to obtain the channel frequency domain response H of the entire frequency band. ’ LS (k). Then, by converting to the time domain through IFFT, 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 first and last 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). The windowed channel time domain response is then transformed into the frequency domain by FFT to obtain the frequency domain response, and finally the channel is smoothed in the frequency domain to obtain the channel estimation value H(k) used for channel equalization. The average window length is 5 (configurable), and the smoothing method after optimization in this embodiment is as follows:

[0215]

[0216] The noise power can be estimated by the channel response before and after smoothing. The specific method of estimating the noise power is as follows:

[0217]

[0218] Channel equalization uses the MMSE equalization algorithm. According to the MMSE algorithm theory, we can derive the equalization coefficient as follows:

[0219]

[0220] After that, the signal is further subjected to MMSE equalization compensation, and the signal after equalization is as follows:

[0221]

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

[0223]

[0224]

[0225] The soft demodulated information is first deinterleaved. Under the bad conditions of low signal-to-noise ratio and multipath, soft information is prone to errors. Statistically speaking, the possibility of errors in both bits of soft information is reduced. Therefore, in this embodiment, the two adjacent deinterleaved soft information are averaged, thereby improving the reliability of the soft information. That is:

[0226] ,

[0227] Among them, LLR'(n) is the soft information after despreading.

[0228] Turbo decoding is performed based on the soft information extracted from the equalized signal.

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

[0230] Component decoder 1 uses information bit soft information and checksum information 1, , extract external information L 12 e , the external information is interleaved and used as the prior information of component decoder 2.

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

[0232] After 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, and combines the relationship characteristics between each sub-segment of the PSS signal and each sub-segment of the corresponding SSS signal, the relationship characteristics between each sub-segment of the PSS signal, the relationship characteristics between each sub-segment of the SSS signal, and the similarity characteristics between all sub-segment signals and the received signal, thereby effectively increasing the characteristics and recognizability of the synchronization signal and improving the time-frequency synchronization performance under low signal-to-noise ratio and large Doppler frequency deviation conditions.

[0234] The method of this embodiment only utilizes the PSS signal and the SSS signal in one SSB time slot for synchronization. Compared with many related technologies that utilize the PSS signal and the 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 and ensures the real-time performance of signal reception.

[0235] Ideally, the phase of each sub-segment of the segmented synchronization signal should change continuously and regularly. Under low signal-to-noise ratio conditions, the influence of noise may destroy 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] In order to facilitate understanding of the signal synchronization method of this embodiment, Figures 4a to 5e Further description is given.

[0237] In the process of signal reception, in order to overcome the large Doppler frequency offset caused by the high-speed movement of the transmitter, as well as the signal crosstalk when the signal-to-noise ratio is low, the main purpose of this application is to achieve high-precision time-frequency synchronization under conditions of large Doppler frequency offset and low signal-to-noise ratio.

[0238] The process of the embodiment of the present application (the algorithm involved is the same as that of the above embodiment) specifically includes:

[0239] S1: Design wireless frames and adopt the frame structure of 5G NTN protocol downlink channel transmission.

[0240] S2: Data symbol transmission processing flow.

[0241] S3: Signal processing flow at the receiving end.

[0242] In step S1, a wireless frame is designed, using the frame structure of a 5G NTN downlink channel. The specific steps include:

[0243] S11: A designed wireless frame has two half frames with a duration of 10ms. The half frame structure is as follows: Figure 4a As shown, it includes half frame 1 and half frame 2. The wireless frame is as follows Figure 4b As shown. A half frame has 10 time slots, 1 time slot is 0.5ms, and each time slot has 14 OFDM symbols. The first OFDM symbol CP is 88 samples long (at 30.72M sampling rate), and the following 13 OFDM symbols CP is 72 samples long (at 30.72M sampling rate). Among them, the first time slot of the half frame carries the PSS and SSS synchronization sequence, called the SSB time slot, and the subsequent 9 time slots only carry data and DMRS (demodulation reference signal), called Data time slots.

[0244] S12: Design the SSB time slot structure. Figure 4cAs shown, OFDM symbols indexed 0 to 3 are data symbols (OFDM symbols indexed 2 are inserted with DMRS), which are modulated as a coding code block and sequentially mapped to the corresponding subcarriers. OFDM symbols indexed 4 to 7 are synchronization symbols and PBCH (Physical Broadcast Channel Symbol) symbols (4 is PSS symbol, 6 is SSS symbol, 5 / 7 is PBCH symbol). OFDM symbols indexed 8 to 10 are data symbols (OFDM symbols indexed 8 are inserted with DMRS), which are used as a coding code block. OFDM symbols indexed 11 to 13 are data symbols (OFDM symbols indexed 11 are inserted with DMRS), which are used as a coding code block. In the DMRS insertion method, data symbols occupy the middle 612 subcarriers, and PSS and SSS occupy the middle 127 subcarriers.

[0245] like Figure 4d and Figure 4e As 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 follows: Figure 5a As shown, the specific steps include:

[0247] S21: In order to improve transmission reliability, the source bits are spread twice.

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

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

[0250] S24: The modulation method adopts QPSK and 16QAM modulation.

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

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

[0253] S27: IFFT: perform 1024-point IFFT transformation.

[0254] S28: Adding CP and framing: For the data after IFFT transformation, the 88 points or 72 points at the end are placed before the data sample points to form an OFDM symbol.

[0255] S29: Oversampling, filtering: perform double oversampling, and control the cutoff frequency of the low-pass filter at around 10M. Figure 5b The transmit filter amplitude-frequency response is shown, with the horizontal axis being frequency and the vertical axis being amplitude.

[0256] In step S3, the receiving end processes the signal, such as Figure 5c The following is a schematic diagram of the signal processing flow at the receiving end, wherein the specific steps include:

[0257] S31: After receiving and filtering, it is now the IQ data of the oversampling level. The amplitude-frequency response of the filter is as follows Figure 5d As shown in the figure, the horizontal axis is frequency and the vertical axis is amplitude. By filtering, out-of-band noise can be filtered out and the receiving performance can be improved.

[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 synchronization correlation performance and cause synchronization failure, it is necessary to first use frequency offsets of different segments to pre-compensate the received signal for frequency offset, and then use the pre-compensated signal and the local PSS sequence and SSS sequence to perform correlation operations and sum them. The time corresponding to the maximum correlation peak when exceeding the threshold is the coarse timing synchronization position, and the frequency offset corresponding to the maximum peak is the coarse frequency offset estimate. The range of the frequency offset segment is set to -60KHz~60KHz, with a step of 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) (in order to reduce the complexity of processing, the signal after decimation by 2 is subjected to correlation operation after the coarse timing synchronous sampling), and w(t) is additive white Gaussian noise. Then the received signal of the terminal can be expressed as follows:

[0260]

[0261] By sampling the received signal at time k, the following expression of the received signal can be obtained:

[0262]

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

[0264]

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

[0266] The symbol coarse timing and coarse frequency offset estimation can be obtained by correlating the received signal with the locally stored PSS synchronization signal and SSS synchronization signal, as shown below:

[0267]

[0268] S PSS *(k) and S SSS *(k) represents the time domain waveform of the local PSS synchronization signal and the local SSS synchronization signal pre-stored by the receiver, P n (Δ) represents S PSS *(k ) and S SSS *(k ) and the received signal sequence r n (k+Δ) and r n The sum of the results after the correlation operation of (k+K+Δ) (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 results of the correlation operation. Find each P n The highest peak of the sequence is then compared, and 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 coarse frequency offset estimation, and the offset Δ corresponding to the maximum value is the offset of the detected initial symbol timing synchronization. It should be noted that in order to reduce the impact of the multipath channel, the correlation value can be windowed and summed before the maximum value is calculated.

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

[0272]

[0273]

[0274]

[0275]

[0276] By summing the above four expressions, we can get the mathematical expression as follows:

[0277]

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

[0279] Assuming that there is a carrier frequency deviation of Δf between the transmitter and the receiver, without considering noise, the received signal can be expressed as follows:

[0280]

[0281] Among them, T S Represents the sampling interval, N S Represents the number of IFFT points. Substituting into the following formula, we can get the following expression:

[0282]

[0283]

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

[0285]

[0286] analyze The result of the operation is to expand the summation term and then perform cross multiplication. Then the corresponding term and The result of the multiplication is a real number, let The result of cross-multiplication of other terms is a complex random variable, with a total of Items, let each item be expressed as . Then the above formula can be expressed as:

[0287]

[0288]

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

[0290]

[0291] Introducing phase parameters , then the frequency deviation based on the autocorrelation of the SSS signal before and after is estimated as:

[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), 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, and obtain the following two operation results:

[0294]

[0295]

[0296] After some mathematical transformations, we can further obtain the following expression:

[0297]

[0298]

[0299] Arranging the above two equations, we can get

[0300]

[0301]

[0302] Introducing the phase main value parameter , the frequency deviation estimation value 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:

[0303]

[0304] Combination and , we can get the final frequency deviation estimate as:

[0305]

[0306] Here, α is a weight factor between 0 and 1. Optimizing this weight factor will affect the effect of the precise frequency deviation 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 an estimated channel gain of H. LS (k) = Y(k) / P(k). Where P(k) is the frequency domain sequence of DMRS. After channel estimation, in order to further reduce the impact of channel estimation noise and improve the accuracy of channel estimation, the frequency domain response of the protection sideband subcarrier is first estimated by extrapolation to obtain the channel frequency domain response H of the entire frequency band. LS (k). Then, by converting to the time domain through IFFT, the following expression can be obtained:

[0308]

[0309] For the obtained channel time domain impulse response, the influence of noise is reduced by windowing, that is, only the first and last 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). The windowed channel time domain response is then transformed into the frequency domain by FFT to obtain the frequency domain response, and finally the channel is smoothed in the frequency domain to obtain the channel estimation value H(k) used 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 from the channel response before and after smoothing as follows:

[0312]

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

[0314]

[0315] After that, the signal is further subjected to MMSE equalization compensation, and the signal after equalization is as follows:

[0316]

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

[0318]

[0319]

[0320] S37: Deinterleaving: The soft demodulated information is first deinterleaved. Under the bad conditions of low signal-to-noise ratio and multipath, soft information is prone to errors. Statistically speaking, the possibility of errors in both bits of soft information is reduced. Therefore, the two adjacent deinterleaved soft information are averaged to improve the reliability of the soft information. That is:

[0321]

[0322] Among them, 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] like Figure 5e As shown, the soft information extracted during channel equalization is divided into information bits and soft information Sum check bit soft information , the check bit soft information is divided into check information 1, Sum verification information 2, y 2p .

[0325] Component decoder 1, DEC1 in the figure, uses information bit soft information and checksum information 1, , extract external information L 12 e , the external information is interleaved and used as the prior information of component decoder 2.

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

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

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

[0329] For the simulation results:

[0330] The channel uses the TDL (Tapped Delay Line) channel specified by 3GPP (3rd Generation Partnership Project). Since the TDL-A channel is a Rayleigh multipath channel, it is the worst. Therefore, this solution simulation selects TDL-A as the simulation channel. The maximum Doppler frequency deviation is set to 52KHz, the frequency deviation change rate is 750Hz / s, and the SNR (Signal to Noise Ratio) is set to change dynamically from -8dB to 4dB.

[0331] Specific results such as Figures 6 to 8 shown. Figure 6 The figure shows the relationship between the capture probability and signal-to-noise ratio of a signal processing system, with the x-axis being the SNR and the y-axis being the capture probability. Figure 7 The trend of the average frequency offset estimation error changing with the signal-to-noise ratio is shown, with the x-axis being the SNR and the y-axis being the frequency offset estimation error. Figure 8 The relationship between bit error rate and signal-to-noise ratio is shown, with the x-axis being SNR and the y-axis being bit error rate (BER).

[0332] Fig. 9 A schematic diagram of the structure of the signal synchronization device provided in this application, such as Fig. 9 As shown, in this embodiment, the signal synchronization device 300 can be set in a communication device, and the signal synchronization device 300 includes:

[0333] The coarse synchronization module 301 is used to perform a preset coarse synchronization process on the received signal and determine a coarse synchronization result corresponding to the received signal.

[0334] The fine synchronization module 302 is used to perform a preset fine synchronization process on the received signal after the coarse synchronization process 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 on the basis of the coarse synchronization result, 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] The signal synchronization module 303 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.

[0336] The signal synchronization device provided in this embodiment can be executed Figure 2 The technical solution of the method embodiment shown in the figure has the same implementation principle and technical effect as Figure 2 The method embodiments shown are similar and will not be described in detail here.

[0337] The signal synchronization device provided in the present application is further refined on the basis of the signal synchronization device provided in the previous embodiment, and the signal synchronization device 300 includes:

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

[0339] The received signal is compensated according to each preset frequency deviation to generate a corresponding compensated received signal. Each compensated received signal, PSS and SSS are input 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, the preset frequency deviation corresponding to the maximum value and the corresponding time offset are determined as the coarse synchronization result.

[0340] Optionally, in this embodiment, the fine synchronization module 302 performs preset fine synchronization processing on the received signal after the 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 to generate a corresponding fine synchronization result, specifically for:

[0341] Determine a first correlation 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 the 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 feature between each third sub-signal segment and the corresponding second sub-signal segment. Determine the moment of precise timing synchronization according to each first correlation feature and each second correlation feature. Determine the frequency deviation of precise 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 determining the first correlation feature between the third sub-signal segment and the corresponding first sub-signal segment, the fine synchronization module 302 is specifically configured to:

[0344] Determine multiple candidate time offsets. The candidate time offsets are based on the coarse synchronization time offset. Input the candidate time offset, 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 feature corresponding to the candidate time offset based on the second preset correlation operation algorithm.

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

[0346] For each candidate time offset, the sum of each corresponding first correlation feature and each corresponding second correlation feature is calculated, and the candidate time offset corresponding to the maximum value of each sum is determined as the moment of precise timing synchronization.

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

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

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

[0350] The second correlation feature and the first correlation feature of the same inverse fast Fourier transform IFFT point area are input into the fourth preset correlation operation algorithm to generate a corresponding fifth correlation feature.

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

[0352] The fourth correlation feature is subjected to phase conversion processing to generate a corresponding first phase parameter. The fifth correlation feature is subjected to phase conversion processing to generate a corresponding intermediate phase parameter. The intermediate phase parameter is subjected to averaging processing to generate a corresponding second phase parameter. The first phase parameter and the second phase parameter are weighted summed to generate a frequency deviation for precise timing synchronization.

[0353] The signal synchronization device provided in this embodiment can be executed Figure 2-Figure 8 The technical solution of the method embodiment shown in the figure has the same implementation principle and technical effect as Figure 2-Figure 8 The method embodiments shown are similar and will not be described in detail here.

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

[0355] like Fig.10 As shown, Fig.10is a schematic diagram of the structure of the communication device provided by the present application. The communication device is intended to be various forms of devices with communication functions, such as workstations, mobile phones, vehicle-mounted terminals, and other suitable computers. The components shown herein, their connections and relationships, and their functions are only examples and are not intended to limit the implementation of the present application described and / or required herein.

[0356] like Fig.10 As shown, the communication device includes: a processor 401 and a memory 402. The various components are connected to each other using different buses and can be installed on a common mainboard or in other ways as required. The processor can process instructions executed in the communication device.

[0357] The memory 402 is a non-transient computer-readable storage medium provided in the present application. The memory stores instructions executable by at least one processor to enable at least one processor to perform the signal synchronization method provided in the present application. The non-transient computer-readable storage medium of the present application stores computer instructions, which are used to enable a computer to perform the signal synchronization method provided in the present application.

[0358] The memory 402 is a non-transient computer-readable storage medium that can be used to store non-transient software programs, non-transient computer executable programs and modules, such as program instructions / modules corresponding to the signal synchronization method in the embodiment of the present application (for example, the attached Fig. 9 The processor 401 executes various functional applications and data processing of the communication device by running the non-transient software programs, instructions and modules stored in the memory 402, that is, the signal synchronization method in the above method embodiment is implemented.

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

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

[0361] Those skilled in the art will readily come up with other implementations of the embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modifications, uses or adaptations of the embodiments of the present application, which follow the general principles of the embodiments of the present application and include common knowledge or customary technical means in the art that are not disclosed in the embodiments of the present application.

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

Claims

1. A signal synchronization method, characterized in that: include: Performing a preset coarse synchronization process on the received signal to determine a coarse synchronization result corresponding to the received signal; Based on the coarse synchronization result, a preset fine synchronization process is performed on the received signal after the coarse synchronization process 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; 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; Signal synchronization compensation is performed on the received signal after fine synchronization processing according to the fine synchronization result to complete signal synchronization.

2. The method according to claim 1, characterized in that 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 deviation 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 related operation results is greater than the preset threshold value, the preset frequency deviation and the corresponding time offset corresponding to the maximum value are determined as the coarse synchronization result.

3. The method according to claim 2, characterized in that The method of performing a preset fine synchronization process on the received signal after the coarse synchronization process 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 includes: Determine a first correlation feature between each third sub-signal segment and the corresponding first sub-signal segment; the third sub-signal segments are obtained by dividing the received signal after the 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; Determining a second correlation feature between each of the third sub-signal segments and the corresponding second sub-signal segment; Determine a precise timing synchronization moment according to each of the first correlation characteristics and each of the second correlation characteristics; A frequency deviation for precise timing synchronization is determined based on the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment.

4. The method according to claim 3, characterized in that The coarse synchronization result includes a coarse synchronization time offset; The determining of a first correlation feature between the third sub-signal segment and the corresponding first sub-signal segment includes: Determine a plurality of candidate time offsets; the candidate time offsets are based on the coarse synchronization time offset; The candidate time offset, the third sub-signal segment, and the first sub-signal segment corresponding to the third sub-signal segment are input 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.

5. The method according to claim 4, characterized in that The step of determining the precise timing synchronization moment according to each of the first correlation characteristics and each of the second correlation characteristics comprises: For each candidate time offset, calculate the sum of each corresponding first correlation feature and each corresponding second correlation feature; The candidate time offset corresponding to the maximum value of each of the sums is determined as the moment of precise timing synchronization.

6. The method according to claim 3, characterized in that: The determining of the frequency deviation of precise timing synchronization according to the first sub-signal segment, the second sub-signal segment, and the third sub-signal segment comprises: Determining a third correlation feature between each of the third sub-signal segments and the corresponding second sub-signal segment; Inputting each of the third correlation features into a third preset correlation operation algorithm to determine a fourth correlation feature between each of the third correlation features based on the third preset correlation operation algorithm; determining a fifth correlation feature between the second correlation feature and the first correlation feature; The frequency offset of the precise timing synchronization is determined according to the fourth correlation feature and the fifth correlation feature.

7. The method according to claim 6, characterized in that The determining of a fifth correlation feature between the second correlation feature and the first correlation feature comprises: The second correlation feature and the first correlation feature of the same inverse fast Fourier transform IFFT point area are input into the fourth preset correlation operation algorithm to generate a corresponding fifth correlation feature.

8. The method according to claim 6, characterized in that The determining the frequency deviation of the precise timing synchronization according to the fourth correlation feature and the fifth correlation feature comprises: Performing phase conversion processing on the fourth correlation feature to generate a corresponding first phase parameter; Performing phase conversion processing on the fifth correlation feature to generate a corresponding intermediate phase parameter; Performing an averaging process on the intermediate phase parameters to generate corresponding second phase parameters; A weighted sum is performed on the first phase parameter and the second phase parameter to generate a frequency deviation for precise timing synchronization.

9. A signal synchronization device, characterized in that: include: A coarse synchronization module, used to perform a preset coarse synchronization process on a received signal and determine a coarse synchronization result corresponding to the received signal; A fine synchronization module, configured to perform preset fine synchronization processing on the received signal after the 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 on the basis of the coarse synchronization result, 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; The signal synchronization module 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.

10. A communication device, characterized in that: include: Memory and processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the signal synchronization method according to any one of claims 1 to 8.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the signal synchronization method according to any one of claims 1 to 8.

12. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the signal synchronization method according to any one of claims 1 to 8 is implemented.

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