Vehicle-to-Everything (V2X) Symbol Synchronization Method, Device and Storage Medium

Abstract

This application provides a method, apparatus, and storage medium for vehicle-to-everything (V2X) symbol synchronization, relating to the field of communication technology. It addresses the problem of poor reliability and accuracy of traditional symbol synchronization algorithms in high-frequency bias and low signal-to-noise ratio (SNR) LTE-V2X practical communication scenarios. The method includes: performing coarse synchronization processing on the received baseband V2X signal and local synchronization signal to obtain a coarse synchronization point; calculating a frequency offset estimate based on the local synchronization signal and the coarsely synchronized baseband V2X signal, and using the frequency offset estimate to compensate the local synchronization signal; based on the coarse synchronization point, extracting the unsampled baseband V2X signal from the received baseband V2X signal; and performing fine synchronization processing on the unsampled baseband V2X signal and the frequency offset-compensated local synchronization signal to obtain a fine synchronization point. The embodiments of this application are used in the process of V2X symbol synchronization.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a method, apparatus and storage medium for synchronizing symbols in a vehicle network. Background Technology

[0002] Long Term Evolution (LTE)-V2X is a comprehensive communication solution for vehicle-to-everything (V2X) communication, which can provide low latency, high reliability, high speed and secure communication capabilities in high-speed mobile environments to meet the needs of various V2X applications.

[0003] Unlike traditional LTE cellular network systems, the relative motion between communication nodes in LTE-V2X systems causes constant changes in the channel state between them. This makes communication between nodes more susceptible to changes in the surrounding environment, which is reflected in the physical layer receiver processing algorithm. Symbol synchronization is a crucial step in the physical layer receiver processing. Only by finding the Fast Fourier Transform (FFT) window through the symbol synchronization algorithm can the receiver begin the subsequent processing. If the FFT window is misplaced, the orthogonality of subcarriers in the Orthogonal Frequency Division Multiplexing (OFDM) system will be disrupted, causing inter-symbol interference and affecting the transmission performance of the communication system.

[0004] Traditional symbol synchronization algorithms are divided into time-domain and frequency-domain types. Time-domain synchronization algorithms complete symbol synchronization by performing sliding correlation between locally known sequences and received signals; frequency-domain synchronization algorithms require finding an FFT window to perform synchronization, which is too complex in LTE-V2X and cannot meet the low-latency synchronization requirements. Therefore, traditional symbol synchronization algorithms have poor reliability and accuracy in real-world LTE-V2X communication scenarios with high frequency bias and low signal-to-noise ratio. Summary of the Invention

[0005] This application provides a method, apparatus, and storage medium for vehicle-to-everything (V2X) symbol synchronization, which can solve the problem of poor reliability and accuracy of traditional symbol synchronization algorithms in actual LTE-V2X communication scenarios with high frequency bias and low signal-to-noise ratio.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a method for vehicular network symbol synchronization, the method comprising: performing coarse synchronization processing on received baseband vehicular network signals and local synchronization signals to obtain a coarse synchronization point; calculating a frequency offset estimate based on the local synchronization signal and the coarsely synchronized baseband vehicular network signals, and using the frequency offset estimate to compensate the local synchronization signal; based on the coarse synchronization point, extracting the unsampled baseband vehicular network signals from the received baseband vehicular network signals; and performing fine synchronization processing on the unsampled baseband vehicular network signals and the frequency offset-compensated local synchronization signals to obtain a fine synchronization point.

[0008] Based on the above technical solution, the vehicle-to-everything (V2X) symbol synchronization method provided in this application performs coarse synchronization processing on the baseband V2X signal and the local synchronization signal to obtain a coarse synchronization point. Based on the local synchronization signal and the coarsely synchronized baseband V2X signal, a frequency offset estimate is calculated to compensate the local synchronization signal. Then, based on the coarse synchronization point, an unsampled portion of the baseband V2X signal is extracted from the received baseband V2X signal. Finally, fine synchronization processing is performed on the unsampled baseband V2X signal and the frequency-offset compensated local synchronization signal to obtain a fine synchronization point. This solution involves two synchronization processes (coarse and fine), i.e., symbol synchronization is completed through a time-domain synchronization algorithm, improving synchronization accuracy. Furthermore, frequency offset estimation and signal extraction are performed during the synchronization process, compensating for the local synchronization signal, thus improving the quality of the baseband V2X signal and the synchronization accuracy of the algorithm. This enhances the reliability and accuracy of symbol synchronization, adapting to the characteristics of high-frequency offset and low signal-to-noise ratio in LTE-V2X, thereby improving reliability and accuracy in actual LTE-V2X communication scenarios with high-frequency offset and low signal-to-noise ratio.

[0009] In a first possible implementation of the first aspect, the aforementioned "performing coarse synchronization processing on the received baseband vehicle-to-everything (V2X) signal and local synchronization signal to obtain a coarse synchronization point" includes: downsampling the received baseband V2X signal and local synchronization signal; sliding the downsampled baseband V2X signal and the downsampled local synchronization signal to a correlation segment to obtain a first correlation value; performing a first peak decision on the first correlation value based on a first threshold to obtain the type of synchronization signal and a first coarse synchronization peak; selecting and adding the values ​​in the first coarse synchronization peak whose relative distance is equal to the length of a downsampled Orthogonal Frequency Division Multiplexing (OFDM) symbol to obtain first data; performing a second peak decision on the first data based on a second threshold to obtain a second coarse synchronization peak, and making a decision on the second coarse synchronization peak to obtain a coarse synchronization point.

[0010] In the second possible implementation of the first aspect, the above-mentioned "sliding the downsampled baseband vehicle network signal and the downsampled local synchronization signal into a segmented correlation to obtain a first correlation value" includes: using a first algorithm to calculate the first correlation value based on the conjugate of the downsampled baseband vehicle network signal, the downsampled local synchronization signal, the type of synchronization signal, the number of segments, and the length of each segment.

[0011] In the third possible implementation of the first aspect, the above-mentioned "calculating the frequency offset estimate based on the local synchronization signal and the baseband vehicle network signal after coarse synchronization processing" includes: extracting the local demodulation reference signal based on the local synchronization signal, and extracting the time domain demodulation reference signal based on the baseband vehicle network signal after coarse synchronization processing; performing successive cross-correlation on the time domain demodulation reference signal and the local demodulation reference signal, and superimposing the obtained correlation values ​​to obtain the frequency offset estimate.

[0012] In the fourth possible implementation of the first aspect, the above-mentioned "performing fine synchronization processing on the unsampled baseband vehicular network signal and the compensated local synchronization signal to obtain a fine synchronization point" includes: sliding the unsampled baseband vehicular network signal and the compensated local synchronization signal to correlation in segments to obtain a second correlation value; performing a first peak decision on the second correlation value based on a third threshold to obtain a first fine synchronization peak; selecting and adding the values ​​in the first fine synchronization peak whose relative distance is equal to the length of one OFDM symbol to obtain second data; performing a second peak decision on the second data based on a fourth threshold to obtain a second fine synchronization peak, and making a decision on the second fine synchronization peak to obtain a fine synchronization point.

[0013] In the fifth possible implementation of the first aspect, the above-mentioned "sliding the unsampled baseband vehicle network signal and the compensated frequency offset local synchronization signal into a correlation segment to obtain a second correlation value" includes: using a second algorithm to calculate the second correlation value based on the conjugate of the unsampled baseband vehicle network signal, the compensated frequency offset local synchronization signal, the number of segments, and the length of each segment.

[0014] Secondly, this application provides a vehicle-to-everything (V2X) symbol synchronization device, comprising: a processing unit for performing coarse synchronization processing on received baseband V2X signals and local synchronization signals to obtain a coarse synchronization point; a calculation unit for calculating a frequency offset estimate based on the local synchronization signal and the coarsely synchronized baseband V2X signals, and using the frequency offset estimate to compensate the local synchronization signal; a truncation unit for truncating unsampled baseband V2X signals from the received baseband V2X signals based on the coarse synchronization point; and a further processing unit for performing fine synchronization processing on the unsampled baseband V2X signals and the frequency offset-compensated local synchronization signal to obtain a fine synchronization point.

[0015] In a first possible implementation of the second aspect, the aforementioned processing unit is specifically configured to: downsample the received baseband vehicle network signal and local synchronization signal; slide the downsampled baseband vehicle network signal and the downsampled local synchronization signal into a segmented correlation to obtain a first correlation value; perform a first peak decision on the first correlation value based on a first threshold to obtain the type of synchronization signal and a first coarse synchronization peak; select and add the values ​​in the first coarse synchronization peak whose relative distance is equal to the length of a downsampled orthogonal frequency division multiplexing (OFDM) symbol to obtain first data; perform a second peak decision on the first data based on a second threshold to obtain a second coarse synchronization peak, and make a decision on the second coarse synchronization peak to obtain a coarse synchronization point.

[0016] In a second possible implementation of the second aspect, the aforementioned processing unit is specifically used to employ a first algorithm to calculate a first correlation value based on the conjugate of the downsampled baseband vehicle network signal, the downsampled local synchronization signal, the type of synchronization signal, the number of segments, and the length of each segment.

[0017] In the third possible implementation of the second aspect, the above-mentioned computing unit is specifically used to: extract a local demodulation reference signal based on the local synchronization signal, and extract a time-domain demodulation reference signal based on the baseband vehicle network signal after coarse synchronization processing; perform successive cross-correlation between the time-domain demodulation reference signal and the local demodulation reference signal, and superimpose the obtained correlation values ​​to obtain a frequency offset estimate.

[0018] In the fourth possible implementation of the second aspect, the aforementioned processing unit is specifically used to: slide the unsampled baseband vehicle network signal and the compensated frequency offset local synchronization signal into a segmented correlation to obtain a second correlation value; perform a first peak decision on the second correlation value based on a third threshold to obtain a first fine synchronization peak; select and add the values ​​in the first fine synchronization peak whose relative distance is equal to the length of one OFDM symbol to obtain second data; perform a second peak decision on the second data based on a fourth threshold to obtain a second fine synchronization peak, and make a decision on the second fine synchronization peak to obtain a fine synchronization point.

[0019] In the fifth possible implementation of the second aspect, the aforementioned processing unit is specifically used to employ a second algorithm to calculate a second correlation value based on the conjugate of the unsampled baseband vehicle network signal, the local synchronization signal after frequency offset compensation, the number of segments, and the length of each segment.

[0020] Thirdly, this application provides a vehicle network symbol synchronization device, which includes: a processor and a communication interface; the communication interface and the processor are coupled, and the processor is used to run computer programs or instructions to implement the vehicle network symbol synchronization method as described in the first aspect and any possible implementation of the first aspect.

[0021] Fourthly, this application provides a computer-readable storage medium storing instructions that, when executed on a terminal, cause the terminal to perform the vehicle network symbol synchronization method as described in the first aspect and any possible implementation thereof.

[0022] Fifthly, embodiments of this application provide a computer program product containing instructions that, when run on a vehicle network symbol synchronization device, cause the vehicle network symbol synchronization device to execute the vehicle network symbol synchronization method as described in the first aspect and any possible implementation thereof.

[0023] In a sixth aspect, embodiments of this application provide a chip including a processor and a communication interface, the communication interface being coupled to the processor, the processor being used to run computer programs or instructions to implement the vehicle network symbol synchronization method as described in the first aspect and any possible implementation thereof.

[0024] Specifically, the chip provided in this application embodiment also includes a memory for storing computer programs or instructions. Attached Figure Description

[0025] Figure 1 A flowchart illustrating a vehicle-to-everything (V2X) symbol synchronization method provided in this application embodiment;

[0026] Figure 2 A schematic diagram illustrating an example of the symbol position of a primary synchronization signal in a subframe, provided in an embodiment of this application;

[0027] Figure 3 A schematic diagram illustrating an example of a successive cross-correlation process for a demodulated reference signal provided in an embodiment of this application;

[0028] Figure 4 A flowchart of an LTE-V2X symbol synchronization algorithm for complex channel scenarios in vehicle-to-everything (V2X) networks is provided as an embodiment of this application;

[0029] Figure 5 This is a schematic diagram of the structure of a vehicle-to-everything (V2X) symbol synchronization device provided in an embodiment of this application;

[0030] Figure 6 A schematic diagram of another vehicle-to-everything (V2X) symbol synchronization device provided in this application embodiment;

[0031] Figure 7 This is a schematic diagram of the structure of a chip provided in an embodiment of this application. Detailed Implementation

[0032] The method, apparatus, and storage medium for synchronizing vehicle network symbols provided in the embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0033] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0034] The terms "first" and "second," etc., used in the specification and drawings of this application are used to distinguish different objects or to distinguish different treatments of the same object, rather than to describe a specific order of objects.

[0035] Furthermore, the terms "comprising" and "having," and any variations thereof, used in the description of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0036] It should be noted that in the embodiments of this application, the words "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0037] In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0038] The following describes the vehicle network symbol synchronization method provided in this application through specific scenarios and implementation methods.

[0039] Currently, the main traditional time-domain symbol synchronization algorithms are as follows:

[0040] (1) Traditional sliding correlation method: The traditional sliding correlation method directly performs sliding correlation on the received signal for different types of local signals, obtains the correlation value, and then performs maximum likelihood decision to obtain the type and symbol position of the local signal. It is simple to implement, but the algorithm complexity is high when the received signal is long or the correlation window is large; and when the frequency offset is large, a "secondary peak" will be generated near the correct peak position, resulting in the failure of peak decision; and the performance is poor under low signal-to-noise ratio conditions, so it cannot meet the synchronous detection requirements of vehicle networking scenarios.

[0041] (2) Segmented correlation algorithm: This algorithm reduces the length of the effective correlation window by segmenting the received signal, thereby reducing the cumulative effect of frequency offset. However, as the number of segments increases, noise is superimposed more often, resulting in poor performance of the algorithm under low signal-to-noise ratio conditions, and it is also unable to adapt well to the actual scenario of vehicle networking.

[0042] (3) Selective Addition Method: Since the synchronization signal of LTE-V2X occupies two consecutive OFDM symbols in the time domain, the robust synchronization signal detection algorithm, the selective addition method, was proposed. This algorithm uses the distance between the two synchronization signals known at the local receiver to selectively add the peak values ​​of the correlation values, which greatly improves the performance of the algorithm under low signal-to-noise ratio conditions. However, when the propagation channel is at a large frequency offset or has a large multipath, a "secondary peak" will appear near the synchronization peak. When the distance between the "secondary peaks" is the distance between the two synchronization signals, the selective addition algorithm will also add their peak values, resulting in synchronization failure.

[0043] In summary, existing traditional time-domain symbol synchronization algorithms do not perform well in LTE-V2X systems: on the one hand, the antennas of vehicle-mounted communication equipment are generally installed at the shark fin position on the top of the vehicle, which is easily blocked by large vehicles or other obstacles during relative movement, resulting in a sharp drop in the signal-to-noise ratio of the received signal; on the other hand, the communication frequency of the LTE-V2X system is much higher than that of the cellular network, and the relative speed between communication nodes can reach up to 240 km / h, resulting in a large Doppler frequency offset.

[0044] The aforementioned traditional time-domain synchronization algorithms (sliding correlation method, segmented correlation algorithm, and selected addition method) are all unsuitable for the low signal-to-noise ratio and high-frequency bias characteristics of LTE-V2X scenarios. Therefore, the reliability and accuracy of traditional symbol synchronization algorithms are poor in actual LTE-V2X communication scenarios with high-frequency bias and low signal-to-noise ratio.

[0045] To address the poor reliability and accuracy of traditional symbol synchronization algorithms in high-frequency, low-signal-to-noise-ratio LTE-V2X communication scenarios, this application provides a vehicle-to-everything (V2X) symbol synchronization method. This method performs coarse synchronization processing on the baseband V2X signal and the local synchronization signal to obtain a coarse synchronization point. Based on the local synchronization signal and the coarsely synchronized baseband V2X signal, a frequency offset estimate is calculated and used to compensate the local synchronization signal. Then, based on the coarse synchronization point, an unsampled portion of the baseband V2X signal is extracted from the received baseband V2X signal, and the unsampled baseband V2X signal is then processed and compensated. The local synchronization signal after frequency offset undergoes fine synchronization processing to obtain the fine synchronization point. This scheme involves two synchronization processes (coarse synchronization processing and fine synchronization processing). Symbol synchronization is completed through a time-domain synchronization algorithm, which improves the synchronization accuracy. During the synchronization process, frequency offset estimation and signal truncation are performed to compensate for the local synchronization signal, thereby improving the quality of the baseband vehicle network signal and the synchronization accuracy of the algorithm. This enhances the reliability and accuracy of symbol synchronization, adapting to the characteristics of high frequency offset and low signal-to-noise ratio in LTE-V2X. In other words, it improves the reliability and accuracy in actual LTE-V2X communication scenarios with high frequency offset and low signal-to-noise ratio.

[0046] like Figure 1 The diagram shows a flowchart of a vehicle network symbol synchronization method provided in an embodiment of this application. The method includes the following steps S101 to S104:

[0047] S101. Perform coarse synchronization processing on the received baseband vehicle network signal and local synchronization signal to obtain the coarse synchronization point.

[0048] In one implementation, the above S101 can be specifically implemented by the following S101a to S101e.

[0049] S101a: Downsample the received baseband vehicle networking signal and local synchronization signal.

[0050] In this embodiment of the application, the received baseband vehicle networking signal R(θ) and two local synchronization signals P are... i (θ) is used for downsampling. This reduces computational complexity, saves computational resources, and improves computational efficiency.

[0051] For example, the downsampling factor of the baseband vehicle network signal and the local synchronization signal can be set to 8. This is because under the 20M bandwidth of the vehicle network, the length of one local synchronization signal is 2048 points. After 8 times downsampling, it becomes 256 points, which is 4 times its frequency domain length (64). Choosing an 8 times downsampling factor can achieve higher synchronization accuracy without losing information.

[0052] S101b: The downsampled baseband vehicle network signal and the downsampled local synchronization signal are segmented and slid to correlation to obtain the first correlation value.

[0053] In one implementation, the above S101b can be specifically implemented through the following S101b1.

[0054] S101b1. Using the first algorithm, the first correlation value is calculated based on the conjugate of the downsampled baseband vehicle network signal, the downsampled local synchronization signal, the type of synchronization signal, the number of segments, and the length of each segment.

[0055] In this embodiment of the application, the downsampled baseband vehicle networking signal r(θ) and the downsampled local synchronization signal p are used to... i (θ) Piecewise sliding correlation yields the correlation value C. 1i (θ), is calculated by the first algorithm (i.e., formula (1)):

[0056]

[0057] Where, r * (θ) represents the conjugate of r(θ), p i (θ) represents the local synchronization signal after downsampling, i represents the type of synchronization signal, J represents the number of segments, and L represents the length of each segment.

[0058] S101c: Perform a peak value determination on the first correlation value based on the first threshold to obtain the type of synchronization signal and a coarse synchronization peak.

[0059] In this embodiment of the application, the relevant value C 1i (θ) is used to apply the first threshold (i.e., the threshold is T). 11 The first peak decision of (θ) yields the type i of the received synchronization signal and the first coarse synchronization peak S. 11 (θ), where the decision threshold T 11 (θ) is calculated using formula (2):

[0060] T 11 (θ) = 0.2 * max(C) 1i (θ)) (2)

[0061] The coarse synchronization peak S in S101c 11 (θ) is calculated according to formula (3):

[0062] S 11 (θ)=arg{C 1i (θ)-T 11 (θ)>0} (3)

[0063] S101d: Select and sum the values ​​in the first coarse synchronization peak whose relative distance is equal to the length of an OFDM symbol after downsampling to obtain the first data.

[0064] In this embodiment of the application, the first coarse synchronization peak S 11 The first data is obtained by selecting and adding the values ​​of the relative distances in (θ) that are equal to the length of a downsampled OFDM symbol. Calculated using formula (4):

[0065]

[0066] Where d is the distance of an OFDM symbol.

[0067] S101e, Perform a second threshold peak judgment on the first data to obtain a second coarse synchronization peak, and make a judgment on the second coarse synchronization peak to obtain a coarse synchronization point.

[0068] In this embodiment of the application, for Perform a second threshold (threshold is T) 12 The second peak decision of (θ) yields the second coarse synchronization peak S. 12 (θ), and determine the coarse synchronization point by performing a judgment on it. The decision threshold is calculated using formula (5):

[0069]

[0070] Furthermore, according to the physical frame structure of the LTE-V2X broadcast channel, such as Figure 2 As shown, the main synchronization signal is located in the 2nd and 3rd OFDM symbols of the subframe, therefore the subframe start position is the coarse synchronization point. Calculated using formula (6):

[0071]

[0072] Where N is the number of FFT points. Coarse synchronization points. The position of the first synchronization symbol of the received signal.

[0073] Based on the LTE-V2X physical frame format, the frame header is further obtained.

[0074] S102. Based on the local synchronization signal and the baseband vehicle network signal after coarse synchronization processing, the frequency offset estimate is calculated, and the frequency offset estimate is used to compensate the local synchronization signal.

[0075] In this embodiment of the application, a local synchronization signal p is used. i The estimated frequency offset is calculated from (θ) and the received signal r(θ). Using estimated frequency offset The compensated local synchronization signal is obtained by compensating the local synchronization signal.

[0076] In one implementation, the "calculation of frequency offset estimate based on local synchronization signal and baseband vehicle network signal after coarse synchronization processing" in S102 above can be specifically implemented by the following S102a and S102b.

[0077] S102a. Based on the local synchronization signal, extract the local demodulation reference signal, and based on the baseband vehicle network signal after coarse synchronization processing, extract the time domain demodulation reference signal.

[0078] S102b: Perform successive cross-correlation between the time-domain demodulation reference signal and the local demodulation reference signal, and then superimpose the obtained correlation values ​​to obtain the frequency offset estimate.

[0079] Specifically, the demodulation reference signal of the control channel in the physical pass-through link is used to eliminate the effect of frequency offset on the signal. After obtaining the coarse synchronization point, the four columns of demodulation reference signals of the physical pass-through link control channel in the radio frame are extracted, such as... Figure 3 As shown, the frequency offset is estimated by successively cross-correlated with the local demodulation reference signal and then superimposing the obtained correlation values. Calculate using formula (7):

[0080]

[0081] Where, r k (n) is the received time-domain demodulation reference signal, P k (n) represents the local demodulation reference signal, k = 0, 1, 2, 3 represents the demodulation reference signal at different symbols, and N is the number of FFT points. cp The length of CP.

[0082] Furthermore, using frequency offset estimates Frequency offset compensation is performed on the local synchronization signal, and the compensated local synchronization signal is obtained. Calculated using formula (8):

[0083]

[0084] Among them, f s The sampling frequency.

[0085] S103. Based on the coarse synchronization point, extract the unsampled baseband vehicle network signal from the received baseband vehicle network signal.

[0086] In this embodiment of the application, at the coarse synchronization point S 12 The unsampled baseband vehicular network signal R(θ) is extracted near (θ). To reduce computational complexity, a coarse synchronization point is extracted. The range of the nearby unsampled baseband vehicle-to-everything (V2X) signal R(θ) is as follows: That is, one complete subframe.

[0087] S104. Perform fine synchronization processing on the unsampled baseband vehicle networking signal and the local synchronization signal after frequency offset compensation to obtain the fine synchronization point.

[0088] In one implementation, the above S104 can be specifically implemented by the following S104a to S104d.

[0089] S104a. The unsampled baseband vehicle network signal and the local synchronization signal after frequency offset compensation are segmented and slid to correlation to obtain the second correlation value.

[0090] In one implementation, the above S104a can be specifically implemented by the following S104a1.

[0091] S104a1. Using the second algorithm, the second correlation value is calculated based on the conjugate of the unsampled baseband vehicle network signal, the local synchronization signal after frequency offset compensation, the number of segments, and the length of each segment.

[0092] In this embodiment of the application, the truncated baseband vehicle networking signal R(θ) and the local synchronization signal after frequency offset compensation are used. The second correlation value C is obtained by piecewise sliding correlation. 2i (θ), is calculated by the second algorithm (i.e., formula (10)):

[0093]

[0094] S104b: Perform a peak determination on the second correlation value using the third threshold to obtain a precise synchronization peak.

[0095] In this embodiment of the application, the relevant value C 2i (θ) is used to apply the third threshold (i.e., the threshold is T). 21 A peak decision of (θ) yields a precise synchronization peak S. 21 (θ), where the threshold T 21 (θ) is calculated using formula (11):

[0096] T 21 (θ) = 0.2 * max(C) 2i (θ)) (11)

[0097] S104c: Select and sum the values ​​in the first synchronization peak whose relative distance is equal to the length of one OFDM symbol to obtain the second data.

[0098] In this embodiment of the application, the first precise synchronization peak S 21The values ​​in (θ) whose relative distance is equal to the length of one OFDM symbol are selected and summed, and the result is represented as the second data. Calculated using formula (12):

[0099]

[0100] S104d: Perform a second peak judgment on the second data using the fourth threshold to obtain the second fine synchronization peak, and then make a judgment on the second fine synchronization peak to obtain the fine synchronization point.

[0101] In this embodiment of the application, the relevant values ​​after addition are selected. Perform a fourth threshold (i.e., threshold T) 22 The second peak decision of (θ) is used to obtain the second-order fine synchronization peak S. 22 (θ), where the threshold T 22 (θ) is calculated using formula (13):

[0102]

[0103] In this embodiment of the application, the secondary precision synchronization peak S 22 (θ) is used to make a decision to obtain the accurate position of the received synchronization signal, i.e., the fine synchronization point. Fine synchronization point Calculated using formula (9):

[0104]

[0105] In this embodiment, by designing the correlation value decision threshold and using a fusion algorithm for both coarse and fine synchronization, the improved algorithm effectively overcomes the shortcomings of the traditional algorithm in terms of poor resistance to frequency offset and noise. After coarse synchronization, frequency offset estimation is performed using the local synchronization signal and the received synchronization signal to compensate for the local synchronization signal, greatly improving the algorithm's resistance to frequency offset. Simultaneously, the baseband vehicular network signal is downsampled before coarse synchronization and truncated before fine synchronization, significantly reducing the number of correlation operations at the receiver. This reduces computational complexity, saves computational resources, and improves computational efficiency while ensuring the algorithm's reliability and accuracy.

[0106] For example, such as Figure 4 The diagram shows a flowchart of an LTE-V2X symbol synchronization algorithm for complex channel scenarios in vehicle-to-everything (V2X) networks. Figure 4 As shown, the LTE-V2X symbol synchronization algorithm for complex channel scenarios in vehicle-to-everything (V2X) networks consists of three processes: coarse synchronization processing, frequency offset estimation, and fine synchronization processing. Specifically, the processes are as follows:

[0107] (1) Coarse synchronization process:

[0108] Step 1: Analyze the received baseband vehicle networking signal R(θ) and two local synchronization signals P. i (θ) is used for downsampling. This reduces computational complexity, saves computational resources, and improves computational efficiency.

[0109] Step 2: Combine the downsampled baseband vehicle networking signal r(θ) with the downsampled local synchronization signal p i (θ)

[0110] The correlation value C is obtained by piecewise sliding correlation. 1i (θ) is calculated using the formula (1) above.

[0111] Step 3, for the relevant value C 1i (θ) is thresholded to T 11 The first peak decision of (θ) yields the type i of the received synchronization signal and the first coarse synchronization peak S. 11 (θ).

[0112] Among them, the judgment threshold T 11 (θ) is calculated using formula (2) above. The coarse synchronization peak S in step 3... 11 (θ) is calculated according to the above formula (3).

[0113] Step 4: The first coarse synchronization peak S 11 The relative distance in (θ) is equal to the value of the OFDM symbol length after downsampling. This is obtained by selectively adding the values. It is calculated using the formula (4) above.

[0114] Step 5, for Threshold T 12 The second peak decision of (θ) yields the second coarse synchronization peak S. 12 (θ), and determine the coarse synchronization point by performing a judgment on it.

[0115] The decision threshold is calculated using formula (5) above. Coarse synchronization point. It is calculated using the formula (6) above.

[0116] (2) Frequency offset estimation process:

[0117] Step 6: Use the local synchronization signal p i The estimated frequency offset is calculated from (θ) and the received signal r(θ). Using estimated frequency offset The compensated local synchronization signal is obtained by compensating the local synchronization signal.

[0118] Specifically, the demodulation reference signal of the control channel in the physical direct link is used to eliminate the impact of frequency offset on the signal. After obtaining the coarse synchronization point, the four demodulation reference signals of the physical direct link control channel extracted from the radio frame are successively cross-correlated with the local demodulation reference signal, and the obtained correlation values ​​are superimposed to obtain the frequency offset estimate. It is calculated using the formula (7) above.

[0119] Furthermore, using frequency offset estimates Frequency offset compensation is performed on the local synchronization signal, and the compensated local synchronization signal is obtained. It is calculated using the formula (8) above.

[0120] (3) Fine synchronization process:

[0121] Step 7: At coarse synchronization point S 12 The unsampled baseband vehicular network signal R(θ) is extracted near (θ). To reduce computational complexity, a coarse synchronization point is extracted. The range of the nearby unsampled baseband vehicle-to-everything (V2X) signal R(θ) is as follows: That is, one complete subframe.

[0122] Step 8: Combine the intercepted baseband vehicle networking signal R(θ) with the local synchronization signal after frequency offset compensation. The correlation value C is obtained by piecewise sliding correlation. 2i (θ), is calculated using the formula (10) above.

[0123] Step 9: For the relevant value C 2i (θ) is thresholded to T 21 A peak decision of (θ) yields a precise synchronization peak S. 21 (θ), where the threshold T 21 (θ) is calculated using the formula (11) above.

[0124] Step 10: Simulate the peak S of the first precise synchronization. 21 The values ​​in (θ) whose relative distance is equal to the length of one OFDM symbol are selected and summed, and the result is expressed as follows: It is calculated using the formula (12) above.

[0125] Step 11: Select the relevant values ​​after addition. Perform threshold T 22 The second peak decision of (θ) yields the second-order fine synchronization peak S. 22 (θ), where the threshold T 22 (θ) is calculated using the formula (13) above.

[0126] Step 12: Perform secondary precision synchronization on peak S. 22(θ) is used to make a decision to obtain the accurate position of the received synchronization signal, i.e., the fine synchronization point. Fine synchronization point It is calculated using the formula (9) above.

[0127] This completes the entire symbol synchronization process. The proposed method improves and integrates the segmented correlation algorithm and the selected addition algorithm in traditional symbol synchronization algorithms, thereby overcoming the shortcomings of these traditional algorithms in terms of poor resistance to frequency offset and noise. After coarse synchronization, frequency offset estimation is performed, improving the algorithm's resistance to frequency offset. Coarse synchronization first finds the approximate starting position of the synchronization signal, and then a certain length is truncated near that position for fine synchronization, reducing computational complexity.

[0128] This application provides a method for symbol synchronization in a vehicle-to-everything (V2X) network. It performs coarse synchronization processing on the baseband V2X signal and the local synchronization signal to obtain a coarse synchronization point. Based on the local synchronization signal and the coarsely synchronized baseband V2X signal, a frequency offset estimate is calculated to compensate the local synchronization signal. Then, based on the coarse synchronization point, an unsampled portion of the baseband V2X signal is extracted from the received baseband V2X signal. Fine synchronization processing is then performed on the unsampled baseband V2X signal and the frequency-offset-compensated local synchronization signal to obtain a fine synchronization point. This scheme involves two synchronization processes (coarse and fine), using a time-domain synchronization algorithm to complete symbol synchronization, thus improving synchronization accuracy. Furthermore, the frequency offset estimation and signal extraction during synchronization, along with compensation for the local synchronization signal, improve the quality of the baseband V2X signal and the synchronization accuracy of the algorithm. This enhances the reliability and accuracy of symbol synchronization, adapting to the high-frequency offset and low signal-to-noise ratio characteristics of LTE-V2X, thereby improving reliability and accuracy in real-world LTE-V2X communication scenarios with high frequency offset and low signal-to-noise ratio.

[0129] This application embodiment can divide the vehicle network symbol synchronization device into functional modules or functional units according to the above method example. For example, each function can be divided into a separate functional module or functional unit, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or in software functional modules or functional units. The module or unit division in this application embodiment is illustrative and only represents one logical functional division; other division methods may be used in actual implementation.

[0130] like Figure 5 The diagram shown is a structural schematic of a vehicle-to-everything (V2X) symbol synchronization device provided in an embodiment of this application. The device includes:

[0131] Processing unit 51 performs coarse synchronization processing on the received baseband vehicular network signal and local synchronization signal to obtain a coarse synchronization point. Calculation unit 52 calculates a frequency offset estimate based on the local synchronization signal and the coarsely synchronized baseband vehicular network signal, and uses the frequency offset estimate to compensate the local synchronization signal. Truncation unit 53 extracts unsampled baseband vehicular network signal from the received baseband vehicular network signal based on the coarse synchronization point. Processing unit 51 also performs fine synchronization processing on the unsampled baseband vehicular network signal and the frequency offset-compensated local synchronization signal to obtain a fine synchronization point.

[0132] In one possible implementation, the processing unit 51 is specifically used for: downsampling the received baseband vehicle network signal and local synchronization signal; sliding the downsampled baseband vehicle network signal and the downsampled local synchronization signal to a correlation segment to obtain a first correlation value; performing a first threshold peak decision on the first correlation value to obtain the type of synchronization signal and a first coarse synchronization peak; selecting and adding the values ​​in the first coarse synchronization peak whose relative distance is equal to the length of a downsampled orthogonal frequency division multiplexing (OFDM) symbol to obtain first data; performing a second threshold peak decision on the first data to obtain a second coarse synchronization peak, and making a decision on the second coarse synchronization peak to obtain a coarse synchronization point.

[0133] In one possible implementation, the processing unit 51 is specifically used to employ a first algorithm to calculate a first correlation value based on the conjugate of the downsampled baseband vehicle network signal, the downsampled local synchronization signal, the type of synchronization signal, the number of segments, and the length of each segment.

[0134] In one possible implementation, the aforementioned computing unit 52 is specifically used to: extract a local demodulation reference signal based on the local synchronization signal, and extract a time-domain demodulation reference signal based on the baseband vehicle network signal after coarse synchronization processing; perform successive cross-correlation between the time-domain demodulation reference signal and the local demodulation reference signal, and superimpose the obtained correlation values ​​to obtain a frequency offset estimate.

[0135] In one possible implementation, the processing unit 51 is specifically used to: slide the unsampled baseband vehicle network signal and the compensated frequency offset local synchronization signal into a segmented correlation to obtain a second correlation value; perform a first peak decision on the second correlation value based on a third threshold to obtain a first fine synchronization peak; select and add the values ​​in the first fine synchronization peak whose relative distance is equal to the length of one OFDM symbol to obtain second data; perform a second peak decision on the second data based on a fourth threshold to obtain a second fine synchronization peak, and make a decision on the second fine synchronization peak to obtain a fine synchronization point.

[0136] In one possible implementation, the aforementioned processing unit 51 is specifically used to employ a second algorithm to calculate a second correlation value based on the conjugate of the unsampled baseband vehicle network signal, the local synchronization signal after frequency offset compensation, the number of segments, and the length of each segment.

[0137] When implemented in hardware, the processing unit 51, the calculation unit 52, and the interception unit 53 in this embodiment can be integrated onto the processor. Specific implementation methods are as follows: Figure 6 As shown.

[0138] Figure 6 This diagram illustrates another possible structural design of the vehicle-to-everything (V2X) symbol synchronization device described in the above embodiments. The V2X symbol synchronization device includes a processor 302 and a communication interface 303. The processor 302 controls and manages the operation of the V2X symbol synchronization device, for example, executing the steps performed by the processing unit 51, the calculation unit 52, and the interception unit 53, and / or performing other processes described herein. The communication interface 303 supports communication between the V2X symbol synchronization device and other network entities. The V2X symbol synchronization device may also include a memory 301 and a bus 304. The memory 301 stores the program code and data of the V2X symbol synchronization device.

[0139] The memory 301 may be a memory in a vehicle-to-everything (V2X) symbol synchronization device, and may include volatile memory, such as random access memory; it may also include non-volatile memory, such as read-only memory, flash memory, hard disk or solid-state drive; or it may include a combination of the above types of memory.

[0140] The processor 302 described above can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc.

[0141] Bus 304 can be an Extended Industry Standard Architecture (EISA) bus, etc. Bus 304 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 6 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0142] Figure 7 This is a schematic diagram of the structure of chip 170 provided in an embodiment of this application. Chip 170 includes one or more (including two) processors 1710 and communication interfaces 1730.

[0143] Optionally, the chip 170 also includes a memory 1740, which may include read-only memory and random access memory, and provides operation instructions and data to the processor 1710. A portion of the memory 1740 may also include non-volatile random access memory (NVRAM).

[0144] In some implementations, memory 1740 stores elements such as execution modules or data structures, or subsets thereof, or extended sets thereof.

[0145] In this embodiment of the application, the corresponding operation is executed by calling the operation instructions stored in the memory 1740 (the operation instructions can be stored in the operating system).

[0146] The processor 1710 described above can implement or execute various exemplary logic blocks, units, and circuits described in conjunction with the disclosure of this application. The processor can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, units, and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0147] The memory 1740 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as read-only memory, flash memory, hard disk or solid-state drive; the memory may also include combinations of the above types of memory.

[0148] The Bus 1720 can be an Extended Industry Standard Architecture (EISA) bus, etc. The Bus 1720 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 7 The symbol is represented by only one line, but this does not mean that there is only one bus or one type of bus.

[0149] Through the above description of the embodiments, those skilled in the art will clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0150] This application provides a computer program product containing instructions that, when run on a computer, cause the computer to execute the vehicle network symbol synchronization method described in the above method embodiments.

[0151] This application also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the vehicle network symbol synchronization method in the method flow shown in the above method embodiments.

[0152] The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: electrical connections having one or more wires; portable computer disks; hard disks; random access memory (RAM); read-only memory (ROM); erasable programmable read-only memory (EPROM); registers; hard disks; optical fibers; portable compact disc read-only memory (CD-ROM); optical storage devices; magnetic storage devices; or any suitable combination thereof; or any other form of computer-readable storage medium known in the art. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium may also be a component of the processor. The processor and the storage medium may reside in an application-specific integrated circuit (ASIC). In the embodiments of this application, the computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0153] Embodiments of this application provide a computer program product containing instructions that, when executed on a computer, cause the computer to perform the vehicle network symbol synchronization method described in the above embodiments.

[0154] Since the vehicle network symbol synchronization device, computer-readable storage medium, and computer program product in the embodiments of this application can be applied to the above method, the technical effects that can be obtained can also be referred to the above method embodiments. The embodiments of this application will not be repeated here.

[0155] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0156] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0157] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0158] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for synchronizing symbols in a vehicle-to-everything (V2X) network, characterized in that, The method includes: The received baseband vehicle network signal and local synchronization signal are coarsely synchronized to obtain the coarse synchronization point; Based on the local synchronization signal, a local demodulation reference signal is determined; Based on the local demodulation reference signal and the baseband vehicle network signal after coarse synchronization processing, a time-domain demodulation reference signal is determined. The time-domain demodulation reference signal and the local demodulation reference signal are cross-correlated successively, and the correlation values ​​obtained by the successive cross-correlation are superimposed to obtain the frequency offset estimate. The frequency offset estimate is used to compensate the local synchronization signal; Based on the coarse synchronization point, the unsampled baseband vehicle network signal is extracted from the received baseband vehicle network signal; The unsampled baseband vehicle network signal and the local synchronization signal after frequency offset compensation are subjected to fine synchronization processing to obtain the fine synchronization point.

2. The method according to claim 1, characterized in that, The process of performing coarse synchronization processing on the received baseband vehicle network signal and local synchronization signal to obtain the coarse synchronization point includes: The received baseband vehicle network signal and the local synchronization signal are downsampled; The downsampled baseband vehicle network signal and the downsampled local synchronization signal are segmented and slid to correlation to obtain the first correlation value; A peak value determination based on a first threshold is performed on the first correlation value to obtain the type of synchronization signal and a coarse synchronization peak; The values ​​in the first coarse synchronization peak whose relative distance is equal to the length of a downsampled OFDM symbol are selected and added together to obtain the first data. The first data is subjected to a second threshold for secondary peak determination to obtain a secondary coarse synchronization peak, and the secondary coarse synchronization peak is determined to obtain the coarse synchronization point.

3. The method according to claim 2, characterized in that, The step of segmenting and sliding the downsampled baseband vehicle network signal and the downsampled local synchronization signal to a correlation to obtain a first correlation value includes: The first correlation value is calculated using the first algorithm based on the conjugate of the downsampled baseband vehicle network signal, the downsampled local synchronization signal, the type of synchronization signal, the number of segments, and the length of each segment.

4. The method according to claim 1, characterized in that, The process of performing fine synchronization processing on the unsampled baseband vehicle network signal and the frequency offset-compensated local synchronization signal to obtain a fine synchronization point includes: The unsampled baseband vehicle network signal and the local synchronization signal after frequency offset compensation are segmented and slid together to obtain a second correlation value; A peak value is determined by applying a third threshold to the second correlation value to obtain a precise synchronization peak. The values ​​in the first precise synchronization peak whose relative distance is equal to the length of one OFDM symbol are selected and added together to obtain the second data; The second data is subjected to a second peak determination based on a fourth threshold to obtain a second fine synchronization peak, and the second fine synchronization peak is then determined to obtain the fine synchronization point.

5. The method according to claim 4, characterized in that, The step of segmenting and sliding the unsampled baseband vehicle network signal and the compensated frequency offset local synchronization signal to obtain a second correlation value includes: The second algorithm is used to calculate the second correlation value based on the conjugate of the unsampled baseband vehicle network signal, the local synchronization signal after frequency offset compensation, the number of segments, and the length of each segment.

6. A vehicle-to-everything (V2X) symbol synchronization device, characterized in that, The device includes: The processing unit is used to perform coarse synchronization processing on the received baseband vehicle network signal and local synchronization signal to obtain the coarse synchronization point; The calculation unit is used to determine a local demodulation reference signal based on the local synchronization signal; determine a time-domain demodulation reference signal based on the local demodulation reference signal and the baseband vehicle network signal after coarse synchronization processing; perform successive cross-correlation on the time-domain demodulation reference signal and the local demodulation reference signal, and superimpose the correlation values ​​obtained by successive cross-correlation to obtain a frequency offset estimate; and use the frequency offset estimate to compensate the local synchronization signal. The interception unit is used to intercept the unsampled baseband vehicle network signal from the received baseband vehicle network signal based on the coarse synchronization point; The processing unit is also used to perform fine synchronization processing on the unsampled baseband vehicle networking signal and the local synchronization signal after frequency offset compensation to obtain a fine synchronization point.

7. The apparatus according to claim 6, characterized in that, The processing unit is specifically used for: The received baseband vehicle network signal and the local synchronization signal are downsampled; The downsampled baseband vehicle network signal and the downsampled local synchronization signal are segmented and slid to correlation to obtain the first correlation value; A peak value determination based on a first threshold is performed on the first correlation value to obtain the type of synchronization signal and a coarse synchronization peak; The values ​​in the first coarse synchronization peak whose relative distance is equal to the length of a downsampled OFDM symbol are selected and added together to obtain the first data. The first data is subjected to a second threshold for secondary peak determination to obtain a secondary coarse synchronization peak, and the secondary coarse synchronization peak is determined to obtain the coarse synchronization point.

8. The apparatus according to claim 7, characterized in that, The processing unit is specifically used to employ a first algorithm to calculate the first correlation value based on the conjugate of the downsampled baseband vehicle network signal, the downsampled local synchronization signal, the type of synchronization signal, the number of segments, and the length of each segment.

9. The apparatus according to claim 6, characterized in that, The processing unit is specifically used for: The unsampled baseband vehicle network signal and the local synchronization signal after frequency offset compensation are segmented and slid together to obtain a second correlation value; A peak value is determined by applying a third threshold to the second correlation value to obtain a precise synchronization peak. The values ​​in the first precise synchronization peak whose relative distance is equal to the length of one OFDM symbol are selected and added together to obtain the second data; The second data is subjected to a second peak determination based on a fourth threshold to obtain a second fine synchronization peak, and the second fine synchronization peak is then determined to obtain the fine synchronization point.

10. The apparatus according to claim 9, characterized in that, The processing unit is specifically used to employ a second algorithm to calculate the second correlation value based on the conjugate of the unsampled baseband vehicle network signal, the local synchronization signal after frequency offset compensation, the number of segments, and the length of each segment.

11. A vehicle-to-everything (V2X) symbol synchronization device, characterized in that, include: A processor and a communication interface; the communication interface is coupled to the processor, the processor being used to run computer programs or instructions to implement the vehicle-to-everything (V2X) symbol synchronization method as described in any one of claims 1-5.

12. A computer-readable storage medium storing instructions, characterized in that, When the computer executes the instruction, the computer performs the vehicle network symbol synchronization method as described in any one of claims 1-5.

Images