A synchronization point calculation method based on LTE-V2X

Abstract

The application discloses a synchronization point calculation method based on LTE-V2X, and belongs to the technical field of measurement, and comprises the following steps: receiving a reference signal and reducing sampling; timing synchronization, obtaining a synchronization point, an S-PSS time domain sequence; intercepting two length reference signals; calculating a coarse synchronization point; calculating a fine synchronization point; and calculating a final synchronization point of LTE-V2X. The method can reduce the load of the system, especially when a large amount of data is processed, which helps to avoid system overload and improve the stability and performance of the system. Since the data amount is reduced by reducing sampling, data can be transmitted faster, and the transmission efficiency is improved, which is very useful for remote data synchronization or data transmission under the condition that the network bandwidth is limited.

Description

Technical Field

[0001] This invention belongs to the field of measurement technology, specifically relating to a synchronization point calculation method based on LTE-V2X. Background Technology

[0002] EVM (Error Vector Magnitude) is an important metric used in digital communications to measure the quality of modulated signals. It is defined as the root mean square value of the error vector at the symbol clock transition, representing the difference between the measured signal and the ideal reference signal. EVM is commonly used to assess the amplitude and phase errors of digital modulated signals and is an ideal measurement tool for analyzing and diagnosing faults in the baseband, intermediate frequency, or radio frequency (RF) sections of communication systems.

[0003] When measuring EVM, a vector analyzer is typically used to receive and sample the digitally modulated signal under test, and then compare it with a reference vector signal. The difference vector signal between the measured vector signal and the reference vector signal is called the error vector signal, which contains amplitude and phase error information. The smaller the EVM value, the better the quality of the modulated signal and the smaller the amplitude of the error vector.

[0004] In communication systems like LTE-V2X, EVM is one of the key parameters for evaluating wireless communication performance. Measuring EVM can help determine the quality of transmitted signals and evaluate the performance of various communication standards.

[0005] In LTE-V2X, the accuracy and stability of the synchronization algorithm can affect the EVM (Effective Virtualization) metric. Large errors in the synchronization algorithm can lead to an increase in the EVM value, thereby reducing communication quality. Therefore, to achieve high-quality LTE-V2X communication, it is necessary to select and optimize a suitable synchronization algorithm and ensure its stability under various conditions.

[0006] However, the specific impact of EVM varies depending on various factors, including wireless channel conditions, multipath interference, and signal attenuation. Therefore, in order to accurately evaluate the impact of the LTE-V2X synchronization algorithm on EVM metrics, detailed system-level simulations and experimental tests are required.

[0007] In LTE-V2X, several synchronization algorithms exist, including time-based and distance-based synchronization. The primary goal of these algorithms is to ensure time synchronization between network nodes, which is crucial for many real-time communication applications, such as V2X communication. However, the time synchronization accuracy of LTE-V2X is affected by network clock stability and transmission latency. Due to potential network clock deviations and various interferences during signal transmission, time synchronization accuracy can be low. This poses a limitation for V2X applications requiring high-precision time synchronization, such as vehicle collision avoidance and cooperative driving. Summary of the Invention

[0008] In view of the above-mentioned technical problems in the prior art, the present invention proposes a synchronization point calculation method based on LTE-V2X. The method is reasonably designed, overcomes the shortcomings of the prior art, and has good results.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A synchronization point calculation method based on LTE-V2X includes the following steps: Step 1: Obtain the downsampled data from the receiving end; When the bandwidth exceeds 5MHz, the data received is downsampled by 16 times; When the bandwidth does not exceed 5MHz, the received data is not downsampled; Step 2: Obtain the S-PSS time-domain sequence; Step 3: Calculate the coarse synchronization point; Step 4: Calculate the precise synchronization point; Step 5: Calculate the final synchronization point for LTE-V2X.

[0010] Preferably, step 3 includes the following steps: Step 3.1: Perform sliding correlation between the received data and the S-PSS time-domain sequence obtained in Step 2; Step 3.2: According to the timing coarse synchronization algorithm, the point with the largest correlation value is taken as the coarse synchronization point; Define the relevant function as shown in formula (1): (1); in, Indicates the preamble signal. This represents the inner product sum of the downlink received signals. Indicates an offset of The similarity between the received preamble signal and the received downlink signal at a given time point; The energy of the relevant window is shown in formula (2): (2); in, The target time offset is The energy value of the downlink received signal over a period of time is a characteristic quantity that reflects the channel state; Indicates an offset of At that point in time, the downlink received signal A symbol, This symbol represents the energy. The measurement function is shown in formula (3): (3); in, The target time offset is The metric function is used to evaluate the matching degree between the preamble signal and the received signal, as well as the quality of the downlink channel; According to the timed coarse synchronization algorithm, the point with the largest correlation value is taken as the coarse synchronization point. As shown in formula (4): (4).

[0011] Preferably, step 4 includes the following steps: Step 4.1: Define the range of fine synchronization M; Step 4.2: Perform a synchronous search within the range M; Step 4.3: Autocorrelation calculation; Autocorrelation function As shown in formula (5): (5); Step 4.4: Refine the synchronization point; Find the maximum value of formula (5) to obtain the maximum value point. : (6).

[0012] Preferably, step 5 includes the following steps: Step 5.1: Process the obtained coarse synchronization points and fine synchronization points according to the preset LTE-V2X synchronization algorithm; Step 5.2: Obtain the final synchronization point As shown in formula (7): (7); in, It's experience points.

[0013] The beneficial technical effects of this invention are as follows: The method of this invention, by obtaining coarse synchronization point, fine synchronization point value, and final synchronization point value, can reduce the system load compared with traditional time synchronization without downsampling, especially when processing large amounts of data. This helps to avoid system overload and improve system stability and performance. Since downsampling reduces the amount of data, data can be transmitted faster, improving transmission efficiency. This is very useful for remote data synchronization or data transmission under conditions of limited network bandwidth. Attached Figure Description

[0014] Figure 1 A flowchart for LTE-V2X coarse synchronization; Figure 2 A flowchart for LTE-V2X fine synchronization; Figure 3 This is the overall flowchart of the present invention. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: A synchronization point calculation method based on LTE-V2X, the process of which is as follows: Figure 3 As shown, it includes the following steps: Step 1: Obtain the downsampled data from the receiving end; When the bandwidth exceeds 5MHz, the data received is downsampled by 16 times; When the bandwidth does not exceed 5MHz, the received data is not downsampled; Step 2: Obtain two sets of S-PSS time-domain sequences; Two sets of time-domain S-PSS sequences (corresponding to cyclic shift values ​​u=26 and u=37 respectively, and corresponding to the group identifiers) ); Step 3: Calculate the coarse synchronization point; the process is as follows: Figure 1 As shown, it includes the following steps: Step 3.1: Perform sliding correlation between the received data and the S-PSS time-domain sequence obtained in Step 2; specifically, this includes the following steps: Step 3.1.1: Start the autocorrelation function processor; define the autocorrelation function as shown in formula (1): (1); in, Indicates the preamble signal. This represents the inner product sum of the downlink received signals. Indicates an offset of The similarity between the received preamble signal and the received downlink signal at a given time point; Step 3.1.2: Activate the relevant window's energy. The energy of the relevant window is shown in formula (2): (2); in, The target time offset is The energy value of the downlink received signal over a period of time is a characteristic quantity that reflects the channel state; Indicates an offset of At that point in time, the downlink received signal A symbol, This symbol represents the energy. The measurement function is shown in formula (3): (3); in, The target time offset is The metric function is used to evaluate the matching degree between the preamble signal and the received signal, as well as the quality of the downlink channel; Step 3.1.3: Autocorrelation calculation; Step 3.2: According to the timing coarse synchronization algorithm, the point with the largest correlation value is taken as the coarse synchronization point, as shown in formula (4): (4).

[0016] Since V2X synchronization frames are sent periodically, while the synchronization transmission period for Mode 3 is fixed at 160, it is necessary to first estimate the possible number of synchronization frames based on the length of the received data. Furthermore, V2X transmits a PSS sequence within two OFDM symbols in a synchronization frame. To obtain the coarse synchronization point, the position of the first S-PSS needs to be known. Because the ZC sequence used in the S-PSS has the advantage of good autocorrelation and poor cross-correlation, two good autocorrelation values ​​will appear within a synchronization frame when performing time-domain autocorrelation. Due to noise, the largest autocorrelation value is not necessarily the first S-PSS; therefore, it is necessary to sort and find the index of the smaller autocorrelation value to determine the coarse synchronization point. Autocorrelation is performed between the two sets of S-PSS (corresponding to u=26 and u=37) and the received data. The larger of the two maximum correlation values ​​is considered the coarse synchronization point. .

[0017] Step 4: Calculate the precise synchronization point; the process is as follows: Figure 2 As shown, it includes the following steps: Step 4.1: Define the range of fine synchronization M; Step 4.2: Perform a synchronous search within the range M; Step 4.3: Autocorrelation calculation; The autocorrelation function is shown in formula (5): (5); Step 4.4: Refine the synchronization point; Find the maximum value of formula (5) to obtain the maximum value point: (6).

[0018] Step 5: Calculate the final synchronization point for LTE-V2X, including the following steps: Step 5.1: Process the obtained coarse synchronization points and fine synchronization points according to the preset LTE-V2X synchronization algorithm; Step 5.2: Obtain the final synchronization point; as shown in formula (7): (7); in, It's experience points.

[0019] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A synchronization point calculation method based on LTE-V2X, characterized in that: Includes the following steps: Step 1: Obtain the downsampled data from the receiving end; When the bandwidth exceeds 5MHz, the data received is downsampled by 16 times; When the bandwidth does not exceed 5MHz, the received data is not downsampled; Step 2: Obtain the S-PSS time-domain sequence; Step 3: Calculate the coarse synchronization point; Step 4: Calculate the precise synchronization point; Step 5: Calculate the final synchronization point for LTE-V2X; Step 3 includes the following steps: Step 3.1: Perform sliding correlation between the received data and the S-PSS time-domain sequence obtained in Step 2; Step 3.2: According to the timing coarse synchronization algorithm, the point with the largest correlation value is taken as the coarse synchronization point; Define the relevant function as shown in formula (1): （1）； in, Indicates the preamble signal. This represents the inner product sum of the downlink received signals. Indicates an offset of The similarity between the received preamble signal and the received downlink signal at a given time point; The energy of the relevant window is shown in formula (2): （2）； in, The target time offset is The energy value of the downlink received signal over a period of time is a characteristic quantity that reflects the channel state; Indicates an offset of At that point in time, the downlink received signal A symbol, This symbol represents the energy. The measurement function is shown in formula (3): （3）； in, The target time offset is The metric function is used to evaluate the matching degree between the preamble signal and the received signal, as well as the quality of the downlink channel; According to the timed coarse synchronization algorithm, the point with the largest correlation value is taken as the coarse synchronization point. As shown in formula (4): （4）； Step 4 includes the following steps: Step 4.1: Define the range of fine synchronization M; Step 4.2: Perform a synchronous search within the range M; Step 4.3: Autocorrelation calculation; Autocorrelation function As shown in formula (5): （5）； Step 4.4: Refine the synchronization point; Find the maximum value of formula (5) to obtain the maximum value point. : （6）； Step 5 includes the following steps: Step 5.1: Process the obtained coarse synchronization points and fine synchronization points according to the preset LTE-V2X synchronization algorithm; Step 5.2: Obtain the final synchronization point As shown in formula (7): （7）； in, It's experience points.

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