CN118283557A - Internet of vehicles system and time synchronization method and device thereof - Google Patents

Abstract

The invention provides a vehicle networking system and a time synchronization method and device thereof, wherein the vehicle networking system comprises a plurality of V2X devices, and the time synchronization method comprises the following steps: acquiring a synchronous broadcast signal provided by a first V2X device in a time synchronous state; acquiring a target time offset value; according to the method and the device, the final accurate time for synchronizing with the first V2X device is determined according to the target time offset value and the synchronous broadcast signal, so that the V2X device in the out-of-step state can acquire accurate time information, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

Description

Internet of vehicles system and time synchronization method and device thereof

Technical Field

The invention relates to the technical field of vehicles, in particular to a vehicle networking system and a time synchronization method and device thereof.

Background

With the rapid development of communication technology, the wireless communication technology also has new application scenarios, such as V2X (Vehicle to Everything, internet of vehicles), and vehicle-road cooperation schemes based on the V2X technology are gradually deployed, so that large-area coverage and popularization of V2X equipment are realized in the future.

Currently, GNSS (global navigation SATELLITE SYSTEM, global satellite navigation system) signals are usually introduced into a GNSS non-coverage area by means of a wired or optical fiber connection, or LTE/5G base stations are deployed for time service, so that V2X time source synchronization and usability are ensured.

However, the method has higher cost and complex specific construction, is difficult to construct for tunnels with longer distance, such as tunnels larger than 5km, has higher deployment time source and deployment cost, has longer period generally, and is not promoted on a large scale by using V2X.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art.

Therefore, an object of the present invention is to provide a time synchronization method for a vehicle networking system, which enables a V2X device in an out-of-step state to obtain accurate time information, so that communication of the V2X device is not interrupted, V2X is ensured to be suitable for more scenes, and accident occurrence rate of the system in a tunnel is prevented and reduced.

To this end, a second object of the invention is to propose a time synchronization device for a vehicle networking system.

To this end, a third object of the present invention is to propose a car networking system.

To achieve the above object, an embodiment of a first aspect of the present invention proposes a time synchronization method of an internet of vehicles system, the method comprising: acquiring a synchronous broadcast signal provided by a first V2X device in a time synchronous state; acquiring a target time offset value; and determining the final accurate time synchronized with the first V2X device according to the target time offset value and the synchronous broadcast signal.

According to the time synchronization method of the Internet of vehicles system, after the V2X equipment enters the out-of-step state, the synchronous broadcast signals and the target time deviation value provided by the first V2X equipment in the time synchronization state are obtained, the V2X equipment in the out-of-step state is subjected to time calibration according to the target time deviation value, so that the final accurate time of the V2X equipment in the out-of-step state is obtained, the problems of high cost and complicated construction caused by optical fiber or wired connection are avoided, the V2X equipment in the out-of-step state can obtain accurate time information by obtaining the synchronous broadcast signals provided by the first V2X equipment, the communication of the V2X equipment is not interrupted, the V2X is ensured to be applicable to more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

In some embodiments, obtaining the target time offset value includes: analyzing the synchronous broadcast signals to obtain initial accurate time; acquiring flight time according to the initial accurate time; and acquiring the target time offset value according to the flight time.

In some embodiments, parsing the synchronized broadcast signal for initial precision time includes: analyzing the synchronous broadcast signal to obtain source time, demodulation processing time and frequency offset of the synchronous broadcast signal; and determining the initial accurate time according to the source time, the demodulation processing time and the frequency offset.

In some embodiments, obtaining the time of flight from the initial precision time comprises: continuously receiving the synchronous broadcast signal for a plurality of times; analyzing the synchronous broadcast signals received each time to obtain initial accurate time corresponding to the synchronous broadcast signals each time; acquiring a preset receiving interval time of the initial accurate time continuously for a plurality of times; and acquiring the flight time according to the initial accurate time and the preset receiving interval time.

In some embodiments, obtaining the target time offset value from the time of flight comprises: determining an initial time offset value according to the time of flight, the demodulation processing time and the frequency offset; determining a confidence percentage from the initial time offset value; and when the confidence percentage is larger than a preset confidence threshold, taking the initial time offset value as the target time offset value.

In some embodiments, determining a final precision time to synchronize with the first V2X device based on the target time offset value and the synchronization broadcast signal comprises: determining a source time of receiving the synchronous broadcast signal; and determining the final accurate time for synchronization of the V2X equipment according to the source time and the target time offset value.

In some embodiments, acquiring a synchronized broadcast signal provided by a first V2X device in a time synchronized state includes: establishing a synchronous channel; and acquiring the synchronous broadcast signal provided by the first V2X equipment in the time synchronous state by adopting the synchronous channel.

In some embodiments, before acquiring the synchronized broadcast signal provided by the first V2X device in the time synchronized state, the method further includes: and determining that the V2X equipment enters a step-out state, and controlling the V2X equipment to stop sending the synchronous broadcast signal.

In some embodiments, obtaining the target time offset value includes: acquiring a plurality of standard reference times; determining a plurality of time offset values and a plurality of confidence percentages corresponding to the time offset values according to the standard reference time correspondence; the target time offset value is determined from a plurality of the time offset values and a plurality of the confidence percentages.

In some embodiments, determining the target time offset value from a plurality of the time offset values and a plurality of the confidence percentages comprises: if at least two of the confidence coefficient percentages are larger than a preset confidence coefficient threshold value, weighting calculation is carried out on time offset values corresponding to the at least two confidence coefficient percentages, and a target time offset value is obtained; and if one of the confidence percentages is larger than the preset confidence threshold, taking a time offset value corresponding to the confidence threshold larger than the preset confidence threshold as the target time offset value.

To achieve the above object, an embodiment of a second aspect of the present invention proposes a time synchronization device of an internet of vehicles system, the device comprising: the first acquisition module is used for acquiring a synchronous broadcast signal provided by the first V2X equipment in a time synchronous state; the second acquisition module is used for acquiring a target time offset value; and the determining module is used for determining the final accurate time synchronized with the first V2X device according to the target time offset value and the synchronous broadcast signal.

According to the time synchronization device of the Internet of vehicles system, after the V2X equipment enters the out-of-step state, the synchronous broadcast signals and the target time deviation value provided by the first V2X equipment in the time synchronization state are obtained, the V2X equipment in the out-of-step state is subjected to time calibration according to the target time deviation value, so that the final accurate time of the V2X equipment in the out-of-step state is obtained, the problems of high cost and complicated construction caused by optical fiber or wired connection are avoided, the V2X equipment in the out-of-step state can obtain accurate time information by obtaining the synchronous broadcast signals provided by the first V2X equipment, the communication of the V2X equipment is not interrupted, the V2X is ensured to be applicable to more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

To achieve the above object, an embodiment of a third aspect of the present invention proposes an internet of vehicles system, the system comprising: the time synchronization device of the internet of vehicles system according to the above embodiment; and the V2X equipment is communicated with the time synchronization device.

According to the Internet of vehicles system provided by the embodiment of the invention, after the V2X equipment enters the out-of-step state, the synchronous broadcast signal and the target time deviation value provided by the first V2X equipment in the time synchronous state are obtained, and the V2X equipment in the out-of-step state is time-calibrated according to the target time deviation value, so that the final accurate time of the V2X equipment in the out-of-step state is obtained, the problems of high cost and complicated construction caused by optical fiber or wired connection are avoided, the V2X equipment in the out-of-step state can obtain accurate time information by obtaining the synchronous broadcast signal provided by the first V2X equipment, the communication of the V2X equipment is not interrupted, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

In some embodiments, the V2X device comprises a roadside unit and/or an in-vehicle communication unit.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an Internet of vehicles system according to one embodiment of the invention;

FIG. 2 is a flow chart of a method of time synchronization of an Internet of vehicles system according to one embodiment of the invention;

FIG. 3 is a schematic diagram of a high-precision clock estimation system of an Internet of vehicles system according to one embodiment of the invention;

FIG. 4 is a block diagram of a time synchronization device of an Internet of vehicles system according to an embodiment of the present invention;

FIG. 5 is a flow chart of a method of time synchronization of an Internet of vehicles system according to an embodiment of the invention;

FIG. 6 is a block diagram of a time synchronization device of an Internet of vehicles system according to an embodiment of the present invention;

Fig. 7 is a block diagram of an internet of vehicles system according to an embodiment of the present invention.

Reference numerals: a time synchronization device 2 of the Internet of vehicles system;

A first acquisition module 21; a second acquisition module 22; a determining module 23;

a car networking system 3; V2X device 31.

Detailed Description

Embodiments of the present invention will be described in detail below, by way of example with reference to the accompanying drawings.

V2X is called a vehicle networking in 3GPP (3 rdGeneration Partnership Project, third generation partnership project) standards, and is a key technology of future intelligent transportation systems based on cellular networks, so that vehicles can communicate with each other, between vehicles and between infrastructures such as roadside communication units, and between multiple roadside infrastructures, so that vehicles can obtain a series of traffic information such as real-time road conditions, traffic road information, pedestrian information, and the like, and the perception capability of the vehicles is enhanced, thereby improving driving safety, reducing congestion, improving traffic efficiency, providing vehicle-mounted entertainment information, and the like.

The V2X technology senses the surrounding conditions of the vehicles in real time by means of wireless communication among the vehicles, between the vehicles and road side infrastructure and between the vehicles and passers-by so as to perform early warning in time, help prevent various traffic accidents of 80%, and make the V2X technology become a research hotspot for solving the road safety problem in various countries in the world at present.

In 3GPP, the LTE V2X trusted communication delay should be less than 100ms, and the maximum advantage of V2X communication is low delay, and the low delay is premised on that time synchronization is required between communication devices, but V2X development is a progressive process, and the V2X technology is premised on that the requirement of meeting time-specific precision, and the 3GPP standard is defined as time deviation less than 391ns. However, when the V2X device enters a long tunnel, because there is no wireless signal and a GNSS signal is lost, if there is no unified time service server, the time accuracy of the V2X device will not be guaranteed, so that the V2X communication is not available, so in the whole internet of vehicles, it will be important to keep the available state of the V2X, so that it is an important premise that the V2X can work normally.

In the related art, when a vehicle does not enter a tunnel, the vehicle can communicate with a GNSS, and acquire the time sent by the GNSS in real time so as to perform time synchronization; when a vehicle enters a tunnel, communication with the GNSS cannot be carried out to obtain time, traffic accidents can be generated due to time errors, a time source server such as a time service server is built in a GNSS non-coverage area, or wired and optical fiber connection is built, time synchronization is carried out on the vehicle, the requirements of the wired and optical fibers on deployment environment and period are high, and production cost is increased.

Therefore, in the Internet of vehicles system of the embodiment of the invention, after a vehicle enters a tunnel, the vehicle is controlled to enter a V2X out-of-step state, synchronous broadcast signals of other V2X devices in a time synchronous state in the tunnel are received, the signals are used as reference signals, a target time offset value is calculated, and the corrected final accurate time is obtained, so that the V2X devices in the out-of-step state can acquire accurate time information.

The internet of vehicles system according to the embodiment of the present invention is first illustrated.

As shown in fig. 1, the internet of vehicles system in the embodiment of the present invention includes a plurality of V2X devices, for example, RSUs (Road Side units) supporting V2X communication functions and/or OBUs (On Board units) mounted On vehicles, which are disposed at two sides of a tunnel, and each communication body may communicate and interact through V2X technology, so as to further improve the sensing capability of the vehicle to the whole traffic system. The inside of the tunnel is an area losing GNSS coverage, generally, the entrance and the exit of the tunnel are covered by GNSS, but the inside is not covered by GNSS, the RSU in the tunnel is divided into an anchor point RSU and other RSUs, and the RSU which is positioned at the entrance and the exit of the tunnel and can receive GNSS signals can acquire GNSS time sources, so that the V2X state can work normally and is marked as the anchor point RSU; the RSUs located inside the tunnel can only acquire time information in other ways, due to the inability to receive GNSS, and are marked as other RSUs.

Among them, GNSS is a global navigation satellite system, which is an air-based radio navigation positioning system capable of providing all-weather three-dimensional coordinates and speed and time information to a user at any place on the surface of the earth or near-earth space.

The RSU, i.e. the road side unit, provides V2X and wireless connection capability for the infrastructure, such as roadside signal lamps, cameras, various ETC (Electronic Toll Collection, electronic toll collection system) devices, etc., and the RSU can provide information broadcast based on V2X, such as traffic light time, intersection speed limit information, traffic jam conditions, and can provide services such as high-precision maps for vehicles.

The OBU, i.e. the on-board unit, is usually a TBOX (TELEMATICS BOX, remote communication terminal), TCAN (TELEMATICS CONTROLLER AREA NETWORK, remote controller area network) or a vehicle mounted mainly on the vehicle, collects vehicle signals and information, provides V2X connection capability and wireless internet connection for the vehicle, the internet communication connection module (e.g. 5G/4G module) is an optional device, some scenarios or settings may be that only the V2X module is not configured with wireless internet (e.g. 5G/4G module) through V2X communication, provides or receives early warning information for the vehicle owner to view, and may also provide partial auxiliary function control for the vehicle, and interact and information share with the vehicle autopilot system, providing information input and network connection for the autopilot system.

The following describes a time synchronization method of an internet of vehicles system according to an embodiment of the present invention with reference to fig. 1 to 3.

As shown in fig. 2, the time synchronization method of the internet of vehicles system according to the embodiment of the present invention at least includes steps S1 to S3.

Step S1, a synchronous broadcast signal provided by a first V2X device in a time synchronous state is acquired.

Wherein the time synchronization state comprises a non-step-out state and a time synchronization state which is completed after the step-out state; the first V2X device includes an RSU device, an OBU device, and any other V2X enabled device that has completed time synchronization, and the synchronized broadcast signal includes a device identification, a source time stamp, a subframe interval, and a frequency offset field, and provides a data basis for time synchronization of the internet of vehicles system by acquiring the synchronized broadcast signal.

In an embodiment, after the V2X device enters the out-of-sync state, determining a first V2X device in a time synchronization state around the out-of-sync V2X device, and establishing a correlation channel with the first V2X device in the time synchronization state, where the first V2X device sends a synchronous broadcast signal to the out-of-sync V2X device through the correlation channel, such as a device identifier, a subframe interval, a source timestamp, and a frequency offset field, it is understood that the device identifier is generally obtained through a device IMEI (International Mobile Equipment Identity, mobile equipment identifier) or a device vendor code identifier; the source time stamp is accurate to nanosecond level, the step-out V2X device obtains a synchronous broadcast signal provided by the first V2X device through a relevant channel, and a time stamp field and a crystal oscillator offset are added into the synchronous broadcast signal to provide a data base for time synchronization of the vehicle networking system.

Step S2, obtaining a target time offset value.

The target time offset value is a time difference value between the out-of-step V2X device and the first V2X device in the synchronous state, and the out-of-step V2X device can be time-calibrated by acquiring the target time offset value.

In an embodiment, after a synchronous broadcast signal provided by a first V2X device in a time synchronization state is obtained, a target time offset value is determined according to a device identifier, a source time stamp, a subframe interval, and a frequency offset field in the synchronous broadcast signal, so as to accurately calibrate time of the V2X device in real time.

And step S3, determining the final accurate time synchronized with the first V2X device according to the target time offset value and the synchronous broadcast signal.

In an embodiment, after determining the target time offset value, determining a final accurate time synchronized with the first V2X device according to a source time stamp of the synchronized broadcast signal and combining the target time offset value, and after determining the final accurate time synchronized with the first V2X device, inputting the final accurate time into the out-of-step V2X device to perform time synchronization on the out-of-step V2X device, so that time information of the out-of-step V2X device is recovered to be normal, and the recovered V2X device can normally perform transmission and reception of the synchronized broadcast signal.

According to the time synchronization method of the Internet of vehicles system, after the V2X equipment enters the out-of-step state, the synchronous broadcast signals provided by the first V2X equipment in the time synchronization state are obtained, the target time deviation value is obtained according to the synchronous broadcast signals, the time is corrected according to the target time deviation value, the final accurate time is obtained, and the time synchronization is carried out according to the synchronous broadcast signals provided by the first V2X equipment, so that the V2X equipment in the out-of-step state can obtain accurate time information, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

In some embodiments, obtaining the target time offset value includes: analyzing the synchronous broadcast signals to obtain initial accurate time; acquiring flight time according to the initial accurate time; and acquiring a target time offset value according to the flight time.

In an embodiment, after a synchronous broadcast signal provided by a first V2X device in a time synchronization state is obtained, the synchronous broadcast signal is parsed, and initial accurate time is obtained according to a device identifier, a source timestamp, a subframe interval and a frequency offset field in the synchronous broadcast signal; after the initial accurate time is acquired, as the synchronous broadcast signal is transmitted at a fixed subframe position with a fixed transmission bandwidth through a fixed PRB (Physical resource blocks, physical resource block) in a relatively fixed period, for example, every 500ms, a time stamp field and a crystal oscillator offset are added in the synchronous broadcast signal, if the initial accurate time may deviate, a difference value between the initial accurate time and the relatively fixed period time is calculated, and the flight time is acquired according to the difference value; after the time of flight is acquired, a target time offset value is determined based on a time difference between the time of flight and a relatively fixed cycle time.

In some embodiments, parsing the synchronized broadcast signal for initial precision time includes: analyzing the synchronous broadcast signal to obtain source time, demodulation processing time and frequency offset of the synchronous broadcast signal; and determining initial accurate time according to the source time, the demodulation processing time and the frequency offset.

In an embodiment, after a synchronous broadcast signal provided by a first V2X device in a time synchronization state is obtained, a source time stamp in the synchronous broadcast signal is used to indicate an accurate time of a time point of sending the synchronous broadcast signal, and the source time of the synchronous broadcast signal is synchronized according to the source time stamp; the subframe interval in the synchronous broadcast signal is used for indicating the subframe position in the synchronous broadcast signal transmission, and the subframe offset and the demodulation processing time are acquired according to the subframe interval; the frequency offset field in the synchronous broadcast signal is used to calculate the frequency offset of the first V2X device transmitting the synchronous broadcast signal, and the source time, the demodulation processing time and the frequency offset are obtained by analyzing the synchronous signal, so as to determine the initial accurate time.

In some embodiments, obtaining the time of flight from the initial precision time includes: continuously receiving the synchronous broadcast signal for a plurality of times; analyzing the synchronous broadcast signals received each time to obtain initial accurate time corresponding to the synchronous broadcast signals each time; acquiring preset receiving interval time of continuous multiple initial accurate time; and acquiring the flight time according to the initial accurate time and the preset receiving interval time.

In an embodiment, the synchronous broadcast signal is continuously received for multiple times, the synchronous broadcast signal received each time is analyzed to obtain the source time, the demodulation processing time and the frequency offset of the synchronous broadcast signal each time, so that the initial accurate time corresponding to multiple times is determined according to the parameters, after the initial accurate time corresponding to multiple times is determined, the initial accurate time is averaged to reduce errors, the preset receiving interval time of the continuous initial accurate time is obtained, the difference value between the continuous initial accurate time and the preset receiving interval time is calculated to obtain the flight time, and the network delay time in the air can be calculated by obtaining the flight time, so that the final accurate time is calculated.

For example, the two-time synchronous broadcast signal is received, the first synchronous broadcast signal B1 is received, the source time is T1, the demodulation processing time is T1, the subframe interval is n1, the frequency offset is T1', the initial accurate time tm1 is calculated from the above parameters, i.e., tm1=t1+t1+t1'; the second synchronous broadcast signal B2 is received, the source time is T2, the demodulation processing time T2, the subframe interval n2, the frequency offset is T2', the initial precision time tm2 is calculated from the above parameters, i.e. tm2=t2+ t2+t2'.

After determining the initial accurate time for two times, determining the preset receiving interval time of the initial accurate time for two times to be 500ms, wherein the flight time is the difference between the source time T2 of the second synchronous broadcast signal and the source time T1 of the first synchronous broadcast signal and the preset receiving interval time, namely T2-T1-500ms.

In some embodiments, obtaining the target time offset value from the time of flight includes: determining an initial time offset value according to the flight time, the demodulation processing time and the frequency offset; determining a confidence percentage from the initial time offset value; and when the confidence percentage is larger than a preset confidence threshold value, taking the initial time offset value as a target time offset value.

In an embodiment, after the flight time is acquired, determining an initial time offset value, which is a time offset value between the initial accurate time and the synchronous broadcast signal, according to the demodulation processing time, the frequency offset and the flight time, and determining the confidence percentage according to the initial time offset value and the signal strength and the temperature of the synchronous broadcast signal received by the user.

The confidence coefficient may be a time synchronization accuracy range preset by each time calculation unit, or the respective confidence coefficient may be calculated periodically, for example, the initial time offset value may be calculated separately in a period of time, and compared with the GNSS time, and an error weighted average duty ratio is performed to obtain the confidence coefficient.

After the confidence coefficient percentage is determined, judging the magnitude relation between the confidence coefficient percentage and a preset confidence coefficient threshold value, and when the confidence coefficient percentage is larger than the preset confidence coefficient threshold value, considering that the time synchronization precision of the V2X equipment is met, taking the initial time offset value as a target time offset value; and when the confidence percentage is smaller than or equal to the preset confidence threshold, the time synchronization precision of the V2X equipment is not met, and the synchronous broadcast signal is re-analyzed.

In some embodiments, determining a final precise time to synchronize with the first V2X device based on the target time offset value and the synchronized broadcast signal comprises: determining a source time for receiving the synchronous broadcast signal; and determining the final accurate time for V2X equipment synchronization according to the source time and the target time offset value.

In the embodiment, after the target time offset value is determined, the self time information of the received synchronous broadcast signal, namely the source time, is determined, the difference value between the source time and the target time offset value is calculated, and the difference value is used as the final accurate time of the V2X device synchronization, so that the ns-level time precision requirement is met, all time synchronization is completed in a physical layer or a media access control layer, high-layer protocol intervention analysis data and decoding are not needed, the time consumption of internal processing is greatly reduced, and the time precision is improved.

In some embodiments, acquiring a synchronized broadcast signal provided by a first V2X device in a time synchronized state includes: establishing a synchronous channel; and acquiring the synchronous broadcast signal provided by the first V2X equipment in the time synchronous state by adopting a synchronous channel.

In an embodiment, as shown in fig. 3, a schematic structural diagram of a high-precision clock estimation system of an internet of vehicles system according to an embodiment of the present invention is shown. On the basis that the out-of-step V2X equipment and the first V2X equipment establish a data channel, the first V2X equipment sends a synchronous broadcast signal to the out-of-step V2X equipment through the synchronous channel, and the out-of-step V2X equipment acquires the synchronous broadcast signal provided by the first V2X equipment in a time synchronous state by adopting the synchronous channel, wherein the data channel is a traditional 3GPP definition related channel and is commonly used for transmitting V2X data; the synchronization channel is typically used to broadcast a synchronization signal.

The first V2X device performs time source time service for the out-of-step V2X device, the time service does not adopt a traditional message or data transmission mechanism, but adopts the introduction of a synchronous channel in the V2X time domain frequency domain, the synchronous channel can be monitored only when the V2X device is in the out-of-step state, and the V2X device is in the synchronous state for transmission, so that the occupation of system resources is greatly reduced.

In some embodiments, before acquiring the synchronized broadcast signal provided by the first V2X device in the time synchronized state, the method further includes: and determining that the V2X equipment enters an out-of-step state, and controlling the V2X equipment to stop sending synchronous broadcast signals.

In the embodiment, before the synchronous broadcast signal provided by the first V2X device in the time synchronization state is obtained, whether the V2X device enters the out-of-synchronization state is determined, if the V2X device is in a state that positioning data and time source data cannot be normally obtained from the GNSS, because the V2X message is sensitive to time, the packet loss rate of the whole system is increased due to the error delay message, and other devices cannot determine the specific time of the data, and error determination is caused to auxiliary driving, the V2X device is controlled to stop sending the synchronous broadcast signal, so that the V2X devices normally sent in the control system are all V2X time trusted devices, and the precision requirement of time synchronization is met.

In some embodiments, obtaining the target time offset value includes: acquiring a plurality of standard reference times; determining a plurality of time offset values and a plurality of confidence percentages corresponding to the plurality of time offset values according to the plurality of standard reference time correspondences; a target time offset value is determined based on the plurality of time offset values and the plurality of confidence percentages.

In an embodiment, as shown in fig. 4, a schematic structural diagram of a high-precision clock estimation system of an internet of vehicles system according to an embodiment of the present invention is shown. The estimation system includes: DR (Dead-reckoning) data module, V2X time module, wireless network time module, vehicle ECU (Electronic Control Unit, electronic controller unit) time module, offset calculation module, and clock output module, wherein,

The DR technology is a common navigation positioning technology, and the basic principle of the DR technology is to utilize a direction sensor and a speed sensor to calculate the instantaneous position of a vehicle, obtain the estimation of the motion track and time accuracy of the self-body through measuring the acceleration and the rotation angle, and take charge of calculating the GNSS time estimation after the vehicle enters a tunnel so as to realize continuous autonomous positioning. In general, the vehicle-mounted positioning combines DR and GPS (Global Positioning System ), which make up for the defects of the DR and GPS, and ensure that V2X equipment can provide accurate navigation information for the vehicle at any time, on one hand, the accurate positioning result of the GPS can be utilized to assist the initialization of DR, and the positioning error of DR can be corrected on line by the GPS periodically; on the other hand, when the GPS cannot be positioned, the V2X equipment can be automatically switched to the DR navigation mode until the GPS is recovered to normal reception, and the system returns to the combined navigation mode of the GPS and the DR. Therefore, when the vehicle enters the tunnel and is in the out-of-step state, standard reference time can be acquired through the DR data module, and the time offset value is correspondingly determined, and the confidence percentage corresponding to the time offset value is correspondingly determined.

The V2X time module is responsible for receiving the synchronous broadcast signals of the RSU, so that when the vehicle enters the tunnel and is in a step-out state, standard reference time can be acquired through the V2X time module, a time offset value is correspondingly determined, and the confidence percentage corresponding to the time offset value is correspondingly determined.

The wireless network time module is responsible for synchronizing equipment information through a wireless network, so that when a vehicle enters a tunnel and is in a step-out state, standard reference time can be acquired through the wireless network time module, a time offset value and a confidence percentage corresponding to the time offset value are correspondingly determined, and when the vehicle receives wireless network time service information of other cellular networks such as 5G and the like, time synchronization can be performed through the wireless network.

When the vehicle enters the tunnel and is in a step-out state, the vehicle-mounted ECU time module acquires standard reference time through other ECU components of the vehicle, such as an intelligent module controller, and correspondingly determines a time offset value and a confidence percentage corresponding to the time offset value. Thus, the final accurate time is obtained by other parts of the vehicle, namely the ECU or the connected equipment.

When the vehicle enters the tunnel and is in a step-out state, the offset calculation module takes the GNSS time estimated by the V2X time module and the DR data module as an input source, acquires standard reference time, correspondingly determines a time offset value, corrects a local clock signal, and can determine different standard reference time and time offset values according to different algorithms.

The module is used for acquiring a plurality of time offset values and a plurality of confidence percentages, so that the target time offset value is determined according to the time offset values and the confidence percentages.

In some embodiments, determining the target time offset value from the plurality of time offset values and the plurality of confidence percentages includes: if at least two of the confidence percentages are larger than a preset confidence threshold, weighting calculation is carried out on the time offset values corresponding to the at least two confidence percentages to obtain a target time offset value; and if one of the confidence percentages is larger than the preset confidence threshold, taking the time offset value corresponding to the confidence threshold larger than the preset confidence threshold as the target time offset value.

In an embodiment, after a plurality of time offset values and a plurality of confidence coefficient percentages are obtained, judging whether at least two of the plurality of confidence coefficient percentages are larger than a preset confidence coefficient threshold value, and if at least two of the plurality of confidence coefficient percentages are larger than the preset confidence coefficient threshold value, weighting and calculating the time offset values corresponding to the at least two confidence coefficient percentages by an offset calculation module to obtain a target time offset value; and if one of the confidence percentages is larger than the preset confidence threshold, taking the time offset value corresponding to the confidence threshold larger than the preset confidence threshold as the target time offset value.

The offset calculation module determines final accurate time according to the target time offset value, and the final accurate time is input into the V2X module as a time source, so that the V2X module can work normally.

The clock output module is responsible for outputting a reference clock signal, and after the time synchronization of the out-of-step V2X equipment is completed, the clock output module normally outputs 1pps pulse, and the V2X equipment enters the transmission and the reception of the normal transmission synchronous broadcast signal.

The following describes an example of a time synchronization method of the internet of vehicles system according to an embodiment of the present invention with reference to fig. 5.

As shown in fig. 5, the time synchronization method of the internet of vehicles system according to the embodiment of the present invention at least includes step S11-step S22.

Step S11, determining that the V2X equipment enters an out-of-step state, and controlling the V2X equipment to stop sending synchronous broadcast signals.

Step S12, a synchronous channel is established, and a synchronous broadcast signal provided by the first V2X device in a time synchronous state is acquired by adopting the synchronous channel.

Step S13, analyzing the synchronous broadcast signal to obtain the source time, the demodulation processing time and the frequency offset of the synchronous broadcast signal, and determining the initial accurate time according to the source time, the demodulation processing time and the frequency offset.

Step S14, continuously receiving the synchronous broadcast signals for a plurality of times, analyzing the synchronous broadcast signals received each time to obtain initial accurate time corresponding to the synchronous broadcast signals each time, obtaining preset receiving interval time of the continuous and multiple initial accurate time, and obtaining the flight time according to the initial accurate time and the preset receiving interval time.

Step S15, determining an initial time offset value according to the flight time, the demodulation processing time and the frequency offset, and determining the confidence percentage according to the initial time offset value.

Step S16, judging whether the confidence coefficient percentage is larger than a preset confidence coefficient threshold value, if so, executing step S17; otherwise, step S13 is performed.

Step S17, taking the initial time offset value as a target time offset value.

Step S18, determining source time for receiving the synchronous broadcast signals, and determining final accurate time for V2X device synchronization according to the source time and the target time offset value.

Step S19, a plurality of standard reference times are obtained, and a plurality of time offset values and a plurality of confidence percentages corresponding to the time offset values are determined according to the correspondence of the standard reference times.

Step S20, judging whether at least two confidence percentages are larger than a preset confidence threshold value or not, if yes, executing step S21; otherwise, step S22 is performed.

And S21, carrying out weighted calculation on the time offset values corresponding to the at least two confidence percentages to obtain a target time offset value.

Step S22, taking the time offset value corresponding to the confidence coefficient threshold value being larger than the preset confidence coefficient threshold value as a target time offset value.

According to the time synchronization method of the Internet of vehicles system, after the V2X equipment enters the out-of-step state, the synchronous broadcast signals provided by the first V2X equipment in the time synchronization state are obtained, the target time deviation value is obtained according to the synchronous broadcast signals, the time is corrected according to the target time deviation value, the final accurate time is obtained, and the time synchronization is carried out according to the synchronous broadcast signals provided by the first V2X equipment, so that the V2X equipment in the out-of-step state can obtain accurate time information, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

The following describes a time synchronization device 2 of an internet of vehicles system according to an embodiment of the present invention with reference to fig. 6.

As shown in fig. 6, a time synchronization device 2 of an internet of vehicles system according to an embodiment of the present invention includes: a first acquisition module 21, a second acquisition module 22 and a determination module 23, wherein,

The first acquiring module 21 is configured to acquire a synchronous broadcast signal provided by a first V2X device in a time synchronization state; the second obtaining module 22 is configured to obtain a target time offset value; the determining module 23 is configured to determine a final accurate time synchronized with the first V2X device according to the target time offset value and the synchronized broadcast signal.

In an embodiment, when the V2X device enters the out-of-sync state, the first obtaining module 21 determines a first V2X device in a time-synchronization state around the out-of-sync V2X device, and establishes a correlation channel with the first V2X device in the time-synchronization state, and the first V2X device sends a synchronous broadcast signal, such as a device identifier, a subframe interval, a source timestamp, and a frequency offset field, to the out-of-sync V2X device through the correlation channel, and it is understood that the device identifier is generally obtained through a device IMEI (International Mobile Equipment Identity, mobile equipment identifier) or a device vendor code identifier; the source time stamp is accurate to nanosecond level, the step-out V2X device obtains a synchronous broadcast signal provided by the first V2X device through a relevant channel, and a time stamp field and a crystal oscillator offset are added into the synchronous broadcast signal to provide a data base for time synchronization of the vehicle networking system. Wherein the time synchronization state comprises a non-step-out state and a time synchronization state which is completed after the step-out state; the first V2X device includes an RSU device, an OBU device, and any other V2X enabled device that has completed time synchronization, and the synchronized broadcast signal includes a device identification, a source time stamp, a subframe interval, and a frequency offset field, and provides a data basis for time synchronization of the internet of vehicles system by acquiring the synchronized broadcast signal.

The second acquisition module 22 determines a target time offset value according to the device identifier, the source timestamp, the subframe interval, and the frequency offset field in the synchronous broadcast signal, so as to accurately calibrate the time of the V2X device in real time. The target time offset value is a time difference value between the out-of-step V2X device and the first V2X device in the synchronous state, and the out-of-step V2X device can be time-calibrated by acquiring the target time offset value.

The determining module 23 determines a final accurate time synchronized with the first V2X device according to the source timestamp of the synchronized broadcast signal and in combination with the target time offset value, and inputs the final accurate time into the out-of-step V2X device after determining the final accurate time synchronized with the first V2X device, so as to perform time synchronization on the out-of-step V2X device, so that time information of the out-of-step V2X device is recovered to be normal, and the recovered V2X device can normally perform transmission and reception of the synchronized broadcast signal.

According to the time synchronization method of the Internet of vehicles system, after the V2X equipment enters the out-of-step state, the synchronous broadcast signals provided by the first V2X equipment in the time synchronization state are obtained, the target time deviation value is obtained according to the synchronous broadcast signals, the time is corrected according to the target time deviation value, the final accurate time is obtained, and the time synchronization is carried out according to the synchronous broadcast signals provided by the first V2X equipment, so that the V2X equipment in the out-of-step state can obtain accurate time information, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

The internet of vehicles system 3 according to the embodiment of the present invention is described below with reference to fig. 7.

As shown in fig. 7, the internet of vehicles system 3 according to the embodiment of the present invention includes: the time synchronization device 2 and the V2X device 31 of the internet of vehicles system according to the above embodiment, the V2X device 31 communicates with the time synchronization device 2 of the internet of vehicles system.

According to the Internet of vehicles system 3 provided by the embodiment of the invention, after the V2X equipment enters the out-of-step state, the synchronous broadcast signal provided by the first V2X equipment in the time synchronous state is obtained, the target time deviation value is obtained according to the synchronous broadcast signal, the time is corrected according to the target time deviation value, the final accurate time is obtained, and the time synchronization is carried out according to the synchronous broadcast signal provided by the first V2X equipment, so that the V2X equipment in the out-of-step state can obtain accurate time information, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

In some embodiments, the V2X device includes a roadside unit and/or an in-vehicle communication unit.

According to the Internet of vehicles system 3 provided by the embodiment of the invention, after the V2X equipment enters the out-of-step state, the synchronous broadcast signal provided by the first V2X equipment in the time synchronous state is obtained, the target time deviation value is obtained according to the synchronous broadcast signal, the time is corrected according to the target time deviation value, the final accurate time is obtained, and the time synchronization is carried out according to the synchronous broadcast signal provided by the first V2X equipment, so that the V2X equipment in the out-of-step state can obtain accurate time information, the V2X is ensured to be suitable for more scenes, and the accident rate of the system in a tunnel is prevented and reduced.

In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples.

While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.

Claims (13)

1. A time synchronization method of an internet of vehicles system, wherein the internet of vehicles system includes a plurality of V2X devices, the time synchronization method comprising:

Acquiring a synchronous broadcast signal provided by a first V2X device in a time synchronous state;

Acquiring a target time offset value;

and determining the final accurate time synchronized with the first V2X device according to the target time offset value and the synchronous broadcast signal.

2. The method of time synchronization of a vehicle networking system of claim 1, wherein obtaining the target time offset value comprises:

analyzing the synchronous broadcast signals to obtain initial accurate time;

acquiring flight time according to the initial accurate time;

And acquiring the target time offset value according to the flight time.

3. The method for time synchronization of an internet of vehicles system according to claim 2, wherein analyzing the synchronized broadcast signal to obtain an initial accurate time comprises:

analyzing the synchronous broadcast signal to obtain source time, demodulation processing time and frequency offset corresponding to the synchronous broadcast signal;

And determining the initial accurate time according to the source time, the demodulation processing time and the frequency offset.

4. The time synchronization method of an internet of vehicles system according to claim 2, wherein acquiring a time of flight from the initial accurate time comprises:

continuously receiving the synchronous broadcast signal for a plurality of times;

analyzing the synchronous broadcast signals received each time to obtain initial accurate time corresponding to the synchronous broadcast signals each time;

acquiring a preset receiving interval time of the initial accurate time continuously for a plurality of times;

And acquiring the flight time according to the initial accurate time and the preset receiving interval time.

5. A time synchronization method of an internet of vehicles system according to claim 3, wherein obtaining the target time offset value from the time of flight comprises:

determining an initial time offset value according to the time of flight, the demodulation processing time and the frequency offset;

Determining a confidence percentage from the initial time offset value;

And when the confidence percentage is larger than a preset confidence threshold, taking the initial time offset value as the target time offset value.

6. The method of time synchronization of an internet of vehicles system according to claim 1, wherein determining a final accurate time for synchronization with the first V2X device according to the target time offset value and the synchronization broadcast signal comprises:

determining a source time of receiving the synchronous broadcast signal;

and determining the final accurate time for synchronization of the V2X equipment according to the source time and the target time offset value.

7. The method for time synchronization of an internet of vehicles system according to claim 1, wherein acquiring the synchronized broadcast signal provided by the first V2X device in the time synchronized state comprises:

establishing a synchronous channel;

and acquiring the synchronous broadcast signal provided by the first V2X equipment in the time synchronous state by adopting the synchronous channel.

8. The method for time synchronization of an internet of vehicles system according to claim 1, further comprising, before acquiring the synchronized broadcast signal provided by the first V2X device in the time synchronized state:

and determining that the V2X equipment enters a step-out state, and controlling the V2X equipment to stop sending the synchronous broadcast signal.

9. The method of time synchronization of a vehicle networking system of claim 1, wherein obtaining the target time offset value comprises:

Acquiring a plurality of standard reference times;

Determining a plurality of time offset values and a plurality of confidence percentages corresponding to the time offset values according to the standard reference time correspondence;

The target time offset value is determined from a plurality of the time offset values and a plurality of the confidence percentages.

10. The method of time synchronization of a vehicle networking system of claim 8, wherein determining the target time offset value from a plurality of the time offset values and a plurality of the confidence percentages comprises:

If at least two of the confidence coefficient percentages are larger than a preset confidence coefficient threshold value, weighting calculation is carried out on time offset values corresponding to the at least two confidence coefficient percentages, and a target time offset value is obtained;

And if one of the confidence percentages is larger than the preset confidence threshold, taking a time offset value corresponding to the confidence threshold larger than the preset confidence threshold as the target time offset value.

11. A time synchronization device for an internet of vehicles system, comprising:

the first acquisition module is used for acquiring a synchronous broadcast signal provided by the first V2X equipment in a time synchronous state;

The second acquisition module is used for acquiring a target time offset value;

And the determining module is used for determining the final accurate time synchronized with the first V2X device according to the target time offset value and the synchronous broadcast signal.

12. An internet of vehicles system, comprising:

The time synchronization device of the internet of vehicles system of claim 10;

and the V2X equipment is communicated with the time synchronization device.

13. The internet of vehicles system of claim 12, wherein the V2X device comprises a roadside unit and/or an in-vehicle communication unit.