CN112040448A - Time synchronization method for V2X equipment applied to tunnel - Google Patents

Time synchronization method for V2X equipment applied to tunnel Download PDF

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CN112040448A
CN112040448A CN202010934355.3A CN202010934355A CN112040448A CN 112040448 A CN112040448 A CN 112040448A CN 202010934355 A CN202010934355 A CN 202010934355A CN 112040448 A CN112040448 A CN 112040448A
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CN112040448B (en
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黄小岛
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Guangzhou Its Communication Equipment Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
    • H04W4/44—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for communication between vehicles and infrastructures, e.g. vehicle-to-cloud [V2C] or vehicle-to-home [V2H]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/001—Synchronization between nodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention provides a time synchronization method of V2X equipment applied to a tunnel, wherein, GNSS gives time service to a main RSU, and the main RSU obtains time; the method comprises the steps that a main RSU carries out synchronous message instruction and time broadcast to equipment in a tunnel through a PTP (precision time protocol) module in a certain period, a slave RSU carries out delay measurement request after receiving a main RSU message, the main RSU responds to the delay measurement request, and time delay is calculated through delay detection and data interaction of a master station and a slave station, so that high-precision time synchronization is obtained; setting a minimum N-time synchronous statistic, and judging whether the minimum mean square error meets the minimum mean square error RMS _ limit; and when the minimum mean square error meets the minimum mean square error RMS _ limit set by the system, the time synchronization is completed, the time synchronization method of the V2X equipment applied to the tunnel combines the PTP protocol and the calculation of the minimum mean square error based on the weight to realize the time synchronization of the equipment, and the synchronization time error can be controlled in nanosecond level.

Description

Time synchronization method for V2X equipment applied to tunnel
Technical Field
The invention relates to a time synchronization method, in particular to a time synchronization method of a V2X device applied to a tunnel.
Background
V2X (Vehicle to assessing) is based on technologies such as wireless communication, sensing detection and the like to acquire Vehicle and road information, realize real-time information interaction of vehicles, roads, people and networks, perform Vehicle safety control and road cooperative management, guarantee traffic safety and improve traffic efficiency. The V2X includes Vehicle networking communication technologies such as V2V (Vehicle to Vehicle), V2I (Vehicle to Infrastructure), V2P (Vehicle to Pedestrian), and V2N (Vehicle to Network), which are key technologies in future intelligent transportation systems.
RSU: the system is an English abbreviation of Road Side Unit, and the interpretation means roadside Unit, namely a V2X system, is installed at the roadside, and is communicated with an On-Board Unit (OBU) by adopting technologies such as DSRC (differentiated Short Range communication)/C-V2X and the like, so that information interaction between the roadside and pedestrians, vehicles and networks is realized.
PTP: precision Time Protocol is a high Precision Time synchronization Protocol that can reach sub-microsecond Precision.
GNSS: the gnss positioning is an observed quantity using pseudoranges, ephemeris, satellite transmission time and the like of a group of satellites, and a user clock error must be known, and the gnss is a space-based radio navigation positioning system which can provide all-weather three-dimensional coordinates and speed and time information for the user at any place on the earth surface or in a near-earth space, so that in a colloquial way, if you want to know the altitude in addition to the longitude and the latitude, the accurate positioning must be performed by four satellites.
The existing network adopting a PTP high-precision time synchronization protocol is usually controlled in synchronization precision at millisecond level and can reach microsecond level under ideal conditions, the vehicle-road cooperation is based on position and time service, a more precise time synchronization mechanism needs to be adopted, and the synchronization time error required for signal positioning of high-speed running vehicles in the vehicle-road cooperation application is controlled at nanosecond level, but the prior art cannot achieve the synchronization time error required for signal positioning of high-speed running vehicles in the vehicle-road cooperation application.
The invention provides a time synchronization method which can control errors in a nanosecond level and can be applied to a tunnel by V2X equipment, wherein the time synchronization method is implemented with high precision by combining a PTP synchronization protocol of the existing network with a minimum mean square error strategy based on weight and a synchronization mechanism.
Disclosure of Invention
Based on the defects of the prior art, the invention provides a time synchronization method for a V2X device applied to a tunnel, which is characterized by comprising the following steps:
firstly, a GNSS gives time to a master RSU, and the master RSU acquires time;
after the master RSU obtains stable time service, the master RSU carries out synchronous message instruction and time broadcast to equipment in the tunnel through a PTP (precision time protocol) module in a certain period, the slave RSU carries out a delay measurement request after receiving the master RSU message, the master RSU receives the delay measurement request of the slave RSU and responds to the delay measurement request, and time delay is calculated through delay detection and data interaction of a master station and a slave station, so that high-precision time synchronization is obtained;
thirdly, setting a minimum N-time synchronization statistic, and judging whether the minimum mean square error meets the minimum mean square error RMS _ limit, wherein the minimum mean square error RMS _ limit directly determines the time synchronization precision of the system;
and fourthly, continuously performing the time synchronization process until the minimum mean square error meets the minimum mean square error RMS _ limit set by the system, and finishing the time synchronization.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the time delay measurement formula of the second step of the time synchronization method of the V2X device applied to the tunnel is as follows:
Figure 421414DEST_PATH_IMAGE001
Figure 64885DEST_PATH_IMAGE002
wherein
Figure 400052DEST_PATH_IMAGE003
To be the average delay time of the link,
Figure 315924DEST_PATH_IMAGE004
is the master-slave time offset.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the time synchronization method of the V2X device applied to the tunnel of the present invention assigns different weight coefficients to the measurement results of different times through the delay distribution rules of each slave RSU, and the minimum mean square error determines the value of the delay time, and when the minimum mean square error is smaller than the minimum mean square error RMS _ limit set by the system, the synchronization process is completed, that is, as shown in the following formula:
Figure 394738DEST_PATH_IMAGE005
wherein
Figure 830399DEST_PATH_IMAGE006
Time delay, i.e.
Figure 336467DEST_PATH_IMAGE007
；
Figure 552684DEST_PATH_IMAGE008
Weight coefficients, representing:
Figure 622140DEST_PATH_IMAGE009
a weight value of the sub-sample; the real-time measurement result is more influenced than historical data;
Figure 974624DEST_PATH_IMAGE010
the result of each measurement;
Figure 854856DEST_PATH_IMAGE011
a time parameter is desired.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the time synchronization system of the V2X device applied to the tunnel of the V2X device applied to the time synchronization method of the tunnel comprises a master RSU, one or more slave RSUs, an MEC and a router, wherein the master RSU, the slave RSUs and the MEC are connected with the router through wires or wireless connection.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the master RSU, the slave RSU, the router and the MEC of the time synchronization method of the V2X device applied to the tunnel are located outside the tunnel, the slave RSU is located inside the tunnel, and the router and the MEC are located inside or outside the tunnel.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the router of the time synchronization method of the V2X device applied to the tunnel includes a PTP protocol module, and the slave RSU, the MEC and the master RSU are time-synchronized through the PTP protocol module of the router and a minimum mean square error based on weight.
As an improvement of the method for time synchronization of the inventive V2X device applied to the tunnel, the MEC of the inventive V2X device applied to the method for time synchronization of the tunnel controls the master RSU and the slave RSU through the router after time synchronization.
Compared with the prior art, the time synchronization method of the V2X equipment applied to the tunnel has the following beneficial effects: the conventional V2X equipment is usually installed at a position capable of receiving satellite time service signals, no satellite signals exist in a tunnel, and the equipment in the tunnel cannot obtain accurate time service directly, so in order to solve the problem of time synchronization of the V2X equipment in the tunnel, the invention combines a high-precision time synchronization protocol with a weight-based minimum mean square error, and the slave RSU and the MEC realize the time synchronization with the master RSU through the PTP protocol module of the router and the calculation of the weight-based minimum mean square error, so that the accurate time synchronization of the slave RSU, the MEC and the master RSU is realized, and the method is applied to the field of vehicle-road cooperation to enable the time synchronization error of the V2X equipment in the tunnel to be controlled at nanosecond level.
Drawings
Fig. 1 is a synchronization flowchart of the high-precision time synchronization protocol of the preferred embodiment of the time synchronization method of the V2X device applied to the tunnel according to the present invention.
Fig. 2 is a schematic distribution diagram of the master RSU, the slave RSU, the MEC, and the router inside and outside a tunnel according to a preferred embodiment of the time synchronization method for applying the V2X device to the tunnel of the present invention.
Fig. 3 is a flowchart of the operation of the time synchronization system applied to the device of V2X in the tunnel according to the preferred embodiment of the time synchronization method applied to the tunnel by the device of V2X in the present invention.
Detailed Description
The time synchronization method of the V2X equipment applied to the tunnel is mainly suitable for time synchronization of the equipment inside and outside the tunnel.
Referring to fig. 1, 2 and 3, the time synchronization method of the V2X device applied to the tunnel according to the present invention will be described in detail.
Referring to fig. 3, a method for time synchronization of a V2X device applied to a tunnel in this embodiment includes the following steps:
firstly, setting an RSU as a master RSU, and obtaining time by the master RSU when the master RSU is timed by GNSS;
after the master RSU obtains stable time service, the master RSU carries out synchronous message instruction and time broadcast to equipment in the tunnel through a PTP (precision time protocol) protocol in a certain period, the slave RSU carries out time delay measurement request after receiving the master RSU message, the master RSU responds to the time delay measurement request, time delay is calculated through time delay detection and data interaction of the master station and the slave station, and then high-precision time synchronization is obtained;
thirdly, setting a minimum N-time synchronization statistic, and judging whether the minimum mean square error meets the minimum mean square error RMS _ limit, wherein the minimum mean square error RMS _ limit directly determines the synchronization precision of the system;
and fourthly, continuously carrying out the synchronization process until the minimum mean square error meets the minimum mean square error RMS _ limit set by the system, and finishing time synchronization.
Referring to fig. 1, in this embodiment, the formula of the delay measurement of the second step of the time synchronization method applied to the tunnel by the V2X apparatus of the present invention is as follows:
Figure 292790DEST_PATH_IMAGE001
Figure 713407DEST_PATH_IMAGE002
wherein
Figure 372928DEST_PATH_IMAGE003
To be the average delay time of the link,
Figure 220798DEST_PATH_IMAGE004
is the master-slave time offset.
PTP is a high-precision time synchronization protocol, which adopts a relative time synchronization mechanism, and calculates time delay by selecting or setting one RSU as a master station, namely a master time clock, sending synchronization information to other slave RSUs and MECs, and through delay detection and data interaction of the master RSU and the slave RSUs, and further obtains high-precision time synchronization.
The master time clock is that RSU equipment outside a tunnel obtains high-precision time information through GNSS, then synchronous messages are provided for slave RSU and MEC in the tunnel through the PTP protocol module of the router, and the master equipment is V2X equipment positioned at a tunnel entrance or special GNSS time service clock equipment; the slave devices are V2X system devices which can not obtain satellite time service in the tunnel, and comprise a slave RSU, an MEC and the like in the tunnel.
In this embodiment, the time synchronization method for applying the V2X device to the tunnel according to the delay distribution rule of each slave RSU, assigns different weight coefficients to the measurement results at different times, determines the value of the delay time by the minimum mean square error, and completes the synchronization process when the minimum mean square error is less than the minimum mean square error RMS _ limit set by the system, that is, as shown in the following formula:
Figure 146029DEST_PATH_IMAGE012
wherein
Figure 308020DEST_PATH_IMAGE006
Time delay, i.e.
Figure 635096DEST_PATH_IMAGE007
；
Figure 939405DEST_PATH_IMAGE008
Weight coefficient, representing
Figure 351932DEST_PATH_IMAGE009
A weight value of the sub-sample; the real-time measurement result is more influenced than historical data;
Figure 114352DEST_PATH_IMAGE010
the result of each measurement;
Figure 233617DEST_PATH_IMAGE011
a time parameter is desired.
Figure 688869DEST_PATH_IMAGE007
The parameter is determined by adopting a statistical strategy, considering the distribution rule of time delay, giving different weight coefficients to the measurement results of different times, determining the value of the time delay by adopting the minimum mean square error, and when the minimum mean square error is smaller than that set by a system
Figure 775643DEST_PATH_IMAGE013
The time synchronization process is completed.
Referring to fig. 2, in this embodiment, the time synchronization method of the V2X device applied to the tunnel is applied to the time synchronization system of the V2X device in the tunnel, and the time synchronization system includes a master RSU, one or more slave RSUs, an MEC, and a router, and the master RSU, the slave RSU, and the MEC are connected to the router by wire or wirelessly.
In this embodiment, the master RSU, the slave RSU, the router and the MEC of the time synchronization method of the V2X apparatus of the present invention are located outside the tunnel, and the slave RSU is located inside the tunnel.
In other embodiments, the master RSU, the slave RSU, and the router and the MEC of the time synchronization method of the V2X apparatus of the present invention are located outside the tunnel, and the slave RSU is located inside the tunnel.
In this embodiment, the router of the time synchronization method applied to the tunnel by the V2X device of the present invention includes a PTP protocol module, and the slave RSU and the MEC are time-synchronized with the master RSU through the PTP protocol module of the router and a minimum mean square error based on weight.
In this embodiment, the MEC of the time synchronization method applied to the tunnel by the V2X device of the present invention controls the master RSU and the slave RSU through the router after time synchronization.
In this embodiment, the specific synchronization process of the time synchronization method applied to the tunnel by the V2X device of the present invention is as follows:
firstly, after a system is started, firstly, acquiring a master clock of an RSU (remote subscriber Unit), wherein the master clock is used for acquiring high-precision time information through a GNSS (global navigation satellite system) by RSU equipment outside a tunnel, and the master RSU equipment is V2X equipment positioned at a tunnel entrance or clock equipment specially used for GNSS time service;
secondly, after the master RSU equipment obtains stable GNSS time service, a master clock (master RSU) broadcasts a synchronous message instruction and time with the router in a certain period, each slave clock receives a message from the router and then carries out a delay measurement request, and the master clock obtains the delay measurement request of the slave clock from the router and responds to the delay measurement request;
the delay measurement formula is:
Figure 341753DEST_PATH_IMAGE001
Figure 377843DEST_PATH_IMAGE002
wherein
Figure 941679DEST_PATH_IMAGE003
To be the average delay time of the link,
Figure 328798DEST_PATH_IMAGE004
is the master-slave time offset.
Thirdly, when the minimum N times of synchronization statistics set by the system are met, judging whether the minimum mean square error meets RMS _ limit, wherein the RMS _ limit directly determines the synchronization precision of the system;
i.e. as shown in the following formula:
Figure 619971DEST_PATH_IMAGE005
wherein
Figure 776146DEST_PATH_IMAGE006
Time delay, i.e.
Figure 573201DEST_PATH_IMAGE007
；
Figure 119720DEST_PATH_IMAGE008
Weight coefficient, representing
Figure 293212DEST_PATH_IMAGE009
A weight value of the sub-sample; the real-time measurement result is more influenced than historical data;
Figure 490844DEST_PATH_IMAGE010
the result of each measurement;
Figure 458800DEST_PATH_IMAGE011
a time parameter is desired.
And fourthly, continuously carrying out a synchronization process by the system until the RMS _ limit index set by the system is met, and completing time synchronization.
Compared with the prior art, the time synchronization method of the V2X equipment applied to the tunnel has the following beneficial effects: the conventional V2X equipment is usually installed at a position capable of receiving satellite time service signals, no satellite signals exist in a tunnel, and the equipment in the tunnel cannot obtain accurate time service directly, so in order to solve the problem of time synchronization of the V2X equipment in the tunnel, the invention combines a high-precision time synchronization protocol with a weight-based minimum mean square error, and the slave RSU and the MEC realize the time synchronization with the master RSU through the PTP protocol module of the router and the calculation of the weight-based minimum mean square error, so that the accurate time synchronization of the slave RSU, the MEC and the master RSU is realized, and the method is applied to the field of vehicle-road cooperation to enable the time synchronization error of the V2X equipment in the tunnel to be controlled at nanosecond level.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims (7)

1. A time synchronization method of a V2X device applied to a tunnel is characterized by comprising the following steps:
firstly, a GNSS gives time to a master RSU, and the master RSU acquires time;
after the master RSU obtains stable time service, the master RSU carries out synchronous message instruction and time broadcast to equipment in the tunnel through a PTP (precision time protocol) module in a certain period, the slave RSU carries out a delay measurement request after receiving the master RSU message, the master RSU receives the delay measurement request of the slave RSU and responds to the delay measurement request, and time delay is calculated through delay detection and data interaction of a master station and a slave station, so that high-precision time synchronization is obtained;
thirdly, setting a minimum N-time synchronization statistic, and judging whether the minimum mean square error meets the minimum mean square error RMS _ limit, wherein the minimum mean square error RMS _ limit directly determines the time synchronization precision of the system;
and fourthly, continuously performing the time synchronization process until the minimum mean square error meets the minimum mean square error RMS _ limit set by the system, and finishing the time synchronization.
2. The time synchronization method of the V2X device applied to the tunnel according to claim 1, wherein: the formula of the delay measurement in the second step is as follows:
Figure 933899DEST_PATH_IMAGE002
Figure 379924DEST_PATH_IMAGE004
wherein
Figure DEST_PATH_IMAGE005
To be the average delay time of the link,
Figure 697642DEST_PATH_IMAGE006
is the master-slave time offset.
3. The time synchronization method of the V2X device applied to the tunnel according to claim 2, wherein: different weight coefficients are given to the measurement results of different time through the delay distribution rule of each slave RSU, the minimum mean square error determines the value of the delay time, and when the minimum mean square error is smaller than the minimum mean square error RMS _ limit set by the system, the synchronization process is completed, namely, the following formula is shown:
Figure 774182DEST_PATH_IMAGE008
wherein
Figure DEST_PATH_IMAGE009
For time delay, i.e.
Figure 541631DEST_PATH_IMAGE010
；
Figure DEST_PATH_IMAGE011
Weight coefficients, representing:
Figure 791347DEST_PATH_IMAGE012
a weight value of the sub-sample; the real-time measurement result is more influenced than historical data;
Figure DEST_PATH_IMAGE013
the result of each measurement;
Figure 714304DEST_PATH_IMAGE014
a time parameter is desired.
4. The time synchronization method of the V2X device applied to the tunnel according to claim 3, wherein: the time synchronization system applied to the equipment of the V2X in the tunnel comprises a main RSU, one or more auxiliary RSUs, an MEC and a router, wherein the main RSU, the auxiliary RSU and the MEC are connected with the router through wires or wirelessly.
5. The method for time synchronization of the V2X device applied to the tunnel according to claim 4, wherein: the master RSU is located outside the tunnel, the slave RSU is located inside the tunnel, and the router and the MEC are located inside or outside the tunnel.
6. The time synchronization method of the V2X device applied to the tunnel according to claim 5, wherein: the router includes a PTP protocol module, and the slave RSU and the MEC are time-synchronized with the master RSU through a combination of the PTP protocol module and weight-based minimum mean square error of the router.
7. The time synchronization method of the V2X device applied to the tunnel according to claim 6, wherein: and the MEC controls the master RSU and the slave RSU through the router after time synchronization.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112929851A (en) * 2021-03-10 2021-06-08 重庆长安汽车股份有限公司 Time synchronization method based on V2X
WO2022237502A1 (en) * 2021-05-08 2022-11-17 华为技术有限公司 Synchronization method and apparatus

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105187150A (en) * 2015-09-30 2015-12-23 南京务本信息科技有限责任公司 SDH network-based clock synchronizing system
CN105207767A (en) * 2015-10-09 2015-12-30 国网冀北电力有限公司信息通信分公司 Method and device for synchronizing frequencies of PTP master clock and slave clock

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105187150A (en) * 2015-09-30 2015-12-23 南京务本信息科技有限责任公司 SDH network-based clock synchronizing system
CN105207767A (en) * 2015-10-09 2015-12-30 国网冀北电力有限公司信息通信分公司 Method and device for synchronizing frequencies of PTP master clock and slave clock

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112929851A (en) * 2021-03-10 2021-06-08 重庆长安汽车股份有限公司 Time synchronization method based on V2X
WO2022237502A1 (en) * 2021-05-08 2022-11-17 华为技术有限公司 Synchronization method and apparatus

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