CN112040448B - Time synchronization method for applying V2X equipment to tunnel - Google Patents
Time synchronization method for applying V2X equipment to tunnel Download PDFInfo
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- CN112040448B CN112040448B CN202010934355.3A CN202010934355A CN112040448B CN 112040448 B CN112040448 B CN 112040448B CN 202010934355 A CN202010934355 A CN 202010934355A CN 112040448 B CN112040448 B CN 112040448B
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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]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/001—Synchronization between nodes
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- 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, which is characterized in that GNSS gives time to a main RSU, and the main RSU acquires time; the method comprises the steps that a master RSU sends synchronous message instructions and time broadcasting to equipment in a tunnel through a PTP protocol module in a certain period, a slave RSU sends a delay measurement request after receiving the master RSU message, the master 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 the synchronization statistics for the minimum N times, and judging whether the minimum mean square error meets the minimum mean square error (RMS_limit); and the V2X equipment is applied to the time synchronization method of the tunnel to combine the PTP protocol and the calculation of the weight-based minimum mean square error to realize the time synchronization of the equipment until the minimum mean square error meets the minimum mean square error RMS_limit set by the system and complete the time synchronization, and the synchronization time error can be controlled at nanosecond level.
Description
Technical Field
The invention relates to a time synchronization method, in particular to a time synchronization method of V2X equipment applied to a tunnel.
Background
V2X (Vehicle to everything) is based on technologies such as wireless communication, sensing and detection to acquire road information, realize real-time information interaction of vehicles, roads, people and networks, and perform vehicle safety control and road collaborative management, so that traffic safety is ensured, and traffic efficiency is improved. V2X comprises V2V (Vehicle to Vehicle, vehicle-to-vehicle), V2I (Vehicle to Infrastructure, vehicle-to-infrastructure), V2P (Vehicle to Pedestrian, vehicle-to-pedestrian), V2N (Vehicle to Network, vehicle-to-network) and other modes of vehicle networking communication technologies, and is a key technology in future intelligent transportation systems.
RSU: the method is characterized in that English abbreviations of Road Side units are interpreted, meaning Road Side units, namely the V2X system is installed On a Road Side, and the V2X system is communicated with an On Board Unit (OBU) by adopting DSRC (Dedicated Short Range Communication)/C-V2X technology and the like, so that information interaction between the Road Side and pedestrians, vehicles and networks is realized.
PTP: precision Time Protocol is a high precision time synchronization protocol that can achieve sub-microsecond precision.
And (3) GNSS: the global navigation satellite system positioning is an air-based radio navigation positioning system which utilizes the observables of pseudo-range, ephemeris, satellite transmitting time and the like of a group of satellites, meanwhile, the clock error of a user is required to be known, and the global navigation satellite system is an all-weather three-dimensional coordinate and speed and time information can be provided for the user at any place on the surface of the earth or in the near-earth space, so that the accurate positioning can be realized through four satellites only if you want to know the longitude and the latitude and know the altitude.
The existing network adopting the PTP high-precision time synchronization protocol is usually controlled to be in a millisecond level in synchronization precision, microsecond level can be achieved under ideal conditions, vehicle-road coordination is based on position and time service, a more accurate time synchronization mechanism is needed to be adopted, signal positioning of vehicles running at high speed in vehicle-road coordination application needs to be controlled to be in a nanosecond level, but the prior art cannot achieve that the signal positioning of the vehicles running at high speed in the vehicle-road coordination application needs to be controlled to be in the nanosecond level.
The invention provides a time synchronization method which can control errors in nanosecond level and can be applied to tunnels by V2X equipment through a PTP synchronization protocol of the existing network and combining 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 applying V2X equipment to a tunnel, which is characterized by comprising the following steps:
firstly, a GNSS gives time to a main RSU, and the main RSU acquires time;
secondly, after the master RSU obtains stable time service, the master RSU carries out synchronous message instruction and time broadcasting on equipment in a tunnel through a PTP protocol module in a certain period, a slave RSU carries out 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 the time delay is calculated through delay detection and data interaction of the master station and the slave station, so that high-precision time synchronization is obtained;
thirdly, different weight coefficients are given to measurement results of different time according to the time delay distribution rule of each slave RSU, and the minimum mean square error determines the value of the time delay, namely the value is shown in the following formula:
wherein t is the time delay, i.e. t delay And t offset ；
w i : weight coefficient, representing: weight value of n times of sampling; the effect of real-time measurement results is larger than that of historical data;
t sub : the result of each measurement;
T cal : a time parameter is desired.
Fourthly, when the synchronization statistics of the minimum N times are set, judging whether the minimum mean square error meets the minimum mean square error (RMS_limit) or not, wherein the minimum mean square error (RMS_limit) directly determines the time synchronization precision of the system;
and fifthly, 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 completing 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:
t delay ＝[(t 2 -t 1 )+(t 4 -t 3 )]/2
t offset ＝[(t 2 -t 1 )-(t 4 -t 3 )]/2
wherein t is delay For the average delay time of the link, t offset For master-slave time deviation, t 1 Is the moment of sending the frame by the "master clock", t 2 Is the moment of receiving the frame from the clock, t 3 Time t, which is the time at which the frame is transmitted from the clock 4 Is the time at which the frame is received by the "master clock".
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 V2X device in the tunnel of the present invention comprises a master RSU, one or more slave RSUs, MEC and a router, wherein the master RSU, the slave RSU and MEC are connected with the router by wires or wirelessly.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the master RSU of the time synchronization method of the V2X device applied to the tunnel 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.
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 time-synchronize with the master RSU through the PTP protocol module of the router and a weight-based minimum mean square error.
As an improvement of the time synchronization method of the V2X device applied to the tunnel, the MEC of the time synchronization method of the V2X device applied to 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 device applied to the tunnel has the following beneficial effects: the prior V2X equipment is usually arranged at a position capable of receiving satellite time service signals, no satellite signals exist in a tunnel, and the equipment in the tunnel cannot directly obtain accurate time service, 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 minimum mean square error based on weight, and the slave RSU and the MEC realize time synchronization with the master RSU through the PTP protocol module of the router and the calculation based on the minimum mean square error of the weight, thereby realizing accurate time synchronization of the slave RSU and the MEC with the master RSU, and the time synchronization error of the V2X equipment in the tunnel can be controlled at nanosecond level in the field of vehicle-road cooperation.
Drawings
Fig. 1 is a synchronization flow chart of the high-precision time synchronization protocol of a preferred embodiment of the time synchronization method of the present invention applied to a tunnel by a V2X device.
Fig. 2 is a schematic diagram of the distribution of the master RSU, the slave RSU, the MEC and the router inside and outside the tunnel according to a preferred embodiment of the time synchronization method of the present invention in which the V2X device is applied to the tunnel.
Fig. 3 is a flowchart of a time synchronization system of V2X devices in a tunnel according to a preferred embodiment of the time synchronization method of V2X devices in a tunnel according to the present invention.
Detailed Description
The time synchronization method of the V2X device applied to the tunnel is mainly applicable to time synchronization of devices inside and outside the tunnel.
Referring to fig. 1, 2 and 3, a time synchronization method of the V2X device of the present invention applied to a tunnel will be described in detail.
Referring to fig. 3, a time synchronization method of a V2X device applied to a tunnel in this embodiment includes the following steps:
firstly, setting an RSU as a main RSU, giving time to the main RSU by a GNSS, and acquiring time by the main RSU;
secondly, after the master RSU obtains stable time service, the master RSU carries out synchronous message instruction and time broadcasting on equipment in a tunnel through a PTP protocol in a certain period, the slave RSU carries out delay measurement request after receiving the master RSU message, and the master RSU responds to the delay measurement request, calculates time delay through delay detection and data interaction of the master station and the slave station, and further obtains high-precision time synchronization;
thirdly, different weight coefficients are given to measurement results of different time according to the time delay distribution rule of each slave RSU, and the minimum mean square error determines the value of the time delay, namely the value is shown in the following formula:
wherein t is the delay time, i.e. t delay And t offset ；
w i : weight coefficient, representing: weight value of n times of sampling; the effect of real-time measurement results is larger than that of historical data;
t sub : the result of each measurement;
T cal : desired timeParameters.
Fourthly, when the minimum N times of synchronization statistics are set, judging whether the minimum mean square error meets the minimum mean square error (RMS_limit) or not, wherein the minimum mean square error (RMS_limit) directly determines the synchronization precision of the system;
and fifthly, continuously performing the synchronization process until the minimum mean square error meets the minimum mean square error RMS_limit set by the system, and completing time synchronization.
Referring to fig. 1, in this embodiment, the delay measurement formula of the second step of the time synchronization method applied to the tunnel by the V2X device of the present invention is:
t delay ＝[(t 2 -t 1 )+(t 4 -t 3 )]/2
t offset ＝[(t 2 -t 1 )-(t 4 -t 3 )]/2
wherein t is delay For the average delay time of the link, t offset For master-slave time deviation, t 1 Is the moment of sending the frame by the "master clock", t 2 Is the moment of receiving the frame from the clock, t 3 Time t, which is the time at which the frame is transmitted from the clock 4 Is the time at which the frame is received by the "master clock".
The PTP is a high precision time synchronization protocol, and adopts a relative time synchronization mechanism, and by selecting or setting an RSU as a master station, i.e. a master time clock, it will send synchronization information to other slave RSUs and MECs, and by delay detection and data interaction of the master RSU and the slave RSUs, the time delay is calculated, so as to obtain high precision time synchronization.
The master time clock is a slave RSU and a MEC in the tunnel, wherein the RSU equipment outside the tunnel acquires high-precision time information through GNSS, and then synchronous messages are provided for the slave RSU and the MEC in the tunnel through the PTP protocol module of the router, and the master equipment is V2X equipment or special GNSS time service clock equipment at the tunnel portal; the slave equipment is V2X system equipment which cannot acquire satellite time service in the tunnel, and comprises a slave RSU, a MEC and the like in the tunnel.
In the embodiment, the time synchronization method of the V2X device applied to the tunnel passes through the delay distribution rule of each slave RSU,different weight coefficients are given to measurement results of different times, and the value of the delay time, t, is determined by minimum mean square error delay And t offset The parameter determination adopts a statistical strategy, different weight coefficients are given to measurement results of different time in consideration of the time delay distribution rule, the value of the time delay time is determined by adopting the minimum mean square error, and when the minimum mean square error is smaller than the RMS_limit set by the system, the time synchronization process is completed.
Referring to fig. 2, in this embodiment, the time synchronization method applied to a tunnel by a V2X device of the present invention is applied to a time synchronization system of a V2X device in a tunnel, and includes a master RSU, one or more slave RSUs, an MEC, and a router, where the master RSU, the slave RSU, and the MEC are connected to the router through wires or wirelessly.
In this embodiment, the master RSU of the time synchronization method applied to the tunnel by the V2X device of the present invention is located outside the tunnel, the slave RSU is located inside the tunnel, and the router and the MEC are located inside the tunnel.
In other embodiments, the master RSU of the V2X apparatus of the present invention applied to the time synchronization method of the tunnel is located outside the tunnel, the slave RSU is located inside the tunnel, and the router and the MEC are located outside the tunnel.
In this embodiment, the router of the time synchronization method of the V2X device according to the present invention includes a PTP protocol module, and the slave RSU, the MEC perform time synchronization with the master RSU through the PTP protocol module of the router and a weight-based minimum mean square error.
In this embodiment, after the MEC of the time synchronization method applied to the tunnel by the V2X device of the present invention is time-synchronized, the master RSU and the slave RSU are controlled by the router.
In this embodiment, a specific synchronization procedure of the time synchronization method of the V2X device applied to the tunnel of the present invention is as follows:
firstly, after a system is started, firstly acquiring an RSU master clock, wherein the master clock is time information with high precision acquired by RSU equipment outside a tunnel through GNSS, and the master RSU equipment is V2X equipment or clock equipment special for GNSS time service at a tunnel portal;
secondly, after the master RSU equipment obtains stable GNSS time service, a master clock (master RSU) broadcasts synchronous message instructions and time with the router in a certain period, each slave clock receives messages from the router and then carries out delay measurement requests, and the master clock obtains the delay measurement requests of the slave clocks from the router and responds to the delay measurement requests;
the delay measurement formula is:
t delay ＝[(t 2 -t 1 )+(t 4 -t 3 )]/2
t offset ＝[(t 2 -t 1 )-(t 4 -t 3 )]/2
wherein t is delay For the average delay time of the link, t offset For master-slave time deviation, t 1 Is the moment of sending the frame by the "master clock", t 2 Is the moment of receiving the frame from the clock, t 3 Time t, which is the time at which the frame is transmitted from the clock 4 Is the time at which the frame is received by the "master clock".
Thirdly, different weight coefficients are given to measurement results of different time according to the time delay distribution rule of each slave RSU, and the minimum mean square error determines the value of the time delay, namely the value is shown in the following formula:
wherein t is the delay time, i.e. t delay And t offset ；
w i : weight coefficient, representing: weight value of n times of sampling; the effect of real-time measurement results is larger than that of historical data;
t sub : the result of each measurement;
T cal : a time parameter is desired.
Fourth, when the minimum N times of synchronous statistics are set for the system, judging whether the minimum mean square error meets RMS_limit or not, wherein the RMS_limit directly determines the synchronous precision of the system;
and fifthly, continuously performing 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 device applied to the tunnel has the following beneficial effects: the prior V2X equipment is usually arranged at a position capable of receiving satellite time service signals, no satellite signals exist in a tunnel, and the equipment in the tunnel cannot directly obtain accurate time service, 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 minimum mean square error based on weight, and the slave RSU and the MEC realize time synchronization with the master RSU through the PTP protocol module of the router and the calculation based on the minimum mean square error of the weight, thereby realizing accurate time synchronization of the slave RSU and the MEC with the master RSU, and the time synchronization error of the V2X equipment in the tunnel can be controlled at nanosecond level in the field of vehicle-road cooperation.
The foregoing disclosure is only illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (6)
1. A time synchronization method for applying V2X devices to tunnels, comprising the steps of:
firstly, a GNSS gives time to a main RSU, and the main RSU acquires time;
secondly, after the master RSU obtains stable time service, the master RSU carries out synchronous message instruction and time broadcasting on equipment in a tunnel through a PTP protocol module in a certain period, a slave RSU carries out 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 the time delay is calculated through delay detection and data interaction of the master station and the slave station, so that high-precision time synchronization is obtained;
thirdly, different weight coefficients are given to measurement results of different time according to the time delay distribution rule of each slave RSU, and the minimum mean square error determines the value of the time delay, namely the value is shown in the following formula:
wherein t is the delay time, i.e. t delay And t offset ；
w i Weight coefficient, representing the weight value of n times of sampling; the effect of real-time measurement results is larger than that of historical data;
t sub the result of each measurement;
T cal expected time parameters;
fourthly, when the synchronization statistics of the minimum N times are set, judging whether the minimum mean square error meets the minimum mean square error (RMS_limit) or not, wherein the minimum mean square error (RMS_limit) directly determines the time synchronization precision of the system;
and fifthly, 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 completing the time synchronization.
2. The time synchronization method for applying the V2X device to the tunnel according to claim 1, wherein: the delay measurement formula of the second step is as follows:
t delay ＝[(t 2 -t 1 )+(t 4 -t 3 )]/2
t offset ＝[(t 2 -t 1 )-(t 4 -t 3 )]/2
wherein t is delay For the average delay time of the link, t offset For master-slave time deviation, t 1 Is the moment of sending the frame by the "master clock", t 2 Is the moment of receiving the frame from the clock, t 3 Time t, which is the time at which the frame is transmitted from the clock 4 Is the time at which the frame is received by the "master clock".
3. The time synchronization method for applying the V2X device to the tunnel according to claim 1, wherein: the time synchronization system applied to the V2X device in the tunnel comprises a master RSU, one or more slave RSUs, an MEC and a router, wherein the master RSU, the slave RSU and the MEC are connected with the router through wires or wirelessly.
4. A time synchronization method for application of a V2X device to a tunnel according to claim 3, characterized in that: 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.
5. The method for time synchronization of V2X devices for use in tunnels according to claim 4, wherein: the router comprises a PTP protocol module, and the slave RSU, the MEC time synchronize with the master RSU through a combination of the PTP protocol module of the router and a weight-based minimum mean square error.
6. The method for time synchronization of V2X devices for use in tunnels according to claim 5, wherein: and after the MEC is subjected to time synchronization, the master RSU and the slave RSU are controlled by the router.
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| 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 |
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| 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 |
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