Communication method for internet of vehicles, vehicle-mounted communication device and basic communication infrastructure

Abstract

The application relates to a communication method, a vehicle-mounted communication device and infrastructure for vehicle networking. The method comprises the following steps: selecting a clock module of a plurality of vehicle communication devices as a master clock module, and taking the clocks of the plurality of vehicle communication devices as slave clocks; based on the master clock of the master clock module and the slave clocks, calculating the deviation between the master clock and the slave clocks, and the time delay of at least one available communication path of the vehicle communication device; and selecting the communication path with the minimum time delay for communication. The embodiment of the application can realize high-precision time synchronization of the master clock and the slave clock, and minimize the communication time delay between nodes in vehicle networking.

Description

Technical Field

[0001] This invention relates to a communication method, an in-vehicle communication device, and basic communication infrastructure for vehicle networking. Background Technology

[0002] In the network topology of the Internet of Vehicles (IoV), vehicles, as high-speed moving nodes, experience significantly higher latency than fixed nodes in the network. Furthermore, network handover between base stations occurs during movement. However, certain IoV application scenarios place even greater demands on latency, requiring faster system responses. For example, in using IoV to support real-time control of autonomous vehicles, real-time manipulation of these vehicles is necessary to respond to various emergencies and improve driving safety. In this scenario, the requirements for the transmission and processing latency of real-time vehicle sensing and control data are significantly higher. In the future, each intelligent vehicle may generate up to 1GB of data per second. Such instantaneous processing and transmission of massive amounts of data necessitates the use of low-latency communication technologies.

[0003] In existing technologies, methods for reducing network latency mainly employ the following approaches: First, predictive latency compensation methods; however, dynamic latency prediction is uncertain, leading to unstable latency reduction effects. Second, control plane optimization methods such as radio resource control link / EPS bearer establishment / core network segmented deployment. Third, user plane optimization methods such as air interface uplink and downlink licensed resources / air interface processing time / separate channel allocation. The latter two methods rely on the network and infrastructure provided by operators; when the network is disconnected or the synchronization source is lost, the clock cannot maintain accuracy. Some networks use Network Time Protocol (NTP) time synchronization technology, but NTP time synchronization accuracy is low, typically at the millisecond level, making it difficult to meet the needs of practical applications in vehicle-to-everything (V2X) networks.

[0004] Therefore, it is necessary to improve existing vehicle-to-everything (V2X) communication technologies to reduce V2X communication latency. Summary of the Invention

[0005] The purpose of this invention is to provide a communication method, in-vehicle communication device, and basic communication infrastructure for vehicle-to-everything (V2X) networks, so as to reduce the communication latency of V2X networks.

[0006] Embodiments of the present invention provide a method for communication in a vehicle network, wherein the vehicle network includes multiple vehicles and at least one basic communication facility; each vehicle's communication device and each basic communication facility include a clock module; the method includes: selecting a clock module independent of the communication devices of the multiple vehicles as a master clock module, and using the clocks of the communication devices of the multiple vehicles as slave clocks; calculating the deviation between the master clock and the slave clock, and the delay of at least one available communication path of the vehicle's communication device, based on the master clock of the master clock module and the slave clock; and selecting the communication path with the minimum delay for communication.

[0007] Embodiments of the present invention also provide a communication device for a vehicle, including a clock module and a communication module; wherein the clock of the clock module is configured as a slave clock for communication in a vehicle network, and the clock module and the communication module are configured to perform the vehicle network communication method described in the embodiments of the present invention.

[0008] An embodiment of the present invention provides a basic communication facility for vehicle networking, including a clock module and a communication module; wherein, the clock of the clock module is configured as a master clock or slave clock for communication in the vehicle networking, and the clock module and the communication module are configured to coordinate with the communication devices of multiple vehicles to execute the vehicle networking communication method described in the embodiment of the present invention. Attached Figure Description

[0009] Figure 1 This is a flowchart of a method for communication in a vehicle network according to an embodiment of the present invention;

[0010] Figure 2 This is a schematic diagram illustrating the selection of the communication path with the lowest latency from multiple communication paths in the Internet of Vehicles (IoV) in an embodiment of the present invention.

[0011] Figure 3 This is a schematic diagram illustrating the process of calculating the deviation between the master clock and the slave clock, as well as the transmission delay of the communication path, in an embodiment of the present invention. Detailed Implementation

[0012] The embodiments of the present invention are further described below with reference to the accompanying drawings.

[0013] Figure 1 A flowchart illustrating a method for communication in a vehicle-to-everything (V2X) network according to an embodiment of the present invention is shown. The V2X network includes multiple vehicles and at least one basic communication facility; each vehicle's communication device and each basic communication facility include a clock module. Figure 1As shown, method 100 includes: selecting a clock module of a communication device independent of multiple vehicles as a master clock module, and using the clocks of the communication devices of multiple vehicles as slave clocks (step 110); calculating the deviation between the master clock and the slave clock, and the delay of at least one available communication path of the vehicle's communication device based on the master clock and slave clock of the master clock module (step 120); and selecting the communication path with the minimum delay for communication (step 130).

[0014] By selecting an independent master clock module and accordingly calculating the latency of available communication paths, the communication path with the lowest latency can be accurately selected in the vehicle-to-everything (V2X) network, thus minimizing communication latency. The independent master clock module can be installed on a separate signal tower, attached to a building, or other communication facility.

[0015] The master clock module, acting as the master node, may not be included in the central processing unit (CPU) of the vehicle's infotainment system or basic communication infrastructure; it can be a separate clock module. For example, IEEE 1588v2 can be implemented using both independent software and hardware, while the traditional Network Time Protocol (NTP) is implemented solely in software. The master clock module can also be independent of the vehicle's communication devices and basic communication infrastructure, or it can be one of several clock modules selected from multiple basic communication infrastructures. Using a separate hardware clock module allows for more accurate timestamp recording. Each slave clock will synchronize with the master clock module's master clock, thus maintaining consistency and accuracy in timing across the entire vehicle network. The vehicle's communication devices, acting as slave nodes, can be on-board units (OBUs), smart terminals (T-BOXs), or other wireless communication modules included in the vehicle's infotainment system for vehicle-to-everything (V2X) communication. Basic communication infrastructure can be roadside units (RSUs), base stations, or other communication devices used for V2X.

[0016] In V2V and V2I networks, when communication nodes (such as vehicle-to-everything systems) achieve high-precision time synchronization and can measure the latency of each communication path in real time, the communication path with lower latency can be selected for message forwarding between nodes, thereby reducing communication latency. The vehicle's communication device can establish connections with all communication facilities and vehicles within its communication range, for example, by referencing a hybrid topology in the network topology, thus selecting the communication path with the lowest latency from multiple available communication paths.

[0017] In embodiments of this invention, the master clock and slave clock are Precision Time Protocol (PTP) clocks conforming to the IEEE 1588 protocol. The full name of the IEEE 1588 standard is "IEEE 1588 Precision Clock Synchronization Protocol for Network Measurement and Control Systems," abbreviated as PTP. Its main principle is to periodically correct and synchronize the clocks of all nodes in the network using a synchronization signal, enabling precise synchronization in Ethernet-based distributed systems. The PTP clock synchronization process includes recording the transmitted and received time information, and adding a "timestamp" to each piece of information. With the time record, the receiving end (such as the slave clock) can calculate its own clock error and delay in the network, thus maintaining synchronization. PTP clocks can achieve sub-microsecond level time synchronization accuracy, significantly superior to NTP time synchronization technology, and can function as both master and slave clocks. PTP clocks containing crystal oscillators can enter a holdover state in the event of a lost synchronization source, maintaining a high-precision frequency output for a certain period, ensuring accurate time output until network communication is restored. In a specific implementation, by using a high-precision PTP clock in the vehicle's communication device and basic communication infrastructure, the vehicle's communication device, as a slave clock, can quickly track the time change rate of the master clock. Hardware (such as the IEEE1588v2 crystal oscillator included in the slave clock) is used to record the time when messages enter and leave the communication device. The slave clock can correspondingly achieve coordination and synchronization with the master clock, so that the vehicle's communication device and the master clock module maintain the same frequency and time.

[0018] In embodiments of the present invention, by real-time monitoring of the latency of each communication link and using an independent high-precision master clock module to record timestamps, the PTP clock module, acting as a slave clock, can have a latency feedback function to adapt to the constantly adjusting vehicle network latency and select the optimal communication link for communication. Furthermore, with the master and slave clocks synchronized at high precision, it is easier to calculate the accurate real-time latency of each link in V2V (vehicle-to-vehicle) and V2I (vehicle-to-infrastructure) network communications, allowing each communication node in the network to select a communication link with lower latency, thereby reducing communication latency.

[0019] In a variant of one implementation, the PTP clock on the vehicle's communication device is synchronized with the PTP clock (as the master clock) on the mobile communication base station.

[0020] Those skilled in the art should understand that the present invention is not limited to using a PTP clock, and other high-precision time synchronization technologies may also be employed.

[0021] In an embodiment of the present invention, step 110 of selecting the master clock module includes: selecting a master clock module from multiple clock modules according to the BMCA optimal master clock algorithm in the IEEE 1588 protocol; and / or selecting a master clock module from other clock modules from multiple clock modules as the next master clock module when the current master clock module fails.

[0022] In an embodiment of the present invention, method 100 further includes: using the calculated deviation between the master clock and the slave clock to correct the slave clock, so that the slave clock remains synchronized with the master clock. For example, when a time deviation between the slave clock and the master clock is detected to exceed a predetermined range, the calculated time deviation is used to correct the slave clock to maintain time synchronization with the master clock.

[0023] In embodiments of the present invention, the vehicle-to-everything (V2I) network may include multiple basic communication facilities, each of which includes a Precision Time Protocol (PTP) clock conforming to the IEEE 1588 protocol. Step 110 of method 100, which selects a master clock module, includes: selecting a master clock module from multiple PTP clock modules of the multiple basic communication facilities according to the BMCA optimal master clock algorithm in the IEEE 1588 protocol; other PTP clock modules among the multiple PTP clock modules are controlled to synchronize with the clock of the selected master clock module. In one example, PTP clocks are installed on multiple basic communication facilities in the V2I network, and one or more clocks that can stably track GPS timing are selected as the master clock. This master clock can be selected from multiple basic communication facilities through the BMCA optimal master clock algorithm in IEEE 1588; only one master clock is selected in a domain and synchronized based on the PTP clock. Neither the master clock nor the slave clock relies on the CPU's clock module, but rather on the 1588v2 clock; other vehicle systems and basic communication facilities also install IEEE 1588v2 clocks. When the current master clock module malfunctions, a new master clock module can be selected from other basic communication facilities. Each vehicle infotainment system remains a slave clock, while the non-optimal master clocks of the other basic communication facilities that failed to win the selection process enter a passive, silent state. Typically, two or more basic communication facilities should participate in the master clock selection process within a domain, but only one master clock can exist at a time to provide timing services to other devices. Within a domain, the remaining PTP clocks can act as first-level boundary clocks to synchronize with the master clock. The master clock sends time synchronization messages to each boundary clock to maintain consistent time and crystal oscillation frequency.

[0024] PTP clocks include general-purpose clocks and boundary clocks. Boundary clocks typically have multiple physical ports, each with two logical interfaces: time and general-purpose. Each port of a boundary clock is essentially the same as a general-purpose clock. All ports of a boundary clock share a common clock dataset and a common local time. Each protocol engine has additional functionality to parse the status of all ports, thereby determining which port is used to provide the time signal to synchronize the local clock.

[0025] In the above embodiments, method 100 may further include: calculating the deviation between the clocks of other PTP clock modules and the slave clock of the vehicle's communication device; and correcting the slave clock of the vehicle's communication device to synchronize it with the clocks of at least one other PTP clock module when the deviation between the clocks of at least one other PTP clock module and the slave clock of the vehicle's communication device exceeds a predetermined range. This allows the vehicle's communication device to use slave clocks from other vehicles to modify its own slave clock, thus enabling slave clock correction even when correction via the master clock is inconvenient.

[0026] In an embodiment of the present invention, step 130 of selecting a communication path with the minimum latency for communication includes: calculating the latency of an available communication path between the clock modules of at least two of the communication devices of a plurality of vehicles based on the master clock and slave clock of the master clock module; and selecting a communication path with the minimum latency for communication between the communication devices of at least two vehicles; and when the deviation between the master clock and the slave clock is within a predetermined range, using the slave clock of the communication devices of the plurality of vehicles to calculate the latency of an available communication path between the clock modules of the communication devices of at least two vehicles.

[0027] In one example, such as Figure 2As shown, vehicles A, B, C, and D traveling on the road are all autonomous vehicles, while the other two are ordinary vehicles. Only vehicle A is within the communication range of basic communication facility 201, and vehicle D is within the communication range of basic communication facility 202. The PTP clocks in basic communication facilities 201 and 202 can serve as primary boundary clocks, and the PTP clocks in the communication devices of the autonomous vehicles can serve as secondary boundary clocks, precisely transmitting time to various modules within the vehicle via IEEE 802.1as. Assume the communication delay from vehicle A to vehicle B is 4 seconds, from vehicle A to vehicle C is 1 second, from vehicle C to vehicle B is 1 second, from vehicle C to vehicle D is 3 seconds, and from vehicle B to vehicle D is 1 second. When vehicle A needs to exchange information with vehicle D, the communication is limited due to the greater distance, and the two vehicles cannot communicate directly. Information from vehicle A needs to be transmitted to vehicle D. There are four available communication paths: (1) ACD, with a total communication delay of 4s; (2) ABD, with a total communication delay of 5s; (3) ACBD, with a total communication delay of 3s; and (4) ABCD, with a total communication delay of 8s. By calculating the total communication delay of each available communication path, it can be determined that the final communication path between vehicle A and vehicle D is the ACBD link with the lowest delay.

[0028] In another example, when an autonomous vehicle equipped with a PTP clock enters the communication range of various Level 1 boundary clocks (such as those on basic communication infrastructure), it first checks whether its own generated timestamps and oscillation frequencies are within the allowable error range of the Level 1 boundary clocks. If they exceed the allowable error range, the PTP clock on the vehicle needs to be synchronized. Before clock synchronization, the PTP clock needs to be tuned, and the tuning results are used to correct the timestamps generated by the clock (on the vehicle).

[0029] In an embodiment of the present invention, step 120 of calculating the deviation between the master clock and the slave clock, and the transmission delay of the available communication path of the vehicle's communication device, includes: using the available communication path, sending a synchronization message from the master clock module to the vehicle's communication device, which is the slave clock, and recording the local transmission time T1 of the synchronization message; the vehicle's communication device receiving the synchronization message and recording its local reception time T2; the vehicle's communication device sending a Delay_Req message to the master clock module to initiate the calculation of the reverse transmission delay, and recording the transmission time T3 locally; the master clock module receiving the Delay_Req message and recording the reception time T4; and calculating the deviation between the master clock and the slave clock, and the transmission delay of the available communication path, based at least on the recorded times T1, T2, T3, and T4.

[0030] For specific details of this embodiment, please refer to... Figure 3 Further description. In this embodiment, the mechanism for synchronous message passing is a delayed request-response mechanism, and the entire synchronization process can be divided into two distinct phases:

[0031] The first stage is the time deviation T. offset During the measurement phase, the process is as follows: a) The master clock periodically sends synchronization messages (Sync messages) to the slave clock, with a default interval of 1 second. The master clock records the transmission time T1 locally. The slave clock receives the synchronization message and records the time value T2 of receiving the synchronization message. b) After the synchronization message is sent, the master clock immediately sends a follow-up message, which transmits the precise time T1 of the synchronization message transmission to the slave clock. c) The slave clock sends a Delay_Req message to the master clock to initiate the calculation of the reverse transmission delay and records the transmission time T3 locally. After receiving this message, the master clock records the reception time T4. d) After receiving the Delay_Req message, the master clock replies with a Delay_Response message carrying the time value T4. The contents of the sync, Follow-up, Delay_Req, and delay_Resp messages include the timestamp added for each message transmission step.

[0032] The second stage is the communication path delay T. delay Measurement Phase. To prevent collisions during message transmission, after receiving the synchronization message from the slave clock, a delay request message (Delay-Req message) is not sent immediately. Instead, a random waiting period is observed, and the delay request message is sent at time T3. The master clock receives the delay request message and records the time value T4 at which it was received. It then sends a delay response message containing the time value T4 to the slave clock.

[0033] In the above process, four time values ​​were obtained from the master clock: T1, T2, T3, and T4. The transmission delay from the master clock to the slave clock is T2-T1, and the transmission delay from the slave clock to the master clock is T4-T3. Based on the received time information and the time it sent its own message, the slave clock can calculate the time deviation from the master clock and the line delay. The line delay includes the communication delay between vehicles, between vehicles and basic communication facilities, and between basic communication facilities themselves. Combined with... Figure 3 Based on the above, we can obtain the following equation:

[0034] T1-T offset +T delay =T2 T3+T offset +T delay =T4

[0035] Combining the above equations, we can conclude that:

[0036] T offset = (T1-T2+T4-T3) / 2 T delay = (T2-T1+T4-T3) / 2

[0037] From the clock, based on the calculated T offset and T delay The value is used to adjust the local clock, thereby achieving time synchronization between the slave clock and the master clock.

[0038] According to an embodiment of the present invention, the vehicle's communication device includes a clock module and a communication module; the clock of the clock module is configured as a slave clock for communication in a vehicle network, and the clock module and the communication module are configured to perform the vehicle network communication methods described in the above embodiments of the present invention. The clock module may also be included in the communication module and use a PTP clock; the communication device may be included in the vehicle infotainment system.

[0039] According to embodiments of the present invention, the basic communication infrastructure for vehicle-to-everything (V2X) communication includes a clock module and a communication module. The clock of the clock module is configured as a master clock or slave clock for communication within the V2X network. The clock module and the communication module are configured to coordinate with the communication devices of multiple vehicles to execute the V2X communication methods described in the various embodiments of the present invention. The clock module may also be included in the communication module and use a PTP clock.

[0040] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Those skilled in the art, after understanding the content and principles of the present invention, can make various modifications and variations in form and detail without departing from the principles of the present invention, and such modifications and variations based on the principles of the present invention are still within the protection scope defined by the claims of this patent.

Claims

1. A method for communicating in a vehicle-to-everything, wherein, The vehicle networking includes a plurality of vehicles and at least one infrastructure; each communication device of each vehicle and each infrastructure includes a clock module; the method includes: selecting a clock module of one infrastructure of the at least one infrastructure as a master clock module, which is independent of the communication devices of the plurality of vehicles, and selecting the clocks of the communication devices of the plurality of vehicles as slave clocks, wherein the master clock in the master clock module is a primary boundary clock, and each slave clock is a secondary boundary clock; calculating the offset between the master clock of the one infrastructure and each slave clock of the communication devices of the plurality of vehicles, and the transmission delay of at least one available communication path of the communication devices of the plurality of vehicles, based on the master clock of the master clock module of the one infrastructure as the primary boundary clock and each slave clock of the communication devices of the plurality of vehicles as the secondary boundary clock; selecting a communication path with the shortest delay for communication between the plurality of vehicles, wherein selecting a communication path with the shortest delay for communication between the plurality of vehicles includes: calculating the transmission delay of the available communication path between the clock modules of the communication devices of at least two vehicles of the plurality of vehicles, based on the master clock of the master clock module as the primary boundary clock and each slave clock as the secondary boundary clock; and selecting a communication path with the shortest delay for communication between the communication devices of the at least two vehicles; wherein when the offset between the master clock as the primary boundary clock and each slave clock as the secondary boundary clock is within a predetermined range, the slave clock of the communication devices of the plurality of vehicles as the secondary boundary clock is used to calculate the transmission delay of the available communication path between the clock modules of the communication devices of the at least two vehicles.

2. The method of claim 1, wherein, The master clock and each slave clock are Precision Time Protocol (PTP) clocks conforming to IEEE 1588 protocol.

3. The method of claim 2, wherein, Selecting a clock module as a master clock module includes: selecting a clock module as a master clock module from a plurality of clock modules according to the BMCA Best Master Clock Algorithm in IEEE 1588 protocol; and / or selecting a clock module as a master clock module from other clock modules in the plurality of clock modules when the current master clock module fails.

4. The method of claim 1, wherein, Calculating the offset between the master clock and each slave clock, and the transmission delay of the available communication path of the communication devices of the plurality of vehicles includes: sending a synchronization message from the master clock module to the communication device of the vehicle as a slave clock using the available communication path, and recording the local sending time T1 of the synchronization message; the communication device of the vehicle receives the synchronization message and records the local receiving time T2 of the vehicle receiving the synchronization message; the communication device of the vehicle sends a Delay_Req message to the master clock module to initiate calculation of the reverse transmission delay, and records the sending time T3 locally; the master clock module receives the Delay_Req message and records the receiving time T4; and the master clock module receives the Delay_Req message and records the receiving time T4; and Based on at least said times T1, T2, T3 and T4, a deviation between said master clock and slave clocks of said vehicles, and a transmission delay of said available communication path are calculated.

5. The method of claim 1, further comprising: correcting each slave clock with the calculated deviation between said master clock and each slave clock to keep each slave clock synchronized with said master clock.

6. The method of claim 1 or 2, wherein, said master clock module is independent of communication devices of said plurality of vehicles and said infrastructure communication; 7. The method of claim 1 or 2, wherein, said vehicle-to-vehicle network comprises a plurality of infrastructure communications, each of said plurality of infrastructure communications comprising a Precision Time Protocol (PTP) clock module compliant with IEEE 1588 protocol; said step of selecting a master clock module comprises: electing said master clock module from said plurality of PTP clock modules of said plurality of infrastructure communications according to a BMCA Best Master Clock Algorithm of IEEE 1588 protocol; wherein other PTP clock modules of said plurality of PTP clock modules are controlled to synchronize with the clock of said master clock module.

8. The method of claim 7, further comprising: calculating a deviation between the clock of said other PTP clock module and a slave clock of a communication device of said vehicle; and correcting the slave clock of said communication device of said vehicle to synchronize with the clock of said at least one other PTP clock module when the deviation between the clock of said at least one other PTP clock module and the slave clock of said communication device of said vehicle is outside a predetermined range.

9. A communication device for a vehicle comprising a clock module and a communication module; wherein, said clock module is configured as a slave clock for communication in a vehicle-to-vehicle network, said clock module and said communication module are configured to perform the method of any one of claims 1 to 8.

10. A base communication infrastructure for Internet of Vehicles, comprising a clock module and a communication module; wherein, said clock module is configured as a master clock or a slave clock for communication in a vehicle-to-vehicle network, said clock module and said communication module are configured to coordinate with communication devices of a plurality of vehicles to perform the method of any one of claims 1 to 8.

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