Apparatus and method for minimizing delay in a V2X communication network

Abstract

The present invention relates to a method implemented in a V2X device (2) for exchanging V2X messages including data packets with one or more receiving V2X devices connected via a cellular communication network (4), the method comprising the steps of: (a) running one or more V2X applications, running the V2X applications including generating V2X message data associated with the V2X applications, (b) transmitting the V2X message data to a distribution interface (203) at an injection time, and (c) transmitting the V2X message to the receiving V2X device via a radio link at a transmission time using a radio access technology in a format encoded using the message data retrieved from the distribution interface (203). The injection time is determined based on an initial injection time defined by a predefined period. The method comprises the step of calculating the injection time of a current message based on the initial injection time and time information associated with at least one previous V2X message transmitted by the V2X device via the radio link, the time information associated with the previous message including the injection time of the previous message into the distribution interface and the transmission time of the previous V2X message transmitted by the V2X communication device via the radio link.

Description

Technical Field

[0001] The present invention generally relates to a communication network, and more particularly to a V2X device and a method for sending a V2X message in a V2X communication network. Background Art

[0002] In recent years, inter-vehicle communication technologies have undergone significant development in order to improve road safety and optimize road traffic. Such communication technologies are deployed in intelligent transportation systems (ITS) between connected vehicles to allow communication between the vehicles and their environment.

[0003] ITS systems are based on the broadcast of short Basic Safety Messages (BSM) according to so-called ITS radio access technologies between stations, such as between vehicles (V2V), between vehicles and infrastructure (V2I) and between vehicles and pedestrians (V2P). The broadcast of this message makes it possible to trigger appropriate actions in real-time situations, such as warnings in the case of collision detection, or emergency stop actions in the case of detected danger.

[0004] V2X (Vehicle to Everything) messages (particularly V2V, V2I and V2P) can be exchanged according to different types of communications depending on the radio access technology, such as:

[0005] - Direct V2V communication based on short-range technology, such as Dedicated Short Range Communication (DSRC) which may be based on the IEEE 802.11p standard, PC5-mode 4 technology derived from cellular technology based on the 3GPP version 14 standard, or 5G technology based on the 3GPP version 16 standard;

[0006] - Indirect communication (V2N2V) using 4G or 5G connections (via the air interface (also known as Uu interface) for LTE and 5G networks).

[0007] Time synchronization between ITS stations is essential since the information broadcast in the V2X messages is time stamped and needs to be correctly interpreted by the receiving ITS stations.A known practice is to synchronize the time of existing ITS devices using a public GNSS (Global Navigation Satellite System) satellite positioning system source.

[0008] In existing methods, V2X messages transmitted through a V2X communication network are time-stamped by an ITS station that transmits the V2X messages by using a V2X message data generation time, which is typically periodic when the V2X messages are transmitted periodically.

[0009] ITS stations transmit their V2X messages in the V2X network with better clock accuracy. In particular, the ITS system is configured so that when the absolute value of the maximum difference between the clock time of an ITS station and the time base (the time reference of the ITS system) is higher than the time threshold currently set to 200ms, the ITS station is not authorized to send a V2X message.

[0010] Different types of V2X messages can be exchanged. For example, for messages of the CAM (Collaborative Awareness Message) type, a specific model can be used for the total delay of the message. Sending a message by an ITS station includes encoding by the transmitting ITS station during an encoding time, delivering the message to the receiving ITS station via the radio access technology during a transmission time, and decoding the V2X message by the ITS station during a decoding time. The transmission time of a message according to the radio access technology cannot be compressed. In fact, this transmission time is standardized and cannot be significantly reduced without changing the interoperability with other ITS stations.

[0011] To send a V2X message, the V2X application of the ITS station first places the V2X message on the distribution interface at the injection time (or generation time). At the injection time, the message is sampled but not yet sent over the radio access network. The message is then encoded and sent over the radio link with the help of the radio access technology.

[0012] Therefore, each V2X message that must be sent by an ITS station to a receiving ITS station carries a timestamp information corresponding to the time of its injection. The time difference between the time of generation of a V2X message and the time at which the message is effectively sent through the radio access network may constitute a significant delay. Furthermore, the time difference between the time of transmission of a V2X message through a distribution interface and the time at which the message is sent cannot be predicted a priori and therefore cannot be compensated for.

[0013] Certain use cases require particularly short delays to function. Examples that may be cited include the case of cooperative systems such as platooning (grouping of a large number of vehicles), which require information to be exchanged between vehicles with a delay of less than 10 ms. Summary of the invention

[0014] Problem that the invention aims to solve

[0015] Therefore, there is a need for methods and apparatus for minimizing delays in ITS stations.

[0016] [Methods used to solve problems]

[0017] The present invention improves the situation by proposing a method implemented in a V2X device for exchanging V2X messages including data packets with one or more receiving V2X devices connected via a cellular communication network.

[0018] The method comprises the following steps:

[0019] - running one or more V2X applications, running the V2X applications including generating V2X message data associated with the V2X applications,

[0020] - at the injection time, transmitting the V2X message data via the distribution interface, and

[0021] - at a sending time, transmitting the V2X message to the one or more receiving V2X devices via a radio link using a radio access technology, wherein the V2X message is in a format encoded based on the message data retrieved through the distribution interface.

[0022] Advantageously, the injection time is determined based on an initial injection time defined by a predefined period, and the method comprises the following steps: calculating the injection time of the current message based on the initial injection time and time information related to at least one previous V2X message sent by the V2X device via the radio link, wherein the time information related to the previous message comprises the injection time of the previous message on the distribution interface and the time when the V2X device sent the previous V2X message via the radio link.

[0023] In one embodiment, the step of calculating the injection time comprises calculating a time difference between a time associated with a transmission time of the previous V2X message and an injection time of the previous message, and calculating the injection time of the V2X message by determining whether at least one condition associated with the time difference and at least one predetermined threshold is satisfied.

[0024] The injection time of the current V2X message can be an affine function of an initial injection time defined by the period, the affine function having a steering coefficient equal to 1 and a positive or negative ordinate at the origin, the ordinate being a function of the condition related to the time difference and at least one predetermined threshold.

[0025] According to certain aspects, the period is a multiple of a reference time value, and the ordinate at the origin is set to a negative value if the time difference is greater than or equal to the reference time value.

[0026] If the time difference is strictly below a predefined upper threshold, the ordinate at the origin is set to a negative value.

[0027] Alternatively, the ordinate at the origin is set to a positive value if the time difference is strictly above a predefined upper threshold.

[0028] The value of the ordinate at the origin depends on the processing load of the communication module of the V2X device.

[0029] In particular, the ordinate at the origin depends on the load of a processor for executing the method.

[0030] After the trigger injection, the information generated in the V2X message is collected synchronously or asynchronously.

[0031] A V2X device is also proposed, which is configured to exchange V2X messages including data packets with one or more receiving V2X devices connected to the V2X device via a cellular communication network, the V2X device comprising:

[0032] - an application module, which runs one or more V2X applications, the application module being capable of generating V2X message data associated with the one or more V2X applications of the application module,

[0033] - a distribution interface on which the V2X message data generated by the V2X application of the application module (202) at the injection time is placed,

[0034] - A V2X communication module configured to receive the V2X message data via the distribution interface and to transmit the V2X message in a coded format to the one or more receiving V2X devices via a radio link using a radio access technology at a transmit time.

[0035] In one embodiment, the injection time is determined based on an initial injection time defined by a time period. Advantageously, the V2X device comprises an injection time computer configured to calculate the injection time of the V2X message based on the initial injection time and time information related to at least one previous V2X message sent by the V2X device via the radio link, the time information related to the message comprising the injection time of the data of the previous V2X message on the distribution interface and the time when the V2X device sent the previous V2X message via the radio link.

[0036] In one embodiment, the injection time computer is configured to calculate a time difference between a time associated with a transmission time of the previous V2X message and an injection time of the previous message, and calculate the injection time of the current V2X message by determining whether at least one condition associated with the time difference and at least one predetermined threshold is satisfied.

[0037] In one embodiment, the communication module is configured to send a notification to the application module in response to sending a V2X message to the receiving V2X device, and the time related to the sending time of the previous V2X message on which the time difference depends is the sending time of the notification.

[0038] In one embodiment, the processing load of the V2X communication module depends on the position of the V2X device sent by a positioning system, and the device implements a synchronization mechanism to obtain position information from the positioning system at an optimal time defined relative to the initial injection time of new V2X messages.

[0039] The value of the ordinate at the origin may depend on the processing load of the V2X communication module.

[0040] The communication unit may be implemented on a computer system comprising at least one processor, and the ordinate at the origin may depend on the load of the processor.

[0041] A computer readable medium is also proposed, which stores computer program instructions, which implement the above method when executed by one or more processors.

[0042] Therefore, embodiments of the present invention allow reducing the delay between the time (injection time) of transmitting a message through the distribution interface (generation time) and the actual time the V2X communication module sends the message over the air via the radio link. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other characteristics, details and advantages of the invention will emerge on reading the description given with reference to the accompanying drawings, which are given by way of example and represent respectively:

[0044] [ Figure 1 ] Figure 1 An example of an operating environment in which the present invention may be implemented is shown.

[0045] [ Figure 2 ] Figure 2 An exchange between two ITS stations connected to each other via a communication network is shown.

[0046] [ Figure 3 ] Figure 3 is a block diagram of a VXU communication unit of an ITS station according to some embodiments.

[0047] [ Figure 4 ] Figure 4 is a diagram showing a processing time for sending a V2X message in a transmitting ITS station according to an embodiment of the present invention.

[0048] [ Figure 5 ] Figure 5is a block diagram illustrating the interaction between the application module and the communication module.

[0049] [ Figure 6 ] Figure 6 is a diagram illustrating a sequence of injecting message data on a distribution interface and sending a V2X message over the air in time according to an exemplary embodiment.

[0050] [ Figure 7 ] Figure 7 is a flow chart representing a method for calculating injection time according to some embodiments.

[0051] [ Figure 8 ] Figure 8 The gain obtained by using a V2X device and a V2X message sending method according to an embodiment of the present invention is shown.

[0052] [ Fig. 9 ] Fig. 9 is a diagram showing the reduction of delay by applying a method according to an embodiment of the present invention compared to the prior art. DETAILED DESCRIPTION

[0053] Figure 1 1 shows an example of an operating environment 100 of an intelligent transport system ITS according to some embodiments, in which ITS stations (also referred to as ITS devices) may be used.

[0054] The ITS system allows the exchange of V2X messages between a transmitting ITS station (e.g. 2A) and a receiving ITS station (e.g. 2B). In this specification, the ITS station is also more generally referred to as a V2X device.

[0055] The transmission of V2X messages between two ITS stations 2 can be accomplished with the aid of a wireless communication network.

[0056] Environment 100 forms a smart transport architecture that can be used to manage safety and optimize the efficiency of road traffic by using V2X wireless communications between connected transmitting ITS stations (e.g., 2A) and receiving ITS stations (e.g., 2B).

[0057] The ITS stations designed by reference 2 can generally be:

[0058] - a vehicle device 2A or 2B;

[0059] - a pedestrian device 2C, such as a mobile device equipped by a pedestrian;

[0060] - Road Infrastructure 2D (also known as Roadside Unit or RSU); or

[0061] -Application server 2E.

[0062] ITS stations 2 of the same or different types may exchange (send or receive) V2X messages with each other via 3GPP-compliant data transport. V2X communication may be, in particular, V2V, V2I or V2N communication, depending on the type of ITS stations communicating with each other in pairs:

[0063] - In V2V communication, V2X communication occurs between a transmitting vehicle 2A and a receiving vehicle 2B, each of which runs a V2V application;

[0064] - In V2I communication, V2X communication occurs between a vehicle 2B and a road infrastructure 2D (RSU), each of the two ITS stations using a V2I application; the road infrastructure 2D supports a V2I service for sending and / or receiving data to and from the vehicle 2B by using the V2I application;

[0065] - In V2N communication, V2N communication occurs between the vehicle 2B and a V2X application server 2E, which distributes V2X services to receiving ITS stations 2 via a cellular communication network.

[0066] like Figure 2 As shown, each ITS station 2 is equipped with a communication unit 20 (hereinafter also referred to as a “VXU unit”) configured to allow communication of V2X messages related to one or more V2X applications with other ITS stations.

[0067] For example, each ITS station of vehicle 2B (or 2A) type may use its communication unit 20 to allow communications related to one or more V2X applications:

[0068] - Communication between a vehicle 2B (or 2A) and an application server 2E that distributes V2X services to receiving ITS stations, or

[0069] - Exchanging V2X data packets related to one or more V2X applications between the vehicle 2B (or 2A) and a receiving ITS station 2 located within a distance area corresponding to the shortest distance of the ad hoc radio technology by means of one or more ad hoc radio access technologies.

[0070] Radio access technology (RAT) corresponds to the underlying physical connection method used for a radio communication network, such as, for example but not limited to, third, fourth or fifth generation (3G, 4G, 5G) radio access technology, 802.11p type ad hoc communication, PC5 type ad hoc communication.

[0071] The vehicle type ITS station may be equipped with wireless communication means (transmission and reception) suitable for communicating with the cellular network 4 and / or for communicating with a receiving ITS station 2 based on a radio access technology.

[0072] The ITS station 2 runs one or more V2X applications that trigger the exchange of V2X messages between the ITS stations. The V2X applications can be linked to various smart services and use the environmental data acquired by the ITS stations with the help of sensors and / or cameras.

[0073] The cellular communication network 4 may include base stations 40 and a cellular core network 41. The communication network 4 allows transmission of ITS stations (e.g., 2 emi ) accesses the V2X service corresponding to the V2X application and transmits the V2X data packet to the receiving ITS station (e.g., 2 rec ) sends a V2X message. The receiving ITS station receives the V2X data packet transmitted by the transmitting ITS station and decodes the received packet.

[0074] An ITS station 2 of a vehicle type (eg 2A or 2B) may receive data from an application server 2E via a base station or station 40 and / or a core network 41 .

[0075] The transmitting ITS station 2 of the vehicle type (2A or 2B) can use the application server 2E in particular to relay, multicast or broadcast road traffic information or safety information or road application information to the receiving ITS station running the V2X application corresponding to the V2X application of the transmitting ITS station.

[0076] For example, a transmitting ITS station of type vehicle 2 (e.g., 2A) can simultaneously (e.g., in parallel) broadcast V2V messages to several other vehicles 2B located nearby, or broadcast V2I messages to a single road infrastructure 2D, or broadcast V2P messages to all pedestrian devices equipped with mobile devices 2C located nearby.

[0077] The application server 2E may be any type of server that appears on the network (eg, a cloud server or a distributed server), which implements the data processing function of sending the information required by the ITS station.

[0078] The cellular communication network 4 may be, for example, an LTE network, and the base station is an eNB node of the LTE network.

[0079] Embodiments of the present invention make it possible to optimize the delay in processing V2X messages transmitted by the ITS station 2. emi The VXU communication unit transmits via a radio link using radio access technology and is received by the ITS station 2 recReception is via a radio link using a radio access technology.

[0080] Figure 3 Schematic diagram showing a VXU communication unit 20 implemented in an ITS station according to an embodiment of the present invention.

[0081] The VXU communication unit 20 is used at each ITS station to encode the V2X messages to be transmitted and decode the received V2X messages.

[0082] The VXU communication unit 20 may be connected to or even incorporated into the ITS station's electronic control unit (UCE) 50 , which is an embedded computer that controls the physical devices of the ITS station 2 .

[0083] The VXU communication unit 20 includes a V2X communication module 202 (V2X stack) that provides an interface set to an application module 201 (V2X layer). The application module 201 is configured to run one or more V2X applications, thereby allowing V2X services to be delivered to other components by transmitting a given type of V2X message. The V2X application module may include an application element for transmitting a V2X object or receiving a V2X event.

[0084] The V2X communication module 202 (V2X stack) communicates with the distribution interface 203 to generate V2X message data. In order to send a V2X message, the V2X application of the application module 201 distributes the V2X message data to the component 2012 of the V2X communication module 202 via the distribution interface 203. The V2X application of the application module 201 can also receive data from the component 2012 by using a suitable protocol (e.g., CAN). Therefore, the application module 201 is configured to distribute the V2X data to the component 2012 via the distribution interface 203 to allow the V2X message corresponding to the component 2012 (e.g., the CAM component responsible for sending CAM type messages) to be sent. Therefore, the V2X message containing V2X information can be transmitted to other ITS stations periodically or regularly.

[0085] In one embodiment, the distribution interface may access the V2X message data injected at the V2X communication module, for example by opening a socket. The communication module 202 may then retrieve the V2X message data (e.g., on the socket) and store the V2X message data in its internal variables to process the V2X message data in order to send the V2X message. The communication module 202 may, in particular, store V2X message timestamp information corresponding to the time of injection of the message data on the distribution interface 203, and may update the values ​​of all fields included in the message data (e.g., the speed and / or position of the ITS station) to encode the fields and encapsulate them in the next V2X message to be sent over the radio link via the radio access technology 2014.

[0086] Hereinafter, in the specification, the injection of the V2X message will refer to the injection of the V2X message data on the distribution interface 203 .

[0087] The VXU communication unit 20 of the ITS station can send different types of V2X messages. Each message type is handled by a corresponding component 2012 of the V2X communication module.

[0088] For example, cooperative awareness related to road traffic consists in ensuring that road users (such as vehicles 2A and 2B or pedestrian devices 2C) and road infrastructure D are each informed of the location, dynamics and properties of each other road user or infrastructure. Examples of road users include, but are not limited to, vehicles, motorcycles, bicycles or pedestrians. Examples of road infrastructure include, but are not limited to, traffic signs, traffic lights, level crossing barriers, bridges, etc. In order to ensure such mutual awareness, information is exchanged regularly. This cooperative awareness information is encapsulated in a specific V2X message called CAM (Collaborative Awareness Message) that is periodically transmitted by each ITS station.

[0089] Each CAM message includes its timestamp information, which corresponds to the injection time of the message on the distribution interface 203 .

[0090] ITS stations may transmit other V2X messages that are time-stamped, such as:

[0091] - messages called DENM (acronym for Decentralized Environmental Notification Message). DENM messages are used to transmit information related to special events or situations (such as, for example, warnings indicating road works, traffic jams, etc.);

[0092] - MAP messages for transmitting geographical data; MAP messages make it possible to encode and transmit the geographical configuration of road intersections;

[0093] - SPAT (acronym for Signal Phase and Timing) message; the SPAT message encodes the phase and time information of the traffic light signal. The message includes information about the signal and reference of the identifier of the MAP message to assign the phase and time information to a specific channel;

[0094] - IVI messages transmitted by an ITS station, including vehicle information (IVI: acronym for Vehicle Information Message); such messages are transmitted to transmit data relating to information external to the vehicle, such as, for example, traffic signals on roads located in close proximity to the vehicle;

[0095] - CPM (acronym for Collaborative Perception Message) messages containing raw and processed data from sensors with which ITS stations of vehicle type are equipped.

[0096] In existing embodiments, the V2X application can only obtain data from other components asynchronously by using a specific protocol (e.g., using the CAN data bus), and must deliver these data to the distribution interface 203 of the V2X layer without knowing in advance when the next V2X message will be sent.

[0097] The V2X message data generated by the application is associated with an injection time (hereinafter referred to as initial injection time) defined by a time period, for example according to the ETSI EN 102894-2 standard. In existing solutions, the message data is injected on the distribution interface 203 at the initial injection time defined by the time period.

[0098] Embodiments of the present invention advantageously provide an ITS station capable of injecting message data on a distribution interface at an optimized injection time calculated by the injection time computer 6 .

[0099] The injection time computer 6 is advantageously configured to calculate the injection time t based on an initial injection time defined by the period and time information related to at least one V2X message previously sent by the ITS station via the radio link. inj , the time information related to the previous message includes the injection time of the data of the previous V2X message on the distribution interface and the time when the V2X communication device sent the previous V2X message through the radio link, which makes it possible to reduce the delay of the ITS station.

[0100] In the following, a description will be given as a non-limiting example with reference to an injection time computer 6 using time information related only to previous messages. A person skilled in the art will readily appreciate that the present invention is equally applicable to an injection time computer 6 using time information related to multiple previous messages by using a sliding window.

[0101] Therefore, regardless of the type of message sent, the VXU unit 20 of the ITS station 2 can generate a V2X message including the latest time information.

[0102] Although embodiments of the present invention are applicable to any type of V2X messages (such as CAM, DENM, SPAT, etc. messages), as a non-limiting illustrative example, the following description of embodiments of the present invention will be made primarily with reference to CAM type messages.

[0103] Figure 4 Figure 2 shows an example of sending a V2X message of type CAM from a transmitting ITS station to a receiving ITS station.

[0104] like Figure 4 As shown, the transmission from ITS station 2 em To receiving ITS station 2 recSending V2X messages includes:

[0105] -Transmitted by ITS Station 2 em At time T enc During this period, V2X messages are encoded;

[0106] - At time T RAT During the transmission of V2X messages via radio access technology 2014;

[0107] -By V2X receiving station 2 rec At time T dec Decoding of V2X messages during the process.

[0108] Transmission time T of V2X message by radio access technology RAT Includes the time for access to each radio channel and transmission of messages.

[0109] The transmission time T cannot be compressed RAT In fact, the transmission time T cannot be easily estimated RAT , because the transmission time T RAT Depends on the number of messages transmitted in the frequency band used at time T.

[0110] According to an embodiment of the present invention, the VXU communication unit 20 of the ITS station 2 is configured to calculate the injection time T by using inj (hereinafter also referred to as generation time) is used to timestamp each V2X message to be sent in the V2X network to reduce latency.

[0111] With the aim of transmitting from ITS station 2 em Send to one or more receiving ITS stations 2 rec The timestamp information (injection time) associated with the V2X message corresponds to the time T inj , the time T inj Corresponds to placing the V2X message on the distribution interface.

[0112] Embodiments of the invention advantageously make it possible to minimize the time difference between the injection time and the actual sending of the V2X message over the air interface, and thus minimize the delay linked to the message transmission.

[0113] The VXU communication unit 20 according to an embodiment of the invention is advantageously configured to reduce the difference between the generation time Tinj of a message and the actual time of sending the message to the receiving ITS station 2R by using the radio access technology, by using information related to previously sent V2X messages.

[0114] The ITS station 2 is configured to transmit V2X messages, for example periodically, at different consecutive transmission times.

[0115] like Figure 3 As shown, the application module 201 of the VXU unit 20 may include an injection time computer 6, which is configured to be based on the V2X message M previously sent by the ITS station at a previous time. i-l One or more parameters related to adjusting the V2X message M to be sent by the time period i The initial injection time of (current message). The V2X message may then be sent by the radio access layer 2014 of the V2X communication module 202 over the radio link.

[0116] In one embodiment, the injection time computer 6 may be configured to calculate a time difference injectionDelayMs between a time related to a transmission time of a previous V2X message and an injection time of the previous message, and calculate the injection time of a new V2X message by determining whether at least one threshold condition related to the time difference injectionDelayMs and at least one predefined threshold is satisfied. Thus, the calculation makes it possible to calculate the injection time of a new V2X message at T inj A servo control loop is established on the controller.

[0117] In particular, the injection time t of the V2X message Mi inj_i The initial injection time t may be defined by the time period inj_init_i The affine function t inj_i =f(t inj_init_i ), the function f() having a steering coefficient equal to 1 and a positive or negative ordinate N at the origin as a function of a threshold condition associated with the time difference injectionDelayMs and one or more predefined thresholds:

[0118] t inj_i =t inj_init_i +N

[0119] In an embodiment, the period defining the initial injection time is a multiple of a reference time value (e.g. 100 ms in the case of a CAM type message), which reference time value may in particular represent a calculation time interval of a computer or a call time interval of a function block. In such an embodiment, it may be checked in advance whether the difference InjectionDelayMs is greater than or equal to the reference time value (preliminary condition) before testing the threshold condition. If the preliminary condition is met, the next injection may be triggered at the time TIME_REMOVING_STACK_MISSED_MS (e.g. (5 ms)) to advance the next injection.

[0120] If the preliminary condition is not met, the threshold condition may be tested.

[0121] In particular, if the difference InjectionDelayMs is strictly below a predefined minimum threshold DELTA_INJECTION_TIME_MIN_MS (first threshold condition), the parameter N may be set to a negative value. Thus, the injection of the next V2X message may be advanced relative to the initial injection time (eg, 2 ms in advance).

[0122] If the first threshold condition is not met, the parameter N may be set to a positive value if the difference InjectionDelayMs is strictly above a predefined upper threshold DELTA_INJECTION_TIME_MAX_MS (second threshold condition). Thus, the injection of the next message may be delayed relative to the initial injection time (eg, by 2ms).

[0123] In one embodiment, the parameter N (the time added or subtracted based on the threshold condition) may depend on the processing load of the V2X communication module 202 (the time it takes the communication module to encode the message).

[0124] The communication unit 20 may be implemented on a computer system comprising at least one processor. In an embodiment, the parameter N (the time added or subtracted according to the threshold condition) may then also depend on the processing load of the processor (eg, CPU load) or be a variant of the processing load of the processor.

[0125] In one embodiment, when the VXU communication unit 20 of the ITS station 2 sends a V2X message via a radio link by using the radio access technology 2014, the V2X application 202 responsible for sending the message can receive the following notifications: the effective transmission of the message (sent by the ITS station to the receiving station) and the transmission time corresponding to the message sent via the radio link.

[0126] In such an embodiment, the difference InjectionDelayMs depends on the previous V2X message M i-1 The time associated with the sending time of the previous message is the time when the application module 201 receives the notification associated with the sending of the previous message. notif Therefore, by taking M i-1 The actual injection time of the previous message is denoted as t inj_(i-1) :

[0127] InjectionDelayMs=t Notif –t inj_(i-1)

[0128] Therefore, the injection time computer 6 can adjust the injection time T of the next message on the distribution interface from the time N before the initial injection time defined by the time period inj In one embodiment, the time N may be N milliseconds.

[0129] The figure is a block diagram representing the interaction between the application module 201 and the V2X communication module 202 according to some embodiments.

[0130] The application module 201 may include an injection synchronization manager 2026 configured to adjust the time after sending each V2X message notified by the V2X communication module 202 in order to avoid time offset.

[0131] The application module 201 may further include a V2X message injector 2024, which is configured to inject the V2X message at the calculated injection time T inj Inject V2X message data on the distribution interface.

[0132] In an embodiment, the application module 201 may also include a parameter update module 2025, which is configured to receive discrete signals from the ITS station 2 and update the discrete signals. For example, in a vehicle-type ITS station, such discrete signals may include signals from sensors (sensor data) or positioning signals (position data) received from a positioning system such as a GNSS system 70. Such discrete signals may be sent periodically in time and may be stored when updated. In embodiments where the GNSS signal may be queried, the signal may be queried after the message injector 2024 has decided to trigger a new V2X message injection so that the information obtained by such an inquiry is as accurate as possible.

[0133] Therefore, the V2X message injector 2024 may inject the V2X message data at the calculated injection time on the distribution interface 2020 of the V2X communication module 202 by using the parameters updated by the update module 2024 .

[0134] Therefore, the V2X communication module can access the V2X message data to prepare to send the corresponding type of V2X message. The data is encoded by the message encoder 2015. A Geonet encoder 2016 may also be applied, for example, the Geonet encoder 2016 encodes the Geonet 3GPP header and adds it to the message. Then, the access layer 2018 sends the encoded message over the air by using the radio access technology.

[0135] Figure 6 1 is a timing diagram showing an example of a V2X station continuously sending V2X messages, where the time period between the sending of two messages varies with time. inj Inject at t enc Encoded at t env Sent from Figure 6It can be seen that the time period between two consecutive transmissions of a message is long at first and then becomes shorter as time goes by. Such a trend in the time period may be caused by the increase in the vehicle speed forcing the communication module to encode more messages per second.

[0136] In an embodiment where the initial injection time is defined by a period (e.g. set by an ETSI standard), the period may be a multiple of a reference time value and be between the reference time value and a maximum period threshold. The reference value may in particular be defined in milliseconds (ms), while the maximum period threshold may be of the order of seconds. For example, for a CAM type V2X message, the reference value currently set by the ETSI standard is equal to 100 ms and the maximum threshold is equal to 1 s: Thus, according to the ETSI standard, the CAM message sending period is a multiple of 100 ms and is between 100 ms and 1 s.

[0137] In an embodiment, the frequency of the generation of messages (V2X message injection) may be determined based on information about changes in the state of the ITS station, such as, for example, the position or speed of the ITS station, or even the load of the radio channel which may be determined by a decentralized congestion controller DCC of the ITS station 2.

[0138] In one embodiment, the message injector 2024 can trigger the update of the ITS station parameters through the update module 2025 according to a minimum period equal to a reference time value (e.g., 100 ms). Therefore, the V2X message injector 2024 can always supply the ITS station parameters at the right time.

[0139] As a variation, the message injector 2024 may calculate the transmission time t of the next V2X message based on the determined ITS station parameters. env , so as to minimize the load on the distribution interface 203.

[0140] In the prior art, the injection of V2X messages occurs randomly in the message processing window, so that the injection time t inj The effective transmission time t of the message on the air link can be env much earlier and generates significant latency. Figure 6 As shown, the embodiment of the present invention enables the effective time t of the message sent by the access layer 2018 of the ITS station 2 to be reduced. env The time t calculated by the injection time computer 6 when the injector 2024 injects the message on the distribution interface 203 inj The difference between them is minimized, which makes it possible to reduce the delay of the prior art.

[0141] In practice, it may be difficult to accurately update all ITS station 2 parameters at the time of injection, except for continuously updating them. However, some parameters may be important, such as the latitude and / or longitude position parameters of the ITS station stored in the memory, which can be updated by the update module 2025. In order to optimize the accuracy of the data sent by the injector 2024 to the communication module 202, embodiments of the present invention make it possible to match the ITS station location parameters stored in the memory with the effective position of the ITS station when injecting the message to prevent the receiving ITS station from not being notified of the dangerous situation when receiving the V2X message. The ITS station location information (including the latitude and / or longitude of the ITS station location) is typically provided by the GNSS system 70, which delivers the location information in the form of GPS data. However, such a GNSS system does provide location information according to a given period (e.g., every X milliseconds, X is greater than a threshold (e.g., equal to 100ms)).

[0142] In order to obtain such improvements in the accuracy of the injector 2024, the synchronization manager 2026 can also be configured to implement a synchronization mechanism that is capable of, in particular, continuously collecting the latest (that is, corresponding to the actual position of the ITS station) ITS station 2 position information when the injector 2024 calculates the injection time.

[0143] In such an embodiment, the synchronization manager 2026 can ensure that the GPS component (GPS daemon) responsible for retrieving the position information (GPS information) from the GNSS system is synchronized with the calculation of the injection time performed regularly. In particular, the synchronization can be performed by querying the GPS component or by starting the reporting cycle at the right moment (i.e., so as not to make the optimal injection time T inj delay), that is, so as not to delay the optimal injection time.

[0144] Figure 7 is a flow chart showing a method for determining a time for a V2X application of an ITS station to inject V2X message data according to an embodiment.

[0145] When the application module 201 receives the previous message M sent over the air from the communication module 202 i-1 When the associated notification is received, the time T when the application module 201 receives the notification is calculated in step 700. Notif The message M previously sent via the radio link with the ITS station i-1 The injection time T inj_(i-1) The difference between InjectionDelayMs:

[0146] InjectionDelayMs=t Notif –t inj_(i-1)

[0147] The injection is considered to have a minimum period CHECK_PERIOD_MS defined by a period equal to the reference time value (e.g. 100 ms for CAM messages). Therefore, the minimum period (or minimum period) CHECK_PERIOD_MS corresponds to the minimum period that must be observed between sending two V2X messages.

[0148] If the application module 201 injects message data at an injection time that is too close to the transmission time of the V2X message sent by the communication module 202 over the air, that is, the difference InjectionDelayMs is less than the reference time value (minimum period), the V2X communication module 202 must actually use previously received injection data and parameters, and these injection data and parameters are outdated because the communication module has no time to process the current injection. The injection time is then corrected to converge towards the reference time value.

[0149] Therefore, in step 702, if the time T of receiving the notification Notif and the message injection time T inj If the delay between InjectionDelayMs is greater than or equal to the reference time value (for example, 100ms), it is determined that the preliminary condition is met:

[0150] injectionDelayMs>=CHECK_PERIOD_MS (1)

[0151] If preliminary condition (1) holds, the minimum transmission time defined for the considered V2X message type has been exceeded.

[0152] Then in step 703, at a defined initial injection time t inj_init The V2X application is activated by a time TIME_REMOVING_STACK_MISSED_MS of a predefined value N (e.g., of the order of a few milliseconds) before. In such an embodiment, the injection has not been performed correctly, and in order to compensate for the injection failure, the application is woken up earlier, and the new injection of the V2X message data is therefore earlier than the initially defined injection time t inj_init Do it earlier.

[0153] Otherwise, if condition (1) does not hold, then in step 704 (minimum threshold condition), it is determined whether the difference InjectionDelayMs is strictly below the lower threshold DELTA_INJECTION_TIME_MIN_MS:

[0154] injectionDelayMs <DELTA_INJECTION_TIME_MIN_MS (2)

[0155] If the minimum threshold condition (2) holds, the previous injection corresponds to a delay that is satisfactory but remains below the optimal threshold. Then, in step 706, the injection time of the next message is determined so that the difference InjectionDelayMs between the injection time and the actual sending time of the message converges towards an optimal value, which may be closest to 0 and depends on the CPU (in particular its load, its computing power, etc.). In one embodiment, N can be chosen to be negative, by the V2X application responsible for sending the message of the considered type relative to the initial injection time t inj-init Step 706 is performed by activating the injection of message data earlier (the injection may be advanced by 2 ms, for example).

[0156] The function f() for activating the injection of a message at a given time may correspond to a wake-up function of the V2X application of the application module 201, which activates the injection of V2X message data each time the wake-up is triggered. Therefore, in step 706, the application may be woken up earlier.

[0157] In step 708, if the minimum threshold condition (2) is not met, it can be determined whether the difference InjectionDelayMs is strictly higher than the upper threshold DELTA_INJECTION_TIME_MAX_MS (upper threshold condition):

[0158] injectionDelayMs>DELTA_INJECTION_TIME_MAX_MS (3)

[0159] If the maximum threshold condition (3) holds, the previous injection generated an excessive delay between the transmission of the previous message and the injection time of the previous message. Then in step 710, the injection time of the next message is determined so that the difference InjectionDelayMs between the injection time and the actual transmission time of the message converges towards an optimal value again. The optimal value may be a value as close to 0 as possible. The optimal value may depend, in particular, on the CPU processor. For example, the optimal value may be equal to 20 ms, or preferably equal to 10 ms. In one embodiment, by selecting N to be positive (N may be, for example, equal to 2 ms), step 710 may be performed later by activating the injection of message data by the V2X application responsible for transmitting the V2X message of the type under consideration.

[0160] For example, in step 710 , the application of the application module 201 may be awakened later when the next message is injected.

[0161] Otherwise, if conditions (1) to (3) are not met, the delay represented by the difference injectionDelayMs is between the lower threshold (DELTA_INJECTION_TIME_MIN_MS) and the upper threshold DELTA_INJECTION_TIME_MAX_MS and is therefore satisfactory. Then in step 712, the injection time is not adjusted and the application can be woken up at the default defined time.

[0162] As a variation, conditions (2) and (3) of steps 704 and 708 may be replaced by a single condition by comparing the absolute value of the difference injectionDelayMs with a single threshold and by performing step 706 or 710 based on the comparison result.

[0163] Therefore, embodiments of the present invention make it possible to reduce the V2X message processing delay at the receiving ITS station side, thereby ensuring better responsiveness at the receiving ITS station and facilitating the implementation of applications or use cases where the delay must be below a certain threshold.

[0164] Figure 8 Two graphs representing the gains obtained according to embodiments of the present invention are shown.

[0165] The first graph 8A shows the injection time t of a message on the distribution interface 203 according to an embodiment of the present invention. inj and the actual transmission time t of the message via the radio link env .

[0166] The second graph 8B shows the injection time t of a message through the distribution interface 203 according to the prior art. inj and the actual transmission time t of the message via the radio link env .

[0167] As shown in the first graph 8A, according to an embodiment of the present invention, after the previous message is actually sent by the access layer 2018 of the V2X module 201 via the radio link, the injection time T of the current V2X message is calculated according to the parameters associated with the previous message. inj As shown in line 8A, the injection time of the first V2X message is calculated randomly, but the next injection time is optimized based on parameters associated with previously sent messages. The encoding of the message is performed by the V2X communication module 202 after the injection. Therefore, although the injection time of the first message may be far away from the actual transmission of the message via the radio link, the difference between the injection time and the transmission time of the subsequent message is minimized. Therefore, in the case of a significant time difference between the injection of a message and its transmission, the injection frequency can be variable.

[0168] In contrast, in the embodiment of the prior art, the injection time of the message after the injection of the first message is random, as shown in FIG8B. Therefore, the injection time t of the message inj The time t at which the message is sent via the radio link env The difference between can be significant and strongly affects the latency.

[0169] Fig. 9 Three curves representing the delays captured by an ITS station receiving a CAM type message from a transmitting ITS station are shown.

[0170] The first two curves 9A and 9B represent the delay of two ITS stations sending V2X messages according to two different radio access technologies (PC5 and 802.11p) according to the prior art. The last curve 9C represents the reduction of the delay obtained by calculating the injection time according to an embodiment of the present invention for an ITS station using two radio access technologies PC5 and 802.11p.

[0171] As shown in curve 9A, the delay of the prior art ITS station is greater than 500ms. Such a delay is due to the fact that the injection time of the message on the distribution interface is usually random.

[0172] The delay corresponds to the access time of each radio channel and the transmission time of the message.

[0173] Therefore, embodiments of the invention provide an ITS station whose delay is below the minimum period of a message defined by a reference time value (eg 100 ms for CAM type messages) regardless of the speed of the ITS station and the transmission period of CAM messages.

[0174] It will be appreciated by those skilled in the art that the system or subsystem according to an embodiment of the present invention can be implemented in various ways by hardware, software or a combination of hardware and software, especially in the form of program code that can be distributed in the form of various forms of program products. In particular, the program code can be distributed using a computer-readable medium, which can include a computer-readable storage medium and a communication medium. The methods described in this specification can be implemented in particular in the form of computer program instructions, which can be executed by one or more processors in a computer computing device. These computer program instructions can also be stored in a computer-readable medium.

[0175] Furthermore, the present invention is not limited to the embodiments described above by way of non-limiting examples. It encompasses all variant embodiments that a person skilled in the art would be able to envision. In particular, a person skilled in the art would understand that the present invention is not limited to a particular type of ITS station and is generally applicable to any device (e.g., any vehicle, such as a car, truck, motorcycle, bus, cyclist or pedestrian user device) that is capable of exchanging V2X messages with other devices according to the V2X protocol. Furthermore, the present invention is not limited to a particular physical access layer and is generally applicable to any radio access technology (e.g., 802.11p, C-V2X, 5G, etc.). Furthermore, the present invention is not limited to a particular type of V2X message.

Claims

1. A method implemented in a V2X device for exchanging V2X messages including data packets with one or more receiving V2X devices connected via a cellular communication network, the method comprising the following steps: running one or more V2X applications, wherein running the V2X applications includes generating V2X message data associated with the V2X applications, At the injection time, transmitting the V2X message data via the distribution interface, and transmitting, at a transmission time, the V2X message to the one or more receiving V2X devices via a radio link using a radio access technology, wherein the V2X message is in a format encoded based on message data retrieved via the distribution interface, It is characterized in that the injection time is determined based on an initial injection time defined by a predefined period, and the method comprises the following steps: calculating the injection time of the current message based on the initial injection time and time information related to at least one previous V2X message sent by the V2X device via the radio link, wherein the time information related to the previous V2X message includes the injection time of the previous V2X message on the distribution interface and the time when the V2X device sent the previous V2X message via the radio link.

2. The method according to claim 1, characterized in that The step of calculating the injection time comprises calculating a time difference between a time associated with a transmission time of the previous V2X message and an injection time of the previous V2X message, calculating the injection time of the V2X message by determining whether at least one condition associated with the time difference and at least one predetermined threshold is satisfied, The time related to the sending time of the previous V2X message is the sending time of the notification when the communication module sends the notification to the application module in response to sending the V2X message to the receiving V2X device.

3. The method according to claim 2, characterized in that The injection time of the current V2X message is an affine function of an initial injection time defined by the period, the affine function having a steering coefficient equal to 1 and a positive or negative ordinate at the origin, the ordinate being a function of the condition related to the time difference and at least one predetermined threshold.

4. The method according to claim 3, characterized in that The period is a multiple of a reference time value, and the ordinate at the origin is set to a negative value if the time difference is greater than or equal to the reference time value.

5. The method according to claim 3 or 4, characterized in that: If the time difference is strictly below a predefined upper threshold, the ordinate at the origin is set to a negative value.

6. The method according to claim 3, characterized in that The ordinate at the origin is set to a positive value if the time difference is strictly above a predefined upper threshold.

7. The method according to any one of claims 3, 4 and 6, characterized in that: The value of the ordinate at the origin depends on the processing load of the communication module of the V2X device.

8. The method according to any one of claims 3, 4 and 6, characterized in that: The ordinate at the origin depends on the load of the processor used to execute the method.

9. The method according to any one of claims 2 to 4 and 6, characterized in that: After the trigger injection, the information generated in the V2X message is collected synchronously or asynchronously.

10. A V2X device configured to exchange V2X messages including data packets with one or more receiving V2X devices connected to the V2X device via a cellular communication network, the V2X device comprising: an application module that runs one or more V2X applications, the application module being capable of generating V2X message data associated with the one or more V2X applications of the application module, a distribution interface on which the V2X message data generated by the V2X application of the application module at the injection time is placed, a V2X communication module configured to receive the V2X message data via the distribution interface and, at a transmission time, transmit the V2X message in a coded format to the one or more receiving V2X devices via a radio link using a radio access technology, It is characterized in that the injection time is determined based on an initial injection time defined by a time period, and the V2X device includes an injection time computer, which is configured to calculate the injection time of the V2X message based on the initial injection time and time information related to at least one previous V2X message sent by the V2X device via the radio link, and the time information related to the previous V2X message includes the injection time of the data of the previous V2X message on the distribution interface and the time when the V2X device sent the previous V2X message through the radio link.

11. The device according to claim 10, characterized in that The injection time computer is configured to calculate a time difference between a time associated with a transmission time of the previous V2X message and an injection time of the previous V2X message, and calculate the injection time of the current V2X message by determining whether at least one condition associated with the time difference and at least one predetermined threshold is satisfied, The V2X communication module is configured to send a notification to the application module in response to sending a V2X message to the receiving V2X device, and the time related to the sending time of the previous V2X message on which the time difference depends is the sending time of the notification.

12. The device according to claim 11, characterized in that The processing load of the V2X communication module depends on the position of the V2X device sent by a positioning system, and the device implements a synchronization mechanism to obtain position information from the positioning system at an optimal time defined relative to the initial injection time of new V2X messages.

13. A computer readable medium storing computer program instructions, which when executed by one or more processors implement the method of any one of claims 1 to 9.

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