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This standard is one of the technical standards of LTE-based vehicular communication, of which, the composition and titles are as follows:
a) YD/T 3400-2018 General technical requirements of LTE-based vehicular communication;
b) YD/T 3340-2018 Technical requirements for air interface of LTE-based vehicular communication;
c) YD/T 3707-2020 Technical requirements of network layer of LTE-based vehicular communication;
d) YD/T 3709-2020 Technical requirements of message layer of LTE-based vehicular communication.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This standard was proposed by and is under the jurisdiction of China Communications Standards Association.
Technical requirements of message layer of LTE-based vehicular communication
1 Scope
This standard specifies the technical requirements of message layer of LTE-based vehicular communication, including the architecture of message layer data set, specific data definitions and encoding modes.
This standard is applicable to message layer of LTE-based vehicular communication.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 2312-1980 Code of Chinese graphic character set for information interchange - Primary set
GB 5768.2-2009 Road traffic signs and markings - Part 2: Road traffic signs
GB 14886 Specifications for road traffic signal setting and installation
GB/T 27967-2011 Format of weather forecast on highway traffic
GB/T 29100-2012 Road traffic information service - Traffic event classification and coding
YD/T 3340-2018 Technical requirements for air interface of LTE-based vehicular communication.
YD/T 3400-2018 General technical requirements of LTE-based vehicular communication
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purpose of this document, the following term and definition apply.
3.1.1
vehicle to everything, V2X
communication between on-board unit and other devices, including but not limited to communication between on-board units, between on-board unit and road side unit, between on-board unit and pedestrian equipment, and between on-board unit and network
3.2 Abbreviations
For the purposes of this document, the following abbreviations apply.
ASN.1 Abstract Syntax Notation One
BSM Basic Safety Message
DE Data Element
DF Data Frame
DSM Dedicated Short Message
DSMP Dedicated Short MessageProtocol
ID IDentification
ITS Intelligent Transportation Systems
LTE Long Term Evolution
LTE-V2X LTE Vehicle to Everything
RSI Road Side Information
RSM Road Side Message
RSU Road Side Unit
SPAT Signal Phase and Timing Message
UPER Unaligned Packet Encoding Rules
UTC Coordinated Universal Time
4 Message layer of LTE-based vehicular communication
4.1 System introduction
The LTE Vehicle to Everything (LTE-V2X) realizes the information interaction among different subsystems of intelligent transportation system, thus realizing different applications such as road safety, traffic efficiency and information service. In terms of communication mode, the message exchange corresponding to this standard adopts broadcast communication mode, that is, the message is sent through broadcast mechanism, without specific receiving object, and all traffic participants within the communication reach may receive the corresponding message. Figures 1 and 2 show the relationship between communication nodes involved in this standard.
Figure 1 Communication between vehicles
Figure 2 Communication between vehicle and road side facility
4.2 Message layer architecture
See Figure 3 for the message layer of LTE Vehicle to Everything; The message layer is located inside the application layer, connecting the data sub-layer of the network layer downward and supporting specific user applications upward. The message layer may support all kinds of data transmission defined by the network layer of the LTE Vehicle to Everything.
Note:
1 The message layer interacts with the data sublayer of the network layer by operating primitives;
2 The technical requirements of the message layer defined in this standard mainly include the data set in the layer, and its concrete implementation and API docking technology with the upper user application are not the content of this standard.
Figure 3 Framework of message layer of LTE Vehicle to Everything
5 Technical requirements of message layer
5.1 Basic introduction and requirements of message layer
The message layer data set shall be defined by the ASN.1 standard, and is formulated according to the multilevel nested logic of "message frame-message body-data frame-data element” layer by layer.
The encoding and decoding mode of data set interaction follows the unaligned packet encoding rules (UPER).
5.2 Message layer data set definition
The message layer data set defined in this standard mainly consists of one message frame format, five basic message bodies and corresponding data frames and data elements, as shown in Figure 4.
Figure 4 Data set composition of message layer of LTE Vehicle to Everything
5.2.1 Message frame
Message frame is a unified packaging format of single application layer message, and is the only operation object of data encoding and decoding. Message frames are composed of different types of message bodies and support extension.
[ASN.1 code]
5.2.2 Message body (Message)
5.2.2.1 Msg_BSM
[Definition]
Vehicle basic safety message is the most widely used application layer message, which is used to exchange safety status data between vehicles. The vehicle informs the surrounding vehicles of its real-time status through the broadcast of this message, so as to support a series of applications such as collaborative security.
[ASN.1 code]
5.2.2.2 Msg_MAP
[Definition]
For map messages, the map information of local areas is transmitted to vehicles through road side unit broadcast, including intersection information, link information, lane information, connection relationship between roads and so on.
A single map message may contain map data of multiple intersections or regions. The signal light information at the intersection is defined in detail in SPAT message.
The major structure of MAP message is given in Figure 5, which is a multilevel nested form. Among them, the solid box is mandatory, and the dotted box is optional.
Figure 5 Major structure of MAP message
[ASN.1 code]
5.2.2.3 Msg_RSI
[Definition]
The message is applicable to traffic incident information issued by the road side unit to the surrounding on-board units as well as traffic sign information.
Among them, traffic incident information supports GB/T 29100-2012; and traffic sign information supports GB 5768.2-2009. The message frame may package one or more traffic incident information or traffic sign information, and at the same time contains the road side unit number and the reference position coordinates for sending the message.
On-board units judge the effective area of incident or sign based on their own positioning and running direction, and such effectiveness information, associated area/link range as are provided by the message itself. In the message body, the field of refPos is used to provide the reference 3D position coordinates within the action range of the message, and all the position offsets in the message are calculated based on the reference coordinates. The actual position coordinates are equal to the offset plus the reference coordinates.
[ASN.1 code]
5.2.2.4 Msg_RSM
[Definition]
Road side safety message: the real-time status information of its surrounding traffic participants obtained by the road side unit through the corresponding detection means owned by the road side itself (here, the traffic participants include the road side unit itself, surrounding vehicles, non-motor vehicles, pedestrians, etc.), which is arranged into the format defined by the message body as the basic safety status information of these traffic participants (similar to Msg_BSM), and broadcasted to the surrounding vehicles to support the related applications of these vehicles.
The existence of Msg_RSM makes vehicles free from the dependence only on Msg_BSM message in the perception of surrounding conditions. Road side units are based on road side sensors, which help vehicles detect their surroundings and transmit real-time information to vehicles through Msg_RSM messages.
In the Msg_RSM message, the field of refPos is used to provide the reference 3D position coordinates within the action range of the message, and all the position offsets in the message are calculated based on the reference coordinates. The actual position coordinates are equal to the offset plus the reference coordinates.
[ASN.1 code]
5.2.2.5 Msg_SPAT
[Definition]
The signal light message contains the current status information of one or more intersection signal lights, which, combining with MAP message, provides real-time front signal light phase information for vehicles.
Figure 6 shows the major structure of SPAT message, in which the solid box is mandatory and the dotted box is optional.
Figure 6 Major structure of SPAT message
[ASN.1 code]
5.2.3 Data frame
Data frame is composed of other data units or data types, which has specific practical significance and is an integral part of message body.
5.2.3.1 DF_AccelerationSet4Way
[Definition]
It defines the 4-axis acceleration of vehicle.
Long: longitudinal acceleration.The forward acceleration is positive, while the reverse one is negative.
Lat: lateral acceleration. The rightward acceleration is positive, while the reverse one is negative.
Vert: vertical acceleration. The downward acceleration along gravity direction is positive, while the reverse one is negative.
Yaw: Yaw rate. The clockwise rotation is positive, while the reverse one is negative.
[ASN.1 code]
5.2.3.2 DF_BrakeSystemStatus
[Definition]
It defines the brake system status of the vehicle, including the following 7 different types of status:
brakePadel: the condition of brake pedal being pressed;
wheelBrakes: the braking condition of vehicle wheels;
traction: the action condition of traction control system;
abs: the action condition of anti-lock braking system;
scs: the action condition of vehicle stability control system;
brakeBoost: the action condition of brake boost system;
auxBrake: the condition of auxiliary brake system (generally refers to handbrake).
[ASN.1 code]
5.2.3.3 DF_ConnectingLane
[Definition]
Downstream lane used to locate the upstream lane steering connection.
It contains the downstream lane ID and the allowed driving behavior of the steering, and the action range of the downstream lane ID is the link where the lane is located.
[ASN.1 code]
5.2.3.4 DF_Connection
[Definition]
It defines the connection between the current lane and the lane in the downstream link.
It includes the exit node ID of downstream link, the basic information of lane to be connected in the downstream link, and the corresponding signal light phase No. The phase No. defined in lane connection is a supplement to the phase No. that defines steering in DF_Movement. When some particular signal light phases (instead of the default phase defined in the DF_Movement) are required to be referenced for the steering in certain lanes, they shall be defined in this data frame.
[ASN.1 code]
5.2.3.5 DF_ConnectsToList
[Definition]
It defines the list of connections (for steering purposes) between each lane in the link at the downstream intersection and the lane in the downstream link.
[ASN.1 code]
5.2.3.6 DF_DDateTime
[Definition]
It defines a complete date and time data unit.
[ASN.1 code]
5.2.3.7 DF_Description
[Definition]
It defines the text description information and provides two encoding forms.
It provides the text form of ASCII character, and supports the length from 1 byte to 512 bytes.
It supports the encoding of Chinese characters that complies with the encoding rules of GB 2312-1980, with a Chinese character encoded by 2 bytes of information, and it supports a length of 1 to 256 Chinese characters.
[ASN.1 code]
5.2.3.8 DF_FullPositionVector
[Definition]
It defines the complete reference path point information and is used for the data unit of vehicle path history, as the reference point data of a string of continuous path.
[ASN.1 code]
5.2.3.9 DF_IntersectionState
[Definition]
It defines the attribute and current state of one intersection signal light.
It includes intersection ID, signal light working state, time stamp and the phase list of signal light.
[ASN.1 code]
5.2.3.10 DF_IntersectionStateList
[Definition]
It defines the collection of intersection signal light.
[ASN.1 code]
5.2.3.11 DF_Lane
[Definition]
It defines the lane.
It includes the lane ID, lane sharing attribute, allowable steering behavior at lane exit, list of connections between the lane and the lane in the downstream link as well as list of lane midpoint.
[ASN.1 code]
5.2.3.12 DF_LaneAttributes
[Definition]
It defines lane attributes.
It includes lane sharing condition and lane type characteristic.
[ASN.1 code]
5.2.3.13 DF_LaneList
[Definition]
It defines the list of lanes in a link.
[ASN.1 code]
5.2.3.14 DF_LaneTypeAttributes
[Definition]
It defines the collection of attributes of different types of lanes.
[ASN.1 code]
5.2.3.15 DF_Link
[Definition]
Definition of link: The road from one node to the other adjacent node is called a directed link.
Its attributes include name, upstream node ID, speed limit collection and lane width, as well as lane collection and the collection of traffic signs contained in the link.
[ASN.1 code]
5.2.3.16 DF_LinkList
[Definition]
It defines the list of links.
[ASN.1 code]
5.2.3.17 DF_MotionConfidenceSet
[Definition]
It describes the confidence of vehicle operating state.
It includes speed confidence, heading confidence and steering wheel angle confidence.
[ASN.1 code]
5.2.3.18 DF_Movement
[Definition]
It defines the connection between the road and the downstream link, and the phase ID of the corresponding signal light at the local intersection.
The phase ID here is in fact the only connection between the MAP message and the SPAT message. After the steering behavior of the vehicle is determined, this phase ID data can be used to check the real-time state of the corresponding phase in SPAT, so as to obtain the signal light data assistance during driving.
[ASN.1 code]
5.2.3.19 DF_MovementList
[Definition]
It describes the list of connections between a link and the downstream links.
[ASN.1 code]
5.2.3.20 DF_Node
[Definition]
Map node: node is the most basic component of a map, which may be an intersection or the end point of a link. On the map, a directed link is determined by two nodes in sequence.
Node attributes include name, ID, location, and the collection of upstream links connected by nodes.
The node is used as the downstream end point for every link included in it. The link starting from this node belongs to the data of the downstream node of the link.
In the data frame of Node, the field of refPos is used to provide the reference 3D position coordinates within the action range of the current data frame, and all the position offsets in the frame are calculated based on the reference coordinates. The actual position coordinates are equal to the offset plus the reference coordinates.
[ASN.1 code]
5.2.3.21 DF_NodeList
[Definition]
It defines the list of map nodes.
[ASN.1 code]
5.2.3.22 DF_NodeReferenceID
[Definition]
It defines the node ID.
The node ID consists of a globally unique region ID and a locally unique node ID.
Foreword i
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
4 Message layer of LTE-based vehicular communication
5 Technical requirements of message layer
Annex A (Informative) DE_EventType type and value
