YD/T 3709-2020Technical requirements of message layer of LTE-based vehicular communication (English PDF)

3.1 Terms and definitions

The following terms and definitions apply to this document.

3.1.1 Vehicle to everything, V2X

The communication, BETWEEN the on-board unit AND other devices, which includes, but is not limited to, the communication between the on-board units, the communication between the on-board unit and the roadside unit, the communication between the on-board unit and the pedestrian equipment, the communication between the on-board unit and the network.

3.2 Abbreviations

The following abbreviations apply to this document.

ASN.1.Abstract Syntax Notation One

BSM. Basic Safety Message

DE. Data Element

DF. Data Frame

DSM. Dedicated Short Message

4.1 System introduction

The LTE-based vehicular communication technology realizes the information interaction, BETWEEN the different subsystems of the intelligent transportation system, thereby realizing different applications such as road safety, traffic efficiency, information services.

4.2 Architecture of message layer

The framework of the message layer of the LTE-based vehicular communication technology is as shown in Figure 3.The message layer is located inside the application layer, which connects with the data sublayer of the network layer downwards, AND supports specific user applications upwards.

The message layer can support various data transmissions, which are defined by the network layer of the LTE-based vehicular communication technology.

5.1 Basic introduction and requirements of the message layer

The data set at message layer is defined by the ASN.1 standard. It is formulated according to the layered nesting logic of "message frame - message body - data frame - data element".

5.2 Definition of data set of message layer

The data set of message layer, which is defined in this standard, mainly consists of 1 message frame format, 5 most basic message bodies, corresponding data frames and data elements, as shown in Figure 4.

5.2.1 Message frame

The message frame is a unified packaging format of a single application layer message. It is the only operation object for data encoding and decoding. The message frame is composed of different types of message bodies; it supports expansion.

5.2.3 Data Frame

The data frame is composed of other data units or data types. It has a specific practical meaning AND is a component of the message body.

5.2.3.1 DF_AccelerationSet4Way

[Definition]

It defines the four-axis acceleration of the vehicle.

5.2.3.36 DF_Position_-LL-28B

[Definition]

The 28-bit relative latitude and longitude position, which indicates the latitude and longitude deviation of the current position point, with respect to the reference position point. It is composed of two 14-bit longitude and latitude deviation values.

5.2.3.37 DF_Position-LL-32B

[Definition]

The 32-bit relative latitude and longitude position, which indicates the latitude and longitude deviation of the current position point, with respect to the reference position point. It consists of two 16-bit longitude and latitude deviation values.

5.2.3.38 DF_Position-LL-36B

[Definition]

The 36-bit relative longitude and latitude position, which indicates the latitude and longitude deviation of the current position point, with respect to the reference position point. It is composed of two 18-bit longitude and latitude deviation values.

[ASN.1 code]

5.2.4.70 DE_SpeedLimitType

[Definition]

Define the speed limit type; indicate the reference type corresponding to the given speed limit size.

[ASN.1 code]

5.2.4.71 DE_StabilityControlStatus

[Definition]

Define the state of the vehicle's dynamic stability control system.

Unavailable. The system is not equipped or unavailable.

Off. The system is off.

On. The system is on, but not triggered.

Engaged. The system is triggered and is active.

[ASN.1 code]

5.2.4.72 DE_SteeringWheelAngle

[Definition]

Define the steering wheel angle of the vehicle. To the right is positive; to the left is negative.

The resolution is 1.5��. The value 127 is invalid value.

[ASN.1 code]

5.2.4.73 DE_SteeringWheelAngleConfidence

[Definition]

Describe the accuracy of the vehicle steering wheel angle, at the 95% confidence level, in numerical value.

[ASN.1 code]

5.2.4.74 DE_TimeConfidence

[Definition]

Describe the time accuracy, at the 95% confidence level, in numerical value.

The accuracy theoretically only considers the error of the current timing system itself. However, when the system can automatically detect and correct errors, the corresponding accuracy values shall also be improved.

[ASN.1 code]

5.2.4.75 DE_TimeMark

[Definition]

Define the time in one hour, in units of 0.1 seconds. It can represent the time in the current hour, OR it can represent a time period that does not exceed 1 hour in length.

The resolution is 0.1 second. The valid range is 0 ~ 35999.The value 36000 indicates the length of time, which is greater than 1 hour. The value 36001 indicates an invalid value.

[ASN.1 code]

5.2.4.78 DE_TransmissionState

[Definition]

Vehicle gear status.

5.2.4.79 DE_VehicleEventFlags

[Definition]

Define the special status of a series of vehicles. If a bit of the data is set to 1, it means that the vehicle is in the state corresponding to that bit. When at least one corresponding state is activated or restored from the activated state, the flag value shall be set and interacted.

5.2.4.87 DE_VertOffset-B10

[Definition]

A 10-bit data, which defines the deviation of the vertical direction (Z axis), with respect to the reference position point. The direction along the Z axis is positive.

The data resolution is 10 cm.

The -512 value indicates an unknown size.

[ASN.1 code]

5.2.4.88 DE_VertOffset-B11

[Definition]

An 11-bit data, which defines the deviation of the vertical direction (Z axis), with respect to the reference position point. The direction along the Z axis is positive.

The data resolution is 10 cm.

The -1024 value indicates an unknown size.

[ASN.1 code]

5.2.4.89 DE_VertOffset-B12

[Definition]

A 12-bit data, which defines the deviation of the vertical direction (Z axis), with respect to the reference position point. The direction along the Z axis is positive.

The data resolution is 10 cm.

The -2048 value represents an unknown size.

[ASN.1 code]

5.2.4.90 DE_YawRate

[Definition]

The yaw rate of the vehicle. Refers to the deflection of the car, around the vertical axis. The magnitude of the deflection represents the stability of the car.

If the deflection angular velocity reaches a threshold, it indicates that dangerous conditions such as lateral slip or drift have occurred in the car.

Clockwise rotation is positive; counterclockwise is negative.

Data resolution is 0.01��/s.

[ASN.1 code]

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