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GB/T 31024 consists of the following four parts under the general title Cooperative intelligent transportation systems—Dedicated short range communications:
——Part 1: General technical requirement;
——Part 2: Specification of medium access control layer and physical layer;
——Part 3: Network layer and application layer specification;
——Part 4: Equipment application specification.
This part is Part 3 of GB/T 31024.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part was proposed by and is under the jurisdiction of the National Technical Committee on Intelligent Transportation Systems of Standardization Administration of China (SAC/TC 268).
Cooperative intelligent transportation systems—
Dedicated short range communications—
Part 3: Network layer and application layer specification
1 Scope
This part of GB/T 31024 specifies the technical requirements of network layer and application layer for dedicated short range communication of cooperative intelligent transportation system.
This part is applicable to the design and development of network layer and application layer for dedicated short range communication of cooperative intelligent transportation system.
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 5768.2 Road traffic signs and markings—Part 2: Road traffic signs
GB 14886 Specifications for road traffic signal setting and installation
GB/T 16262.1 Information technology—Abstract Syntax Notation One (ASN.1)—Part 1: Specification of basic notation
GB/T 16262.2 Information technology—Abstract Syntax Notation One (ASN.1)—Part 2: Information object specification
GB/T 16262.3 Information technology—Abstract Syntax Notation One (ASN.1)—Part 3: Constraint specification
GB/T 16262.4 Information technology—Abstract Syntax Notation One (ASN.1)—Part 4: Parameterization of ASN.1 specifications
GB/T 16263.2 Information technology—ASN.1 encoding rules—Part 2: Specification of Packed Encoding Rules (PER)
GB 25280 Road traffic signal controller
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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3.1
dedicated short range communication
wireless communication method for short range communication among traffic elements such as vehicles, infrastructures and pedestrians
3.2
dedicated short range communication management entity
a universal set of dedicated short range communication management services that provides management interfaces for all data layer entities
3.3
management information base
an entity used to store application configuration and status information
4 Abbreviations
For the purposes of this document, the following abbreviations apply.
AID Application ID
DME DSRC Management Entity
DSA DSRC Service Advertisement
DSM DSRC Short Message
DSMP DSRC Short Message Protocol
DSRC Dedicated Short Range Communication
GNSS Global Navigation Satellite System
IP Internet Protocol
LLC Logical Link Control
LTE Long Term Evolution
LTE-V2X LTE Vehicle to Everything
MAC Media Access Control
MIB Management Information Base
SAP Service Access Point
TCP Transmission Control Protocol
UDP User Data Protocol
UPER Unaligned Packet Encoding Rules
5 Technical requirements of network layer
5.1 Network layer framework
The DSRC network layer framework of cooperative intelligent transportation system is shown in Figure 1.
Note 1: The network layer consists of data sublayer and management sublayer.
Note 2: The data sublayer mainly comprises adaptation layer, IP and TCP/UDP, as well as DSMP of cooperative intelligent transportation system. The IP protocol and the DSMP protocol are optional. The data sublayer transmits both data streams between application layers and data streams between different device management layer entities or between management layer entities and applications.
Note 3: The management sublayer mainly performs functions such as system configuration and maintenance. It transmits management data streams between different devices by using the data sublayer service. The DME of cooperative intelligent transportation system is a universal set of management services, which provides management interfaces for all data sublayer entities, including DSMP protocol.
Figure 1 DSRC network layer framework of cooperative intelligent transportation system
5.2 Technical requirements of data sublayer
5.2.1 General
The data sublayer in the DSRC network layer of the cooperative intelligent transportation system comprises TCP/UDP, IP, DSMP and adaptation layer, wherein the IP protocol and the TCP/UDP protocol are not within the definition of this part.
The IP data stream and the DSMP data stream are defined in the DSRC network layer of the cooperative intelligent transportation system. The IP data stream is shown in Figure 2, and the DSMP data stream is shown in Figure 3.
Figure 2 IP data stream
Figure 3 DSMP data stream
5.2.2 Adaptation layer
The adaptation layer provides the transmission adaptation function between the underlying access technology and the upper layer protocol stack. The adaptation layer receives the DSMP data packet, the IP data packet, or the DME data packet sent by the upper layer, distinguishes the underlying access technology used by the data packet to be sent, and delivers the corresponding data packet to the bottom layer in line with the corresponding access technology for transmission; or receives the data packet from the bottom layer, distinguishes the upper layer protocol type to which the corresponding data packet belongs, and delivers the data packet to the specified upper layer protocol stack.
The DSRC network layer services of the cooperative intelligent transportation system shall support the unacknowledged connectionless LLC operation, subnetwork access protocol and IP data transmission protocol.
The adaptation layer frame format is shown in Figure 4. The adaptation layer frame contains the header and the payload. The adaptation layer payload is used to encapsulate the upper layer data packets. The bit sequence in the adaptation layer frame format is high bit first.
Note: The Protocol Type is used to indicate the type of protocol used by the upper layer data packet. See Annex A for specific values.
Figure 4 Adaptation layer frame format
5.2.3 DSMP
5.2.3.1 DSM data frame format
The layer-by-layer packaging process of DSM is shown in Figure 5.
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Figure 5 Layer-by-layer packaging process of DSM
The DSM data frame format is shown in Table 1. The bit sequence in the DSM data frame format is high bit first.
Table 1 DSM data frame format
Field 1 Field 2 Field 3 Field 4 Field 5 Field 6 Field 7
3 bits 1 bit 4 bits Var Var 2octets Var
DSMP Version DSMP Option Indicator Reserved Extension AID Length Data
DSMP Version DSMP Option Indicator Reserved Extension Application ID Data Length Data
Note 1: DSMP Version distinguishes different DSMP version numbers (0 to 7). The DSMP Version in this part is 0.
Note 2: DSMP Option Indicator indicates that the following extension appears when the value is 1 and that the following extension does not appear when the value is 0.
Note 3: Reserved indicates the reserved bits, which are all zero for this version.
Note 4: Extension, reserved for other information, including other information identifier, other information length and other information content, wherein other information identifier refers to Element ID, as detailed in 5.2.3.3. Information such as extension length and content will be associated with the standard version.
Note 5: Application ID (AID) refers to the AID of application service provider, which is used to distinguish different applications.
Note 6: Length indicates the byte length of the application layer data entity.
Note 7: Data refers to the data entity hosted in application layer or management sublayer.
5.2.3.2 AID
The DSMP protocol layer is responsible for data interaction with different applications. The DSMP entity transmits the short message of interest to the application layer and receives the data packet from the application layer. In DSM, AID is used to distinguish different application layer services.
In the service interaction communication process, the communication process between the application service provider (Provider) and the User is shown in Figure 6.
Figure 6 Communication process between Provider and User
AID is represented by variable-length byte. At present, it supports representation of up to 2 bytes, and at least 1 byte is used. See Table 2 for the representation method and Annex B for allocation suggestions.
Table 2 AID representation method
Highest bit of byte 0 (x indicates no concern) b7 b6 AID length (byte(s)) AID range (hex)
0 x 1 00~7F
1 0 2 80-00~BF-FF
1 1 Length ≥3 reserved Reserved
Note: Each Provider can apply for an AID based on specific service requirements.
5.2.3.3 Element ID
The Element ID is used to indicate the different roles of the data information and the identifier of other information in the frame structure. The specifications of Element ID are shown in Table 3.
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Table 3 Specifications of Element ID
Element ID No. Application field Number of bytes Description
— 0 Reserved — —
— 1 Reserved — —
— 2 Reserved — —
— 3 Reserved — —
Transmit power used 4 Service advertisement header 1 byte A signed number, indicating the transmit power of DSM data frame, in dBm
2D Location 5 Service advertisement header 8 bytes Location of 2D; 4 bytes for latitude and the other 4 bytes for longitude, to the nearest of 0.1 microdegrees
3D Location And Confidence 6 Service advertisement header 15 bytes Location of 3D; 4 bytes for latitude and 4 bytes for longitude, to the nearest of 0.1 microdegrees; 2 bytes for altitude, to the nearest of 0.1 m; 4 bit for position confidence; 4 bit for altitude confidence; 4 bytes for position accuracy
Advertiser identifier 7 Service advertisement header 1 to 32 bytes A string, identification number of the Provider, ID string of the Provider
Provider Service Context 8 Service advertisement application information 1 to 31 bytes A string, providing additional information associated with the upper layer service
IPv6 address 9 Service advertisement application information 16 bytes IPv6 address
Service port 10 Service advertisement application information 2 bytes Port number of the upper layer entity of the Provider host, available for services using IP address
Provider MAC address 11 Service advertisement application information 6 bytes Providing the MAC address of the Provider host
Channel Number 12 DSMP header 1 byte Indicating the channel number
Data Rate 13 DSMP header 1 byte Indicating the data transmission rate, in 500 kbit/s
Broadcast Frequency 14 Service advertisement header 1 byte Indicating the broadcast frequency of the DSA service advertisement, that is, the number of times the service advertisement is repeatedly sent within 1 s. This parameter can be used to evaluate the link quality.
Area String 15 Service advertisement header 3 bytes Indicating the area to which the device belongs
DSA RCPI Threshold 16 Service advertisement application information 1 byte Indicating the minimum channel power, in dBm, used by the receiving end of the DSA service advertisement message to identify whether the service is available; if below this threshold, the service can be ignored.
DSA Count Threshold 17 Service advertisement application information 1 byte Indicating the minimum number of received advertisement messages used by the receiving end of the DSA service advertisement message to identify whether the service is available; if the number of received messages at a DSA Count Threshold Interval is less than this value, the receiving end may ignore this service.
DSA Count Threshold Interval 18 Service advertisement application information 1 byte Indicating the corresponding time interval for counting the number of DSA received, in 100 ms, valid between 1 and 255. If not specified, it is 1 s by default.
— 19~255 Reserved —
5.3 Technical requirements of management sublayer
5.3.1 Application registration
Before using management sublayer services, the application needs to be registered with the DME first. An application running on a DSRC device needs to be registered as a user application, so that the DME can send the received DSM to the corresponding application.
5.3.2 Service management
Service management belongs to the internal operation of the device, and the corresponding functions are optional. When an application issues a service usage request to the DME, the DME will initialize the requested service. An example of the service management process is shown in Figure 7.
Figure 7 Example of service request information flow
The main forms of service requests include Provider Service Request, User Service Request, Short Message Service Request, and Timing Notification Service Request. These four forms of service request are described as follows:
a) For DME, the Provider Service Request indicates that the upper layer wants it to send the DSA. After accepting the Provider Service Request, the DME will generate a corresponding provider service request entry in the MIB and consider the service request when deciding the channel access allocation.
b) For DME, the User Service Request indicates that the upper layer entity is interested in the available services that meet the specified standards. The request indicates the action to be taken when the DME identifies such available services. After accepting the User Service Request, the DME will generate a corresponding user service request entry in the MIB and consider the service request when deciding the channel access allocation.
c) For DME, the Short Message Service Request indicates that the upper layer entity wants to receive a DSM with the specified AID. After accepting the Short Message Service Request, the DME will generate a corresponding short message service request entry in the MIB and deliver any received DSM with the matching AID to the requested upper layer entity.
d) For DME, the Timing Notification Service Request indicates that another management entity wants it to send a timing notification frame on its behalf. After accepting the Timing Notification Service Request, the DME will consider the service request when deciding the channel access allocation, and generate a timing notification to the access layer management entity.
When the DME receives a service request of a different action type, it will take different countermeasures, as follows:
a) When receiving a service request whose action type is "Add", corresponding service information should be added in the MIB;
b) When receiving a service request whose action type is "Update", corresponding service information should be updated in the MIB;
c) When receiving a service request whose action type is "Delete", corresponding service information should be deleted in the MIB.
5.3.3 MIB maintenance
The MIB operation process is shown in Figure 8. The MIB is responsible for management and maintenance of the application configuration and status information of the DSRC modules of the cooperative intelligent transportation system. The DME sets and queries the MIB information through specified signaling. After receiving a service request message, the DME establishes a MIB information table corresponding to the service in the MIB. The information table item includes application configuration and status information, and the transmission environment configuration of the service data is based on the status information.
Figure 8 MIB operation process
See Annex C for a list of MIB messages.
5.3.4 Service advertisement
The DSRC Service Advertisement (DSA) of the cooperative intelligent transportation system shall be encapsulated in the data part of the DSM, and the AID in the DSM shall be set to the value of the AID corresponding to the DSA. The DSA information flow is shown in Figure 9.
Note: The interaction between the application layer and the DME has no chronological requirements at the sending and receiving ends.
Figure 9 DSA information flow
The DSA message frame format is shown in Table 4, and the bit sequence in the DSA frame format is high bit first.
Table 4 DSA message frame format
Variable Variable
Header Application Info
Frame header Application information
The DSA Header extension format is shown in Table 5.
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Table 5 DSA Header extension format
Field 1 Field 2 Field 3 Field 4 Field 5 Field 6
4 bits 1 bit 3 bits 4 bits 4 bits Var
DSA Version DSA Header Option Indicator Reserved DSA Identifier Content Count Header Extension
DSA Version DSA Header Option Indicator Reserved DSA ID Content Count Header Extension
Note 1: DSA Version distinguishes different DSA version numbers (0 to 15). The DSA Version in this part is 0.
Note 2: DSA Header Option Indicator indicates that the Header Extension appears when the value is 1 and that the Header Extension does not appear when the value is 0.
Note 3: Reserved, for extension.
Note 4: DSA ID is used to identify the uniqueness of the DSA.
Note 5: Content Count is used to identify whether it is a repetition of the previous DSA when the DSA ID is the same.
Note 6: Header Extension, reserved for other information.
The Application Info extension is shown in Table 6. It can be repeated multiple times except for the first field.
Table 6 Application Info field format
1 byte Variable Variable
Application Info Count AID Application Extension
Application Info Count Application ID Application Extension
Note 1: The Application Info Count indicates the total number of Application Info.
Note 2: The AID format is shown in 5.2.3.2.
Note 3: The Application Extension indicates the application-related information.
5.4 Access point and service primitive
5.4.1 Service Access Point (SAP)
The SAP of the DSRC network layer is shown in Figure 10.
Figure 10 SAP of DSRC network layer of the cooperative intelligent transportation system
5.4.2 Access layer service primitive
5.4.2.1 ACCESS-LAYER.request
ACCESS-LAYER.request is used to send the access data requested by the upper layer.
Service primitive parameters:
The ACCESS-LAYER.request service primitive parameters are shown in Table 7.
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Table 7 ACCESS-LAYER.request service primitive parameters
Name Type Effective range Description
Source_address MAC address — Source MAC address
Destination_address MAC address — Destination MAC address
Data Byte string N/A Data sent by the upper layer to the access layer
Priority Integer 1~8 8 priority descriptions
PDCP SDU type Enumeration {IP, Non-IP} When the upper layer data packet is an IP data packet, the value is set to IP; when the upper layer data packet is a DSMP data packet or a DME data packet, the value is set to Non-IP.
Extension Bit string Not defined For extension
Note 1: See the underlying standard for the MAC address.
Note 2: The supporting device randomly generates the source MAC address and the AID-based destination MAC address. The mapping relation between the AID and the destination MAC address is given in the underlying standard.
5.4.2.2 ACCESS-LAYER.indication
ACCESS-LAYER.indication is used to indicate that the upper layer has received the access data.
Service primitive parameters:
The ACCESS-LAYER.indication service primitive parameters are shown in Table 8.
Table 8 ACCESS-LAYER.indication service primitive parameters
Name Type Effective range Description
Source_address MAC address — Source MAC address
Destination_address MAC address — Destination MAC address
Priority Integer 1~8 8 priority descriptions
Data Byte string N/A Data sent by the access layer to the upper layer
Note: See the underlying standard for the MAC address.
5.4.3 Adaptation layer service primitive
5.4.3.1 ADAPTATION-LAYER.request
ADAPTATION-LAYER.request is used to send the adaptation layer data requested by the upper layer.
Service primitive parameters:
The ADAPTATION-LAYER.request service primitive parameters are shown in Table 9.
Table 9 ADAPTATION-LAYER.request service primitive parameters
Name Type Effective range Description
ApplicationIdentifier String — Provider AID
ProtocolType Integer See Annex A See Annex A
Source_address Adaptation layer address Any effective unicast adaptation layer address From its own device, see Annex D
Destination_address Adaptation layer address Any effective adaptation layer address From DSM.request, see Annex D
Data String All DSM data
Priority Integer 1~8 From DSM.request
Extension Bit string Not defined For extension
5.4.3.2 ADAPTATION-LAYER.indication
ADAPTATION-LAYER.indication is used to indicate that the upper layer has received the adaptation layer data.
Service primitive parameters:
The ADAPTATION-LAYER.indication service primitive parameters are shown in Table 10.
Table 10 ADAPTATION-LAYER.indication service primitive parameters
Name Type Effective range Description
ProtocolType Integer See Annex A See Annex A
Source_address Adaptation layer address Any effective unicast adaptation layer address See Annex D
Destination_address Adaptation layer address Any effective adaptation layer address See Annex D
Data String All —
Priority Integer 1~8 From ACCESS-LAYER.indication
5.4.4 DSM service primitive
5.4.4.1 DSM.request
DSM.request is used by the upper layer to request to send the DSM data.
Service primitive parameters:
The DSM.request service primitive parameters are shown in Table 11.
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Table 11 DSM.request service primitive parameters
Name Type Effective range Description
ApplicationIdentifier String — Provider AID
ProtocolType Integer See Annex A See Annex A
Priority Integer 1~8 Inserted into ADAPTATION-LAYER.request
Length Integer 1~65 535 Byte length of the DSM data entity
Data String Not defined DSM data entity
Peer MAC address MAC address Any effective unicast, multicast or broadcast MAC address Optional, if any, inserted into ADAPTATION-LAYER.request
DsmpHeaderExtensions Bit string Not defined Specified frame header extension
5.4.4.2 DSM.indication
DSM.indication is used to indicate that the upper layer or the entity in the DSM service request table in the MIB has received the DSM data. For example, if the AID in the DSM indicates that the message is a DSA, the DSMP will send DSM.indication to the DME.
Service primitive parameters:
The DSM.indication service primitive parameters are shown in Table 12.
Table 12 DSM.indication service primitive parameters
Name Type Effective range Description
DSMP Version Integer 0~7 Obtained from DSMP header
ApplicationIdentifier String — Provider AID, obtained from DSMP header
Length Integer 1~65 535 Obtained from DSMP header
Data String Not defined Obtained from DSMP header
Peer MAC address MAC address Any effective unicast MAC address Obtained from ADAPTATION-LAYER.indication
Priority Integer 1~8 Obtained from the bottom layer
5.4.5 DME service primitive
5.4.5.1 DME-ProviderService.request
DME-ProviderService.request indicates that the upper layer entity of the Provider requests to transmit a DSA, which is generated by the upper layer entity as needed. After received, the DME generates a DME-ProviderService.confirm, indicating whether the request is accepted.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Abbreviations
5 Technical requirements of network layer
6 Interactive data set of application layer
Annex A (Informative) Classification and value of Protocal Type
Annex B (Informative) Preferred AID port number allocation
Annex C (Informative) MIB message
Annex D (Informative) Example of source/destination address design for adaptation layer
Bibliography
