7 General message format and information elements coding
24.3863GPPProtocol aspectsRelease 17Stage 3TSUser Equipment (UE) to V2X control function
7.1 V2X message family encoding
The following values are specified to identify the V2X message family:
0 Reserved
1 IEEE 1609, see IEEE 1609.3 [5]
2 ISO, see ISO 29281-1 [6]
3 ETSI-ITS, see ETSI EN 302 636-3 [23]
4 CCSA, see CCSA YD/T 3707-2020 [24]
5-255 Reserved
7.2 V2X MBMS configuration
7.2.1 Minimum components of V2X MBMS configuration
The V2X MBMS configuration is provided to the UE to enable the UE to discover and acquire the V2X communication carried in IP multicast datagrams by the MBMS Bearer Service. It contains at least the following parameters:
a) a TMGI encoded as specified in 3GPP TS 24.008 [12] excluding the Temporary Mobile Group Identity IEI and Length of Temporary Mobile Group Identity contents;
b) a list of MBMS Service Area Identifiers (SAIs), with each SAI encoded as specified in 3GPP TS 23.003 [14];
c) in case of multicarrier support, a frequency encoded as specified in 3GPP TS 29.468 [15]; and
d) a V2X MBMS configuration SDP encoded as specified in subclause 7.2.2.
7.2.2 Encoding of V2X MBMS configuration SDP
7.2.2.1 Minimum components of V2X MBMS configuration SDP
The V2X MBMS configuration SDP shall contain at least the following parameters:
a) IP multicast address used for V2X communication over LTE-Uu using MBMS; and
b) a list of UDP port numbers used for V2X communication over LTE-Uu using MBMS, each associated with a V2X message family or IP type of data as defined in subclause 7.1.
These shall be expressed in SDP syntax (see IETF RFC 4566 [16]) according to the following subclauses.
In a V2X MBMS configuration SDP body, sending entity shall not include any media announcement field ("m=") other than the one specified in subclause 7.2.2.3.
In a V2X MBMS configuration SDP body, receiving entity shall ignore any media announcement field ("m=") other than the one specified in subclause 7.2.2.3.
7.2.2.2 IP multicast address
The IP multicast address shall be defined according to the "connection data" field ("c=") of IETF RFC 4566 [16].
7.2.2.3 List of UDP port numbers and associated V2X message family
The association between a UDP port number and a V2X message family is defined according to the media announcement field ("m=") of IETF RFC 4566 [16], with:
a) the <port> portion set to the UDP port number;
b) the <media> portion set to "application";
c) the <transport> portion set to "udp";
d) the <fmt> portion set to "vnd.3gpp.v2x"; and
e) an fmtp attribute:
1) with the <format> portion set to "vnd.3gpp.v2x"; and
2) with the <format specific parameters> portion containing a semicolon separated list of parameters as specified in subclause A.1.2 with:
A) a type parameter set to IP or non-IP; and
B) if a UDP port is used for exchange of V2X messages of non-IP type of data, a v2x-message-family parameter set to the value of the associated V2X message family as specified in subclause 7.1.
If multiple parameters are indicated in the <format specific parameters> portion of an fmpt attribute with the <format> portion set to "vnd.3gpp.v2x", the order of parameters is not significant.
Sending entity shall not include any parameter not defined in the present version of the present specification in the <format specific parameters> portion of an fmpt attribute with the <format> portion set to "vnd.3gpp.v2x".
Receiving entity shall ignore any parameter included in the <format specific parameters> portion of an fmpt attribute with the <format> portion set to "vnd.3gpp.v2x", such that the parameter is not specified in the present version of the present specification.
Receiving entity shall ignore the media announcement field ("m=") if the type parameter does not contain a value or contains a value not specified in the present version of the present specification.
Editor’s note: The vnd.3gpp.v2x application MIME type needs to be registered with IANA.
7.2.2.4 Example of V2X MBMS configuration SDP
Here is an example of a V2X MBMS configuration SDP:
v=0
o=user123 2890844526 2890842807 IN IP6 2201:056D::112E:144A:1E24
s=V2X MBMS configuration SDP example
c=IN IP6 FF15::101
m=application 1234 udp vnd.3gpp.v2x
a=fmtp:vnd.3gpp.v2x type=non-IP;v2x-message-family=1
m=application 1235 udp vnd.3gpp.v2x
a=fmtp:vnd.3gpp.v2x v2x-message-family=2;type=non-IP
m=application 1236 udp vnd.3gpp.v2x
a=fmtp:vnd.3gpp.v2x v2x-message-family=3;type=non-IP
m=application 1237 udp vnd.3gpp.v2x
a=fmtp:vnd.3gpp.v2x type=ip
7.3 V2X AS MBMS configuration
7.3.1 Introduction
The V2X AS MBMS configuration is provided to the UE to enable the UE to discover and acquire the V2X local service information carried in IP multicast datagrams by the MBMS Bearer Service. It contains at least the following parameters:
a) a TMGI encoded as specified in 3GPP TS 24.008 [12] excluding the Temporary Mobile Group Identity IEI and Length of Temporary Mobile Group Identity contents;
b) a list of MBMS Service Area Identifiers (SAIs), with each SAI encoded as specified in 3GPP TS 23.003 [14] ;
c) in case of multicarrier support, a frequency encoded as specified in 3GPP TS 29.468 [15]; and
d) a V2X AS MBMS configuration SDP encoded as specified in subclause 7.3.2.
The V2X local service information is carried using the application/vnd.3gpp-v2x-local-service-information MIME type defined in subclause 7.4.
7.3.2 Encoding of V2X AS MBMS configuration SDP
7.3.2.1 Minimum components of V2X AS MBMS configuration SDP
The V2X AS MBMS configuration SDP shall contain at least the following parameters:
a) IP multicast address used for V2X application server discovery using MBMS; and
b) UDP port number used for V2X application server discovery using MBMS;
These shall be expressed in SDP syntax (see IETF RFC 4566 [16]) according to the following subclauses.
7.3.2.2 IP multicast address
The IP multicast address shall be defined according to the "connection data" field ("c=") of IETF RFC 4566 [16].
7.3.2.3 Port number
The UDP port number shall be defined according to the <port> sub-field of the media announcement field ("m=") of IETF RFC 4566 [16].
7.3.2.4 Example of V2X AS MBMS configuration SDP
Here is an example of a V2X AS MBMS configuration SDP:
v=0
o=user123 2890844526 2890842807 IN IP6 2201:056D::112E:144A:1E24
s=V2X AS MBMS configuration SDP example
c=IN IP6 FF15::101
m=application 1234 UDP vnd.3gpp-v2x-local-service-information
7.4 Encoding of V2X local service information
7.4.1 General
This subclause defines the format of the V2X local service information.
This subclause also defines the MIME type used to convey the V2X local service information over MBMS bearers.
7.4.2 application/vnd.3gpp-v2x-local-service-information
The MIME type is used to carry information related to the local V2X application server, and optionally the V2X MBMS configuration. It shall be coded in binary ASN.1 PER as specified below.
— ASN1START
V2X-local-service-information-definitions DEFINITIONS AUTOMATIC TAGS ::= BEGIN
V2X-local-service-information ::= SEQUENCE {
V2X-as-info-list ListOfV2X-as-info,
V2X-MBMS-configuration-list ListOfV2X-MBMS-configuration OPTIONAL,
…
}
ListOfV2X-as-info :: = SEQUENCE OF V2X-as-info
ListOfV2X-MBMS-configuration :: = SEQUENCE OF V2X-MBMS-configuration
V2X-as-info :: = SEQUENCE {
V2X-service-identifier OCTET STRING (SIZE (1…4)),
V2X-as-address VisibleString,
UDP-port INTEGER,
…
}
V2X-MBMS-configuration :: = SEQUENCE {
V2X-service-identifier OCTET STRING (SIZE (1…4)),
tmgi OCTET STRING (SIZE (8)),
SAI-list ListOfSAIs,
Frequency INTEGER (0…262143) OPTIONAL,
IP-multicast-address VisibleString,
UDP-port INTEGER,
…
}
ListOfSAIs :: = SEQUENCE OF SAI
SAI :: = INTEGER (0…65535)
— ASN1STOP
7.4.3 Semantics
The V2X-local-service-information contains the following elements:
a) one or more V2X-AS-info element(s) containing an association between a V2X service identifier and one or more V2X application server address(es). Each V2X-AS-info element consists of:
1) one V2X-service-identifier element containing a 4 octet V2X service identifier;
2) one V2X-as-address element containing a V2X application server IP address or FQDN; and
3) one udp-port element containing a UDP port; and
b) zero, one or more V2X-MBMS-configuration element(s) containing the information enabling the UE to discover and acquire V2X communication over LTE-Uu using MBMS. Each V2X-MBMS-configuration element consists of the following:
1) one V2X-service-identifier element containing a 4 octet V2X service identifier;
2) one tmgi element containing the TMGI encoded as specified in 3GPP TS 24.008 [12] excluding the Temporary Mobile Group Identity IEI and Length of Temporary Mobile Group Identity contents;
3) one SAI-list element containing:
A) one or more SAI element(s) containing an MBMS SAI encoded as specified in 3GPP TS 23.003 [14];
4) zero or one frequency element containing a frequency encoded as specified in 3GPP TS 29.468 [15];
5) one ip-multicast-address element containing an IP multicast address; and
6) one udp-port element containing a UDP port.