Content for TS 23.285 Word version: 17.1.0

4.4 High level function 4.4.1 Authorization and Provisioning for V2X communications 4.4.2 V2X message transmission/reception over PC5 reference point 4.4.3 V2X message transmission/reception over LTE-Uu reference point 4.4.4 V2X Application Server discovery 4.4.5 QoS handling for V2X communication 4.4.6 Subscription to V2X services 4.4.7 MBMS bearer announcement for V2X use 4.4.8 Support for V2X communication for UEs in limited service state 4.4.9 Charging support for V2X communication 4.4.10 Security and privacy protection support for V2X communication 4.5 Identifiers
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4.4 High level function p. 15

4.4.1 Authorization and Provisioning for V2X communications p. 15

4.4.1.1 Authorization and provisioning for V2X communications over PC5 reference point p. 15

4.4.1.1.1 General p. 15

The basic principles of service authorization for V2X communications over PC5 reference point:

The UE gets authorization to use V2X communications over PC5 reference point on a per PLMN basis in the serving PLMN by the V2X Control Function in the HPLMN.
The V2X Control Function in the HPLMN requests authorization information from the V2X Control Function of the serving PLMN.
The V2X Control Function in the HPLMN merges authorization information from home and serving PLMNs and informs the UE of the final authorization information.
The V2X Control Function in the VPLMN or HPLMN may revoke the authorization at any time. The V2X Control Function in the HPLMN shall be notified when authorization is revoked by the VPLMN.

4.4.1.1.2 Policy/Parameter provisioning p. 15

The following information for V2X communications over PC5 reference point is provisioned to the UE:

Authorization policy:
- When the UE is "served by E-UTRAN":
  - PLMNs in which the UE is authorized to perform V2X communications over PC5 reference point.
- When the UE is "not served by E-UTRAN":
  - Indicates whether the UE is authorized to perform V2X communications over PC5 reference point when "not served by E-UTRAN".
Radio parameters for when the UE is "not served by E-UTRAN":
- Includes the radio parameters with Geographical Area(s) and an indication of whether they are "operator managed" or "non-operator managed". These radio parameters (e.g. frequency bands) are defined in TS 36.331. The UE uses the radio parameters to perform V2X communications over PC5 reference point when "not served by E-UTRAN" only if the UE can reliably locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorized to transmit.
NOTE 1:
Whether a frequency band is "operator managed" or "non-operator managed" in a given Geographical Area is defined by local regulations.
Policy/parameters:
- The mapping of Destination Layer-2 ID(s) and the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application.
  
  NOTE 2:
  PLMN operators coordinate to make sure Destination Layer-2 ID(s) for different V2X services are configured in a consistent manner.
  
  NOTE 3:
  To pre-configure a UE with the provisioning parameters, at least the "not served by E-UTRAN" parameters of 1) and 2), and the parameters of 3) need to be included.
- The mapping of ProSe Per-Packet Priority and packet delay budget for V2X communication (autonomous resources selection mode).
- The list of V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X applications, with Geographical Area(s) that require privacy support.
- The mapping of service types (e.g. PSIDs, ITS-AIDs or AIDs) to V2X frequencies (see TS 36.300 for further information) with Geographical Area(s).
- The mapping of service types (e.g. PSIDs, ITS-AIDs or AIDs) to Tx Profiles (see TS 36.300 for further information).
- The list of V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X applications, allowed to use a specific PPPR value.
Policy/parameters for NR PC5:
- Same as specified in item 6) in clause 5.1.2.1 of TS 23.287: "Policy/parameters when NR PC5 is selected", and the policy/parameter for NR Tx Profile selection as specified in item 3) in clause 5.1.2.1 of TS 23.287: "Policy/parameters for PC5 RAT selection and for PC5 Tx Profile selection".

Alternatively, the above parameters in 2) and 3) may be configured on the UE through the V1 reference point from the V2X Application Server. The V2X Control Function may also obtain these parameters through the V2 reference point from the V2X Application Server.

The parameters provisioned by the V2X Control Function take precedence over the configured parameters on the UE.

4.4.1.1.3 Principles for applying parameters for V2X communications over PC5 reference point p. 16

For V2X communication over PC5, the operator may pre-configure the UEs with the required provisioning parameters for V2X Communication, without the need for the UEs to connect to the V2X Control Function to get this initial configuration. The following apply:

The provisioning parameters for V2X communications over PC5 may be configured in the UICC, in the ME, or in both the UICC and the ME.
The ME provisioning parameters shall not be erased when a USIM is deselected or replaced.
If both the UICC and the ME contain the same set of provisioning parameters, the set of parameters from the UICC shall take precedence.
The UE shall use radio resources for V2X communications over PC5 reference point as follows:
- While a UE has a serving cell and is camped on a cell and the UE intends to use for V2X service the radio resources (i.e. carrier frequency) operated by this cell, then the UE shall use the radio resource description indicated by this cell the UE is camped on and ignore any radio resource description of the same radio resource provisioned in the ME or the UICC. If the cell does not provide radio resources for V2X service, the UE shall not perform V2X message transmission and reception on radio resources operated by this cell.
- If the UE intends to use "operator-managed" radio resources (i.e. carrier frequency) for V2X service that are not operated by the UE's serving cell, as specified in clause 4.4.1.1.2, or if the UE is out of coverage, the UE shall search for a cell in any PLMN that is operating the provisioned radio resources (i.e. carrier frequency) as defined in TS 36.300 and TS 36.304, and:
  - If the UE finds such cell in the registered PLMN or a PLMN equivalent to the registered PLMN, and authorization for V2X communications over PC5 reference point to this PLMN is confirmed, the UE shall use the radio resource description indicated by that cell. If that cell does not provide radio resources for V2X service, the UE shall not perform V2X message transmission and reception on those radio resources.
  - If the UE finds such cell but not in the registered PLMN or a PLMN equivalent to the registered PLMN, and that cell belongs to a PLMN authorized for V2X communications over PC5 reference point and provides radio resources for V2X service then the UE shall perform PLMN selection triggered by V2X communications over PC5 reference point as defined in TS 23.122. If the UE has an ongoing emergency session, it shall not trigger any PLMN selection due to V2X communication over PC5 reference point.
    
    NOTE 1:
    An ongoing emergency session could be either using IMS or CS as described in TS 23.167.
  - If the UE finds such cell but not in a PLMN authorized for V2X communications over PC5 reference point the UE shall not use V2X communications over PC5 reference point.
  - If the UE does not find any such cell in any PLMN, then the UE shall consider itself "not served by E-UTRAN" and use radio resources provisioned in the ME or the UICC. If no such provision exists in the ME or the UICC or the provision does not authorize V2X communications over PC5 reference point then the UE is not authorized to transmit.
- If the UE intends to use "non-operator-managed" radio resources (i.e. carrier frequency) for V2X service, according to TS 36.331 and as specified in clause 4.4.1.1.2, then the UE shall perform V2X communication over PC5 using resource provisioned in the ME or the UICC. If no such provision exists in the ME or the UICC or the provision does not authorize V2X communications over PC5 reference point then the UE is not authorized to transmit.
The UE provisioning shall support setting Geographical Areas.

NOTE 2:
It is possible for a UE to use other radio resources for V2X service based on the Geographical Area instead of those operated by the serving E-UTRAN cell, when provisioned in the UE, even if the UE's serving cell offers normal service and the SIB21 indicates that the service (V2X communication) is available. This is to cover the scenario when e.g. the radio resources used for V2X communications over PC5 reference point are not owned by the serving network of the UE.

NOTE 3:
When cross-carrier operation is supported, according to TS 36.331, a UE can be instructed by its serving cell to perform V2X communication over a different carrier frequency. The UE is still considered as "served by E-UTRAN" in this case.

NOTE 4:
The scenario that a cell is detected and the cell does not provide support for V2X communications over PC5 reference point when the UE attempts to use a carrier frequency configured for V2X communications over PC5 reference point, is considered a configuration error. Therefore the UE does not transmit on that frequency to avoid interference to the network.
The V2X communications over PC5 reference point is only specified for E-UTRA.

NOTE 5:
It is out of scope of the present specification to define how the UE can locate itself in a specific Geographical Area. When the UE is in coverage of a 3GPP RAT, it can for example, use information derived from the serving PLMN. When the UE is not in coverage of a 3GPP RAT, it can use other techniques, e.g. Global Navigation Satellite System (GNSS). User provided location is not a valid input.

4.4.1.2 Authorization and provisioning for V2X communications over LTE-Uu reference point p. 17

4.4.1.2.1 General p. 17

Additional information may be provisioned to the UE for the use of V2X communications over LTE-Uu reference point, e.g. for unicast or MBMS.

4.4.1.2.2 Policy/Parameter provisioning p. 17

The following information may be configured in V2X Control Function and optionally provisioned to the UE for V2X communications over LTE-Uu reference point:

PLMNs in which the UE is authorized to use MBMS based V2X communication.
- Corresponding V2X USD(s) for receiving MBMS based V2X traffic in the PLMN. The V2X USD(s) may be obtained through the V2 reference point from the V2X Application Server.
NOTE:
The V2 reference point procedure is not specified in this Release.
V2X Application Server address information.
- List of FQDNs or IP addresses of the V2X Application Servers, associated with served geographical area information and list of PLMNs that the configuration applies to.
V2X Application Sever discovery using MBMS.
- List of PLMNs and corresponding V2X Server USDs for receiving V2X Application Server information via MBMS.
Mapping of the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application to:
- V2X Application Server address (consisting of IP address/FQDN and TCP or UDP port) for unicast;
- V2X USD for MBMS.

Information of the V2X USD is described in clause 4.4.7.2 and information of the V2X Server USD is described in clause 4.4.7.3.

4.4.2 V2X message transmission/reception over PC5 reference point p. 18

PC5 reference point as defined in TS 23.303 is used for the transmission and reception of V2X messages. The V2X communication over PC5 reference point supports roaming and inter-PLMN operations. V2X communication over PC5 reference point is supported when the UE is "served by E-UTRAN" and when the UE is "not served by E-UTRAN".

A UE is authorized to transmit and receive V2X messages by the V2X Control Function in its home PLMN as described in clause 5.2.

The V2X communication over PC5 reference point is a type of ProSe Direct Communication with the following characteristics:

The V2X communication over PC5 reference point is connectionless, and there is no signalling over PC5 control plane for connection establishment.
V2X messages are exchanged between UEs over PC5 user plane.
Both IP based and non-IP based V2X messages are supported.
For IP based V2X messages, only IPv6 is used. IPv4 is not supported in this release.

The identifiers used in the V2X communication over PC5 reference point are described in clause 4.5.1. UE decides on the Tx Profile to use for the transmission of a particular packets based on the configuration described in clause 4.4.1.1.2.

When the network scheduled operation mode is used, following additional principle applies:

When the eNB receives a request for PC5 resource from a UE, the eNB may deduce the Tx Profile from the Destination L2 ID.

If the UE has an ongoing emergency session, the communication over the emergency session shall be prioritized over V2X communication over PC5 reference point.

4.4.3 V2X message transmission/reception over LTE-Uu reference point p. 19

4.4.3.1 General p. 19

The LTE-Uu reference point is used for the transmission and reception of V2X messages. The V2X message transmission and reception via unicast is described in clause 4.4.3.2, while the V2X message reception via MBMS is described in clause 4.4.3.3.

4.4.3.2 V2X message transmission/reception via unicast p. 19

The V2X communication via unicast over the LTE-Uu reference point supports roaming operations. Latency reduction for V2X message transfer via unicast may be achieved by using SIPTO@LN or SIPTO above RAN as defined in TS 23.401.

For transport of IP based or non-IP based V2X messages using uplink unicast V2X communication in case of applications identified by e.g. PSID, ITS-AID, or AID for the same applications as over PC5 reference point:

V2X messages are transported over TCP/IP or UDP/IP packets. The UE may learn from V2X Application Server or UE may be configured explicitly about a transport layer protocol to be used, or no restriction is imposed by configuration;

NOTE 2:
When IP multicast is used, only UDP/IP is supported.
the UE sends a V2X message over TCP/IP or UDP/IP to a V2X Application Server address. The destined V2X Application Server address is derived from e.g. the PSID (or the ITS-AID, or the AID) and the UE configuration as described in clause 4.4.1.2.2; and
the V2X Application Server receives the V2X message in a TCP/IP or UDP/IP packet on a V2X Application Server address.

For transport of V2X messages:

for applications different from the applications with e.g. PSID, ITS-AID or AID for PC5 reference point, or
for configured applications with e.g. PSID, ITS-AID or AID sending IP based V2X messages,
existing unicast routing towards application server applies.

4.4.3.3 V2X message reception via MBMS p. 19

V2X messages can be broadcasted via MBMS in which the V2X Application Server transfers V2X messages via MBMS bearer service(s) as shown in Figure 4.2.2-1a.

For MBMS reception of V2X messages, V2X USD per PLMN for V2X services is required for the UE. The UE is provisioned with mapping of e.g. PSID (or ITS-AID, or AID) and V2X USD as described in clause 4.4.1.2.2.

To provide the UE with the V2X USD(s), the following ways may be used:

Existing MBMS service announcement mechanisms specified in TS 23.246 and TS 26.346.
Provisioning as described in clause 4.4.1.2.2, i.e. pre-configuration in the UE and/or configuration from V2X Control Function.
Provisioning from the V2X Application Server via V1 reference point.

The V2X Application Server providing the V2X service identified by e.g. the PSID (or the ITS-AID, or the AID) sends the V2X message via UDP/IP transport using information provided in the V2X USD.

For latency improvements for MBMS, localized MBMS can be considered for localized routing of V2X messages destined to UEs. Some localized MBMS deployment options are described in Annex B.

4.4.4 V2X Application Server discovery p. 20

4.4.4.1 General p. 20

A UE needs to discover the V2X Application Server(s), when V2X communication over LTE-Uu operation mode is used. The V2X Application Server address information may be configured on the UE or provisioned via V3 interface, as specified in clause 4.4.1.2.2.

When the configuration contains the FQDN(s), the UE shall perform DNS to resolve the address(es) of the V2X Application Server. The UE may use the configured V2X Application Server information only in the designated geographical area. When the UE changes serving PLMN or crosses configured geographic areas, it should perform address resolution again.

For a network that has deployed broadcast mechanisms, e.g. MBMS, additional information to assist V2X Application Server discovery can be provided via the MBMS broadcast channel. When a UE has the configuration for receiving V2X Application Server information via MBMS, as specified in clause 4.4.1.2.2, it can perform the procedures specified in clause 5.4.1 to obtain additional local V2X Application Server information. The local V2X Application Server information obtained by MBMS as described in clause 5.4.1 takes precedence over the V2X Application Server information in the UE.

4.4.4.2 Multiple V2X Application Server and Localized V2X Application Server discovery and routing p. 20

Multiple V2X Application Servers may be involved in the V2X communication, each providing particular V2X services and/or serving a particular geographical region. Therefore, the V2X Application Server address information as specified in clause 4.4.1.2.2 can contain multiple servers' information. When multiple V2X Application Servers are configured, the application layer will choose the proper V2X Application Server to use.

When localized V2X Application Servers are deployed, Anycast may be used to conceal the server change from the UE. In this case, a FQDN is configured for a large region, e.g. the entire PLMN, and the UE only needs to resolve it once to an Anycast address. The PDN GW or LGW is responsible for routing the traffic to the appropriate local V2X Application Servers based on Anycast address.

4.4.5 QoS handling for V2X communication p. 20

4.4.5.1 QoS handling for V2X communication over PC5 reference point p. 20

Core Network, i.e. MME, provides the UE-PC5-AMBR based on subscription information to the eNB as part of the UE context information.

When PC5 is used for the transmission of V2X messages, the following principles are followed for both network scheduled operation mode and UE autonomous resources selection mode:

ProSe Per-Packet Priority (PPPP) defined in clause 5.4.6.1 of TS 23.303 applies to the V2X communication over PC5.
ProSe Per-Packet Reliability (PPPR) applies to the V2X communication over PC5 as defined in TS 23.303. PPPR has a value range of 1 to 8, where the higher value represents the lower reliability requirement for that message. The UE may be configured with a list of V2X services, e.g. PSIDs, ITS-AIDs or AIDs allowed to use the specific PPPR value.
The application layer sets the PPPP for each V2X message when passing it to lower layer for transmission.
The application layer may set the PPPR for each V2X message when passing it to lower layer for transmission.
The mapping of application layer V2X message priority to PPPP is configuration on the UE.
The mapping of application layer V2X message reliability to PPPR is configuration on the UE.
The setting of the PPPP value should reflect the latency required in both UE and eNB, i.e. the low PDB is mapped to the high priority PPPP value.
The mapping between V2X service types and V2X frequencies is as defined in clause 4.3.2 and clause 4.4.1.1.2.
The mapping of Destination Layer-2 ID(s) and the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application is as described in clause 4.4.1.1.2.

When the network scheduled operation mode is used, following additional principles apply:

UE provides priority information reflecting PPPP to the eNB for resources request.
When the eNB receives a request for PC5 resource from a UE, the eNB can deduce the packet delay budget from the priority information reflecting PPPP from the UE.
eNB can use the priority information reflecting PPPP for priority handling and UE-PC5-AMBR for capping the UE PC5 transmission in the resources management.
UE may provide PPPR information reflecting reliability requirement described in TS 22.186 to the eNB for resources request.
UE provides Destination Layer-2 ID(s) of the V2X services to the eNB for resources requested as defined in TS 36.321.
When the eNB receives a request for PC5 resource from a UE, the eNB determines the V2X frequency(ies) in which the V2X service is to be scheduled as defined in TS 36.300.

When the autonomous resources selection mode is used, following additional principle applies:

The UE derives the packet delay budget of the V2X message from PPPP based on the provisioned mapping information described in clause 4.4.1.1.2.
The UE derives the frequency in which a V2X service is to be transmitted, from the mapping between V2X service types and V2X frequencies as described in clause 4.4.1.1.2.

4.4.5.1a QoS handling for V2X communication over NR PC5 reference point |R16| p. 21

The QoS handling for V2X communication over NR PC5 reference point as defined in clause 5.4 of TS 23.287 is applied.

4.4.5.2 QoS handling for V2X communication over LTE-Uu reference point p. 21

The V2X messages can be delivered via Non-GBR bearer as well as GBR bearer.

The following standardized QCI values defined in TS 23.203 can be used:

QCI 3 and QCI 79 can be used for the unicast delivery of V2X messages;
QCI 75 is only used for the delivery of V2X messages over MBMS bearers.

4.4.6 Subscription to V2X services p. 21

The user's profile in the HSS contains the subscription information to give the user permission to use V2X services.

At any time, the operator can remove the UE subscription rights for V2X services from user's profile in the HSS, and revoke the user's permission to use V2X services.

The following subscription information is defined for V2X services:

whether the UE is authorized to perform V2X communication over PC5 reference point as Vehicle UE, Pedestrian UE, or both, including for LTE PC5 and for NR PC5.
UE-PC5-AMBR for V2X communication over PC5 reference point, including UE-PC5-AMBR for LTE PC5 and for NR PC5.
the list of the PLMNs where the UE is authorized to perform V2X communication over PC5 reference point. For each PLMN in the list, the RAT(s) over which the UE is authorized to perform V2X communication over PC5 reference point.
PC5 QoS parameters for V2X communication over NR PC5 reference point as defined in clause 5.4.2 of TS 23.287.

The HSS provides a), b) and d) to MME as subscription information and the MME provides a), b) and d) to eNB as part of the UE context information.

The HSS provides c) to V2X Control Function.

4.4.7 MBMS bearer announcement for V2X use p. 22

4.4.7.1 General p. 22

MBMS bearer announcements are needed for V2X message reception via MBMS as defined in clause 4.4.3.3, or V2X Application Server discovery via MBMS as defined in clause 4.4.4.1 and clause 5.4.1.

The method for delivering the per PLMN configuration to the UE is specified in clause 4.4.3.3. The announced service information for V2X use should follow the guidance in clause 4.4.7.2 and clause 4.4.7.3.

4.4.7.2 User Service Description for V2X Communication (V2X USD) p. 22

As the V2X Application Server is out of scope of 3GPP, the exact information to be included in the V2X USD cannot be controlled. However, the V2X Application Server should make sure that the information listed in Table 4.4.7.2-1 is included in the V2X USD it provides.

The V2X message formats are handled by upper layer via Session Description Protocol (SDP).

Table 4.4.7.2-1: Information for V2X USD

Information Element	Description
TMGI	TMGI information
List of service area identifier	A list of service area identifier for the applicable MBMS broadcast area
Frequency	Identification of frequency if multi carrier support is provided
SDP information (NOTE 1)	SDP with IP multicast address and port number used for V2X communication via MBMS. Depending on the V2X application, the V2X message can be carried directly on top of UDP, without any streaming protocols.
NOTE 1: Typical V2X application does not require Codec information in the SDP information.

4.4.7.3 User Service Description for V2X Application Server Discovery (V2X Server USD) p. 22

The V2X Server USD is used to configure the UE for receiving local V2X Application Server information when it is provided over MBMS, as specified in clause 5.4.1.

The local Service Information contained in the broadcast is as described in clause 5.4.1.2, and should include similar information defined in clause 4.4.1.2.2.

Table 4.4.7.3-1: Information for V2X Server USD

Information Element	Description
TMGI	TMGI information
List of service area identifier	A list of service area identifier for the applicable MBMS broadcast area
Frequency	Identification of frequency if multi carrier support is provided
	SDP information SDP with IP multicast address and port number used for V2X Application Server discovery via MBMS. The content of the message carries the local Service Information and should include following information: Mapping of the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application of a PSID, ITS-AID and AID to V2X Application Server address (consisting of IP address/FQDN and TCP or UDP port) for unicast, and V2X USD for V2X communication via MBMS.

4.4.8 Support for V2X communication for UEs in limited service state p. 23

For UE in limited service state, only V2X communication over PC5 is allowed.

UEs that are authorized to use V2X communication over PC5 reference point shall be able to use V2X communication over PC5 reference point when in limited service state following the principles defined in clause 4.4.1.1.3 for V2X communication over PC5 reference point when the UE enters in limited service state:

because it cannot find a suitable cell of the selected PLMN as described in TS 23.122 or
as the result of receiving one of the following reject reasons defined in TS 23.122:
- a "PLMN not allowed" response to a registration request or;
- a "GPRS not allowed" response to a registration request

A UE in limited service state shall only use the radio resources and procedure available in ECM-IDLE mode for V2X communication over PC5 reference point, for details see TS 36.300.

UEs shall not use V2X communication over PC5 reference point using the "operator-managed" radio resources, as specified in clause 4.4.1.1.2, if the UE has entered in limited service state due to all other situations (e.g. no SIM in the MS, an "illegal MS" or "illegal ME" response to a registration request, or an "IMSI unknown in HLR" response to a registration request) defined in TS 23.122, where the UE is unable to obtain normal service from a PLMN. The UEs may use V2X communication over PC5 reference point using the "non-operator-managed" radio resources, as specified in clause 4.4.1.1.2, according to the principles defined in clause 4.4.1.1.3.

4.4.9 Charging support for V2X communication p. 23

4.4.9.1 Charging support for V2X communication over PC5 reference point p. 23

For V2X communication over PC5, the mechanism defined in TS 32.277 for ProSe Direct Communication can be reused for charging support. No enhancement to charging support for V2X communication over PC5 is specified in this Release.

4.4.9.2 Charging support for V2X communication over LTE-Uu reference point p. 24

For V2X communication over LTE-Uu, there are unicast traffic and/or MBMS based broadcast traffic.

For unicast V2X communication, charging is provided with the existing unicast communication mechanism as specified in TS 32.251 where applicable.

For MBMS based broadcast traffic, charging is provided with the existing mechanism as specified in TS 32.273 where applicable.

No enhancement to charging support for V2X communication over LTE-Uu is specified in this Release.

4.4.10 Security and privacy protection support for V2X communication p. 24

The security for the V3 and PC5 reference points is provided with mechanisms defined in TS 33.185.

The security and privacy protection for the PC5 based V2X communication is provided by application layer schemes developed in other SDOs. In addition, the V2X layer also provides an additional mechanism to change Layer-2 ID and source IP address to protect privacy, as described in clause 4.5.1.

The security of LTE-Uu based V2X communication reuses existing EPS security. No privacy enhancement for V2X communication over LTE-Uu is specified for this release.

Details of security and privacy protection mechanisms for V2X communication over PC5 or LTE-Uu reference points are defined in TS 33.185.

4.5 Identifiers p. 24

4.5.1 Identifiers for V2X communication over PC5 reference point p. 24

Each UE has a Layer-2 ID for the V2X communication over PC5 reference point, which is included in the source Layer-2 ID field of every frame that it sends on the layer-2 link. The UE self-assigns the Layer-2 ID for the V2X communication over PC5 reference point.

When IP based V2X messages are supported, the UE auto-configures a link local IPv6 address to be used as the source IP address, as defined in clause 4.5.3 of TS 23.303. The UE may use the auto-configured link local IP address for V2X communication over PC5 reference point without sending Neighbor Solicitation and Neighbor Advertisement message for Duplicate Address Detection.

If the UE has an active V2X application that requires privacy support in the current Geographical Area, as identified by configuration described in clause 4.4.1.1.2, in order to ensure that a source UE (e.g. vehicle) cannot be tracked or identified by any other UEs (e.g. vehicles) beyond a certain short time-period required by the application, the source Layer-2 ID must be changed over time and randomized. For IP based V2X communication over PC5 reference point, the source IP address must be also changed over time and randomized. The change of the identifiers of a source UE must be synchronized across layers used for PC5, e.g. when application layer identifier changes, the source Layer-2 ID and the source IP address need to be changed.

The UE is configured with the destination Layer-2 ID(s) to be used for V2X services. The Layer-2 ID for a V2X message is selected based on the configuration as described in clause 4.4.1.1.