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Content for  TS 23.287  Word version:  17.1.0

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5  High level functionality and featuresWord‑p. 16

5.1  Authorization and Provisioning for V2X communicationsWord‑p. 16

5.1.1  GeneralWord‑p. 16

In 5GS, the parameters for V2X communications over PC5 and Uu reference points may be made available to the UE in following ways:
  • pre-configured in the ME; or
  • configured in the UICC; or
  • preconfigured in the ME and configured in the UICC; or
  • provided/updated by the V2X Application Server via PCF and/or V1 reference point; or
  • provided/updated by the PCF to the UE.
If the same parameters described in clause 5.1.2.1 and clause 5.1.3.1 are provided by different sources, the UE shall consider them in the following priority order:
  • provided/updated by the PCF;
  • provided/updated by the V2X Application Server via V1 reference point;
  • configured in the UICC;
  • pre-configured in the ME.
The parameters provided/updated by the V2X Application Server via V1 reference point may need to be complemented with configuration data from other sources listed above.
The basic principles of service authorization and provisioning for V2X communication over PC5 reference point and provisioning for V2X communication over Uu reference point are:
  • The UE may be authorized to use V2X communication over PC5 reference point on a per PLMN basis by the PCF in the HPLMN.
  • The PCF in the HPLMN merges authorization information from home and other PLMNs and provides the UE with the final authorization information.
  • The PCF in the VPLMN or HPLMN may revoke the authorization (via H-PCF when roaming) at any time by using the UE Configuration Update procedure for transparent UE Policy delivery procedure defined in clause 4.2.4.3 of TS 23.502.
  • The provisioning to UE for V2X communication over PC5 and Uu reference points is controlled by the PCF and may be triggered by UE. The PCF includes the V2X Policy/parameters for V2X communications over PC5 reference point as specified in clause 5.1.2.1 and/or the V2X Policy/parameters for V2X communications over Uu reference point as specified in clause 5.1.3.1 into a Policy Section identified by a Policy Section Identifier (PSI) as specified in clause 6.1.2.2.2 of TS 23.503.
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5.1.2  Authorization and Provisioning for V2X communications over PC5 reference pointWord‑p. 17

5.1.2.1  Policy/Parameter provisioningWord‑p. 17

The following sets of information for V2X communications over PC5 reference point is provisioned to the UE:
  1. Authorization policy:
    • When the UE is "served by E-UTRA" or "served by NR":
      • PLMNs in which the UE is authorized to perform V2X communications over PC5 reference point when "served by E-UTRA" or "served by NR".
        For each above PLMN:
        • RAT(s) over which the UE is authorized to perform V2X communications over PC5 reference point.
    • When the UE is "not served by E-UTRA" and "not served by NR":
      • Indicates whether the UE is authorized to perform V2X communications over PC5 reference point when "not served by E-UTRA" and "not served by NR".
      • RAT(s) over which the UE is authorized to perform V2X communications over PC5 reference point.
  2. Radio parameters when the UE is "not served by E-UTRA" and "not served by NR":
    • Includes the radio parameters per PC5 RAT (i.e. LTE PC5, NR PC5) 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 and TS 38.331. The UE uses the radio parameters to perform V2X communications over PC5 reference point when "not served by E-UTRA" and "not served by NR" only if the UE can reliably locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorized to transmit.
  3. Policy/parameters for PC5 RAT selection and for PC5 Tx Profile selection:
    • The mapping of V2X service types to PC5 RAT(s) (e.g. LTE PC5, NR PC5 or both), and for LTE PC5 to the corresponding Tx Profiles (see TS 36.300 for further information).
  4. Policy/parameters related to privacy:
    • The list of V2X service types, with Geographical Area(s) that require privacy support.
    • A privacy timer value indicating the duration after which the UE shall change each source Layer-2 ID self-assigned by the UE when privacy is required.
  5. Policy/parameters when LTE PC5 is selected:
    Same as specified in TS 23.285, clause 4.4.1.1.2 item 3) Policy/parameters except for the mapping of V2X service types to Tx Profiles and the list of V2X services with Geographical Area(s) that require privacy support.
  6. Policy/parameters when NR PC5 is selected:
    • The mapping of V2X service types to V2X frequencies with Geographical Area(s).
    • The mapping of V2X service types to the default mode of communication (i.e. broadcast mode, groupcast mode or unicast mode).
    • The mapping of V2X service types to Destination Layer-2 ID(s) for broadcast.
    • The mapping of V2X service types to Destination Layer-2 ID(s) for groupcast mode communication.
    • The mapping of V2X service types to default Destination Layer-2 ID(s) for initial signalling to establish unicast connection.
    • The mapping of V2X service types to PC5 QoS parameters defined in clause 5.4.2 (i.e. PQI and conditionally other parameters such as MFBR/GFBR, etc.).
    • AS layer configurations (see TS 38.331), e.g. the mapping of PC5 QoS profile(s) to radio bearer(s), when the UE is "not served by E-UTRA" and "not served by NR".
      • The PC5 QoS profile contains PC5 QoS parameters described in clause 5.4.2, and value for the QoS characteristics regarding Priority Level, Averaging Window, Maximum Data Burst Volume if default value is not used as defined in Table 5.4.4-1.
    • For the PC5 DRX configuration, the reference to RAN specification will be added when defined in RAN WGs.
    • For broadcast and groupcast, PC5 DRX configuration when the UE is "not served by E-UTRA" and "not served by NR".
    • The mapping of PC5 QoS profile to PC5 DRX cycle configuration.
  7. Validity timer indicating the expiration time of the V2X Policy/Parameter.
The above parameter sets from bullet 2) to 6) may be configured in the UE through the V1 reference point by the V2X Application Server.
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5.1.2.2  Principles for applying parameters for V2X communications over PC5 reference pointWord‑p. 18

For V2X communication over PC5 reference point, 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 5GC to get this initial configuration. The following apply:
  • The provisioning parameters for V2X communications over PC5 reference point 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 overlapping provisioning parameters, the set of parameters from the UICC shall take precedence.
  • The provisioning parameters from the PCF or V2X Application Server via V1 reference point shall take precedence over the pre-configured parameters in the ME and UICC as defined in clause 5.1.1.
  • 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 5.1.2.1, 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 (if LTE based PC5 is selected for the V2X communication) or as defined in TS 38.300 and TS 38.304 (if NR based PC5 is selected for the V2X communication), and:
      • If the UE finds such a 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 a 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 via IMS, it shall not trigger any PLMN selection due to V2X communication over PC5 reference point.
      • 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 NR or E-UTRA" 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 or TS 38.331 and as specified in clause 5.1.2.1, 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.
  • The V2X communications over PC5 reference point is only specified for E-UTRA and NR.
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5.1.3  Authorization and provisioning for V2X communications over Uu reference pointWord‑p. 20

5.1.3.1  Policy/Parameter provisioningWord‑p. 20

The following set of information may be provisioned to the UE for V2X communications over Uu reference point:
  1. Mapping of the V2X service types to:
    • PDU Session Type (i.e. IP type or Unstructured type);
    • Transport layer protocol (i.e. UDP or TCP, only applicable for IP PDU Session type);
    • SSC Mode;
    • S-NSSAI(s);
    • DNN(s).
  2. Validity timer indicating the expiration time of the V2X Policy/Parameter.
The following sets of information may be provisioned to the UE and is applicable for V2X communications over both LTE-Uu and Uu reference points:
  1. Mapping of the V2X service types to V2X Application Server address information (consisting of IP address/FQDN and transport layer port#) for unicast.
  2. 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.
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5.2  V2X communicationWord‑p. 20

5.2.1  V2X communication over PC5 reference pointWord‑p. 20

5.2.1.1  GeneralWord‑p. 20

For V2X communication, two types of PC5 reference points exist: the LTE based PC5 reference point as defined in TS 23.285, and the NR based PC5 reference point as defined in clause 4.2.3. A UE may use either type of PC5 or both for V2X communication depending on the services the UE supports. The V2X communication over PC5 reference point supports roaming and inter-PLMN operations. V2X communication over PC5 reference point is supported when UE is "served by NR or E-UTRA" or when the UE is "not served by NR or E-UTRA".
A UE is authorized to transmit and receive V2X messages when it has valid authorization and configuration as specified in clause 5.1.2.
The V2X communication over PC5 reference point has the following characteristics:
  • V2X communication over LTE based PC5 reference point is connectionless, i.e. broadcast mode at Access Stratum (AS) layer, and there is no signalling over PC5 for connection establishment.
  • V2X communication over NR based PC5 reference point supports broadcast mode, groupcast mode, and unicast mode at AS layer. If V2X application layer of the UE indicates the mode of communication to V2X layer, the V2X layer shall set the mode of communication based on the request of the V2X application layer; otherwise, the V2X layer sets the mode of communication based on the mapping information for a V2X service type defined in clause 5.1.2.1. The V2X layer indicates the mode of communication for the V2X service type to the AS layer. Signalling over control plane over PC5 reference point for unicast mode communication management is supported.
  • V2X services communication support between UEs over PC5 user plane.
    • Both IP based and non-IP based V2X services communication are supported over PC5 reference point.
    • For IP based V2X services communication, only IPv6 is used. IPv4 is not supported.
  • V2X messages are exchanged between UEs over PC5 user plane.
    • Both IP based and non-IP based V2X messages are supported over PC5 reference point.
    • For IP based V2X messages, only IPv6 is used. IPv4 is not supported.
The identifiers used in the V2X communication over PC5 reference point are described in clause 5.6.1. UE decides on the type of PC5 reference point and for LTE PC5 Tx Profile also to use for the transmission of a particular packet based on the configuration described in clause 5.1.2. When the LTE based PC5 reference point is selected, the QoS handling corresponding procedures are defined in TS 23.285. When NR based PC5 reference point is selected, the QoS handling and procedures are defined in clause 5.4.1 and clause 6.3.
If the UE has an ongoing emergency session via IMS, the ongoing emergency session via IMS shall be prioritized over V2X communication over PC5 reference point.
The security for V2X communication over PC5 reference point is provided with mechanisms defined in TS 33.536. For broadcast and groupcast mode communication, security is supported in the V2X application layer schemes developed in other SDOs.
The pedestrian UEs may use the PC5 DRX mechanism to perform V2X communication over PC5 reference point with power efficiency as specified in clause 5.9.
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5.2.1.2  Broadcast mode communication over PC5 reference pointWord‑p. 21

Broadcast mode of communication is supported over both LTE based PC5 reference point and NR based PC5 reference point. Therefore, when broadcast mode is selected for transmission over PC5 reference point, PC5 RAT selection needs to be performed based on configuration described in clause 5.1.2. Based on configuration described in clause 5.1.2 and the availability of the corresponding PC5 RAT(s) for the specific V2X service type, the V2X layer in the UE determines PC5 RAT(s) and passes the packet to the applicable PC5 AS (Access Stratum) layer(s) with the appropriate PC5 QoS parameters as defined in clause 5.4.1.1.1
For LTE based PC5 reference point, broadcast mode is the only supported communication mode, and the operation details are defined in TS 23.285.
For NR based PC5 reference point, the broadcast mode also supports enhanced QoS handling as defined in clause 5.4.1.
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5.2.1.3  Groupcast mode communication over PC5 reference pointWord‑p. 21

Groupcast mode communication is only supported over NR based PC5 reference point and applies to all types of groups, i.e. Application Layer connection-less group and Application Layer managed group.
For Application Layer managed group, the following applies:
  • If the V2X application layer provides a group size and a member ID, the V2X layer passes them to the AS layer for groupcast control, as defined in TS 38.300.
QoS handling for groupcast mode communication is defined in clause 5.4.1.
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5.2.1.4  Unicast mode communication over PC5 reference pointWord‑p. 21

Unicast mode of communication is only supported over NR based PC5 reference point. Figure 5.2.1.4-1 illustrates an example of PC5 unicast links.
Copy of original 3GPP image for 3GPP TS 23.287, Figure 5.2.1.4-1: Example of PC5 Unicast Links
Figure 5.2.1.4-1: Example of PC5 Unicast Links
(⇒ copy of original 3GPP image)
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The following principles apply when the V2X communication is carried over PC5 unicast link:
  • A PC5 unicast link between two UEs allows V2X communication between one or more pairs of peer V2X services in these UEs. All V2X services in the UE using the same PC5 unicast link use the same Application Layer ID.
  • One PC5 unicast link supports one or more V2X service types) if these V2X service types are at least associated with the pair of peer Application Layer IDs for this PC5 unicast link. For example, as illustrated in Figure 5.2.1.4-1, UE A and UE B have two PC5 unicast links, one between peer Application Layer ID 1/UE A and Application Layer ID 2/UE B and one between peer Application Layer ID 3/UE A and Application Layer ID 4/UE B.
  • A PC5 unicast link supports V2X communication using a single network layer protocol e.g. IP or non-IP.
  • A PC5 unicast link supports per-flow QoS model as specified in clause 5.4.1.
  • If multiple V2X service types use a PC5 unicast link, one PC5 QoS Flow identified by PFI may be associated with more than one V2X service types.
When the Application layer in the UE initiates data transfer for a V2X service type which requires unicast mode of communication over PC5 reference point:
  • the UE shall reuse an existing PC5 unicast link if the pair of peer Application Layer IDs and the network layer protocol of this PC5 unicast link are identical to those required by the application layer in the UE for this V2X service, and modify the existing PC5 unicast link to add this V2X service type as specified in clause 6.3.3.4; otherwise
  • the UE shall trigger the establishment of a new PC5 unicast link as specified in clause 6.3.3.1.
After successful PC5 unicast link establishment, UE A and UE B use the same pair of Layer-2 IDs for subsequent PC5-S signalling message exchange and V2X service data transmission as specified in clause 5.6.1.4. The V2X layer of the transmitting UE indicates to the AS layer whether a transmission is for a PC5-S signalling message (i.e. Direct Communication Request/Accept, Link Identifier Update Request/Response/Ack, Disconnect Request/Response, Link Modification Request/Accept, Keep-alive/Ack) or V2X service data.
For every PC5 unicast link, a UE self-assigns a distinct PC5 Link Identifier that uniquely identifies the PC5 unicast link in the UE for the lifetime of the PC5 unicast link. Each PC5 unicast link is associated with a Unicast Link Profile which includes:
  • Application Layer ID and Layer-2 ID of UE A; and
  • Application Layer ID and Layer-2 ID of UE B; and
  • network layer protocol used on the PC5 unicast link; and
  • the information about PC5 QoS Flow(s). For each PC5 QoS Flow, the PC5 QoS Context and the PC5 QoS Rule(s) as defined in clause 5.4.1.1.3.
For privacy reason, the Application Layer IDs and Layer-2 IDs may change as described in clause 5.6.1.1 and clause 6.3.3.2 during the lifetime of the PC5 unicast link and, if so, shall be updated in the Unicast Link Profile accordingly. The UE uses PC5 Link Identifier to indicate the PC5 unicast link to V2X Application layer, therefore V2X Application layer identifies the corresponding PC5 unicast link even if there are more than one unicast link associated with one V2X service type (e.g. the UE establishes multiple unicast links with multiple UEs for a same V2X service type).
The Unicast Link Profile shall be updated accordingly after a Layer-2 link modification for an established PC5 unicast link as specified in clause 6.3.3.4 or Layer-2 link identifier update as specified in clause 6.3.3.2.
Upon receiving an indication from the AS layer that the PC5-RRC connection was released due to RLF, the V2X layer in the UE locally releases the PC5 unicast link associated with this PC5-RRC connection. The AS layer uses PC5 Link Identifier to indicate to the V2X layer the PC5 unicast link whose PC5-RRC connection was released.
When the PC5 unicast link has been released as specified in clause 6.3.3.3, the V2X layer of each UE for the PC5 unicast link informs the AS layer that the PC5 unicast link has been released. The V2X layer uses PC5 Link Identifier to indicate the released unicast link.
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5.2.1.5  IP address allocationWord‑p. 23

For unicast mode of V2X communication over PC5 reference point, the following mechanism for IP address/prefix allocation may be used:
  1. IPv6 Stateless Address auto configuration specified in RFC 4862 for assignment of IPv6 prefix, with one of the two UEs acting as IPv6 default router.
  2. IPv6 link-local addresses as defined in RFC 4862 are formed by UEs locally. The IPv6 link-local addresses are exchanged during the establishment of a secure layer-2 link over PC5 reference point as described in clause 6.3.3.1. The UEs shall disable duplicate address detection after the layer-2 link is established.
For broadcast and groupcast modes of V2X communication over PC5 reference point, the following source IP address management applies:
  • The UE 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 this IP address for V2X communication over PC5 reference point without sending Neighbour Solicitation and Neighbour Advertisement message for Duplicate Address Detection.
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5.2.2  V2X communication over Uu reference pointWord‑p. 23

5.2.2.1  V2X communication via unicastWord‑p. 23

The V2X communication via unicast over the Uu reference point supports non-roaming and roaming operations.
For transport of V2X messages over Uu reference point:
  • the mechanisms defined in TS 23.501 and TS 23.502 can be used to establish the suitable PDU Sessions, and V2X messages are routed towards V2X Application Server or towards UEs with existing unicast routing.

5.2.3  V2X communication over PC5 or Uu reference pointWord‑p. 24

5.2.3.1  GeneralWord‑p. 24

V2X communication over PC5 reference point may use different protocols and formats than V2X communication over Uu reference point.
For a V2X service type that can use PC5 reference points or Uu reference point for the transmission of the same V2X messages, the following additional consideration apply for transport of V2X messages over Uu reference point:
  • for transport of non-IP based V2X messages from the application:
    • IP encapsulation (i.e. IP PDU Session type) or Unstructured PDU Session type is used.
    • The UE determines which method between IP encapsulation and Unstructured PDU Session type is used for non-IP based V2X messages based on the UE configuration as described in clause 5.1.3.1. If no such configuration is available, UE can use the method based on the UE implementation.
  • when IP PDU Session type is used for transport of IP based or non-IP based V2X messages:
    • V2X messages are transported over UDP or TCP:
      • for non-IP based V2X messages from the application, UE may learn from V2X Application Server or UE may be configured explicitly about a transport layer protocol needs to be used or no restriction imposed by configuration.
      • for IP based V2X messages from the application, UE uses the transport layer protocol set by the upper layer.
    • the UE sends a V2X message to a V2X Application Server address. The destined V2X Application Server address is derived from the V2X service type and the UE configuration as described in clause 5.1.3.1, and the V2X Application Server receives the V2X message in a UDP/IP packet or a TCP/IP packet on a V2X Application Server address.
  • when Unstructured PDU Session type is used for transport of non-IP based V2X messages:
Latency reduction for V2X message transfer via unicast may be achieved by using various mechanisms, including via e.g., edge computing defined in clauses 5.6.7 and 5.13 of TS 23.501, where the V2X Application Server acts as an Application Function.
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5.3  V2X Application Server discoveryWord‑p. 24

5.3.1  GeneralWord‑p. 24

A UE needs to discover the V2X Application Server(s), when V2X communication over Uu operation mode is used. The V2X Application Server address information may be configured on the UE or provisioned over N1 reference point, as specified in clause 5.1.3.1.
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.
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5.3.2  Multiple V2X Application Server and Localized V2X Application Server discovery and routingWord‑p. 25

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 5.1.3.1 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 UPF is responsible for routing the traffic to the appropriate local V2X Application Servers based on Anycast address.
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