5 High level functionality and features
23.2873GPPArchitecture enhancements for 5G System (5GS) to support Vehicle-to-Everything (V2X) servicesRelease 17TS
5.1 Authorization and Provisioning for V2X communications
5.1.1 General
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 clauses 5.1.2.1 and 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 [7].
– 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 [16].
5.1.2 Authorization and Provisioning for V2X communications over PC5 reference point
5.1.2.1 Policy/Parameter provisioning
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.
NOTE 1: In this specification, {When the UE is "served by E-UTRA" or "served by NR"} and {When the UE is "not served by E-UTRA" and "not served by NR"} are relevant to 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 [14] and TS 38.331 [15]. 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.
NOTE 2: Whether a frequency band is "operator managed" or "non-operator managed" in a given Geographical Area is defined by local regulations.
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 [9] for further information);
– for NR PC5, to the corresponding NR Tx Profiles for broadcast and groupcast (see TS 38.300 [11] and TS 38.331 [15] for further information);
– for NR PC5, to the corresponding NR Tx Profiles for transmitting and receiving initial signalling to establish unicast connection (see TS 38.300 [11] and TS 38.331 [15] for further information).
NOTE 3: The policy/parameter ensures that the UEs of prior Release do not use V2X service types with a mapping of NR Tx Profile indicating the transmission mechanism or format specified in this Release.
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 clause 4.4.1.1.2, item 3) of TS 23.285 [8] 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.
NOTE 4: The same default Destination Layer-2 ID for unicast initial signalling can be mapped to more than one V2X service types. In the case where different V2X services are mapped to distinct default Destination Layer-2 IDs, when the UE intends to establish a single unicast link that can be used for more than one V2X service types, the UE can select any of the default Destination Layer-2 IDs to use for the initial signalling.
– 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 [15]), 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 broadcast, groupcast and initial signalling to establish unicast connection, PC5 DRX configurations (see TS 38.331 [15]), e.g. the mapping of PC5 QoS profile(s) to PC5 DRX cycle(s), default PC5 DRX configuration, when the UE is "not served by E-UTRA" and "not served by NR".
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.
5.1.2.2 Principles for applying parameters for V2X communications over PC5 reference point
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 [9] and TS 36.304 [10] (if LTE based PC5 is selected for the V2X communication) or as defined in TS 38.300 [11] and TS 38.304 [12] (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 [13]. 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 [14] or TS 38.331 [15] 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.
NOTE 1: 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 NG-RAN cell, when provisioned in the UE, even if the UE’s serving cell offers normal service and the SIBs for NR sidelink communication or V2X sidelink communication defined in TS 38.331 [15] 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 2: When cross-carrier operation is supported, according to TS 36.331 [14] or TS 38.331 [15], 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 NR or E-UTRA" in this case.
NOTE 3: 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 and NR.
NOTE 4: 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.
5.1.3 Authorization and provisioning for V2X communications over Uu reference point
5.1.3.1 Policy/Parameter provisioning
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).
NOTE: Above listed information elements are optional and used by UE as UE Local Configuration specified in TS 23.503 [16].
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.
5.2 V2X communication
5.2.1 V2X communication over PC5 reference point
5.2.1.1 General
For V2X communication, two types of PC5 reference points exist: the LTE based PC5 reference point as defined in TS 23.285 [8], 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 the Tx Profile 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 [8]. When NR based PC5 reference point is selected, the QoS handling and procedures are defined in clauses 5.4.1 and 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.
NOTE: The emergency session via IMS setup is based on appropriate regional/national regulatory requirements and operator policies as defined in TS 23.501 [6].
The security for V2X communication over PC5 reference point is provided with mechanisms defined in TS 33.536 [26]. 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.
5.2.1.2 Broadcast mode communication over PC5 reference point
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 [8].
For NR based PC5 reference point, the broadcast mode also supports enhanced QoS handling as defined in clause 5.4.1.
5.2.1.3 Groupcast mode communication over PC5 reference point
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 [11].
NOTE: It is assumed that the V2X application layer provides accurate and up-to-date information on the group size and the member ID.
QoS handling for groupcast mode communication is defined in clause 5.4.1.
5.2.1.4 Unicast mode communication over PC5 reference point
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.
Figure 5.2.1.4-1: Example of PC5 Unicast Links
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.
NOTE 1: An Application Layer ID can change in time as described in clauses 5.6.1.1 and 6.3.3.2, due to privacy. This does not cause a re-establishment of a PC5 unicast link. The UE triggers a Link Identifier Update procedure as specified in clause 6.3.3.2.
– 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.
NOTE 2: A source UE is not required to know whether different target Application Layer IDs over different PC5 unicast links belong to the same target UE.
– 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 clauses 5.6.1.1 and 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.
5.2.1.5 IP address allocation
For unicast mode of V2X communication over PC5 reference point, the following mechanism for IP address/prefix allocation may be used:
a) IPv6 Stateless Address auto configuration specified in RFC 4862 [21] for assignment of IPv6 prefix, with one of the two UEs acting as IPv6 default router.
NOTE 1: Which UE acts as an IPv6 default router is negotiated during secure layer-2 link establishment by exchanging the IP Address Configuration as described in clause 6.3.3.1.
b) IPv6 link-local addresses as defined in RFC 4862 [21] 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 [17]. 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.
NOTE 2: The destination IP address management for broadcast and groupcast modes of V2X communication over PC5 reference point is left to UE implementation.
5.2.2 V2X communication over Uu reference point
5.2.2.1 V2X communication via unicast
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 [6] and TS 23.502 [7] 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 point
5.2.3.1 General
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:
– V2X messages are transported to the V2X Application Server as defined in clause 5.6.10.3 of TS 23.501 [6].
Latency reduction for V2X message transfer via unicast may be achieved by using various mechanisms, including via e.g., edge computing defined in clauses5.6.7 and 5.13 of TS 23.501 [6], where the V2X Application Server acts as an Application Function.
5.3 V2X Application Server discovery
5.3.1 General
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.
NOTE: When the V2X Application Server is notified by SMF indicating the DNAI change, as specified in clause 5.6.7 of TS 23.501 [6], the application layer can trigger the UE to perform DNS to resolve the address(es) of the V2X Application Server.
5.3.2 Multiple V2X Application Server and Localized V2X Application Server discovery and routing
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.
5.4 QoS handling for V2X communication
5.4.1 QoS handling for V2X communication over PC5 reference point
5.4.1.1 QoS model
5.4.1.1.1 General overview
For LTE based PC5, the QoS handling is defined in TS 23.285 [8], based on ProSe Per-Packet Priority (PPPP) and ProSe Per-Packet Reliability (PPPR).
For NR based PC5, a QoS model similar to that defined in TS 23.501 [6] for Uu reference point is used, i.e. based on 5QIs, with additional parameter of Range as described in clauses 5.4.2, 5.4.3 and 5.4.4. For the V2X communication over NR based PC5 reference point, a PC5 QoS Flow is associated with a PC5 QoS Rule and the PC5 QoS parameters as defined in clause 5.4.2. A set of standardized PC5 5QIs (PQI) are defined in clause 5.4.4. The UE may be configured with a set of default PC5 QoS parameters to use for the V2X service types, as defined in clause 5.1.2.1. For NR based unicast, groupcast and broadcast mode communication over PC5, Per-flow QoS model for PC5 QoS management shall be applied. Figure 5.4.1.1.1-1 illustrates an example mapping of Per-flow QoS model for NR PC5. Details of PC5 QoS Rules and PFI related operations are described in clauses 5.4.1.1.2 and 5.4.1.1.3.
Figure 5.4.1.1.1-1: Per-Flow PC5 QoS Model for NR PC5
The following principles apply when the V2X communication is carried over PC5 reference point:
– Application layer may set the V2X Application Requirements for the V2X communication, using either TS 23.285 [8] defined PPPP and PPPR model or the PQI and Range model as described in clause 5.4.4. Depending on the type of PC5 reference point, i.e. LTE based or NR based, selected for the transmission, the UE may map the application layer provided V2X Application Requirements to the suitable QoS parameters to be passed to the lower layer. The mapping between the two QoS models is defined in clause 5.4.2. For V2X communication over NR based PC5, different V2X packets may require different QoS treatments. In that case, the V2X packets shall be sent from the V2X layer to the Access Stratum layer within PC5 QoS Flows identified by different PFIs.
– When groupcast mode of V2X communication over NR based PC5 is used, a Range parameter is associated with the QoS parameters for the V2X communication. The Range may be provided by V2X application layer or use a default value mapped from the V2X service type based on configuration as defined in clause 5.1.2.1. The Range indicates the minimum distance that the QoS parameters need to be fulfilled. The Range parameter is passed to AS layer together with the QoS parameters for dynamic control.
– NR based PC5 supports three communication modes, i.e. broadcast, groupcast, and unicast. The QoS handling of these different modes are described in clauses 5.4.1.2 to 5.4.1.4.
– The UE may handle traffic using broadcast, groupcast, and unicast mode communication by taking all their priorities, e.g. indicated by PQIs, into account as described in clause 5.4.3.3.
– For broadcast and groupcast modes of V2X communication over NR based PC5, standardized PQI values are applied by the UE, as there is no signalling over PC5 reference point for these cases.
– When network scheduled operation mode is used, the UE-PC5-AMBR for NR based PC5 applies to all types of communication modes, and is used by NG-RAN for capping the UE’s NR based PC5 transmission in the resources management. The UE-PC5-AMBR shall be set to the sum of the aggregate maximum bit rate of all types of communication (i.e. unicast, groupcast and broadcast modes) over PC5 reference point.
5.4.1.1.2 Deriving PC5 QoS parameters and assigning PFI for PC5 QoS Flow
The following description applies to for both network scheduled operation mode and UE autonomous resources selection mode.
When a service data packet or request from the V2X application layer is received, the UE determines if there is any existing PC5 QoS Flow matching the service data packet or request, i.e. based on the PC5 QoS Rules for the existing PC5 QoS Flow(s).
If there is no PC5 QoS Flow matching the service data packet or request, the UE derives PC5 QoS parameters defined in clause 5.4.2 as below:
– If the application layer provides the V2X Application Requirements for the V2X service type (e.g. priority requirement, reliability requirement, delay requirement, range requirement), the V2X layer determines the PC5 QoS parameters based on the V2X Application Requirements;
– Otherwise, the V2X layer determines the PC5 QoS parameters based on the mapping of the V2X service type to PC5 QoS parameters defined in clause 5.1.2.1.
NOTE 1: Details of V2X Application Requirements for the V2X service type is up to implementation and out of scope of this specification.
After deriving the PC5 QoS parameters, the UE performs the following:
– If there is no existing PC5 QoS Flow that fulfils the derived PC5 QoS parameters:
– The UE creates a new PC5 QoS Flow for the derived PC5 QoS parameters; and
– The UE then assigns a PFI and derives PC5 QoS Rule for this PC5 QoS Flow.
– Otherwise, the UE updates the PC5 Packet Filter Set in the PC5 QoS Rule for such PC5 QoS Flow.
NOTE 2: It is expected that the application layer is capable of differentiating traffic from different V2X services that is transported within the same PC5 QoS Flow.
For V2X communication over NR PC5 reference point, the PC5 QoS Flow is the finest granularity of QoS differentiation in the same destination identified by Destination Layer-2 ID. User Plane traffic with the same PFI receives the same traffic forwarding treatment (e.g. scheduling, admission threshold). The PFI is unique within a same destination.
5.4.1.1.3 Handling of PC5 QoS Flows based on PC5 QoS Rules
For each communication mode (e.g. broadcast, groupcast, unicast), the UE maintains the PC5 QoS Context and PC5 QoS Rule(s) for each PC5 QoS Flow identified by a PC5 QoS Flow Identifier (PFI) per destination identified by Destination Layer-2 ID.
The following information is maintained in the V2X layer of the UE:
– A PC5 QoS Context includes the following information:
– PFI;
– PC5 QoS parameters (i.e. PQI and conditionally other parameters such as MFBR/GFBR, Range, etc.) as defined in clause 5.4.2; and
– the V2X service type(s).
– One or more PC5 QoS Rule(s). Each PC5 QoS Rule contains the following information:
– PFI;
– a PC5 Packet Filter Set as defined in clause 5.4.1.1.4; and
– a precedence value. The precedence value determines the order in which the PC5 QoS Rules are evaluated. The PC5 QoS Rule with lower precedence value is evaluated before those with the higher precedence values.
NOTE: How to set the precedence value is up to UE implementation.
When the UE assigns a new PFI for V2X service type, the UE stores it with the corresponding PC5 QoS Context and PC5 QoS Rule(s) for the destination. When the UE releases the PFI, the UE removes the corresponding PC5 QoS Context and PC5 QoS Rule(s) for the destination. For unicast, the Unicast Link Profile defined in clause 5.2.1.4 contains additional information mapped from PFI for unicast operation.
The V2X layer provides information for PC5 QoS operations per destination (e.g. identified by Destination Layer-2 ID) to AS layer for Per-flow QoS model operations as below:
1) To add a new PC5 QoS Flow or to modify any existing PC5 QoS Flow, the V2X layer provides the following information for the PC5 QoS Flow to AS layer.
– the PFI;
– the corresponding PC5 QoS parameters; and
– source/destination Layer-2 IDs for broadcast and groupcast mode communication, or the PC5 Link Identifier for unicast.
2) To remove any existing PC5 QoS Flow, the V2X layer provides the following information for the PC5 QoS Flow to AS layer.
– the PFI; and
– source/destination Layer-2 IDs for broadcast and groupcast mode communication, or the PC5 Link Identifier for unicast.
In addition, the V2X layer also provides the communication mode (e.g. broadcast, groupcast, unicast) and radio frequencies to the AS layer for the PC5 operation. The radio frequencies are determined based on the V2X service type. The V2X layer ensures that V2X service types associated with different radio frequencies are classified into distinct PC5 QoS Flows.
Figure 5.4.1.1.3-1 illustrated an example of the classification and marking of user plane traffic using the PC5 QoS Rules, and the mapping of PC5 QoS Flows to radio resources at access stratum layer.
Figure 5.4.1.1.3-1: Handling of PC5 QoS Flows based on PC5 QoS Rules
As illustrated in Figure 5.4.1.1.3-1, for a given pair of source and destination Layer-2 IDs, there can be multiple radio bearers, each corresponding to a different PC5 QoS level. The AS layer can determine the mapping of multiple PC5 QoS Flows to the same radio bearer based on the information provided. For broadcast and groupcast mode communication, the L2 link goes to all UEs in proximity identified by the destination Layer-2 ID.
5.4.1.1.4 PC5 Packet Filter Set
PC5 Packet Filter Set supports two types of packet filters, i.e. the V2X IP Packet Filter Set and the V2X Packet Filter Set. A PC5 QoS Rule contains either the V2X IP Packet Filter Set or the V2X Packet Filter Set.
The V2X IP Packet Filter Set has the same format as the IP Packet Filter Set defined in clause 5.7.6.2 of TS 23.501 [6].
The V2X Packet Filter Set shall support Packet Filters based on at least any combination of:
– V2X service type;
– Source/Destination Layer-2 ID;
– Application Layer ID (e.g. Station ID).
5.4.1.2 QoS handling for broadcast mode V2X communication over PC5 reference point
When PC5 broadcast is used for the transmission of V2X service data, the following principles are followed for both network scheduled operation mode and UE autonomous resources selection mode:
– PC5 QoS parameters defined in clause 5.4.2 are applied.
– The V2X layer determines the PC5 QoS parameters based on the V2X Application Requirements (if available) or the mapping of the V2X service type to PC5 QoS parameters, as defined in clause 5.4.1.1.2.
– The V2X layer assigns a PC5 QoS Flow Identifier (PFI) and derives the PC5 QoS Rule for the PC5 QoS Flow, and associates the PC5 QoS parameters to the PFI.
– The V2X layer provides the PFI and the associated PC5 QoS parameters to AS layer for Per-flow QoS model operations.
– The V2X layer determines the PFI based on the PC5 QoS Rule for the V2X service data from the V2X application layer, and passes the V2X service data along with PFI to the AS layer for transmission.
When the autonomous resources selection mode is used, following additional principle applies:
– The UE can use the PC5 QoS parameters for PC5 QoS handling.
When the network scheduled operation mode for NR PC5 is used, the following additional principles apply:
– The UE provides PC5 QoS information (related to PC5 QoS parameters), Destination Layer-2 ID(s) and communication mode to the NG-RAN and NG-RAN may provide AS layer configurations and configure the mapping of PC5 QoS flow to radio bearer as defined in TS 38.331 [15] and TS 36.331 [14].
– The UE provides PC5 QoS information (related to PC5 QoS parameters) and Destination information (related to Destination Layer-2 ID(s)) to the NG-RAN for resource request as defined in TS 38.331 [15] and TS 36.331 [14].
– The NG-RAN authorizes the UE-provided PC5 QoS information based on PCF-provisioned PC5 QoS parameters as defined in clause 6.5.7.
– The NG-RAN uses UE-PC5-AMBR for capping the UE PC5 transmission in the resources management.
5.4.1.3 QoS handling for groupcast mode V2X communication over PC5 reference point
The QoS handling described in clause 5.4.1.2 is applied.
5.4.1.4 QoS handling for unicast mode V2X communication over PC5 reference point
The QoS handling described in clause 5.4.1.2 is applied with the following additions:
– The PFI and PC5 QoS parameters are negotiated during the Layer-2 link establishment procedure, as described in clause 6.3.3.1, or during the Layer-2 link modification procedure, as described in clause 6.3.3.4.
When the network scheduled operation mode for NR PC5 is used, following additional principle applies:
– NG-RAN uses the PC5 LINK-AMBR for capping the UE PC5 unicast link transmission in the resources management.
5.4.2 PC5 QoS parameters
5.4.2.1 PQI
A PQI is a special 5QI, as defined in clause 5.7.2.1 of TS 23.501 [6], and is used as a reference to PC5 QoS characteristics defined in clause 5.4.3, i.e. parameters that control QoS forwarding treatment for the packets over PC5 reference point.
Standardized PQI values have one-to-one mapping to a standardized combination of PC5 QoS characteristics as specified in Table 5.4.4-1.
5.4.2.2 PC5 Flow Bit Rates
For GBR QoS Flows only, the following additional PC5 QoS parameters exist:
– Guaranteed Flow Bit Rate (GFBR);
– Maximum Flow Bit Rate (MFBR).
The GFBR and MFBR as defined in clause 5.7.2.5 of TS 23.501 [6] are used for bit rate control on PC5 reference point over the Averaging Time Window. For PC5 communication, the same GFBR and MFBR are used for both directions.
5.4.2.3 PC5 Link Aggregated Bit Rates
A PC5 unicast link is associated with the following aggregate rate limit QoS parameter:
– per link Aggregate Maximum Bit Rate (PC5 LINK-AMBR).
The PC5 LINK-AMBR limits the aggregate bit rate that can be expected to be provided across all Non-GBR QoS Flows with a peer UE over PC5 unicast link. The PC5 LINK-AMBR is measured over an AMBR averaging window which is a standardized value. The PC5 LINK-AMBR is not applicable to GBR QoS Flows. PC5 LINK-AMBR is applied to one PC5 unicast link, which means aggregate bit rate of one PC5 unicast link should not exceed PC5 LINK-AMBR.
NOTE: The AMBR averaging window is only applied to PC5 LINK-AMBR measurement.
5.4.2.4 Range
The Range value indicates the applicability of the PC5 QoS parameters in PC5 communication, i.e. when the receiving UEs are not within the Range specified distance from the transmitting UE, the communication is best effort. Lower layer (PHY/MAC layer) may use the Range to determine the corresponding packet handling, e.g. HARQ as defined in TS 38.300 [11], to achieve the QoS guarantee indicated by PC5 QoS parameters.
Range is in the unit of meters. The UE is configured with the maximum Range value it can use for a particular V2X service. A V2X service may request a different range value, and the V2X layer ensures that it does not exceed the maximum Range value.
Range is only used for groupcast mode communication over PC5 reference point.
5.4.2.5 Default Values
A UE may be configured with default values for PC5 QoS parameters for a particular V2X service type as specified in clause 5.1.2.1. The default value will be used if the corresponding PC5 QoS parameter is not provided by upper layer.
5.4.3 PC5 QoS characteristics
5.4.3.1 General
This clause specifies the PC5 QoS characteristics associated with PQI. The following characteristics defined in TS 23.501 [6] applies, with differences explained in following clauses:
1 Resource Type (GBR, Delay critical GBR or Non-GBR);
2 Priority Level;
3 Packet Delay Budget;
4 Packet Error Rate;
5 Averaging window (for GBR and Delay-critical GBR resource type only);
6 Maximum Data Burst Volume (for Delay-critical GBR resource type only).
Standardized or pre-configured PC5 QoS characteristics, are indicated through the PQI value.
V2X layer may derive non-standardized PC5 QoS characteristics by overriding the standardized or pre-configured value of PC5 QoS characteristics based on V2X Application Requirements from V2X application layer and provide the whole set of non-standardized PC5 QoS characteristics to AS layer.
NOTE: Non-standardized PC5 QoS characteristics only applies to UE autonomous resources selection mode.
5.4.3.2 Resource Type
Resource Type is defined in clause 5.7.3.2 of TS 23.501 [6].
5.4.3.3 Priority Level
The Priority Level for NR PC5 has the same format and meaning as the Priority value of the ProSe Per-Packet Priority (PPPP) for LTE PC5 defined in TS 23.285 [8]. For LTE PC5, the PPPP value also reflects the latency requirement and the PDB derivation is according to TS 23.285 [8], i.e. the low PDB is mapped to the high priority PPPP value. On the other hand, for NR PC5, the PDB is derived from the PQI table as defined in clause 5.4.4.
NOTE: Using the same format for Priority Level and PPPP provides better backward compatibility.
The Priority Level shall be used to different treatment of V2X service data across different modes of communication, i.e. broadcast, groupcast, and unicast. In the case when all QoS requirements cannot be fulfilled for all the PC5 service data associated with that PC5 reference point, the Priority Level shall be used to select for which PC5 service data the QoS requirements are prioritized such that a PC5 service data packet with Priority Level value N is prioritized over a PC5 service data packet with higher Priority Level values, i.e. N+1, N+2, etc. (lower number meaning higher priority).
5.4.3.4 Packet Delay Budget
The Packet Delay Budget (PDB) associated with the PQI is equivalent to the PDB defined in clause 5.7.3.4 of TS 23.501 [6]. However, when used for PC5 communication, the PDB associated with the PQI defines an upper bound for the time that a packet may be delayed between sending UE and receiving UE(s) over PC5 reference point.
5.4.3.5 Packet Error Rate
The Packet Error Rate (PER) is defined in clause 5.7.3.5 of TS 23.501 [6].
5.4.3.6 Averaging Window
The Averaging Window is defined in clause 5.7.3.6 of TS 23.501 [6].
5.4.3.7 Maximum Data Burst Volume
Maximum Data Burst Volume (MDBV) is defined in clause 5.7.3.7 of TS 23.501 [6].
MDBV denotes the largest amount of data that the PC5 reference point is required to serve within a period of PDB of the PQI.
The MDBV may also be indicated by upper layer, it shall be used instead of the default value.
5.4.4 Standardized PQI to QoS characteristics mapping
The one-to-one mapping of standardized PQI values to PC5 QoS characteristics is specified in table 5.4.4-1.
Table 5.4.4-1: Standardized PQI to QoS characteristics mapping
|
PQI Value |
Resource Type |
Default Priority Level |
Packet Delay Budget |
Packet Error Rate |
Default Maximum Data Burst Volume |
Default Averaging Window |
Example Services |
|
21 |
GBR |
3 |
20 ms |
10-4 |
N/A |
2000 ms |
Platooning between UEs – Higher degree of automation; Platooning between UE and RSU – Higher degree of automation |
|
22 |
(NOTE 1) |
4 |
50 ms |
10-2 |
N/A |
2000 ms |
Sensor sharing – higher degree of automation |
|
23 |
3 |
100 ms |
10-4 |
N/A |
2000 ms |
Information sharing for automated driving – between UEs or UE and RSU – higher degree of automation |
|
|
55 |
Non-GBR |
3 |
10 ms |
10-4 |
N/A |
N/A |
Cooperative lane change – higher degree of automation |
|
56 |
6 |
20 ms |
10-1 |
N/A |
N/A |
Platooning informative exchange – low degree of automation; Platooning – information sharing with RSU |
|
|
57 |
5 |
25 ms |
10-1 |
N/A |
N/A |
Cooperative lane change – lower degree of automation |
|
|
58 |
4 |
100 ms |
10-2 |
N/A |
N/A |
Sensor information sharing – lower degree of automation |
|
|
59 |
6 |
500 ms |
10-1 |
N/A |
N/A |
Platooning – reporting to an RSU |
|
|
90 |
Delay Critical GBR |
3 |
10 ms |
10-4 |
2000 bytes |
2000 ms |
Cooperative collision avoidance; Sensor sharing – Higher degree of automation; Video sharing – higher degree of automation |
|
91 |
(NOTE 1) |
2 |
3 ms |
10-5 |
2000 bytes |
2000 ms |
Emergency trajectory alignment; Sensor sharing – Higher degree of automation |
|
NOTE 1: GBR and Delay Critical GBR PQIs can only be used for unicast PC5 communications. |
|||||||
NOTE 1: For Standardized PQI to QoS characteristics mapping, the table will be extended/updated to support service requirements for other identified V2X services.
NOTE 2: The PQIs may be used for other services than V2X.
NOTE 3: A PQI may be used together with an application indicated priority, which overrides the Default Priority Level of the PQI.
5.4.5 QoS handling for V2X communication over Uu reference point
5.4.5.1 General
The V2X service data can be delivered via Non-GBR QoS Flow as well as GBR QoS Flow (i.e. using the GBR resource type or the Delay-critical GBR resource type) as specified in TS 23.501 [6].
5.4.5.2 Notification on QoS Sustainability Analytics to the V2X Application Server
5.4.5.2.1 General
A V2X Application Server may request notifications on QoS Sustainability Analytics for an indicated geographic area and time interval in order to adjust the application behaviour in advance with potential QoS change. The V2X Application Server may also request past statistical information for the purposes of adjustment of the application, how V2X Application Server makes use of such data is outside of 3GPP scope. Clause 6.4.1 describes the procedure for such notification from 5GS.
5.4.5.2.2 Functional description
The potential QoS change to assist application adjustment is based on the notification of QoS Sustainability Analytics defined in clause 6.9 of TS 23.288 [20]. The V2X Application Server acting as an Application Function communicates with the NEF which corresponds to the NF consumer in clause 6.9.4 of TS 23.288 [20].
The V2X Application Server can either subscribe to notifications from the NEF (i.e., a Subscribe-Notify model) or request a single notification from the NEF (i.e. a Request-Response model). The V2X Application Server request contains the following parameters:
– Analytics ID = "QoS Sustainability";
– Target of Analytics Reporting: "any UE";
– Analytics Filter Information:
– Optional maximum number of objects;
– QoS requirements:
– 5QI (standardized or pre-configured), and applicable additional QoS parameters and the corresponding values (conditional, i.e., it is needed for GBR 5QIs to know the GFBR); or
– the QoS Characteristics attributes including Resource Type, PDB and PER and their values;
NOTE: The V2X Application Server could provide the 5QIs as input based on SLA with the operator which authorizes the V2X Application Server to use certain 5QIs and to use the QoS Sustainability Analytics only for them.
– Location information (the details are specified in clause 6.9.1 of TS 23.288 [20]);
– S-NSSAI (optional, if available in the V2X Application Server).
– Analytics target period (the details are specified in clause 6.9.1 of TS 23.288 [20]);
– Reporting Threshold(s) (the details are specified in clause 6.9.1 of TS 23.288 [20]);
– In a subscription, the Notification Correlation Id and the Notification Target Address.
5.4.5.3 QoS Change based on Extended NG-RAN Notification to support Alternative Service Requirements
To support V2X applications that can operate with different configurations (e.g. different bitrates or delay requirements), the V2X Application Server (V2X AS), acting as the Application Function, can provide, in addition to the requested level of service requirements, Alternative Service Requirements to the 5GS. This enables the 5GS to act on the Alternative Service Requirements and apply them for the extended NG-RAN notification, as described in TS 23.501 [6] and TS 23.503 [16].
The V2X AS can use the related procedures specified in clause 4.15.6.6 of TS 23.502 [7] to influence the QoS provided to the V2X service. If so, the V2X AS includes Alternative Service Requirements as specified in clause 6.1.3.22 of TS 23.503 [16] when providing service information to the PCF.
The QoS change based on extended NG-RAN notification operates within the 5GS QoS model as specified in TS 23.501 [6] and TS 23.503 [16].
5.5 Subscription to V2X services
The user’s profile in the UDM 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 UDM, and revoke the user’s permission to use V2X services.
The following subscription information is defined for V2X services:
a) 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.
b) UE-PC5-AMBR per PC5 RAT, including UE-PC5-AMBR for LTE PC5 and UE-PC5-AMBR for NR PC5.
c) 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 communications over PC5 reference point.
d) PC5 QoS parameters as defined in clause 5.4.2 used by NG-RAN.
The UDM may retrieve a) and b) from the UDR. a) and b) are provided by the UDM to the AMF during UE Registration procedure as defined in clause 4.2.2.2 of TS 23.502 [7] using Nudm_SDM service for Subscription data type "V2X Subscription data" and the AMF provides a) and b) to NG-RAN as part of the UE context information.
c) and d) are provided by the UDR to the PCF during the UE Policy Association Establishment procedure as defined in clause 4.16.11 of TS 23.502 [7] and UE Policy Association Modification procedure as defined in clause 4.16.12 of TS 23.502 [7] using Nudr service for Data Set "Policy Data" and Data Subset "Policy Set Entry". If the subscription information provided to the PCF from UDR is changed (e.g., PC5 QoS related parameters, the list of PLMNs where the UE is authorized to perform V2X communication over PC5 reference point), the PCF initiates the UE Configuration Update procedure as specified in clause 6.2.2.
5.6 Identifiers
5.6.1 Identifiers for V2X communication over PC5 reference point
5.6.1.1 General
Each UE has one or more Layer-2 IDs for V2X communication over PC5 reference point, consisting of:
– Source Layer-2 ID(s); and
– Destination Layer-2 ID(s).
Source and destination Layer-2 IDs are included in layer-2 frames sent on the layer-2 link of the PC5 reference point identifying the layer-2 source and destination of these frames. Source Layer-2 IDs are always self-assigned by the UE originating the corresponding layer-2 frames.
The selection of the source and destination Layer-2 ID(s) by a UE depends on the communication mode of V2X communication over PC5 reference point for this layer-2 link, as described in clauses 5.6.1.2, 5.6.1.3, and 5.6.1.4. The source Layer-2 IDs may differ between different communication modes.
When IP-based V2X communication is supported for broadcast and groupcast modes of V2X communication over PC5 reference point, the source IP address is allocated as described in clause 5.2.1.5.
If the UE has an active V2X application that requires privacy support in the current Geographical Area, as identified by configuration described in clause 5.1.2.1, 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 shall be changed over time and shall be randomized. For IP-based V2X communication over PC5 reference point, the source IP address shall also be changed over time and shall be randomized. The change of the identifiers of a source UE must be synchronized across layers used for PC5, (e.g. when the Application Layer ID changes, the source Layer-2 ID and the source IP address need to be changed).
5.6.1.2 Identifiers for broadcast mode V2X communication over PC5 reference point
For broadcast mode of V2X communication over PC5 reference point, the UE is configured with the destination Layer-2 ID(s) to be used for V2X services. The destination Layer-2 ID for a V2X communication is selected based on the configuration as described in clause 5.1.2.1.
The UE self-selects a source Layer-2 ID. The UE may use different source Layer-2 IDs for different types of PC5 reference points, i.e. LTE based PC5 and NR based PC5.
5.6.1.3 Identifiers for groupcast mode V2X communication over PC5 reference point
For groupcast mode of V2X communication over PC5 reference point, the V2X application layer may provide group identifier information. When the group identifier information is provided by the V2X application layer, the UE converts the provided group identifier into a destination Layer-2 ID. When the group identifier information is not provided by the V2X application layer, the UE determines the destination Layer-2 ID based on configuration of the mapping between V2X service type and Layer-2 ID, as specified in clause 5.1.2.1.
NOTE: The mechanism for converting the V2X application layer provided group identifier to the destination Layer-2 ID is defined in Stage 3.
The UE self-selects a source Layer-2 ID.
5.6.1.4 Identifiers for unicast mode V2X communication over PC5 reference point
For unicast mode of V2X communication over PC5 reference point, the destination Layer-2 ID used depends on the communication peer. The Layer-2 ID of the communication peer, identified by the Application Layer ID, may be discovered during the establishment of the PC5 unicast link, or known to the UE via prior V2X communications, e.g. existing or prior unicast link to the same Application Layer ID, or obtained from application layer service announcements. The initial signalling for the establishment of the PC5 unicast link may use the known Layer-2 ID of the communication peer, or a default destination Layer-2 ID associated with the V2X service type configured for PC5 unicast link establishment, as specified in clause 5.1.2.1. During the PC5 unicast link establishment procedure, Layer-2 IDs are exchanged, and should be used for future communication between the two UEs, as specified in clause 6.3.3.1.
The Application Layer ID is associated with one or more V2X applications within the UE. If UE has more than one Application Layer IDs, each Application Layer ID of the same UE may be seen as different UE’s Application Layer ID from the peer UE’s perspective.
The UE maintains a mapping between the Application Layer IDs and the source Layer-2 IDs used for the PC5 unicast links, as the V2X application layer does not use the Layer-2 IDs. This allows the change of source Layer-2 ID without interrupting the V2X applications.
When Application Layer IDs change, the source Layer-2 ID(s) of the PC5 unicast link(s) shall be changed if the link(s) was used for V2X communication with the changed Application Layer IDs.
Based on privacy configuration as specified in clause 5.1.2.1, the update of the new identifiers of a source UE to the peer UE for the established unicast link may cause the peer UE to change its Layer-2 ID and optionally IP address/prefix if IP communication is used as defined in clause 6.3.3.2.
A UE may establish multiple PC5 unicast links with a peer UE and use the same or different source Layer-2 IDs for these PC5 unicast links.
5.7 Support for V2X communication for UEs in limited service state
For UE in limited service state, as defined in TS 23.122 [13], V2X communication is only allowed over PC5 reference point.
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 5.1.2.2 for V2X communication over PC5 reference point when the UE enters in limited service state in 5GS:
– because UE cannot find a suitable cell of the selected PLMN as described in TS 23.122 [13]; or
– as the result of receiving one of the following reject reasons defined in TS 23.122 [13]:
– a "PLMN not allowed" response to a registration request or;
– a "5GS services not allowed" response to a registration request or service request.
A UE in limited service state shall only use the radio resources and procedure available in CM-IDLE mode for V2X communication over PC5 reference point, for details see TS 36.300 [9] and TS 38.300 [11].
UEs shall not use V2X communication over PC5 reference point using the "operator-managed" radio resources, as specified in clause 5.1.2.1, 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 [13], 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 5.1.2.1, according to the principles defined in clause 5.1.2.2.
5.8 Interworking between EPS V2X and 5GS V2X
5.8.1 V2X Policy and parameter provisioning
When the UE is in 5GS or EPS, the UE shall use the valid V2X policy and parameters provisioned by the PCF in 5GC or by the V2X Control Function in EPC for V2X communication. The V2X related parameters for EPS defined in TS 23.285 [8] can be either provided by the PCF or by the V2X Control Function, while the V2X policy and parameters involving 5GS are provided by the PCF only. If the UE does not have valid V2X policy and parameters, the UE shall request the network to provision the V2X policy and parameters.
5.8.2 PC5 Operation
PC5 communication can be supported with proper UE configurations by taking into account e.g. regional regulations, deployments, and UE support for LTE PC5 and/or NR PC5 RATs.
V2X communication over NR PC5 reference point in network scheduled operation mode is supported in EPS (i.e. EN-DC architecture defined in TS 37.340 [25]) as defined in TS 23.285 [8] and TS 36.331 [14].
5.8.3 Mobility between EPS and 5GS over Uu
Interworking specified in clause 5.17 of TS 23.501 [6] and clause 4.11 of TS 23.502 [7] is applied to mobility between EPS and 5GS over Uu reference point with the following additions:
– For N26 based handover, V2X related data including the "V2X services authorized" indication per PC5 RAT, UE-PC5-AMBR per PC5 RAT, and PC5 QoS parameters are transferred between AMF and MME, and are included in Handover Request message sent to the target RAN node.
Any Unstructured type PDU Session established in 5GC based on the UE configuration as described in clause 5.1.3.1 is allowed to be transferred to EPC as non-IP PDN connection when non-IP PDN type is supported by UE and EPC as specified in clause 5.17.2.1 of TS 23.501 [6].
5.9 Support of QoS aware NR PC5 power efficiency for pedestrian UEs
For NR based unicast, groupcast and broadcast mode communication over PC5 reference point, PC5 DRX operations are supported to enable pedestrian UE power saving.
The V2X layer determines the respective V2X service types, and derives the corresponding PC5 QoS parameters based on either the mapping of V2X service types to PC5 QoS parameters, or the V2X Application Requirements for the V2X service type provided by the application layer. The V2X layer passes the PC5 QoS parameters and destination Layer-2 ID to the AS layer as specified in clauses 6.3.1, 6.3.2 and 6.3.3. When the V2X layer derives new PC5 QoS parameters for a destination Layer-2 ID that has been provided to the AS layer, i.e. due to changes of V2X service types or V2X Application Requirements, the V2X layer provides the new PC5 QoS parameters for the destination Layer-2 ID to the AS layer.
NOTE 1: For broadcast and groupcast, the AS layer needs PC5 QoS parameters as well to determine the PC5 DRX parameter values for reception operation over PC5 reference point. Therefore, the V2X layer determines the interested V2X service types and derives the PC5 QoS parameters based on its reception needs besides the transmission needs. How to derive the PC5 QoS parameters based on its reception needs (e.g. without establishing the PC5 QoS Flows) depends on UE implementation.
NOTE 2: More than one V2X service types can be related to the groupcast. In this case, the V2X application layer needs to provide all the V2X service types for the groupcast to the V2X layer.
For broadcast or groupcast, the V2X layer maintains a list of all V2X service types, i.e. activated V2X service types and/or V2X service types that the UE is interested for reception, for a given destination Layer-2 ID and determines the NR Tx Profile available to be mapped for the respective V2X service type based on the configuration described in clause 5.1.2.1. Whenever the list of the V2X service types for a given destination Layer-2 ID changes, the V2X layer updates the AS layer for the NR Tx Profiles information. The V2X layer determines whether and how to provide the NR Tx Profiles for the given destination Layer-2 ID to the AS layer as below:
– If all the V2X service types have mapped NR Tx Profiles, the V2X layer provides all the mapped NR Tx Profiles to the AS layer for the given destination Layer-2 ID, e.g. when providing other information such as the destination Layer-2 ID, PC5 QoS parameters;
– If any of the V2X service types does not have mapped NR Tx Profile, the V2X layer does not provide any NR Tx Profile to the AS layer for the given destination Layer-2 ID, e.g. when providing other information such as the destination Layer-2 ID, PC5 QoS parameters.
For broadcast, the mapping from destination Layer-2 ID to NR Tx Profile is configured in the NG-RAN. The NG-RAN may derive the NR Tx Profile from the destination Layer-2 ID to perform the network scheduled operation mode, alignment of Uu DRX and PC5 DRX, etc.
Support for PC5 DRX operations in the AS layer is specified in TS 38.300 [11].
When the PC5 DRX operation is needed, e.g. based on the NR Tx Profile in case of broadcast or groupcast, the AS layer determines the PC5 DRX parameter values for V2X communication over PC5 reference point, taking into account, e.g., PC5 QoS parameters and/or destination Layer-2 ID provided by the V2X layer.
For unicast, two UEs may negotiate the PC5 DRX configuration in the AS layer, and the PC5 DRX parameter values can be configured per pair of source and destination Layer-2 IDs and per direction in the AS layer. For transmitting and receiving Direct Communication Request messages, a default PC5 DRX configuration is used when the PC5 DRX operation is needed, e.g. based on the NR Tx Profile as specified in clause 5.1.2.1.
For broadcast and groupcast when the UE is "not served by E-UTRA" and "not served by NR", the UE uses the provisioned PC5 DRX configuration for PC5 DRX operation as specified in clause 5.1.2.1.