4 Architecture model and concepts

23.2853GPPArchitecture enhancements for V2X servicesRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

4.1 General concept

There are two modes of operation for V2X communication, namely over the PC5 and over LTE-Uu. LTE-Uu can be unicast and/or MBMS. These two operation modes may be used by a UE independently for transmission and reception, e.g. a UE can use MBMS for reception without using LTE-Uu for transmission. A UE may also receive V2X messages via LTE-Uu unicast downlink.

For both operation modes, the following principles apply:

– V2X Application Servers e.g. in different domains can communicate with each other for the exchange of V2X messages. The interface between V2X Application Servers and the methods of the exchange of messages between V2X Application Servers is out of scope of 3GPP.

– ProSe discovery feature (TS 23.303 [5] clause 5.3 ProSe Direct Discovery) is not required for V2X Services.

NOTE: ProSe discovery feature can be used by a V2X supporting UE, but that is up to UE implementation.

– Subject to regional regulations, lawful interception requirements apply to V2X Services.

– An RSU is not an architectural entity, but an implementation option. This is achieved by collocating a V2X application logic/server with some entities of the 3GPP system, as shown in examples in Annex A.

4.2 Architectural reference model

4.2.1 PC5 and LTE-Uu based V2X architecture reference model

4.2.1.1 Non-roaming architecture for PC5 and LTE-Uu based V2X communication

Figure 4.2.1.1-1 shows the high level view of the non-roaming architecture for PC5 and LTE-Uu based V2X communication.

Figure 4.2.1.1-1: Non-roaming reference architecture for PC5 and LTE-Uu based V2X communication

4.2.1.2 Roaming architecture for PC5 and LTE-Uu based V2X communication

Figure 4.2.1.2-1 shows the high level view of the roaming architecture for PC5 and LTE-Uu based V2X communication. In this figure, UE A uses a subscription of PLMN A and UE B uses a subscription of PLMN B; UE A is roaming in PLMN B while UE B is not roaming.

A V2X Application Server may connect to multiple PLMNs, e.g. one V2X Application Server can connect with the V2X Control Function in PLMN A and the V2X Control Function in PLMN B in the figure.

Figure 4.2.1.2-1: Roaming reference architecture for PC5 and LTE-Uu based V2X communication

4.2.1.3 Inter-PLMN architecture for PC5 and LTE-Uu based V2X communication

Figure 4.2.1.3-1 shows the high level view of the inter-PLMN architecture for PC5 and LTE-Uu based V2X communication. In this figure, UE A uses a subscription of PLMN A and UE B uses a subscription of PLMN B; UE A is roaming in PLMN C while UE B is not roaming.

Figure 4.2.1.3-1: Inter-PLMN reference architecture for PC5 and LTE-Uu based V2X communication

4.2.2 MBMS for LTE-Uu based V2X architecture reference model

Figure 4.2.2-1a and figure 4.2.2-1b show the high level view of the reference architectures with MBMS for LTE-Uu based V2X communication. V2X Application Server may apply either MB2 or xMB reference points when managing MBMS service related information via BM-SC, MB2 reference point as defined in TS 23.468 [7] provides functionality related to group communication and xMB reference point as defined in TS 26.348 [29] provides functionality overall for any content and also supports security framework between content provider and BM-SC.

Figure 4.2.2-1a: Reference architecture for MBMS for LTE-Uu based V2X communication via MB2

Figure 4.2.2-1b: Reference architecture for MBMS for LTE-Uu based V2X communication via xMB

4.2.3 Reference points

V1: The reference point between the V2X application in the UE and in the V2X Application Server. This reference point is out of scope of this specification.

V2: The reference point between the V2X Application Server and the V2X Control Function in the operator’s network. The V2X Application Server may connect to V2X Control Functions belonging to multiple PLMNs.

V3: The reference point between the UE and the V2X Control Function in UE’s home PLMN. It is based on the service authorization and provisioning part of the PC3 reference point defined in clause 5.2 of TS 23.303 [5]. It is applicable to both PC5 and LTE-Uu based V2X communication and optionally MBMS and LTE-Uu based V2X communication.

V4: The reference point between the HSS and the V2X Control Function in the operator’s network.

V5: The reference point between the V2X applications in the UEs. This reference point is not specified in this release of the specification.

V6: The reference point between the V2X Control Function in the HPLMN and the V2X Control Function in the VPLMN.

PC5: The reference point between the UEs used for user plane for ProSe Direct Communication for V2X Service.

S6a: In addition to the relevant functions defined in TS 23.401 [6] for S6a, in case of V2X Service S6a is used to download V2X Service related subscription information to MME during E-UTRAN attach procedure or to inform MME subscription information in the HSS has changed.

S1-MME: In addition to the relevant functions defined in TS 23.401 [6] for S1-MME, in case of V2X Service it is also used to convey the V2X Service authorization from MME to eNodeB.

xMB: The reference point between the V2X Application Server (e.g. Content Provider) and the BM-SC, and defined in TS 26.348 [29].

MB2: The reference point between the V2X Application Server and the BM-SC, and defined in TS 23.468 [7].

SGmb/SGi-mb/M1/M3: The SGmb/SGi-mb/M1/M3 reference points are internal to the MBMS system and are defined in TS 23.246 [8].

LTE-Uu: The reference point between the UE and the E-UTRAN.

4.3 Functional entities

4.3.1 V2X Control Function

4.3.1.1 General

The V2X Control Function is the logical function that is used for network related actions required for V2X. In this version of the specification it is assumed that there is only one logical V2X Control Function in each PLMN that supports V2X Services.

NOTE 1: If multiple V2X Control Functions are deployed within the same PLMN (e.g., for load reasons), then the method to locate the specific V2X Control Function (e.g., through a database lookup, etc.) is not defined in this version of the specification.

V2X Control Function is used to provision the UE with necessary parameters in order to use V2X communication. It is used to provision the UEs with PLMN specific parameters that allow the UE to use V2X in this specific PLMN. V2X Control Function is also used to provision the UE with parameters that are needed when the UE is "not served by E-UTRAN".

V2X Control Function may also be used to obtain V2X USDs for UEs to receive MBMS based V2X traffic, through V2 reference point from the V2X Application Server.

V2X Control Function may also obtain the parameters required for V2X communications over PC5 reference point, from the V2X Application Server via V2 reference point.

NOTE 2: The V2X Control Function in HPLMN can be always reached if Home Routed configuration is applied for PDN connection (e.g., the PDN GW is located in the HPLMN), when such function is supported by the HPLMN. In case of Local Breakout (e.g., the PDN GW is located in the VPLMN), a V2X Control Function Proxy can be deployed by the VPLMN to support UE to Home V2X Control Function communication, if inter-PLMN signalling is required. Whether a PDN connection is provided by Local Breakout or Home Routed is determined by the HSS configuration described in TS 23.401 [6]. The UE is not aware of this and, as such, it will not know which APN can be used for communication with the V2X Control Function, unless the specific APN information is configured in the UE indicating that this APN provides signalling connectivity between the UE and the Home V2X Control Function.

4.3.1.2 V2X Control Function discovery

The V2X Control Function of HPLMN is discovered through interaction with the Domain Name Service function. The FQDN of a V2X Control Function in the Home PLMN may either be pre-configured in the UE, provisioned by the network or self-constructed by the UE, e.g., derived from the PLMN ID of the HPLMN. The IP address of a V2X Control Function in the Home PLMN may also be provisioned to the UE.

4.3.2 UE

The UE may support the following functions:

– Exchange of V2X control information between UE and the V2X Control Function over the V3 reference point.

– Procedures for V2X communication over PC5 reference point and/or LTE-Uu reference point.

– Configuration of parameters for V2X communication (e.g., destination Layer-2 IDs, radio resource parameters, V2X Application Server address information, mapping between service types and V2X frequencies). These parameters can be pre-configured in the UE, or, if in coverage, provisioned by signalling over the V3 reference point from the V2X Control Function in the HPLMN.

– Provided with V2X USDs for receiving MBMS based V2X traffic via existing MBMS service announcement mechanisms, or provisioned from V2X Control Function, or provisioned from the V2X Application Server via V1 reference point.

– Provisioned with V2X Server USDs for receiving V2X Application Server information via MBMS.

4.3.3 V2X Application Server

The V2X Application Server (V2X AS) may support the following capabilities:

– Receiving uplink data from the UE over unicast.

– Delivering data to the UE(s) in a target area using Unicast Delivery and/or MBMS Delivery.

– Mapping from geographic location information to appropriate target MBMS SAI(s) for the broadcast.

– Mapping from geographic location information to appropriate target 3GPP ECGI(s) for the broadcast.

– Mapping from UE provided ECGI to appropriate target MBMS SAI(s) for the broadcast.

– Providing the appropriate ECGI(s) and/or MBMS SAI(s) to BM-SC.

– Pre-configured with Local MBMS (L.MBMS) information (e.g. IP multicast address, multicast source (SSM), C-TEID).

– Pre-configured with L.MBMS’s IP address and port number for the user-plane.

– Sending L.MBMS information to the BM-SC.

– Requests BM-SC for allocation/de-allocation of a set of TMGIs.

– Requests BM-SC for activating/deactivating/modifying the MBMS bearer.

– Providing the V2X USDs for UE to receive MBMS based V2X traffic to V2X Control Function.

– Providing the parameters for V2X communications over PC5 reference point to V2X Control Function.

– Providing the parameters for V2X communications over PC5 reference point to UE.

4.3.4 MME

In addition to the functions defined in TS 23.401 [6] and TS 23.246 [8], in case of V2X the MME performs the following functions:

– Obtains subscription information related to V2X as part of the subscription data.

– Provides indication to the E-UTRAN about the UE authorization status on V2X use.

4.3.5 BM-SC

In addition to the functions defined in TS 23.246 [8] and TS 23.468 [7], in case of V2X the BM-SC performs the following functions:

– Receives L.MBMS information from V2X Application Server.

– Sends L.MBMS information to the MBMS-GW.

4.3.6 MBMS-GW

In addition to the functions defined in TS 23.246 [8], in case of V2X the MBMS-GW performs the following functions:

– If receiving L.MBMS information from the BM-SC, skipping the allocation procedure for IP multicast distribution, e.g., allocating an IP multicast address.

4.4 High level function

4.4.1 Authorization and Provisioning for V2X communications

4.4.1.1 Authorization and provisioning for V2X communications over PC5 reference point

4.4.1.1.1 General

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

– The UE gets authorization to use V2X communications over PC5 reference point on a per PLMN basis in the serving PLMN by the V2X Control Function in the HPLMN.

– The V2X Control Function in the HPLMN requests authorization information from the V2X Control Function of the serving PLMN.

– The V2X Control Function in the HPLMN merges authorization information from home and serving PLMNs and informs the UE of the final authorization information.

– The V2X Control Function in the VPLMN or HPLMN may revoke the authorization at any time. The V2X Control Function in the HPLMN shall be notified when authorization is revoked by the VPLMN.

4.4.1.1.2 Policy/Parameter provisioning

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

1) Authorization policy:

– When the UE is "served by E-UTRAN":

– PLMNs in which the UE is authorized to perform V2X communications over PC5 reference point.

– When the UE is "not served by E-UTRAN":

– Indicates whether the UE is authorized to perform V2X communications over PC5 reference point when "not served by E-UTRAN".

2) Radio parameters for when the UE is "not served by E-UTRAN":

– Includes the radio parameters with Geographical Area(s) and an indication of whether they are "operator managed" or "non-operator managed. These radio parameters (e.g. frequency bands) are defined in TS 36.331 [9]. The UE uses the radio parameters to perform V2X communications over PC5 reference point when "not served by E-UTRAN" only if the UE can reliably locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorized to transmit.

NOTE 1: Whether a frequency band is "operator managed" or "non-operator managed" in a given Geographical Area is defined by local regulations.

3) Policy/parameters:

– The mapping of Destination Layer-2 ID(s) and the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application.

NOTE 2: PLMN operators coordinate to make sure Destination Layer-2 ID(s) for different V2X services are configured in a consistent manner.

NOTE 3: To pre-configure a UE with the provisioning parameters, at least the "not served by E-UTRAN" parameters of 1) and 2), and the parameters of 3) need to be included.

– The mapping of ProSe Per-Packet Priority and packet delay budget for V2X communication (autonomous resources selection mode).

– The list of V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X applications, with Geographical Area(s) that require privacy support.

– The mapping of service types (e.g. PSIDs, ITS-AIDs or AIDs) to V2X frequencies (see TS 36.300 [10] for further information) with Geographical Area(s).

– The mapping of service types (e.g. PSIDs, ITS-AIDs or AIDs) to Tx Profiles (see TS 36.300 [10] for further information).

– The list of V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X applications, allowed to use a specific PPPR value.

4) Policy/parameters for NR PC5:

– Same as specified in item 6) in clause 5.1.2.1 of TS 23.287 [30]: "Policy/parameters when NR PC5 is selected", and the policy/parameter for NR Tx Profile selection as specified in item 3) in clause 5.1.2.1 of TS 23.287 [30]: "Policy/parameters for PC5 RAT selection and for PC5 Tx Profile selection".

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

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

NOTE 4: The V2 reference point procedure is not specified in this Release.

4.4.1.1.3 Principles for applying parameters for V2X communications over PC5 reference point

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

– The provisioning parameters for V2X communications over PC5 may be configured in the UICC, in the ME, or in both the UICC and the ME.

– The ME provisioning parameters shall not be erased when a USIM is deselected or replaced.

– If both the UICC and the ME contain the same set of provisioning parameters, the set of parameters from the UICC shall take precedence.

– The UE shall use radio resources for V2X communications over PC5 reference point as follows:

– While a UE has a serving cell and is camped on a cell and the UE intends to use for V2X service the radio resources (i.e. carrier frequency) operated by this cell, then the UE shall use the radio resource description indicated by this cell the UE is camped on and ignore any radio resource description of the same radio resource provisioned in the ME or the UICC. If the cell does not provide radio resources for V2X service, the UE shall not perform V2X message transmission and reception on radio resources operated by this cell.

– If the UE intends to use "operator-managed" radio resources (i.e. carrier frequency) for V2X service that are not operated by the UE’s serving cell, as specified in clause 4.4.1.1.2, or if the UE is out of coverage, the UE shall search for a cell in any PLMN that is operating the provisioned radio resources (i.e. carrier frequency) as defined in TS 36.300 [10] and TS 36.304 [22], and:

– If the UE finds such cell in the registered PLMN or a PLMN equivalent to the registered PLMN, and authorization for V2X communications over PC5 reference point to this PLMN is confirmed, the UE shall use the radio resource description indicated by that cell. If that cell does not provide radio resources for V2X service, the UE shall not perform V2X message transmission and reception on those radio resources.

– If the UE finds such cell but not in the registered PLMN or a PLMN equivalent to the registered PLMN, and that cell belongs to a PLMN authorized for V2X communications over PC5 reference point and provides radio resources for V2X service then the UE shall perform PLMN selection triggered by V2X communications over PC5 reference point as defined in TS 23.122 [23]. If the UE has an ongoing emergency session, it shall not trigger any PLMN selection due to V2X communication over PC5 reference point.

NOTE 1: An ongoing emergency session could be either using IMS or CS as described in TS 23.167 [31].

– If the UE finds such cell but not in a PLMN authorized for V2X communications over PC5 reference point the UE shall not use V2X communications over PC5 reference point.

– If the UE does not find any such cell in any PLMN, then the UE shall consider itself "not served by E-UTRAN" and use radio resources provisioned in the ME or the UICC. If no such provision exists in the ME or the UICC or the provision does not authorize V2X communications over PC5 reference point then the UE is not authorized to transmit.

– If the UE intends to use "non-operator-managed" radio resources (i.e. carrier frequency) for V2X service, according to TS 36.331 [9] and as specified in clause 4.4.1.1.2, then the UE shall perform V2X communication over PC5 using resource provisioned in the ME or the UICC. If no such provision exists in the ME or the UICC or the provision does not authorize V2X communications over PC5 reference point then the UE is not authorized to transmit.

– The UE provisioning shall support setting Geographical Areas.

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

NOTE 3: When cross-carrier operation is supported, according to TS 36.331 [9], a UE can be instructed by its serving cell to perform V2X communication over a different carrier frequency. The UE is still considered as "served by E-UTRAN" in this case.

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

– The V2X communications over PC5 reference point is only specified for E-UTRA.

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

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

4.4.1.2.1 General

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

NOTE: A single V2X Application Server can support multiple V2X applications.

4.4.1.2.2 Policy/Parameter provisioning

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

1) PLMNs in which the UE is authorized to use MBMS based V2X communication.

– Corresponding V2X USD(s) for receiving MBMS based V2X traffic in the PLMN. The V2X USD(s) may be obtained through the V2 reference point from the V2X Application Server.

NOTE: The V2 reference point procedure is not specified in this Release.

2) V2X Application Server address information.

– List of FQDNs or IP addresses of the V2X Application Servers, associated with served geographical area information and list of PLMNs that the configuration applies to.

3) V2X Application Sever discovery using MBMS.

– List of PLMNs and corresponding V2X Server USDs for receiving V2X Application Server information via MBMS.

4) Mapping of the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application to:

– V2X Application Server address (consisting of IP address/FQDN and TCP or UDP port) for unicast;

– V2X USD for MBMS.

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

4.4.2 V2X message transmission/reception over PC5 reference point

PC5 reference point as defined in TS 23.303 [5] is used for the transmission and reception of V2X messages. The V2X communication over PC5 reference point supports roaming and inter-PLMN operations. V2X communication over PC5 reference point is supported when the UE is "served by E-UTRAN" and when the UE is "not served by E‑UTRAN".

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

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

– The V2X communication over PC5 reference point is connectionless, and there is no signalling over PC5 control plane for connection establishment.

– V2X messages are exchanged between UEs over PC5 user plane.

– Both IP based and non-IP based V2X messages are supported.

– For IP based V2X messages, only IPv6 is used. IPv4 is not supported in this release.

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

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

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

NOTE 1: The mapping from Destination L2 ID to Tx Profile is configured in the eNB. The eNB can determine the Tx Profiles that the UE needs to use for transmitting the packets thus utilising the resources available appropriately -i.e. handling of sidelink grant), see TS 36.321 [26] for details.

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

NOTE 2: An ongoing emergency session could be either using IMS or CS as described in TS 23.167 [31].

NOTE 3: The emergency session setup is based on appropriate regional/national regulatory requirements and operator policies as defined in TS 23.401 [6].

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

4.4.3.1 General

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

4.4.3.2 V2X message transmission/reception via unicast

The V2X communication via unicast over the LTE-Uu reference point supports roaming operations. Latency reduction for V2X message transfer via unicast may be achieved by using SIPTO@LN or SIPTO above RAN as defined in TS 23.401 [6].

NOTE 1: In case of SIPTO@LN with L-GW function collocated with an eNB, mobility is not supported.

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

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

NOTE 2: When IP multicast is used, only UDP/IP is supported.

– the UE sends a V2X message over TCP/IP or UDP/IP to a V2X Application Server address. The destined V2X Application Server address is derived from e.g. the PSID (or the ITS-AID, or the AID) and the UE configuration as described in clause 4.4.1.2.2; and

– the V2X Application Server receives the V2X message in a TCP/IP or UDP/IP packet on a V2X Application Server address.

For transport of V2X messages:

– for applications different from the applications with e.g. PSID, ITS-AID or AID for PC5 reference point, or

– for configured applications with e.g. PSID, ITS-AID or AID sending IP based V2X messages,

existing unicast routing towards application server applies.

NOTE 3: In case V2X application uses TCP/IP or UDP/IP transport then existing unicast routing towards application server applies, i.e. no further encapsulation is performed.

4.4.3.3 V2X message reception via MBMS

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

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

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

– Existing MBMS service announcement mechanisms specified in TS 23.246 [8] and TS 26.346 [11].

– Provisioning as described in clause 4.4.1.2.2, i.e. pre-configuration in the UE and/or configuration from V2X Control Function.

– Provisioning from the V2X Application Server via V1 reference point.

NOTE 1: The UE can receive the downlink broadcast from the PLMN other than Serving PLMN based on the V2X USD(s) obtained as described in this clause.

NOTE 2: The operator can configure multiple MBMS Service Areas for a specific V2X service. If any of these MBMS Service Areas overlap, the UE needs to be configured with different TMGIs for these overlapping MBMS Service Areas for this V2X service.

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

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

4.4.4 V2X Application Server discovery

4.4.4.1 General

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

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

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

4.4.4.2 Multiple V2X Application Server and Localized V2X Application Server discovery and routing

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

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

4.4.5 QoS handling for V2X communication

4.4.5.1 QoS handling for V2X communication over PC5 reference point

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

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

– ProSe Per-Packet Priority (PPPP) defined in clause 5.4.6.1 of TS 23.303 [5] applies to the V2X communication over PC5.

– ProSe Per-Packet Reliability (PPPR) applies to the V2X communication over PC5 as defined in TS 23.303 [5]. PPPR has a value range of 1 to 8, where the higher value represents the lower reliability requirement for that message. The UE may be configured with a list of V2X services, e.g. PSIDs, ITS-AIDs or AIDs allowed to use the specific PPPR value.

– The application layer sets the PPPP for each V2X message when passing it to lower layer for transmission.

– The application layer may set the PPPR for each V2X message when passing it to lower layer for transmission.

– The mapping of application layer V2X message priority to PPPP is configuration on the UE.

– The mapping of application layer V2X message reliability to PPPR is configuration on the UE.

– The setting of the PPPP value should reflect the latency required in both UE and eNB, i.e. the low PDB is mapped to the high priority PPPP value.

– The mapping between V2X service types and V2X frequencies is as defined in clause 4.3.2 and clause 4.4.1.1.2.

– The mapping of Destination Layer-2 ID(s) and the V2X services, e.g. PSIDs, ITS-AIDs or AIDs of the V2X application is as described in clause 4.4.1.1.2.

NOTE: The mapping of PPPP to packet delay budget is not specified in this specification.

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

– UE provides priority information reflecting PPPP to the eNB for resources request.

– When the eNB receives a request for PC5 resource from a UE, the eNB can deduce the packet delay budget from the priority information reflecting PPPP from the UE.

– eNB can use the priority information reflecting PPPP for priority handling and UE-PC5-AMBR for capping the UE PC5 transmission in the resources management.

– UE may provide PPPR information reflecting reliability requirement described in TS 22.186 [28] to the eNB for resources request.

– UE provides Destination Layer-2 ID(s) of the V2X services to the eNB for resources requested as defined in TS 36.321 [26].

– When the eNB receives a request for PC5 resource from a UE, the eNB determines the V2X frequency(ies) in which the V2X service is to be scheduled as defined in TS 36.300 [10].

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

– The UE derives the packet delay budget of the V2X message from PPPP based on the provisioned mapping information described in clause 4.4.1.1.2.

– The UE derives the frequency in which a V2X service is to be transmitted, from the mapping between V2X service types and V2X frequencies as described in clause 4.4.1.1.2.

4.4.5.1a QoS handling for V2X communication over NR PC5 reference point

The QoS handling for V2X communication over NR PC5 reference point as defined in TS 23.287 [30] clause 5.4 is applied.

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

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

The following standardized QCI values defined in TS 23.203 [12] can be used:

– QCI 3 and QCI 79 can be used for the unicast delivery of V2X messages;

– QCI 75 is only used for the delivery of V2X messages over MBMS bearers.

4.4.6 Subscription to V2X services

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

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

The following subscription information is defined for V2X services:

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 for V2X communication over PC5 reference point, including UE-PC5-AMBR for LTE PC5 and 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 communication over PC5 reference point.

d) PC5 QoS parameters for V2X communication over NR PC5 reference point as defined in TS 23.287 [30] clause 5.4.2.

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

The HSS provides c) to V2X Control Function.

4.4.7 MBMS bearer announcement for V2X use

4.4.7.1 General

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

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

4.4.7.2 User Service Description for V2X Communication (V2X USD)

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

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

Table 4.4.7.2-1: Information for V2X USD

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

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

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

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

NOTE: Stage 3 defines the format of the local Service information.

Table 4.4.7.3-1: Information for V2X Server USD

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

4.4.8 Support for V2X communication for UEs in limited service state

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

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

– because it cannot find a suitable cell of the selected PLMN as described in TS 23.122 [23] or

– as the result of receiving one of the following reject reasons defined in TS 23.122 [23]:

– a "PLMN not allowed" response to a registration request or;

– a "GPRS not allowed" response to a registration request

A UE in limited service state shall only use the radio resources and procedure available in ECM-IDLE mode for V2X communication over PC5 reference point, for details see TS 36.300 [10].

UEs shall not use V2X communication over PC5 reference point using the "operator-managed" radio resources, as specified in clause 4.4.1.1.2, if the UE has entered in limited service state due to all other situations (e.g. no SIM in the MS, an "illegal MS" or "illegal ME" response to a registration request, or an "IMSI unknown in HLR" response to a registration request) defined in TS 23.122 [23], where the UE is unable to obtain normal service from a PLMN. The UEs may use V2X communication over PC5 reference point using the "non-operator-managed" radio resources, as specified in clause 4.4.1.1.2, according to the principles defined in clause 4.4.1.1.3.

4.4.9 Charging support for V2X communication

4.4.9.1 Charging support for V2X communication over PC5 reference point

For V2X communication over PC5, the mechanism defined in TS 32.277 [18] for ProSe Direct Communication can be reused for charging support. No enhancement to charging support for V2X communication over PC5 is specified in this Release.

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

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

For unicast V2X communication, charging is provided with the existing unicast communication mechanism as specified in TS 32.251 [20] where applicable.

For MBMS based broadcast traffic, charging is provided with the existing mechanism as specified in TS 32.273 [21] where applicable.

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

4.4.10 Security and privacy protection support for V2X communication

The security for the V3 and PC5 reference points is provided with mechanisms defined in TS 33.185 [25].

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

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

Details of security and privacy protection mechanisms for V2X communication over PC5 or LTE-Uu reference points are defined in TS 33.185 [25].

4.5 Identifiers

4.5.1 Identifiers for V2X communication over PC5 reference point

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

When IP based V2X messages are supported, the UE auto-configures a link local IPv6 address to be used as the source IP address, as defined in clause 4.5.3 of TS 23.303 [5]. The UE may use the auto-configured link local IP address for V2X communication over PC5 reference point without sending Neighbor Solicitation and Neighbor Advertisement message for Duplicate Address Detection.

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

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