Content for TS 23.303 Word version: 18.0.0

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4.5 High Level Function 4.5.1 Provisioning for ProSe Direct Discovery and ProSe Direct Communication 4.5.1.1 Authorization and provisioning for ProSe 4.5.1.1.1 General 4.5.1.1.2 Provisioning information for ProSe Direct Discovery and ProSe Direct Communication 4.5.1.1.2.1 General 4.5.1.1.2.2 Authorisation for ProSe Direct Discovery 4.5.1.1.2.3 Provisioning for ProSe Direct Discovery and ProSe Direct Communication (Public Safety UE) 4.5.1.1.2.3.1 General 4.5.1.1.2.3.2 Additional provisioning information for ProSe Direct Discovery 4.5.1.1.2.3.3 Provisioning information for one-to-many ProSe Direct Communication 4.5.1.1.2.3.3a Provisioning information for one-to-one ProSe Direct Communication 4.5.1.1.2.3.4 Provisioning information for ProSe UE-to-Network Relaying 4.5.2 Subscription to ProSe 4.5.3 IP address allocation 4.5.4 ProSe UE-to-Network Relaying 4.5.5 ProSe Proxy Function 4.5.6 Support for ProSe for UEs in limited service state
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4.5 High Level Function p. 20

4.5.1 Provisioning for ProSe Direct Discovery and ProSe Direct Communication p. 20

4.5.1.1 Authorization and provisioning for ProSe p. 20

4.5.1.1.1 General p. 20

The basic principles of service authorization for ProSe Direct Discovery and ProSe Direct Communication are as follows:

the UE gets authorization to use E-UTRA based ProSe Direct Discovery on a per PLMN basis.
for WLAN-based ProSe Direct Discovery the service authorisation information provided by the HPLMN contains a list of PLMNs whose ProSe Application IDs the UE may use.
- the ProSe Function in the HPLMN requests authorisation information from the ProSe Function of the serving PLMN and Local PLMN(s).
NOTE:
The UE does not need to be registered in the Local PLMN.
The ProSe Function in the HPLMN merges authorization information from home, serving and local PLMNs.
Final authorization always comes from the ProSe Function in the Home PLMN.

The ProSe Function in the Local PLMN or the VPLMN or HPLMN may revoke the authorization at any time. The ProSe Function in the HPLMN shall be notified when authorization is revoked by the Local PLMN or the VPLMN.

OMA DM [30] is used as the protocol to provision ProSe related configuration and authorization information in the ME. Provisioning is performed via the PC3 reference point.

4.5.1.1.2 Provisioning information for ProSe Direct Discovery and ProSe Direct Communication p. 21

4.5.1.1.2.1 General p. 21

The following information can be contained in the authorisation info that is provided by the ProSe Function to the UE for authorisation of using ProSe Direct Discovery and ProSe Direct Communication in a particular PLMN.

4.5.1.1.2.2 Authorisation for ProSe Direct Discovery p. 21

The following information is provisioned to the non-Public Safety UE for open ProSe Direct Discovery authorisation:

open ProSe Direct Discovery Model A monitoring authorisation policy:
- PLMNs in which the UE is authorised to perform ProSe Direct Discovery monitoring.
open ProSe Direct Discovery Model A announcing authorisation policy:
- PLMNs in which the UE is authorized to perform announcing.
- Authorised discovery range for announcing per PLMN.

The following information is provisioned to the UE for restricted ProSe Direct Discovery authorisation:

restricted ProSe Direct Discovery Model A monitoring authorisation policy:
- PLMNs in which the UE is authorised to perform restricted ProSe Direct Discovery Model A monitoring.
restricted ProSe Direct Discovery Model A announcing authorisation policy:
- PLMNs in which the UE is authorized to perform restricted ProSe Direct Discovery Model A announcing;
- Authorised discovery range for announcing per PLMN.
restricted ProSe Direct Discovery Model B Discoverer operation authorization policy:
- PLMNs in which the UE is authorized to perform Model B Discoverer operation;
- Authorised discovery range for announcing per PLMN.
restricted ProSe Direct Discovery Model B Discoveree operation authorization policy:
- PLMNs in which the UE is authorized to perform Model B Discoveree operation.
- Authorised discovery range for announcing per PLMN.
restricted ProSe Discovery UE ID for Restricted Direct Discovery, applicable only to non-Public Safety UEs:
- ProSe Discovery UE ID.

4.5.1.1.2.3 Provisioning for ProSe Direct Discovery and ProSe Direct Communication (Public Safety UE) p. 22

4.5.1.1.2.3.1 General p. 22

The content of clause 4.5.1.1.2.3 is applicable to ProSe-enabled Public Safety UEs only.

Clause 3 provides the definition of a ProSe-enabled Public Safety UE. To comply with international and national regulations, the HPLMN shall endeavour to ensure that the UE only uses the specific Public Safety capabilities in territories in which the HPLMN is authorised to permit such rights to the UE.

For Public Safety usage the operator may pre-configure ProSe-enabled Public Safety UEs with the required provisioning parameters for ProSe Direct Discovery and ProSe Direct Communication, without the need for the ProSe-enabled Public Safety UEs to connect to the ProSe Function to get this initial configuration. The following apply:

The provisioning parameters for ProSe Direct Discovery and ProSe Direct Communication may be configured in the UICC, in the ME, or in both the UICC and the ME.
The UICC shall indicate whether the UE is authorized to use provisioning parameters.
ProSe Direct Discovery and ProSe Direct Communication shall be accessible only when a USIM authorized for ProSe Direct Discovery and ProSe Direct Communication is selected.
The ME provisioning parameters shall not be erased when a USIM is deselected or replaced.
If both the USIM 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 ProSe Direct Communication as follows:
- While a UE has a serving cell and is camped on a cell and the UE intends to use for ProSe 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 ProSe, the UE shall not perform ProSe transmission and reception on radio resources operated by this cell.
- If the UE intends to use radio resources (i.e. carrier frequency) for ProSe that are not operated by the UE's serving cell or if the UE is out of coverage, the UE shall search for a cell in any PLMN that is operating the provisioned radio resources (i.e. carrier frequency) as defined in TS 36.300 and TS 36.304, and:
  - If the UE finds such cell in the registered PLMN or a PLMN equivalent to the registered PLMN, and authorisation for ProSe Direct Communication 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 ProSe, the UE shall not perform ProSe 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 authorised for ProSe Direct Communication and provides radio resources for ProSe then the UE shall perform PLMN selection triggered by ProSe Direct Communication as defined in TS 23.122.
  - If the UE finds such cell but not in a PLMN authorised for ProSe Direct Communication the UE shall not use ProSe.
  - If the UE does not find any such cell in any PLMN, then the UE shall 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 authorise ProSe Direct Communication then the UE is not authorised to transmit.
The UE shall use radio resources for ProSe Direct Discovery as follows:
- While a UE has a serving cell, the UE shall use the radio resource description obtained via dedicated signalling or broadcasted by this cell (same or different from that of the serving cell), if the corresponding PLMN is permitted by the configured authorization information.
- If the UE intends to use radio resources (i.e. carrier frequency) not operated by the UE's serving cell for ProSe, which are indicated by the UE's serving cell, and the corresponding PLMN is permitted by the configured authorization information, the UE shall search for a cell with the indicated PLMN operating the indicated radio resources as defined in TS 36.300 and TS 36.304, and obtain the radio resource description for ProSe Direct Discovery from that cell, without performing PLMN selection.
If the UE intends to use provisioned radio resources (i.e. carrier frequency) not operated by the UE's serving cell for ProSe Direct Discovery, the UE shall search for a cell with any PLMN operating the indicated radio resources as defined in TS 36.300 and TS 36.304, and
- If the UE finds such a cell belongs to a PLMN authorised for ProSe Direct Discovery and the cell provides radio resources description for ProSe Direct Discovery, then the UE shall use the indicated radio resources description for Direct Discovery.
- If the UE finds such a cell but not in a PLMN authorised for ProSe Direct Discovery, the UE shall not use ProSe Direct Discovery in that carrier frequency.
- If the UE does not find any such cell in any PLMN, then the UE shall use radio resources provisioned in the ME or the UICC.
The UE provisioning shall support setting Geographical Areas.

NOTE 1:
It is possible for a UE to use other radio resources for ProSe 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 ProSe SIB indicates that the service (discovery or communication or both) is available. This is to cover the scenario when e.g. the radio resources used for ProSe Direct Communication are not owned by the serving network of the UE.

NOTE 2:
The UE can only use ProSe Direct Discovery and ProSe Direct Communication when it contains a UICC that has been configured for ProSe, i.e. the selected USIM indicates that the UE is authorized to use the provisioning parameters for ProSe.

NOTE 3:
The scenario that a cell is detected and the cell does not provide support for ProSe Direct Communications when the UE attempts to use a carrier frequency configured for ProSe Direct Communication, is considered a configuration error. Therefore the UE does not transmit on that frequency to avoid interference to the network.
The ProSe Direct Communication is only specified for E-UTRA.

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, including user provided location, as determined by local regulations.

NOTE 5:
The provisioning and use of of radio resources for ProSe Direct Discovery described in this clause does not apply to WLAN-based ProSe Direct Discovery.

4.5.1.1.2.3.2 Additional provisioning information for ProSe Direct Discovery p. 23

In addition to the parameters indicated in clause 4.5.1.1.2.2, the ProSe-enabled Public Safety UE is provisioned with the following information:

Authorisation policy when the UE is "not served by E-UTRAN":
- Indicates whether the UE is authorised to perform ProSe Direct Discovery for Model A and Model B when "not served by E-UTRAN".
Radio parameters for when the UE is "not served by E-UTRAN":
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able perform ProSe Direct Discovery procedures when not "served by E-UTRAN". These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Discovery (Group Member Discovery, ProSe UE-to-Network Relay Discovery or ProSe UE-to-Network Relay Discovery Additional Information). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.
Group Member Discovery parameters:
- For each discovery group that the UE belongs to include the following parameters that enable the UE to perform Group Member Discovery when provisioned in ME from DPF or configured in UICC:
  - Application Layer Group ID: Identifies an application layer group that the UE belongs to.
  - User Info ID: For Model A, this corresponds to the Announcer Info parameter when the UE is acting as an announcing UE. For Model B, this corresponds to the Discoverer Info in Solicitation messages and the Discoveree Info in Response messages, when the UE is acting as a discoverer or discoveree UE respectively.
    
    NOTE 1:
    The provisioning of radio parameters for ProSe Direct Discovery described in this clause does not apply to WLAN-based ProSe Direct Discovery.
    
    NOTE 2:
    User Info ID is expected to be assigned uniquely to a user within the discovery group.
  - Discovery Group ID: identifier of a discovery group that the UE belongs to.
    
    NOTE 3:
    The relationship between the Discovery Group ID and the ProSe Layer-2 Group ID described in clause 4.5.1.1.2.3.3 is out of scope of this specification. It is expected that the Discovery Group ID and ProSe Layer-2 Group ID are of equal bit size.
- Alternatively these parameters can be provided from the 3rd party public safety provider application server (e.g. GCS AS as in TS 23.468). If UE receives a set of data with the same Application Layer Group ID from AS that has been previously provided by DPF then UE uses the data set provided by AS for Group Member Discovery.
ProSe UE-to-Network Relay Discovery parameters:
- Include the parameters that enable the UE to perform ProSe UE-to-Network Relay Discovery when provisioned in ME from DPF or configured in UICC:
  - User Info ID: For Model A, this corresponds to the Announcer Info parameter when the UE is acting as an announcing UE. For Model B, this corresponds to the Discoverer Info in Solicitation messages and the Discoveree Info in Response messages, when the UE is acting as a discoverer or discoveree UE respectively.
  - Relay Service Code(s): A Relay Service Code identifies a connectivity service the ProSe UE-to-Network Relay provides to Public Safety applications. The Relay Service Codes are configured in the ProSe UE-to-Network Relays that provide connectivity services to Public Safety applications. The Relay Service Codes are configured in the Remote UEs interested in related connectivity services.
- Alternatively these parameters can be provided from the 3rd party public safety provider application server (e.g. GCS AS as in TS 23.468). If UE receives the same set of data from AS that has been previously provided by DPF then UE uses the data set provided by AS for ProSe UE-to-Network Relay Discovery.

4.5.1.1.2.3.3 Provisioning information for one-to-many ProSe Direct Communication p. 24

The following information is provisioned to the UE for one-to-many ProSe Direct Communication:

Authorisation policy:
- When the UE is "served by E-UTRAN":
  - PLMNs in which the UE is authorised to perform one-to-many ProSe Direct Communication.
- When the UE is "not served by E-UTRAN":
  - Indicates whether the UE is authorised to perform one-to-many ProSe Direct Communication procedures when "not served by E-UTRAN".
ProSe Direct Communication policy/parameters:
- For each application layer group supported include the parameters that enable the UE to perform one-to-many ProSe Direct Communication when provisioned from DPF in the ME or configured in the UICC:
  - Application Layer Group ID: Identifies an application layer group that the UE belongs to.
  - ProSe Layer-2 Group ID;
  - ProSe Group IP multicast address
  - Indication whether the UE should use IPv4 or IPv6 for that group
  - For a specific Group configured to operate using IPv4, optionally an IPv4 address to be used by the UE as a source address. If none is provisioned, then the UE shall use Dynamic Configuration of IPv4 Link-Local Addresses RFC 3927 to obtain a link local address for the Group.
  - Include group security related content for one-to-many ProSe Direct Communication.
    
    NOTE 1:
    More details on the necessary security aspect will be defined in SA3 specifications.
  - Alternatively these parameters can be provided from the 3rd party public safety provider application server (e.g. GCS AS as in TS 23.468). If UE receives a set of data with the same Application Layer Group ID from AS that has been previously provided by DPF then UE uses the data set provided by AS for one-to-many ProSe Direct Communication.
Radio parameters for when the UE is "not served by E-UTRAN":
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able perform one-to-many ProSe Direct Communication procedures when "not served by E-UTRAN". These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Communication (one-to-one, one-to-many or ProSe UE-to-Network Relaying). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.
NOTE 2:
The "not served by E-UTRAN" cover the cases when the UE is not served by the E-UTRAN cell operating on the carrier frequency provisioned for ProSe Direct Communication.

4.5.1.1.2.3.3a Provisioning information for one-to-one ProSe Direct Communication p. 25

The following information is provisioned in the UE for one-to-one ProSe Direct Communication:

Authorisation policy:
- When the UE is "served by E-UTRAN":
- PLMNs in which the UE is authorised to perform one-to-one ProSe Direct Communication.
- When the UE is "not served by E-UTRAN":
- Indicates whether the UE is authorised to perform one-to-one ProSe Direct Communication procedures when "not served by E-UTRAN".
ProSe Direct Communication policy/parameters:
- For each application layer group supported include the parameters that enable the UE to perform one-to-one ProSe Direct Communication when provisioned from DPF including Application Layer Group ID and the Layer-2 ID for unicast communication and the related security parameters.
NOTE 1:
More details on the necessary security aspect will be defined in SA WG3 specifications.
Radio parameters for when the UE is "not served by E-UTRAN":
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able to perform one-to-one ProSe Direct Communication procedures when "not served by E-UTRAN". These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Communication (one-to-one, one-to-many or ProSe UE-to-Network Relaying). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.

4.5.1.1.2.3.4 Provisioning information for ProSe UE-to-Network Relaying p. 26

The following information is provisioned in the UE in support of the UE assuming the role of a ProSe UE-to-Network Relay:

Authorisation policy for acting as a ProSe UE-to-Network Relay when "served by E-UTRAN":
- PLMNs in which the UE is authorized to relay traffic for Remote UEs.
ProSe Relay Discovery policy/parameters for ProSe UE-to-Network Relay:
- Includes the parameters that enable the UE to perform ProSe Relay Discovery when provisioned from the DPF in the ME or configured in the UICC:
- ProSe UE-to-Network Relay Discovery parameters (User Info ID, Relay Service Code(s)) as described in clause 4.5.1.1.2.3.2;
- The PDN connection parameters (PDN type, APN) to be used for the relayed traffic for each ProSe Relay Service Code;
  
  NOTE 1:
  The behaviour of the UE in case of missing PDN connection parameters is the behaviour described in TS 23.401. E.g. if PDN type is not pre-configured the UE requests PDN type IPv4v6.
- Includes security related content for ProSe Relay Discovery for each ProSe Relay Service Code.
  
  NOTE 2:
  More details on the necessary security aspects are defined in TS 33.303.
- Alternatively these parameters can be provided from a 3rd party public safety provider application server (e.g. a GCS AS as in TS 23.468). If the UE receives the same set of data from the AS that has previously been provided by the DPF then the UE uses the data set provided by the AS for ProSe Relay Discovery.
Radio parameters for ProSe Relay Discovery:
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able perform ProSe Discovery procedures when acting as a ProSe UE-to-Network Relay. These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Discovery (Group Member Discovery, ProSe UE-to-Network Relay Discovery or ProSe UE-to-Network Relay Discovery Additional Information). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.
  
  NOTE 3:
  The provisioning of radio parameters for ProSe Direct Discovery described in this clause does not apply to WLAN-based ProSe Direct Discovery.
Radio parameters for ProSe Relay Communication:
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able perform ProSe Communication procedures when acting as a ProSe UE-to-Network Relay. These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Communication (one-to-one, one-to-many or ProSe UE-to-Network Relaying). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.
Mapping rules between ProSe Per-Packet Priority and QCI values.
- Includes the rules that determine how the ProSe UE-to-Network Relay maps the QCI of the EPS bearer into a ProSe Per-Packet Priority value to be applied for the downlink relayed unicast packets over PC5.

The following information is provisioned in the UE in support of the UE assuming the role of a Remote UE and thereby enabling the use of a ProSe UE-to-Network Relay:

Authorisation policy for using a ProSe UE-to-Network Relay:
- Indicates whether the UE is authorised to use a ProSe UE-to-Network Relay.
Policy/parameters for ProSe Relay Discovery and for enabling connection to the ProSe UE-to-Network Relay after discovery is performed as defined in clause 5.3.7:
- Includes the parameters for ProSe Relay Discovery and for enabling the UE to connect to the ProSe UE-to-Network Relay after discovery when provisioned from the DPF in the ME or configured in the UICC:
- ProSe UE-to-Network Relay Discovery parameters (User Info ID, Relay Service Code(s)) as described in clause 4.5.1.1.2.3.2;
- IP version(s) that can be used for the relay traffic for each ProSe Relay Service Codes;
- Includes security related content for ProSe Relay Discovery for each ProSe Relay Service Codes.
  
  NOTE 4:
  More details on the necessary security aspect are defined in TS 33.303.
- Alternatively these parameters can be provided from a 3rd party public safety provider application server (e.g. a GCS AS as in TS 23.468). If the UE receives the same set of data from the AS that has previously been provided by the DPF then the UE uses the data set provided by the AS for the use of a ProSe UE-to-Network Relay.
Radio parameters for when the UE is not "served by E-UTRAN":
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able perform ProSe Discovery procedures in the role of a Remote UE when not "served by E-UTRAN". These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Discovery (Group Member Discovery, ProSe UE-to-Network Relay Discovery or ProSe UE-to-Network Relay Discovery Additional Information). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.
- Includes the radio parameters with Geographical Area(s) that need to be configured in the UE in order to be able perform ProSe Communication procedures in the role of a Remote UE when not "served by E-UTRAN". These radio parameters (e.g. frequency bands) are defined in TS 36.331 and are common for all types of ProSe Direct Communication (one-to-one, one-to-many or ProSe UE-to-Network Relaying). The UE uses the radio parameters only if the UE can locate itself in the corresponding Geographical Area. Otherwise, the UE is not authorised to transmit.
  
  NOTE 5:
  The phrase "not served by E-UTRAN" cover the cases when the UE is not served by the E-UTRAN cell operating on the carrier frequency provisioned for ProSe Direct Discovery but may be served by the E-UTRAN cell operating on some other carrier frequency.

4.5.2 Subscription to ProSe p. 27

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

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

The following subscription information is defined for ProSe:

subscription for open ProSe Direct Discovery:
- open ProSe Direct Discovery Model A.
subscription for restricted ProSe Direct Discovery:
- restricted ProSe Direct Discovery Model A;
- restricted ProSe Direct Discovery Model A with application-controlled extension;
- restricted ProSe Direct Discovery Model A with "on demand" announcing;
- restricted ProSe Direct Discovery Model B.
subscription for EPC-level ProSe Discovery.
subscription for EPC support WLAN direct discovery and communication.
subscription for one-to-many ProSe Direct Communication, applicable only to Public Safety subscribers.
subscription for one-to-one ProSe Direct Communication, applicable only to Public Safety subscribers.
subscription for ProSe UE acting as UE-to-Network Relay, applicable only to Public Safety subscribers.
subscription for Remote UE access to ProSe UE-to-Network Relay, applicable only to Public Safety subscribers.

Additional parameters related to the ProSe Direct service may be stored in the user's profile, such as:

the list of the PLMNs where the UE is authorised for open Direct Discovery Model A, i.e. to announce or monitor or both.
the list of the PLMNs where the UE is authorised for restricted ProSe Direct Discovery Model A, i.e. to announce or monitor or both.
the list of the PLMNs whether the UE is authorized for restricted ProSe Direct Discovery Model B , i.e. to perform Discoverer operation or Discoveree operation or both.
the list of the PLMNs where the UE is authorised to perform one-to-many ProSe Direct Communication, applicable only to Public Safety subscribers.
the list of the PLMNs where the UE is authorised to perform one-to-one ProSe Direct Communication, applicable only to Public Safety subscribers.

4.5.3 IP address allocation p. 28

For one-to-many ProSe Direct Communication:

when the UE is configured to use IPv6 on the direct link, the UE auto-configures a link local IPv6 Address following procedures defined in RFC 4862. This address can only be used as the source IP address for one-to-many ProSe Direct Communication.
when the UE is configured to use IPv4 for a certain Group for one-to-many ProSe Direct Communication, then either it uses the configured IPv4 address for the Group or, if it is not configured with an address for the Group, it uses Dynamic Configuration of IPv4 Link-Local Addresses RFC 3927.

For communication with a ProSe UE-to-Network Relay:

When the Remote UE uses IPv4 to access the external PDN:
1. The IPv4 address allocation and IPv4 parameter configuration via DHCPv4 is performed according to RFC 2131 and RFC 4039 procedures. The IPv4 address provided to the Remote UE from the ProSe UE-to-Network Relay by DHCPv4 procedure shall correspond to a local IPv4 address range configured in the ProSe UE-to-Network Relay.
2. The DHCPv4 request from the Remote UE is always sent subsequent to the establishment of the One-to-one ProSe Direct Communication, see details in clause 5.4.4.3.
When the Remote UE uses IPv6 to access the external PDN:
1. IPv6 network prefix allocation via IPv6 Stateless Address auto-configuration. Router solicitation from the Remote UE is always sent subsequent to the establishment of the One-to-one ProSe Direct Communication, see details in clause 5.4.4.2.
2. IPv6 parameter configuration via Stateless DHCPv6: The UE may use stateless DHCPv6 for additional parameter configuration.

The PDN type of the PDN connection used for the relay traffic shall support the IP version used by the Remote UE. If the Remote UE initiates an allocation of IPv4 address or an IPv6 prefix when the requested IP version is not supported in the corresponding PDN connection then IP address/prefix allocation fails.

In case of IPv4 the ProSe UE-to-Network Relay performs IPv4 NAT between IPv4 addresses assigned to the Remote UEs and the IPv4 address assigned to the PDN connection used for the relay traffic. In case of IPv6 the ProSe UE-to-Network Relay assigns IPv6 prefixes from IPv6 prefix range that have been assigned to the PDN connection used for the relay traffic via IPv6 prefix delegation.

For one-to-one ProSe Direct Communication between two UEs neither of which acts as a ProSe UE-to-Network Relay the following mechanism for IP address/prefix allocation may be used:

DHCP-based IPv4 address allocation with one of the two UEs acting as a DHCP server.
IPv6 Stateless Address auto configuration specified in RFC 4862 for assignment of IPv6 prefix, with one of the two UEs acting as IPv6 default router.

NOTE:
Which UE acts as a DHCPv4 server or IPv6 default router is negotiated during secure layer-2 link establishment.
IPv6 link-local addresses as defined in RFC 4862 are formed by UEs locally. The IPv6 link-local addresses are exchanged during the establishment of a secure layer-2 link over PC5. The UEs shall disable duplicate address detection after the layer-2 link is established.

4.5.4 ProSe UE-to-Network Relaying |R13| p. 29

A UE supporting ProSe UE-to-Network Relaying shall include the following functions:

ProSe Direct discovery for ProSe UE-to-Network Relay;
One-to-one ProSe Direct Communication;
Acting as a default router to the Remote UEs forwarding IP packets between the UE-ProSe UE-to-Network Relay point-to-point link and the corresponding PDN connection;
Relaying eMBMS traffic using one-to-many ProSe Direct Communication;
ProSe Per-Packet Priority handling for unicast and eMBMS downlink traffic;
IPv6 prefix allocation and delegation if IPv6 is used;
IPv4 address allocation and IPv4 NAT function if IPv4 is used.

In order to use a ProSe UE-to-Network Relay a ProSe-enabled Public Safety UE shall include the following functions:

ProSe Direct discovery for ProSe UE-to-Network Relay;
One-to-one ProSe Direct Communication with dynamic IP address/prefix allocation.

In order to support mission critical applications (e.g. MCPTT) for Remote UEs, policy control and charging functionality as defined in TS 23.203 needs to be provided for the UE-to-Network Relay UE to enable resource utilisation for Remote UEs.

In this release of the specification, the following functionalities shall be provided to enable support for policy control for Remote UEs:

The Remote UEs shall be assigned a /64 IPv6 Prefix from a shorter IPv6 prefix by the UE-to-Network Relay.
The UE-to-Network Relay UE and the PCRF and the PDN GW supporting the PDN connection shall support the extended TFT filter format, so that services can be authorized separately for each Remote UE.
The UE-to-Network Relay UE and PDN GW shall support the TFT packet filter attribute Local Address and Mask as defined in clause 15.3.2.2A of TS 23.060.
There shall be a dedicated PDN connection to provide support for UE-to-Network Relay connectivity.
The UE-to-Network Relay UE, the PDN GW and PCRF shall be configured with a dedicated APN for UE-to-Network Relay connectivity.

NOTE 2:
If Local Breakout configuration is supported for relay connectivity, the dedicated APN needs to be well-known APN to allow seamless operation across various operators' networks.
The AF determines the PCRF realm using the IPv6 prefix of the Remote UE and contacts the PCRF serving the UE-to-Network Relay PDN connection.

NOTE 3:
If the AF and the PCRF are in different PLMNs, the AF appears as a third party application server as described in clause 5.2.1 of TS 23.203.
The PCRF validates any Remote UE related service information from the AF based on roaming agreement and the dedicated APN for UE-to-Network Relay functionality.

NOTE 4:
Once the AF has derived the PLMN ID of the PCRF and contacted the corresponding domain, then the session binding can continue using procedures defined in TS 23.203.

4.5.5 ProSe Proxy Function p. 30

ProSe Proxy Function enables support for UE to Home ProSe Function/ProSe Key Management Function communication as defined in clause 4.4.1.1 and in TS 33.303, where the Home ProSe Function/ProSe Key Management Function is not located in the same network as the PDN GW for the PDN connection being used. Such proxy functions are needed when requirements on security are not met by signalling over Internet. Inter-PLMN signalling may be used in that case. Due to restrictions on the inter-PLMN network, the UE to Server traffic over the user plane may not be sent between networks directly. Only tunnelled server to server traffic may be sent between networks.

A roaming UE, which has a Local Breakout PDN Connection in the VPLMN, uses this access to reach a ProSe Function in the Home network and a ProSe Key Management Function in the Home network or another network. UE is not aware of the presence of a ProSe Proxy Function.

A ProSe Proxy implemented in the VPLMN on the SGi interface may be used to reach the ProSe Function located in the HPLMN. The ProSe Proxy Function forwards signalling traffic between the UE and the ProSe Function in the HPLMN.

A ProSe Proxy implemented in either the HPLMN or the VPLMN on the SGi interface may be used to reach a ProSe Key Management Function located in a different network. The ProSe Proxy Function forwards the signalling traffic (as defined in clause 6.2.2.3.1 in TS 33.303) between the UE and the ProSe Key Management Function.

4.5.6 Support for ProSe for UEs in limited service state p. 30

ProSe-enabled non-Public Safety UE shall not use ProSe when in limited service state.

ProSe-enabled Public Safety UEs that are authorised to use ProSe Direct Communication and/or ProSe Direct Discovery shall be able to use ProSe Direct Communication and/or ProSe Direct Discovery when in limited service state following the procedures defined in clause 4.5.1.1.2.3.1 for ProSe Direct Communication and ProSe Direct Discovery when the UE enters in limited service state:

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

A ProSe-enabled Public Safety UE in limited service state shall only use ProSe mechanisms available in ECM-IDLE, for details see TS 36.300.

A ProSe-enabled Public Safety UE in limited service state shall not use ProSe in ECM-CONNECTED mode.

ProSe-enabled Public Safety UEs shall not use ProSe Direct Communication or ProSe Direct Discovery if the UE has entered in limited service state due to all other situations (e.g. no SIM in the MS, an "illegal MS" or "illegal ME" response to a registration request, or an "IMSI unknown in HLR" response to a registration request) defined in TS 23.122, where the UE is unable to obtain normal service from a PLMN.