Content for  TS 23.303  Word version:  18.0.0

This is a link layer identifier that is used as a source Layer-2 ID in all the packets the UE sends for one-to-many and one-to-one ProSe Direct Communication. When bearer-level security is configured to be used, the ProSe UE ID is assigned by the ProSe Key Management Function as defined in TS 33.303. The ProSe Key Management Function ensures that the ProSe UE ID is unique in the context of one-to-many ProSe Direct Communication for this group. When bearer-level security is configured not to be used (including the case of Layer-2 broadcast communication required to support Dynamic Configuration of IPv4 Link-Local Addresses RFC 3927]), the ProSe UE ID is either configured in the UE or self-assigned by the UE. Assuming that global uniqueness of ProSe UE ID cannot be ensured, the UE should be prepared to handle conflicts of ProSe UE IDs using mechanisms that are out of scope of this release of the specification (e.g. by self-assigning a new ProSe UE ID when a conflict is detected).

This is a link layer identifier that identifies the group in the context of one-to-many ProSe Direct Communication. It is used as a destination Layer-2 ID in all the packets the UE sends to this group for one-to-many ProSe Direct Communication.

For Open ProSe Discovery, (as described in TS 22.278) the ProSe Application ID is called the Public ProSe Application ID. The geographic scope of the Public ProSe Application ID may be PLMN-specific, country specific or global. Each Public ProSe Application ID is composed of the following parts:

1. The ProSe Application ID Name is described in its entirety by a data structure characterized by different levels e.g., broad-level business category (Level 0) / business sub-category (Level 1) / business name (Level 2) / shop ID (Level 3). For the purpose of presentation, a ProSe Application ID Name is usually displayed as a string of labels in which the labels represent hierarchical levels.
2. The PLMN ID that corresponds to the PLMN that assigned the ProSe Application ID Name.

For the announcing UE, the ProSe Application Code is obtained from the HPLMN ProSe Function using the Announce Request procedure (see clause 5.3.3.1 and clause 5.3.3.2). The ProSe Application Code is contained in the message that is actually transmitted over the radio interface (on PC5) by a UE engaged in the ProSe Direct Discovery procedure (see clause 5.3) to "monitoring" UEs. For the "monitoring" UE, Discovery Filter(s) to monitor the ProSe Application Code(s) over the radio interface (on PC5) are obtained from the HPLMN ProSe Function using the Monitor Request procedure (see clause 5.3.3.4 and clause 5.3.3.5). Each ProSe Application Code is composed of the following parts:

1. A temporary identity that corresponds to the ProSe Application ID Name. Given the data structure associated with the Public ProSe Application ID, each ProSe Application ID can be associated with various temporary identities that contains as many identifiers as there are levels in the corresponding ProSe Application ID Name: this allows partial matching at the monitoring UE side using a ProSe Application Mask (see clause 4.6.4.2b) or a Discovery Filter, making more effective and flexible the filtering of the received temporary identity in a monitoring UE. See clause 4.6.4.2a.
2. The PLMN ID of the ProSe Function that assigned the ProSe Application Code, i.e. Mobile Country Code (MCC) and Mobile Network Code (MNC).

ProSe Application Code matching considers all components listed above. In ProSe Application Code matching, the "monitoring" UE shall consider it a full match, if both PLMN ID and temporary identity match with the corresponding contents of the Discovery Filter. A partial match is obtained if the PLMN ID matches fully and the temporary identity matches partially with the corresponding contents of the ProSe Application Mask (see clause 4.6.4.2b). A ProSe Application Code is allocated per "announcing" UE and per application and has an associated validity timer that runs both in the ProSe Function and in the UE. In case of Open ProSe Discovery:

• when the "announcing" UE wants to announce something, it shall send a Discovery Request containing the Public ProSe Application ID to the ProSe Function, and the ProSe Function assigns a ProSe Application Code.
• when the "monitoring" UE wants to monitor something, it shall send a discovery request containing the full or a subset of the Public ProSe Application ID, e.g. it may provide 2 out of the n levels of the full Public ProSe Application ID.

In open ProSe Direct Discovery, a Discovery Filter consists of a ProSe Application Code, ProSe Application Mask(s) and a time to live (TTL). In restricted ProSe Direct Discovery, a Discovery Filter consists of a ProSe Restricted Code, ProSe Application Masks(s) and a TTL. A TTL indicates for how long the related Discovery Filter is valid after it is received. A Discovery Filter is provided to a monitoring UE by its HPLMN ProSe Function. It is used by the monitoring UE to selectively match ProSe Application Codes or ProSe Restricted Codes received on the PC5 interface. In Model B discovery, Discovery Filters are provided to the Discoveree UE and Discoverer UE. The Discoveree UE needs to obtain a Discovery Query Filter before it can participate in the discovery operation. The Discoveree UE applies the Discovery Query Filter to determine which of the ProSe Query Codes that it monitors is to be responded to. For each of the ProSe Query Codes it is configured to announce, the Discoverer UE needs to be configured with one or more Discovery Response Filters for processing the ProSe Response Codes that may be received in response. Discovery Filters allow full matching and partial matching of as many parts of ProSe Application Code or ProSe Restricted Code as are contained in the ProSe Application Mask. A Discovery Filter may contain more than one mask in order to support allocation of masks for different parts of the ProSe Application Code or ProSe Restricted Code.

A ProSe Application Mask shall be used for partial matching of ProSe Application Codes or ProSe Restricted Codes received on the PC5 interface. A ProSe Application Mask is contained in a Discovery Filter. A ProSe Application Mask consists of one or more applicable parts of temporary identities of ProSe Application Codes or ProSe Restricted Codes to allow partial matching.

The following parameters are used in the UE-to-Network Relay Discovery Announcement message (Model A):

• ProSe Relay UE ID: link layer identifier that is used for direct communication and is associated with a Relay Service Code. A UE-to-Network Relay shall have a distinct ProSe Relay UE ID for each Relay Service Code. For support of multiple PDN Connections, the ProSe UE-to-Network Relay is assigned a different ProSe Relay UE ID for each PDN Connection.
• Announcer Info: provides information about the announcing user.
• Relay Service Code: parameter identifying a connectivity service the ProSe UE-to-Network Relay provides to Public Safety applications. The Relay Service Codes are configured in a ProSe UE-to-Network Relay for advertisement. Additionally, the Relay Service Code also identifies authorized users the ProSe UE-to-Network Relay would offer service to, and may select the related security policies or information e.g. necessary for authentication and authorization between the Remote UE and the ProSe UE-to-Network Relay (e.g. a Relay Service Code for relays for police members only would be different than a Relay Service Code for relays for Fire Fighters only, even though potentially they provided connectivity to same APN e.g. to support Internet Access).

The following parameters are used in the UE-to-Network Relay Discovery Solicitation message (Model B):

• Discoverer Info: provides information about the discoverer user.
• Relay Service Code: information about connectivity that the discoverer UE is interested in. The Relay Service Codes are configured in the Remote UEs interested in related connectivity services.
• ProSe Relay UE ID: link layer identifier of a UE-to-Network Relay that is used for direct communication and is associated with a Relay Service Code. A UE-to-Network Relay shall have a distinct ProSe Relay UE ID for each Relay Service Code. The ProSe Relay UE ID is optional.

The following parameters are used in the UE-to-Network Relay Discovery Response message (Model B):

• ProSe Relay UE ID: link layer identifier that is used for direct communication and is associated with a Relay Service Code. A UE-to-Network Relay shall have a distinct ProSe Relay UE ID for each Relay Service Code.
• Discoveree Info: provides information about the discoveree.

The ProSe Query Code is used for Model B discovery. It is obtained by a Discoverer UE from its HPLMN ProSe Function. The ProSe Query Code is sent by the Discoverer UE over the air.

The ProSe Response Code is used for Model B discovery. It is obtained by a Discoveree UE from its HPLMN ProSe Function before its starts the discovery operation. There is one ore more Discovery Query Filter(s) associated with the ProSe Response Code and provided to the Discoveree UE. The Discoveree UE sends the ProSe Response Code over the air when a monitored ProSe Query Code matches the Discovery Query Filter(s).

The ProSe Restricted Code is used for restricted ProSe Direct Discovery. For the announcing UE, the ProSe Restricted Code is obtained from the HPLMN ProSe Function using the Announce Request procedure (see clause 5.3.3.2A, and 5.3.3.3A). The ProSe Restricted Code is contained in the message that is transmitted over the radio interface (on PC5) by a UE engaged in the ProSe Direct Discovery procedure (see clause 5.3) to monitoring UEs. For the announcing UE requesting "on demand" announcing in restricted ProSe Direct Discovery Model A, the ProSe Restricted Code can be allocated by the HPLMN ProSe Function using the Announcing Alert procedures (see clause 5.3.5). The monitoring UE, a set of Discovery Filter(s) to monitor the ProSe Restricted Code(s) over the radio interface (PC5) are obtained from the HPLMN ProSe Function using the Monitor Request procedure (see clause 5.3.3.4A and 5.3.3.5A). Each ProSe Restricted Code is composed of the following parts:

1. A temporary identifier that corresponds to one or more RPAUIDs.
2. The PLMN ID of the ProSe Function that assigned the ProSe Restricted Code.

It is up to the policy in the ProSe Function whether to allocate the same ProSe Restricted Code for all RPAUIDs or different ProSe Restricted Codes for different RPAUIDs. The ProSe Restricted Code has an associated validity timer that runs both in the ProSe Function and in the UE. The ProSe Function may update the ProSe Restricted Code or the Discovery Filter(s) using the Restricted Discovery Authorization Update procedure in clause 5.3.6A. To support restricted Direct Discovery with application-controlled extension, the ProSe Restricted Code contains a prefix, which is assigned by the ProSe Function in the HPLMN, and a suffix which is assigned by the ProSe Application Server.

The 3GPP layer identity of the UE is concealed from application layer via the creation by the ProSe Function of a corresponding PDUID. The mapping of the PDUID to the 3GPP layer UE ID is maintained by the ProSe Function. The ProSe Protocol layer in the UE gets the PDUID during the procedure of service authorisation for ProSe Direct Discovery, from the ProSe Function of the HPLMN. The PDUID is stored in the ProSe Function as part of the service authorization information, and is associated with a validity timer. The ProSe function may update the PDUID using the ProSe service notification message before the validity timer expires.

The application layer user identity is concealed from 3GPP network via the creation by the ProSe Application Server of a corresponding Restricted ProSe Application User ID. The mapping of the RPAUID to the actual application layer identity is maintained by the ProSe Application Server. The structure and value of the RPAUID is out of scope of 3GPP. The UE obtains the RPAUID using application layer signalling prior to the execution of the Discovery Request procedures described in clause 5.3.3.

The following parameters are used in the Group Member Discovery Announcement message (Model A):

• ProSe UE ID: link layer identifier that is used for subsequent direct one-to-one and one-to-many communication.
• Announcer Info: provides information about the announcing user.
• Discovery Group ID: identifier of a discovery group that the UE belongs to.

The following parameters are used in the Group Member Discovery Solicitation message (Model B):

• Discoverer Info: provides information about the discoverer user.
• Discovery Group ID: identifier of a discovery group that the targeted UE should belong to.
• Target Info: provides information about the targeted discoverees (single user or group). The Target Info is provided by the upper layers of the UE.

The following parameters are used in the Group Member Discovery Response message (Model B):

• ProSe UE ID: link layer identifier that is used for subsequent direct one-to-one and one-to-many communication.
• Discoveree Info: provides information about the discoveree.
• Discovery Group ID: identifier of the discovery group that the discoveree UE belongs to.

The following parameters may be used in the Relay Discovery Additional Information message:

• Relay Service Code: the Relay Service Code associated with the message. The Relay Service Code is used to identify the security parameters needed by the receiving UE to process the discovery message as specified in TS 33.303.
• ProSe Relay UE ID: link layer identifier that is used for direct communication and is associated with a Relay Service Code.
• Announcer info: provides information about the announcing user.
• TMGI: indicates the MBMS the ProSe UE-to-Network Relay is relaying.
• ProSe Layer-2 Group ID: link layer identifier of the group that transmits the MBMS traffic corresponding to the TMGI.
• ECGI: indicates the ECGI of the serving cell of the ProSe UE-to-Network Relay.

A single Relay Discovery Additional Information message may carry:

• the ECGI that the ProSe UE-to-Network Relay is camped on or;
• one or more advertised TMGIs and their corresponding ProSe Layer-2 Group IDs up to the maximum allowed message size or;
• the ECGI that the ProSe UE-to-Network Relay is camped on, and one or more advertised TMGIs and their corresponding ProSe Layer-2 Group IDs up to the maximum allowed message size.

Some bits of the ProSe Application Code may be used as Metadata Index to reflect the current metadata version. It is allocated and updated by the Home ProSe Function when new metadata are uploaded and stored in the ProSe Function for a given ProSe Application ID. The length of the Metadata Index is decided by the ProSe Function under operator's control.

The Metadata Index Mask indicates the part used for the Metadata Index in the ProSe Application Code. It is provided to the monitoring UE during the Match Report procedure for the ProSe Application Code(s) containing a Metadata Index. The monitoring UE can use the Metadata Index Mask to locate the Metadata Index in the ProSe Application Codes.