Step 1.
UE A sends a Proximity Request (EPUID_A, Application ID, ALUID_A, ALUID_B, window, Range, A's location, [WLAN indication]) message to ProSe Function A. The Application ID parameter identifies the 3rd party App Server platform. ALUID_A and ALUID_B are the Application Layer User IDs for users A and B, respectively. The window parameter indicates the time period during which the request is valid. Range is a requested range class for this application chosen from the set of allowed range classes. A's location is the current location of UE A with the best accuracy known by UE A. UE A may optionally request EPC support for WLAN direct discovery and communication with UE B by adding the WLAN indication.
Step 2.
ProSe Function A sends a Map Request (ALUID_A, ALUID_B) message to the App Server, requesting that it provide the EPC ProSe User ID for the targeted user B. ProSe Function A stores the Application Layer User IDs (ALUID_A and ALUID_B) until the execution of the Proximity Alert procedure described in
clause 5.5.7, the Proximity Request Cancellation procedure described in
clause 5.5.9 or until the expiry of the time window during which the request is valid.
Step 3.
The App Server checks user B's application-specific ProSe permissions, confirms that user A is allowed to discover user B, and sends a Map Response (EPUID_B PFID_B) message to ProSe Function A indicating user B's EPC ProSe User ID (EPUID_B) as well as the ProSe Function ID of ProSe Function B (PFID_B), ProSe Function A stores the EPUID_B and PFID_B until the execution of the Proximity Alert procedure described in
clause 5.5.7, the Proximity Request Cancellation procedure described in
clause 5.5.9 or until the expiry of the time window during which the request is valid.
Step 4.
ProSe Function A propagates the Proximity Request (EPUID_B, EPUID_A, Application ID, window, A's location, [WLLID_A], SUPL Config) message to ProSe Function B. A's location is the current location of UE A provided in step 1 expressed in GAD shapes defined in
TS 23.032. WLAN indication is included if UE A has requested EPC support for WLAN direct discovery and communication in step 1. SUPL Config is a set of parameters that enable ProSe Function B to configure SUPL reporting in UE B using the
'"Inside" Trigger with Repeated Reporting' as defined in OMA AD SUPL [2].
Step 5.
Based on EPUID_B received in the previous step, ProSe Function B retrieves subscriber B's record. ProSe Function B may request UE B's last known location via the HSS (step 5a). Based on the last known location of UE B obtained via the HSS and UE A's location and time window provided by ProSe Function A in step 4, ProSe Function B may determine that the users are unlikely to enter proximity within the requested time window and rejects the request by sending a Proximity Request Reject message towards UE A with an appropriate cause value (steps 5b and 5c), in which case the remaining steps of the procedure are skipped.
Step 6.
Depending on UE B's ProSe profile, UE B may be asked to confirm permission for the proximity request (e.g. user B may have temporarily disabled the ProSe function on UE B).
Step 7.
ProSe Function B requests location reporting on UE B from SLP B and acknowledges the proximity request to ProSe Function A and provides UE B's current location (if known). The WLAN Link Layer ID of UE B (WLLID_B) is included if UE A has requested EPC support for WLAN direct discovery and communication in step 1 and if UE B uses a permanent WLAN Link Layer ID.
Step 8.
ProSe Function A requests location reporting on UE A from SLP A. If UE A's current location is available and if UE B's location was included in step 7, ProSe Function A may decide to cancel the Proximity Request procedure if it determines that the UEs are unlikely to enter proximity within the requested time window. Otherwise ProSe Function A acknowledges the proximity request to UE A.