5.8 Procedure for Informing about Potential Network Issues

23.6823GPPArchitecture enhancements to facilitate communications with packet data networks and applicationsRelease 17TS

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

5.8.1 General

This clause contains the detailed description and the procedures for the service capability exposure feature Informing about Potential Network Issues.

An SCS/AS may request for being notified about the network status. The following methods are supported:

– The SCS/AS requests to be informed, one-time, about the network status by providing a geographical area. This procedure is referred to as one-time network status request;

– The SCS/AS requests to be informed, continuously, about the network status by providing a geographical area. This procedure is referred to as continuous network status request.

The procedures described in this clause use the RAN Congestion Awareness Function (RCAF) and corresponding features as defined in TS 23.401 [7] and TS 23.060 [6]. The SCEF communicates with the RCAF via the Ns reference point.

After receiving the request for network status notification from the SCS/AS, the SCEF derives the RCAF(s) responsible for the indicated geographical area, and requests congestion reporting from these RCAF(s).

NOTE 1: The SCEF needs to know the RCAF(s) available in the operator network or the network of the RAN operator in the case of RAN sharing. For every RCAF, the SCEF needs to be configured with the RCAF address and the geographical area the RCAF is responsible for. The Ns reference point does not support roaming.

The RCAF reports to the SCEF the following information from the RUCI (see TS 23.203 [27]) for every cell or eNodeB belonging to the indicated geographical area:

– Congestion level or an indication of the "no congestion" state;

– ECGI, or eNodeB-ID, or SAI for which the congestion level is being provided.

Based on the congestion information the SCEF receives from the identified RCAF(s), the SCEF derives and reports the network status for the geographical area as Network Status Indication (NSI) to the SCS/AS. When reporting to the SCS/AS, the NSI shall not include any 3GPP location information.

NOTE 2: Either exact values for congestion status, as reported by RCAF(s) to SCEF or abstracted values e.g. (High, Medium, Low) can be reported by the SCEF to the SCS/AS. The calculation and the reporting of the NSI to the SCS/AS depends on operator configuration (SLAs, network topology, usage etc.).

When an SCS/AS requests One-time Network Status from the SCEF, the SCEF can optionally provide a time interval at which the SCS/AS is allowed to re-issue the same request for network status.

NOTE 4: The time interval provided by SCEF can be ignored by the SCS/AS if the subsequent request on network status is considerably different wrt. the geographical area.

The request procedure for one-time or continuous reporting of network status is described in clause 5.8.2 and the report procedure for continuous reporting of network status in clause 5.8.3. Clause 5.8.4 contains the removal procedure for the continuous reporting of network status.

5.8.2 Request procedure for one-time or continuous reporting of network status

This procedure is used by an SCS/AS to retrieve Network Status Information (NSI) from the network. This procedure can be used to request a one-time or continuous reporting of network status. Figure 5.8.2-1 illustrates the procedure.

Figure 5.8.2-1: Request procedure for one-time or continuous reporting of network status

1. When the SCS/AS needs to retrieve NSI, the SCS/AS sends a Network Status Request (Geographical area, SCS/AS Identifier, Duration, Threshold) message to the SCEF. Duration indicates the time for which a continuous reporting is requested. The absence of Duration indicates a one-time reporting. Threshold indicates a range at which the SCS/AS wishes to be informed of the network status. Multiple Threshold values may be included. The SCEF assigns a TLTRI that identifies the Network Status Request.

NOTE 1: Geographical area specified by SCS/AS could be at cell level (CGI/ECGI), TA/RA level or other formats e.g. shapes (e.g. polygons, circles etc.) or civic addresses (e.g. streets, districts etc.) as referenced by OMA Presence API [32].

2a. The SCEF authorizes the SCS/AS request for notifications about potential network issues. The SCEF stores SCS/AS Address, TLTRI, Duration, if present, and Threshold, if present. The SCEF assigns an SCEF Reference ID.

2b. The SCEF sends a Network Status Response (TLTRI, cause). The cause value indicates that the network has accepted the request in step 1. Based on operator policies, if either the SCS/AS is not authorized to perform this request (e.g. if the SLA does not allow for it) or the SCS/AS has exceeded its quota or rate of submitting requests, the cause value indicates the error and the flow stops at this step.

3. The SCEF assigns an SCEF Reference ID and identifies, based on local configuration (as described in clause 5.8.1), the RCAF(s) responsible for the provided Geographical Area. For every identified RCAF, the SCEF derives a Location Area from the Geographical Area provided by the SCS/AS. The Location Area is according to operator configuration either a 3GPP location area (e.g. list of TA/RAs, list of cell(s), list of eNodeBs, etc.) or a sub-area of the Geographical Area provided by the SCS/AS. The SCEF sends an Aggregated Congestion Request (SCEF Reference ID, Location Area, Duration, Threshold) message to the identified RCAF(s). Duration indicates the time for which a continuous reporting is requested. The absence of Duration indicates a one-time reporting. The SCEF, based on operator policies, may chose a different Threshold value than the one indicated by the SCS/AS in step 1.

4. The RCAF examines the Aggregated Congestion Request message. If the SCEF provided a Duration, the RCAF stores the SCEF instructions and starts to monitor the set of cells or eNodeBs belonging to the Location Area for a change in the congestion status that is crossing a Threshold (if provided by the SCEF). The RCAF sends an Aggregated Congestion Report to the SCEF including the SCEF Reference ID and, depending on the operator configuration and current RCAF knowledge, the congestion status for every cell or eNodeB belonging to the Location Area requested by the SCEF.

5. The SCEF verifies whether the Network Status Request identified via the SCEF Reference ID is valid and active and stores the report. After receiving reports from all the involved RCAF(s) to which step 3 was executed, the SCEF derives the NSI for the requested Geographical Area by combining all reports with the same SCEF Reference ID in an operator configurable way (governed by SLAs, network topology, usage, etc.).

6. The SCEF sends a Network Status Report (TLTRI, NSI) message to the SCS/AS.

7. The SCS/AS sends a Network Status Acknowledgement to the SCEF.

5.8.3 Report procedure for continuous reporting of network status

This procedure is used by the SCEF to report a change of Network Status Information (NSI) to the SCS/AS which requested a continuous reporting of network status. Figure 5.8.3-1 illustrates the procedure.

Figure 5.8.3-1: Report procedure for continuous reporting of network status

1. The RCAF detects a change in the congestion status that is crossing a Threshold (if provided by the SCEF) for the set of cells or eNodeBs belonging to the Location Area requested by the SCEF. An Aggregated Congestion Report message is sent to this SCEF including the SCEF Reference ID and, depending on the operator configuration, the congestion status for every cell or eNodeB belonging to the Location Area requested by the SCEF.

2. The SCEF acknowledges the report to the RCAF.

NOTE 1: Step 1 and 2 can happen multiple times and the Aggregated Congestion Report message can be sent by any of the involved RCAFs.

3. Whenever a new Aggregated Congestion Report message arrives, the SCEF stores the report and derives a new NSI for the requested geographical area by combining this report with all other reports having the same SCEF Reference ID in an operator configurable way (governed by SLAs, network topology, usage etc.).

4. Triggered by a NSI change (derived in step 3) that is crossing a Threshold (if provided by the SCS/AS), the SCEF sends a Network Status Report (TLTRI, NSI) message to the SCS/AS.

5. The SCS/AS sends a Network Status Acknowledgement to the SCEF.

5.8.4 Removal procedure for continuous reporting of network status

This procedure is used for termination of the continuous reporting of network status. It can be triggered by the SCS/AS at any time before the Duration is over or if no Duration was provided. The SCEF will trigger this procedure when the Duration is over. Figure 5.8.4-1 illustrates the procedure.

Figure 5.8.4-1: Removal procedure for continuous reporting of network status

1a. The SCEF detects that the requested Duration for an ongoing continuous reporting of network status to an SCS/AS is over and identifies the corresponding SCEF Reference ID.

1b. When the SCS/AS needs to terminate an ongoing continuous reporting of network status, the SCS/AS sends a Cancel Network Status Request (SCS/AS Identifier, TLTRI) message to the SCEF.

2b. If the SCS/AS requested to terminate an ongoing continuous reporting of network status in step 1b, the SCEF authorizes the SCS/AS request and identifies the corresponding SCEF Reference ID.

3b. If the SCS/AS requested to terminate an ongoing continuous reporting of network status in step 1b, the SCEF sends a Cancel Network Status Response (Cause) message to the SCS/AS.

4. The SCEF identifies the RCAF(s) involved in the continuous reporting represented by the SCEF Reference ID. The SCEF sends a Cancel Aggregated Congestion Request (SCEF Reference ID) message to the identified RCAF(s).

5. The RCAF removes the related SCEF instructions and stops monitoring the set of cells or eNodeBs belonging to the Location Area for a change in the congestion status. Afterwards, a Cancel Aggregated Congestion Response is sent to the SCEF including the SCEF Reference ID.

6. The SCEF removes all state information related to this continuous reporting represented by the SCEF Reference ID.