21 Application Layer Measurement Collection

38.3003GPPNRNR and NG-RAN Overall descriptionRelease 17Stage 2TS

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

21.1 Overview

The QoE Measurement Collection function enables collection of application layer measurements from the UE. The supported service types are:

– QoE Measurement Collection for DASH streaming services;

– QoE Measurement Collection for MTSI services;

– QoE Measurement Collection for VR services.

The QoE measurement collection is supported in RRC_CONNECTED state only. Both signalling based and management based QoE measurement collection are supported.

NOTE: The naming QoE Measurement is used in NG, Xn, and interfaces between the OAM and the gNB. In the Uu interface, the naming application layer measurement is used and it is equal to QoE Measurement.

21.2 QoE Measurement Configuration

21.2.1 QoE Measurement Collection Activation and Reporting

The feature is activated in the gNB either by direct configuration from the OAM system (management-based activation), or by signalling from the OAM via the 5GC (signalling-based activation), containing UE-associated QoE configuration. One or more QoE measurement collection jobs can be activated at a UE per service type, and each QoE measurement configuration is uniquely identified by a QoE reference. When the UE is configured with MR-DC, only the MN can configure the QoE configuration.

For signalling-based QoE measurements, the OAM initiates the QoE measurement activation for a specific UE via the 5GC, and the gNB receives one or more QoE measurement configurations by means of UE-associated signalling. The QoE measurement configuration for signalling-based activation includes an application layer measurement configuration list and the corresponding information for QoE measurement collection, e.g., QoE reference, service type, MCE IP address, slice scope, area scope, MDT alignment information and the indication of available RAN visible QoE metrics.

For management-based QoE measurement activation, the OAM sends one or more QoE measurement configurations directly to the gNB. The QoE measurement configuration for management-based activation also includes an application layer measurement configuration list and the corresponding information for QoE measurement collection. The gNB selects UE(s) that meet the required QoE measurement capability, area scope and slice scope.

Application layer measurement configuration received by the gNB from OAM or CN is encapsulated in a transparent container, which is forwarded to a UE as Application layer configuration in the RRCReconfiguration message (there can be multiple configurations in the same message). Application layer measurement reports received from UE’s application layer are encapsulated in a transparent container and sent to the network in the MeasurementReportAppLayer message, as specified in TS 38.331 [12]. The UE can send multiple application layer measurement reports to the gNB in one MeasurementReportAppLayer message. In order to allow the transmission of application layer measurement reports which exceed the maximum PDCP SDU size, segmentation of the MeasurementReportAppLayer message may be enabled by the gNB. An RRC identifier conveyed in the RRC signalling is used to identify the application layer measurement configuration and report between the gNB and the UE. The RRC identifier is mapped to the QoE reference in the gNB, and the gNB forwards the application layer measurement report to MCE together with the QoE reference. The gNB can release one or multiple application layer measurement configurations from the UE in one RRCReconfiguration message at any time. The UE may additionally be configured by the gNB to report when a QoE measurement session starts or stops for a certain application layer measurement configuration.

21.2.2 QoE Measurement Collection Deactivation

The QoE Measurement Collection deactivation permanently stops all or some of the QoE measurement collection jobs towards a UE, resulting in the release of the corresponding QoE measurement configuration(s) in the UE. The deactivation of QoE measurement collection is supported by using UE-associated signalling. A list of QoE references is used to deactivate the corresponding QoE measurement collection job(s).

Upon reception of the QoE release message in an application layer measurement configuration, the UE discards any unsent application layer measurement reports corresponding to the released application layer configuration. The UE discards the reports received from application layer when it has no associated application layer measurement configuration configured.

The network can replace a QoE measurement configuration with another one by deactivating an existing QoE measurement configuration and activating another QoE measurement configuration of the same QoE measurement configuration type.

21.2.3 Handling of QMC during RAN Overload

The QoE measurement collection pause/resume procedure is used to pause/resume reporting of one or multiple QoE measurement configurations in a UE in RAN overload situation.

The gNB can use the RRCReconfiguration message to temporarily stop the UE from sending application layer measurement reports associated with one or multiple application layer measurement configurations. When the UE receives the QoE measurement collection pause indication, the UE temporarily stores application layer measurement reports in AS layer. When the UE receives the QoE measurement collection resume indication, the UE sends the stored application layer measurement reports to the gNB.

21.2.4 QoE Measurement Handling in RRC_IDLE and RRC_INACTIVE States

If the UE enters RRC_INACTIVE, the UE AS configuration for the QoE is stored in the UE Inactive AS context.

If the UE enters RRC_IDLE state, the UE releases all application layer measurement configurations.

21.2.5 Per-slice QoE Measurement

When a service is provided within a configured slice, the QoE Measurement for this service type can also be configured together with the corresponding slice scope, so that the user experience of this service can also be evaluated on a per-slice basis. Multiple QoE measurement configurations can be configured for the same service type, and each configuration can pertain to different slices, where each QoE measurement configuration is identified with a QoE reference.

The UE includes the network slice identifier inside the QoE report container when reporting QoE measurement reports.

21.3 QoE Measurement Continuity for Mobility

The QoE measurement collection continuity for intra-system intra-RAT mobility is supported, with the Area Scope parameters configured by the OAM, where the network is responsible for keeping track of whether the UE is inside or outside the Area Scope. A UE continues an ongoing QoE measurement even if it leaves the Area Scope, unless the network indicates to the UE to release the QoE configuration.

For the RRC_CONNECTED state mobility, the source gNB may transmit the QoE measurement configuration(s) and/or the information related to the configuration(s) of a specific UE to the target gNB via XnAP or NGAP. For signalling-based QoE, the service type, QoE reference, MCE IP address, measurement configuration application layer id, MDT alignment information, area scope, slice support list for QMC and measurement status are passed to the target gNB. For management-based QoE, the service type, measurement configuration application layer id, MCE IP address and QoE measurement status are passed to the target gNB. For RRC_INACTIVE state mobility, QoE measurement configuration(s) of a specific UE can be retrieved from the gNB hosting the UE context when it resumes to the RRC_CONNECTED state. Multiple sets of QoE measurement configurations should be supported during mobility.

For signalling based QoE, at handover to a target gNB that supports QoE, the target gNB decides which of the application layer measurement configurations should be kept or released, e.g. based on application layer measurement configuration information received from the source gNB in Xn/NG signalling.

When the UE resumes the connection with a gNB that does not support QoE, the UE releases all application layer measurement configurations.

21.4 RAN Visible QoE Measurements

RAN visible QoE measurements are configured to the UE by the gNB, where a subset of configured QoE metrics is reported from the UE to the gNB as an explicit IE readable by the gNB. The RAN visible QoE measurements can be utilized by the gNB for network optimization. The RAN visible QoE measurements are supported for the DASH streaming and VR services. The gNB configures the RAN visible QoE measurement to collect all or some of the available RAN visible QoE metrics, where the indication of metric availability is received from the OAM or the 5GC. The set of available RAN visible QoE metrics is a subset of the metrics which are already configured as part of QoE measurement configuration encapsulated in the application layer container. The PDU session ID(s) corresponding to the service that is subject to QoE measurements can also be reported by the UE along with the RAN visible QoE measurement results.

The RAN visible QoE measurements can be reported with a reporting periodicity different from the one of the corresponding encapsulated QoE measurements. If there is no reporting periodicity defined in the RAN visible QoE configuration, RAN visible QoE measurement reports are sent together with the encapsulated QoE measurement reports.

Multiple simultaneous RAN visible application layer measurement configurations and reports can be supported for RAN visible application layer measurement, and each RAN visible application layer measurement configuration and report is identified by the same RRC identifier as the application layer measurement configuration and measurement report. After receiving the RAN visible application layer measurement configuration, the UE RRC layer forwards the configuration to the application layer, indicating the service type, the RRC identifier and the periodicity. RAN visible application layer configuration can only be configured if there is a corresponding application layer measurement configuration for the same service type configured at the UE. The application layer sends the RAN visible application layer measurement report associated with the RRC identifier to the UE’s AS layer. UE can send both RAN visible application layer measurement reports and the application layer measurement reports to the gNB in the same MeasurementReportAppLayer message. The gNB can release one or multiple RAN visible application layer measurement configurations from the UE in one RRCReconfiguration message at any time.

During RAN overload, the UE continues to report the configured RAN visible application layer measurements, when the corresponding non RAN visible application layer measurement reporting is paused.

21.5 Alignment of MDT and QoE Measurements

The radio-related measurements may be collected via immediate MDT for all types of supported services for the purpose of QoE analysis. The MCE/TCE performs the correlation of the immediate MDT measurement results and the QoE measurement results collected at the same UE.

The following is supported:

– Alignment between a signalling-based QoE measurement and a signalling-based MDT measurement. In this case, the signalling-based QoE configuration sent to the gNB includes the NG-RAN Trace ID of the signalling-based MDT measurement.

– Alignment between a management-based QoE measurement and a management-based MDT measurement.

The UE configured with QoE measurements sends an indication to inform the gNB about the start or the stop of a QoE measurement session of configured QoE measurements. The gNB can activate the MDT measurements that are to be aligned with the QoE measurements performed by the UE upon/after receiving the QoE measurement session start indication from the UE. The gNB may activate the MDT measurements upon/after receiving the MDT activation message from the OAM. The gNB can deactivate the aligned MDT measurements according to an OAM command which may, e.g., be triggered by the session stop indication.

The gNB includes time stamp information to the QoE measurement reports to enable the correlation of corresponding measurement results of MDT and QoE at the MCE/TCE. In addition, the gNB includes the MDT session identifiers (Trace Reference and Trace Recording Session Reference) in the corresponding QoE measurement report.

Annex A (informative):
QoS Handling in RAN