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full Contents for  TS 23.501  Word version:   16.4.0

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1…   3…   4…   4.2.4   4.2.5…   4.2.8…   4.2.8.2.2   4.2.8.2.3…   4.2.8.4…   4.2.9…   4.3…   4.3.3   4.3.4   4.3.5   4.4…   4.4.6…   4.4.8   5…   5.3…   5.3.3…   5.4…   5.5…   5.6…   5.6.7…   5.7…   5.7.2…   5.7.3…   5.7.4   5.7.5…   5.8…   5.8.2.11…   5.9…   5.10…   5.11…   5.15…   5.16…   5.17…   5.18…   5.19…   5.21…   5.22…   5.27…   5.28…   5.29…   5.30…   5.31…   5.32…   5.33…   5.34…   5.35…   6…   6.3…   7…   7.2…   8…   8.2.4   8.2.5…   8.3…   A…   D…   E…   F   G…   G.3   G.4…   J…

 

5.7.2  5G QoS Parameters
5.7.2.1  5QI
A 5QI is a scalar that is used as a reference to 5G QoS characteristics defined in clause 5.7.4, i.e. access node-specific parameters that control QoS forwarding treatment for the QoS Flow (e.g. scheduling weights, admission thresholds, queue management thresholds, link layer protocol configuration, etc.).
Standardized 5QI values have one-to-one mapping to a standardized combination of 5G QoS characteristics as specified in Table 5.7.4-1.
The 5G QoS characteristics for pre-configured 5QI values are pre-configured in the AN.
Standardized or pre-configured 5G QoS characteristics, are indicated through the 5QI value, and are not signalled on any interface, unless certain 5G QoS characteristics are modified as specified in clauses 5.7.3.3, 5.7.3.4, 5.7.3.6, and 5.7.3.7.
The 5G QoS characteristics for QoS Flows with dynamically assigned 5QI are signalled as part of the QoS profile.
NOTE:
On N3, each PDU (i.e. in the tunnel used for the PDU Session) is associated with one 5QI via the QFI carried in the encapsulation header.
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5.7.2.2  ARPWord-p. 136
The QoS parameter ARP contains information about the priority level, the pre-emption capability and the pre-emption vulnerability. This allows deciding whether a QoS Flow establishment/modification/handover may be accepted or needs to be rejected in the case of resource limitations (typically used for admission control of GBR traffic). It may also be used to decide which existing QoS Flow to pre-empt during resource limitations, i.e. which QoS Flow to release to free up resources.
The ARP priority level defines the relative importance of a QoS Flow. The range of the ARP priority level is 1 to 15 with 1 as the highest level of priority.
The ARP priority levels 1-8 should only be assigned to QoS Flows for services that are authorized to receive prioritized treatment within an operator domain (i.e. that are authorized by the serving network). The ARP priority levels 9-15 may be assigned to QoS Flows for services that are authorized by the home network and thus applicable when a UE is roaming.
NOTE:
This ensures that future releases may use ARP priority level 1-8 to indicate e.g. emergency and other priority services within an operator domain in a backward compatible manner. This does not prevent the use of ARP priority level 1-8 in roaming situation in the case that appropriate roaming agreements exist that ensure a compatible use of these priority levels.
The ARP pre-emption capability defines whether a QoS Flow may get resources that were already assigned to another QoS Flow with a lower ARP priority level. The ARP pre-emption vulnerability defines whether a QoS Flow may lose the resources assigned to it in order to admit a QoS Flow with higher ARP priority level. The ARP pre-emption capability and the ARP pre-emption vulnerability shall be either set to 'enabled' or 'disabled'.
The ARP pre-emption vulnerability of the QoS Flow which the default QoS rule is associated with should be set appropriately to minimize the risk of a release of this QoS Flow.
The details of how the SMF sets the ARP for a QoS Flow are further described in clause 5.7.2.7.
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5.7.2.3  RQA
The Reflective QoS Attribute (RQA) is an optional parameter which indicates that certain traffic (not necessarily all) carried on this QoS Flow is subject to Reflective QoS. Only when the RQA is signalled for a QoS Flow, the (R)AN enables the transfer of the RQI for AN resource corresponding to this QoS Flow. The RQA may be signalled to NG-RAN via the N2 reference point at UE context establishment in NG-RAN and at QoS Flow establishment or modification.
5.7.2.4  Notification control
5.7.2.4.1  General [R16]
The QoS Parameter Notification control indicates whether notifications are requested from the NG-RAN when the "GFBR can no longer (or can again) be guaranteed" for a QoS Flow during the lifetime of the QoS Flow. Notification control may be used for a GBR QoS Flow if the application traffic is able to adapt to the change in the QoS (e.g., if the AF is capable to trigger rate adaptation).
The SMF shall only enable Notification control when the QoS Notification Control parameter is set in the PCC rule (received from the PCF) that is bound to the QoS Flow. The Notification control parameter is signalled to the NG-RAN as part of the QoS profile.
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5.7.2.4.1a  Notification Control without Alternative QoS Profiles [R16]Word-p. 137
If, for a given GBR QoS Flow, Notification control is enabled and the NG-RAN determines that the GFBR, the PDB or the PER of the QoS profile cannot be fulfilled, NG-RAN shall send a notification towards SMF that the "GFBR can no longer be guaranteed". Furthermore, the NG-RAN shall keep the QoS Flow (i.e. while the NG-RAN is not fulfilling the requested QoS profile for this QoS Flow), unless specific conditions at the NG-RAN require the release of the NG-RAN resources for this GBR QoS Flow, e.g. due to Radio link failure or RAN internal congestion. The NG-RAN should try to fulfil the GFBR, the PDB and the PER of the QoS profile again.
NOTE 1:
NG-RAN can decide that the "GFBR can no longer be guaranteed" based on, e.g. measurements like queuing delay or system load.
Upon receiving a notification from the NG-RAN that the "GFBR can no longer be guaranteed", the SMF may forward the notification to the PCF, see TS 23.503.
When the NG-RAN determines that the GFBR, the PDB and the PER of the QoS profile can be fulfilled again for a QoS Flow (for which a notification that the "GFBR can no longer be guaranteed" has been sent), the NG-RAN shall send a notification, informing the SMF that the "GFBR can be guaranteed" again and the SMF may forward the notification to the PCF, see TS 23.503. The NG-RAN shall send a subsequent notification that the "GFBR can no longer be guaranteed" whenever necessary.
NOTE 2:
It is assumed that NG-RAN implementation will apply some hysteresis before determining that the "GFBR can be guaranteed again" and therefore a frequent signalling of "GFBR can be guaranteed again" followed by "GFBR can no longer be guaranteed" is not expected.
NOTE 3:
If the QoS Flow is modified, the NG-RAN restarts the check whether the "GFBR can no longer be guaranteed" according to the updated QoS profile. If the Notification control parameter is not included in the updated QoS profile, the Notification control is disabled.
During a handover, the Source NG-RAN does not inform the Target NG-RAN about whether the Source NG-RAN has sent a notification for a QoS Flow that the "GFBR can no longer be guaranteed". The Target NG-RAN performs admission control rejecting any QoS Flows for which resources cannot be permanently allocated. The accepted QoS Flows are included in the N2 Path Switch Request or N2 Handover Request Acknowledge message from the NG-RAN to the AMF. The SMF shall interpret the fact that a QoS Flow is listed as transferred QoS Flow in the Nsmf_PDUSession_UpdateSMContext Request received from the AMF as a notification that "GFBR can be guaranteed again" for this QoS Flow unless the SMF is also receiving a reference to an Alternative QoS Profile for this QoS Flow (which is described in clause 5.7.2.4.2). After the handover is successfully completed, the Target NG-RAN shall send a subsequent notification that the "GFBR can no longer be guaranteed" for such a QoS Flow whenever necessary. If the SMF has previously notified the PCF that the "GFBR can no longer be guaranteed" and the SMF does not receive an explicit notification that the "GFBR can no longer be guaranteed" for that QoS Flow from the Target NG-RAN within a configured time, the SMF shall notify the PCF that the "GFBR can be guaranteed again".
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5.7.2.4.1b  Notification control with Alternative QoS Profiles [R16]
If, for a given GBR QoS Flow, Notification control is enabled and the NG-RAN has received a list of Alternative QoS Profile(s) for this QoS Flow and supports the Alternative QoS Profile handling, the following shall apply:
  1. If the NG-RAN determines that the GFBR, the PDB or the PER of the QoS profile cannot be fulfilled, NG-RAN shall send a notification towards SMF that the "GFBR can no longer be guaranteed". Before sending a notification that the "GFBR can no longer be guaranteed" towards the SMF, the NG-RAN shall check whether the the GFBR, the PDB and the PER that the NG-RAN currently fulfils match any of the Alternative QoS Profile(s) in the indicated priority order. If there is a match, the NG-RAN shall indicate the reference to the matching Alternative QoS Profile with the highest priority together with the notification to the SMF.
  2. If there is no match, the NG-RAN shall send a notification that the "GFBR can no longer be guaranteed" towards the SMF without referencing any of the Alternative QoS Profile(s) (unless specific conditions at the NG-RAN require the release of the NG-RAN resources for this GBR QoS Flow, e.g. due to Radio link failure or RAN internal congestion).
  3. If a notification that the "GFBR can no longer be guaranteed" has been sent to the SMF and the NG-RAN determines that the currently fulfilled GFBR, PDB or PER are different (better or worse) from the situation indicated in the last notification, the NG-RAN shall send a further notification to the SMF and indicate the currently fulfilled situation.
  4. NOTE 1:
    The fulfilled situation is either the QoS Profile, an Alternative QoS Profile, or an indication that the lowest priority Alternative QoS Profile cannot be fulfilled.
  5. The NG-RAN should always try to fulfil the QoS profile and any Alternative QoS Profile that has higher priority than the currently fulfilled situation.
  6. NOTE 2:
    In order to avoid a too frequent signalling to the SMF, it is assumed that NG-RAN implementation can apply hysteresis (e.g., via a configurable time interval) before notifying the SMF that the currently fulfilled values match the QoS Profile or a different Alternative QoS Profile of higher priority. It is also assumed that the PCF has ensured that the QoS values within the different Alternative QoS Profile(s) are not too close to each other.
  7. Upon receiving a notification from the NG-RAN, the SMF may inform the PCF. If it does so, the SMF shall indicate the currently fulfilled situation to the PCF. See TS 23.503.
  8. If the PCF has not indicated differently, the SMF uses NAS signalling (that is sent transparently through the RAN) to inform the UE about changes in the QoS parameters (i.e., 5QI, GFBR, MFBR) that the NG-RAN is currently fulfilling for the QoS Flow after Notification control has occurred.
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5.7.2.4.2  Usage of Notification control with Alternative QoS Profiles at handover [R16]Word-p. 138
During handover, the prioritized list of Alternative QoS Profile(s) (if available) is provided to the Target NG-RAN per QoS Flow in addition to the QoS profile. If the Target NG-RAN is not able to guarantee the GFBR, the PDB and the PER included in the QoS profile and if Alternative QoS Profiles are provided to the Target NG-RAN and the Target NG-RAN supports Alternative QoS Profiles, the Target NG-RAN checks whether the GFBR, the PDB and the PER values that it can fulfil match any of the Alternative QoS Profile(s) taking the priority order into account. If there is a match between one of the Alternative QoS Profiles and the GFBR, the PDB and the PER values that Target NG-RAN can fulfil, the Target NG-RAN shall accept the QoS Flow and indicate the reference to that Alternative QoS Profile to the Source NG-RAN.
If there is no match to any Alternative QoS Profile, the Target NG-RAN rejects QoS Flows for which the Target NG-RAN is not able to guarantee the GFBR, the PDB and the PER included in the QoS profile.
After the handover is completed and a QoS Flow has been accepted by the Target NG-RAN based on an Alternative QoS Profile, the Target NG-RAN shall treat this QoS Flow in the same way as if it had sent a notification that the "GFBR can no longer be guaranteed" with a reference to that Alternative QoS Profile to the SMF (as described in clause 5.7.2.4.1b).
If a QoS Flow has been accepted by the Target NG-RAN based on an Alternative QoS Profile, the reference to the matching Alternative QoS Profile is provided from the Target NG-RAN to the AMF (which forwards the message to the SMF) during the Xn and N2 based handover procedures as described in TS 23.502. After the handover is completed successfully, the SMF shall send a notification to the PCF that the "GFBR can no longer be guaranteed" for a QoS Flow (see TS 23.503 for details) if the SMF has received a reference to an Alternative QoS Profile and this reference indicates a change in the previously notified state of this QoS Flow. If the PCF has not indicated differently, the SMF shall also use NAS signalling (that is sent transparently through the RAN) to inform the UE about the QoS parameters (i.e. 5QI, GFBR, MFBR) corresponding to the new state of the QoS Flow.
NOTE:
A state change for the QoS Flow comprises a change from QoS profile fulfilled to Alternative QoS Profile fulfilled as well as the state change between fulfilled Alternative QoS Profiles.
If a QoS Flow has been accepted by the Target NG-RAN based on the QoS Profile, the SMF shall interpret the fact that a QoS Flow is listed as transferred QoS Flow in the message received from the AMF as a notification that "GFBR can be guaranteed again" for this QoS Flow. After the handover is successfully completed, the Target NG-RAN performs as described in clause 5.7.2.4.1b. If the SMF has previously notified the PCF that the "GFBR can no longer be guaranteed" and the SMF does not receive an explicit notification that the "GFBR can no longer be guaranteed" for that QoS Flow from the Target NG-RAN within a configured time, the SMF shall notify the PCF that the "GFBR can be guaranteed again".
If a QoS Flow has been accepted by the Target NG-RAN and SMF did not receive from the Target NG-RAN a reference to any Alternative QoS Profile and the SMF has previously informed the UE about QoS parameters corresponding to any of the Alternative QoS Profile(s), the SMF shall use NAS signalling to inform the UE about the QoS parameters corresponding to the QoS Profile.
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5.7.2.5  Flow Bit RatesWord-p. 139
For GBR QoS Flows only, the following additional QoS parameters exist:
  • Guaranteed Flow Bit Rate (GFBR) - UL and DL;
  • Maximum Flow Bit Rate (MFBR) -- UL and DL.
The GFBR denotes the bit rate that is guaranteed to be provided by the network to the QoS Flow over the Averaging Time Window. The MFBR limits the bit rate to the highest bit rate that is expected by the QoS Flow (e.g. excess traffic may get discarded or delayed by a rate shaping or policing function at the UE, RAN, UPF). Bit rates above the GFBR value and up to the MFBR value, may be provided with relative priority determined by the Priority Level of the QoS Flows (see clause 5.7.3.3).
GFBR and MFBR are signalled to the (R)AN in the QoS Profile and signalled to the UE as QoS Flow level QoS parameter (as specified in TS 24.501) for each individual QoS Flow.
NOTE 1:
The GFBR is recommended as the lowest acceptable service bitrate where the service will survive.
NOTE 2:
For each QoS Flow of Delay Critical GBR resource type, the SMF can ensure that the GFBR of the QoS Flow can be achieved with the MDBV of the QoS Flow using the QoS Flow binding functionality described in clause 6.1.3.2.4 in TS 23.503.
NOTE 3:
The network can set MFBR larger than GFBR for a particular QoS Flow based on operator policy and the knowledge of the end point capability, i.e. support of rate adaptation at application / service level.
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5.7.2.6  Aggregate Bit Rates
Each PDU Session of a UE is associated with the following aggregate rate limit QoS parameter:
  • per Session Aggregate Maximum Bit Rate (Session-AMBR).
The Session-AMBR is signalled to the appropriate UPF entity/ies to the UE and to the (R)AN (to enable the calculation of the UE-AMBR). The Session-AMBR limits the aggregate bit rate that can be expected to be provided across all Non-GBR QoS Flows for a specific PDU Session. The Session-AMBR is measured over an AMBR averaging window which is a standardized value. The Session-AMBR is not applicable to GBR QoS Flows.
Each UE is associated with the following aggregate rate limit QoS parameter:
  • per UE Aggregate Maximum Bit Rate (UE-AMBR).
The UE-AMBR limits the aggregate bit rate that can be expected to be provided across all Non-GBR QoS Flows of a UE. Each (R)AN shall set its UE-AMBR to the sum of the Session-AMBR of all PDU Sessions with active user plane to this (R)AN up to the value of the received UE-AMBR from AMF. The UE-AMBR is a parameter provided to the (R)AN by the AMF based on the value of the subscribed UE-AMBR retrieved from UDM or the dynamic serving network UE-AMBR retrieved from PCF (e.g. for roaming subscriber). The AMF provides the UE-AMBR provided by PCF to (R)AN if available. The UE-AMBR is measured over an AMBR averaging window which is a standardized value. The UE-AMBR is not applicable to GBR QoS Flows.
NOTE:
The AMBR averaging window is only applied to Session-AMBR and UE-AMBR measurement and the AMBR averaging windows for Session-AMBR and UE-AMBR are standardised to the same value.
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5.7.2.7  Default values
For each PDU Session Setup, the SMF retrieves the subscribed Session-AMBR values as well as the subscribed default values for the 5QI and the ARP and optionally, the 5QI Priority Level, from the UDM. The subscribed default 5QI value shall be a Non-GBR 5QI from the standardized value range.
NOTE 1:
The 5QI Priority Level can be added to the subscription information to achieve an overwriting of the standardized or preconfigured 5QI Priority Level e.g. in scenarios where dynamic PCC is not deployed or the PCF is unavailable or unreachable.
The SMF may change the subscribed values for the default 5QI and the ARP and if received, the 5QI Priority Level, based on interaction with the PCF as described in TS 23.503 or, if dynamic PCC is not deployed, based on local configuration, to set QoS parameters for the QoS Flow associated with the default QoS rule.
For QoS Flow(s) of the PDU Session other than the QoS Flow associated with the default QoS rule, the SMF shall set the ARP priority level, the ARP pre-emption capability and the ARP pre-emption vulnerability to the respective values in the PCC rule(s) bound to that QoS Flow (as described in TS 23.503). If dynamic PCC is not deployed, the SMF shall apply the subscribed value for the ARP priority level, and shall set the ARP pre-emption capability and the ARP pre-emption vulnerability based on local configuration.
If dynamic PCC is not deployed, the SMF can have a DNN based configuration to enable the establishment of a GBR QoS Flow as the QoS Flow that is associated with the default QoS rule. This configuration contains a standardized GBR 5QI as well as GFBR and MFBR for UL and DL.
NOTE 2:
Interworking with EPS is not possible for a PDU Session with a GBR QoS Flow as the QoS Flow that is associated with the default QoS rule.
The SMF may change the subscribed Session-AMBR values (for UL and/or DL), based on interaction with the PCF as described in TS 23.503 or, if dynamic PCC is not deployed, based on local configuration, to set the Session-AMBR values for the PDU Session.
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5.7.2.8  Maximum Packet Loss RateWord-p. 140
The Maximum Packet Loss Rate (UL, DL) indicates the maximum rate for lost packets of the QoS flow that can be tolerated in the uplink and downlink direction. This is provided to the QoS flow if it is compliant to the GFBR
NOTE:
In this Release of the specification, the Maximum Packet Loss Rate (UL, DL) can only be provided for a GBR QoS flow belonging to voice media.
5.7.2.9  Wireline access network specific 5G QoS parameters [R16]
QoS parameters that are applicable only for or wireline access networks (W-5GAN) are specified in TS 23.316.

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