The conceptual model identifies three areas of prioritization: prioritization at the transport layer (3GPP System and UE), prioritization between and within calls, and inter-system prioritization. At the Application Layer a generic, network side, functional entity, "MCPTT Priority and QoS Control", processes with each request static, preconfigured information about users and groups participating in MCPTT, as well as dynamic (or situational) information about them. Based on the results of this processing, the "MCPTT Priority and QoS Control" provides information to and directs interactions with other functional entities, systems, or layers to ensure, to the extent possible, that from a quality of experience point of view, calls, and transmissions are handled properly in accordance to established policy rules.
The User Static Attributes include information categorizing the user, possibly by several criteria (e.g., first responder, second responder, supervisor, dispatcher, administrator), as well as jurisdictional boundaries and possibly a preconfigured system-wide individual priority level.
The Group Static Attributes include information about the nature/type of the group and the owning organization(s), the jurisdictional boundaries for transmitters and receivers within the group, the normal hours of operation for the group, pre-emption dispositions relative to other groups, and the default minimum priority of the group, i.e., the minimum priority characteristics that are provided to all the Participants in a group call associated with this group, regardless of their individual priority characteristics.
The User Dynamic Attributes include the user/Participant's operational status (e.g., on/off duty), his location, the type of incident (e.g., MCPTT Emergency or Imminent Peril) he might be involved in, and whether or not he initiated it, whether or not he is individually involved in a formally managed incident and if yes, the boundaries of the incident area, the incident severity and his assigned role in the resolution of the incident.
The Group Dynamic Attributes include the type of incident (e.g., MCPTT Emergency or Imminent Peril), if any, the group is currently handling and in case of involvement in a formally managed incident the boundaries of the incident area and the incident severity.

​

3GPP TS 22.179 "Mission Critical Push to Talk (MCPTT); Stage 1" (V17.1.0 (2022-03)) (22179-h10) clause 4.6.2 "Mission Critical Push To Talk overview - Overview of MCPTT priorities - Generic processing of priority information"

 

4.6.2 Generic processing of priority information

This functionality applies to MCPTT Call initiations and transmissions for the management of potentially contended resources (e.g., GBR bearers) and also for Floor control during an MCPTT Group Call.
Each request for exclusive access to resource(s) or for preferential treatment over a contending request arrives accompanied by priority information. This information stays associated with the companion request, whether the request is granted or is queued. The priority information is used for comparison between requests and facilitates the adding and removing of requests from queues and/or authorized interruption of service associated with a previously granted request, if still active. For each request, whether initially queued or not, the requesting party is informed (directly or indirectly) when his request is granted or denied. Other users/Participants are also notified of the disposition of a request and the notification includes the identity of the requestor, as needed. In addition, each requestor can be notified of the position of his request in the queue and he is allowed to cancel his requests while queued.

​

3GPP TS 22.179 "Mission Critical Push to Talk (MCPTT); Stage 1" (V17.1.0 (2022-03)) (22179-h10) clause 4.6.4 "Mission Critical Push To Talk overview - Overview of MCPTT priorities - Handling of MCPTT priority information for interactions at the transport layer"

​

4.6.4 Handling of MCPTT priority information for interactions at the transport layer
At the Transport Layer, the MCPTT Service uses 3GPP controls to adapt the overall behavior of the MCPTT System to the needs for resources and/or preferential treatment over other contenders, based on the priority information accompanying the request.
The following four controls are available, to be used as necessary, based on the phase of the MCPTT call: 

• 3GPP System Access Controls;

• UE Access Controls;

• 3GPP System Admission Controls; and

• 3GPP System Scheduling Controls.

3GPP System Access Controls and UE Access Controls are used to allow preferential treatment of public-safety UEs in situations of access congestion. The controls use Priority and QoS mechanisms (e.g., using mechanisms like Access Class Barring, Service Specific Access Control, Access Control for Circuit Switched Fallback, and Extended Access Barring).
3GPP System Admission Controls are used for the establishment and maintenance of the priority levels and of the pre-emption vulnerability and capability of bearers associated with transmissions and calls. At the start of an MCPTT call, the MCPTT Service requires bearers with proper ARP (Allocation and Retention Priority) and pre-emption characteristics to be in place prior to the call proceeding.
3GPP System Scheduling Controls (e.g., QCI (QoS Class Identifier) and bandwidth for the bearers) are used to assuring the appropriate QoS necessary for meeting the Participants' expectations in the perceived quality of the delivered information, primarily in terms of when the service starts and the real-time characteristics of the delivered traffic (e.g., perceived delay, choppiness, clarity).

​

3GPP TS 22.280 "Mission Critical Services Common Requirements (MCCoRe); Stage 1" (V18.2.0 (2022-06)) (22280-i20) clause 6.8 "MCX Service requirements specific to on-network use - MCX Service priority requirements"

 

6.8 MCX Service priority requirements

6.8.1 [...]

6.8.2 3GPP System Access Controls: [R-6.8.2-001] The 3GPP system shall, subject to operator policy, provide a means for the MCX Service to influence the modification of the access parameters used by the network to admit MCX UEs within a defined area. NOTE: It is believed that the existing UE network access mechanisms could be utilized to meet the above requirement.
6.8.3 3GPP System Admission Controls: [R-6.8.3-001] The 3GPP system shall, subject to operator policy, provide a means for the MCX Service to influence the selection and/or modification of admission and retention controls for the bearers assigned or about to be assigned to an MCX UE based on the MCX User's and MCX Service Group attributes used for the priority determination. NOTE: It is believed that the existing 3GPP mechanisms for network priority and QoS could be utilized to meet the above requirement.
6.8.4 3GPP System Scheduling Controls: [R-6.8.4-001] The 3GPP system shall, subject to operator policy, provide a means for the MCX Service to influence the selection and/or modification of the bearer scheduling controls for the bearers assigned or about to be assigned to an MCX UE based on the MCX User's and MCX Service Group attributes used for the priority determination. NOTE: It is believed that the existing 3GPP mechanisms for network priority and QoS could be utilized to meet the above requirement.
6.8.5 UE Access Controls: [R-6.8.5-001] The MCX Service shall allow the MCX UE to temporarily modify selected 3GPP system access parameters, according to configuration established by an MCX Service Administrator in agreement with the operator's policy. NOTE: It is believed that the existing network access mechanisms, e.g., ACDC [Application specific Congestion control for Data Communication] (see 3GPP TS 22.011 [applicable to 2G GSM, 3G UMTS, 4G LTE] and 3GPP TS 23.122 [applicable to 2G GSM, 3G UMTS, 4G LTE, 5GS]), could be utilized to meet the above requirement.

​

3GPP System Access Controls

​

TCCA White Paper "Public Safety Prioritisation on Commercial Networks" June 2019 §5.1 "Available Prioritisation Mechanisms in 4G on shared network -​ Access Class Barring (ABR)": ACB prevents congestion at signaling level (random access procedure) when too many UEs try simultaneously to get a radio resource assigned (RRC (Radio Resource Control) connection). [...] The network can automatically activate ACB based on certain overload thresholds at a cell level. [...]

​

3GPP TS 22.179 "Mission Critical Push to Talk (MCPTT); Stage 1" (V17.1.0 (2022-03)) (22179-h10) clause 6.8.1 "MCPTT Service requirements specific to on-network use - MCPTT priority requirements - General": [R-6.8.1-002] The MCPTT Service shall provide an access control mechanism to support multiple Access Priorities to prioritize MCPTT MO (Mobile Originated) call initiation attempts, depending on their Access Priorities.

​

3GPP TS 22.011 "Service accessibility" (V17.0.0 (2019-12)) (22011-h00) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 4.2 "Access control - Allocation": All UEs are members of one out of ten randomly allocated mobile populations, defined as Access Classes 0 to 9. The population number is stored in the SIM/USIM. In addition, UEs may be members of one or more out of five special categories (Access Classes 11 to 15), also held in the SIM/USIM. These are allocated to specific high-priority users as follows. (The enumeration is not meant as a priority sequence):
  • Access Class 11: for PLMN (Public Land Mobile Network) Use;
  • Access Class 12: for Security Services;
  • Access Class 13: for Public Utilities (e.g. water/gas suppliers);
  • Access Class 14: for Emergency Services;
  • Access Class 15: for PLMN Staff

​

3GPP TS 22.011 "Service accessibility" (V17.0.0 (2019-12)) (22011-h00) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 4.3.1 "Access control - Operation - ACB (Access Class Barring)": If the UE is a member of at least one Access Class that corresponds to the permitted classes as signaled over the air interface, and the Access Class is applicable in the serving network, access attempts are allowed. [...] Also, the serving network can indicate that UEs are restricted to perform location registration, although common access is permitted. [...] Note: The network operator can take the network load into account when allowing UEs access to the network. [...]

3GPP TS 22.011 "Service accessibility" (V17.0.0 (2019-12)) (22011-h00) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 4.4 "Access control - Emergency Calls": An additional control bit known as "Access Class 10" is also signaled over the air interface to the UE. This indicates whether or not network access for Emergency Calls is allowed for UEs with Access Classes 0 to 9 or without an IMSI. For UEs with Access Classes 11 to 15, Emergency Calls are not allowed if both "Access class 10" and the relevant Access Class (11 to 15) are barred. Otherwise, Emergency Calls are allowed.

​

3GPP System Admission Controls

​

TCCA White Paper "Public Safety Prioritisation on Commercial Networks" June 2019 §5.2 "Available Prioritisation Mechanisms in 4G on shared network -​ Admission control through Allocation and Retention Priority (ARP)":

Admission control prevents congestion at Evolved Packet System (EPS) bearer level, once Radio Resource Control (RRC) is established.
3GPP has defined different levels of Allocation and Retention Priority (ARP) that are assigned to the EPS bearers. The range of the ARP priority level is 1 to 15 with 1 as the highest level of priority. An existing lower-priority bearer can be pre-empted by a higher-priority bearer, if the lower-priority bearer has pre-emption vulnerability set and the higher-priority bearer has pre-emption capability set.
ARP value is valid for both GBR (Guaranteed Bit Rate) bearers and non-GBR bearers. A typical Public-Safety example could be prioritization of GBR bearer for MCPTT service over regular Voice over LTE (VoLTE) call or any other bearer. The dedicated GBR bearer for MCPTT call could have ARP priority level 3 and dedicated GBR bearer for VoLTE could have ARP priority level 10. If all GBR resources were consumed in a cell and pre-emption enabled, then a new MCPTT call could pre-empt general internet traffic or video streaming.
ARP is part of QoS parameters. For default bearers the ARP priority is included in subscription data in the Home Subscriber Server (HSS) for each allowed Access Point Name (APN). Pre-emption capability and vulnerability for default bearers are set by the Mobility Management Entity (MME) according to operator policy. ARP priority and pre-emption settings can be also modified by the Packet Data Network Gateway (P-GW) based on interaction with the Policy and Charging Rules Function (PCRF). ARP for dedicated bearers is set by P-GW based on subscription or based on interaction with PCRF.

3GPP TS 23.401 "GPRS enhancements for E-UTRAN access" (V17.5.0 (2022-06)) (23401-h50) clause 4.3.2.1 "Architecture model and concepts - High-level functions - Network access control functions - General": Network access is the means by which a user is connected to the Evolved Packet Core system.

​

3GPP TS 23.401 "GPRS enhancements for E-UTRAN access" (V17.5.0 (2022-06)) (23401-h50) clause 4.3.2.4 "Architecture model and concepts - High-level functions - Network access control functions - Admission control function": The purpose of admission control is to determine if the requested resources are available, and then reserve those resources.

​

3GPP TS 23.401 "GPRS enhancements for E-UTRAN access" (V17.5.0 (2022-06)) (23401-h50) clause 4.7.3 "Architecture model and concepts - Overall QoS concept - Bearer level QoS parameters": 

The EPS bearer QoS profile includes the parameters QCI (QoS Class Identifier), ARP, GBR (Guaranteed Bit Rate) and MBR (Maximum Bit Rate), described in this clause. This clause also describes QoS parameters which are applied to an aggregated set of EPS Bearers: APN(Access Point Name)-AMBR(Aggregate Maximum Bit Rate) and UE-AMBR.
Each EPS bearer (GBR and Non-GBR) is associated with the following bearer-level QoS parameters:
  - QoS Class Identifier (QCI);
  - Allocation and Retention Priority (ARP).
[...]
  NOTE 2: When required by operator policy, the eNodeB can be configured to also use the ARP priority level in addition to the QCI to control bearer level packet forwarding treatment in the eNodeB for SDFs [Service Data Flows] having high priority ARPs.
[...]
The ARP shall contain information about the priority level (scalar), the pre-emption capability (flag) and the pre-emption vulnerability (flag). The primary purpose of ARP is to decide whether a bearer establishment / modification request can be accepted or needs to be rejected due to resource limitations (typically available radio capacity for GBR bearers). The priority level information of the ARP is used for this decision to ensure that the request of the bearer with the higher priority level is preferred. In addition, the ARP can be used (e.g. by the eNodeB) to decide which bearer(s) to drop during exceptional resource limitations (e.g. at handover). The pre-emption capability information of the ARP defines whether a bearer with a lower ARP priority level should be dropped to free up the required resources. The pre-emption vulnerability information of the ARP defines whether a bearer is applicable for such dropping by a pre-emption capable bearer with a higher ARP priority level.
Once a bearer has been successfully established, the packet handling (e.g. scheduling and rate control) within the eNodeB, PDN GW, and Serving GW should be solely determined by the following EPS bearer QoS parameters: QCI, GBR and MBR, and by the AMBR parameters. However, when required by operator policy, the eNodeB can be configured to also use a bearer's ARP priority level in addition to the QCI to determine the relative priority of the SDFs [Service Data Flows] for packet handling (e.g. scheduling and rate control) in the eNodeB as defined in TS 23.203 "Policy and Charging Control Architecture" (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 6.1.7.2  ["Functional description - Overall description - Standardized OoS characteristics - Standardized QCI characteristics"]. This configuration applies only for bearers with high-priority ARPs as defined in TS 23.203 clause 6.1.7.3.
The ARP priority level may be used in addition to the QCI to determine the transport level packet marking, e.g. to set the DiffServ Code Point. The ARP is not included within the EPS QoS Profile sent to the UE.
  NOTE 3:    The ARP should be understood as "Priority of Allocation and Retention"; not as "Allocation, Retention, and Priority".
  NOTE 4:    Video telephony is one use case where it may be beneficial to use EPS bearers with different ARP values for the same UE. In this use case an operator could map voice to one bearer with a higher ARP, and video to another bearer with a lower ARP. In a congestion situation (e.g. cell edge) the eNodeB can then drop the "video bearer" without affecting the "voice bearer". This would improve service continuity.
  NOTE 5:    The ARP may also be used to free up capacity in exceptional situations, e.g. a disaster situation. In such a case the eNodeB may drop bearers with a lower ARP priority level to free up capacity if the pre-emption vulnerability information allows this.
[...]
The HSS [Home Subscriber Server] defines, for each PDN subscription context, the 'EPS subscribed QoS profile' which contains the bearer level QoS parameter values for the default bearer (QCI and ARP) and the subscribed APN-AMBR value. The subscribed ARP shall be used to set the priority level of the EPS bearer parameter ARP for the default bearer while the pre-emption capability and the pre-emption vulnerability information for the default bearer are set based on MME operator policy. In addition, the subscribed ARP shall be applied by the P-GW for setting the ARP priority level of all dedicated EPS bearers of the same PDN connection unless a different ARP priority level setting is required (due to P-GW configuration or interaction with the PCRF).
  NOTE 7:    The ARP parameter of the EPS bearer can be modified by the P-GW (e.g. based on interaction with the PCRF due to e.g. MPS [Multimedia Priority Service] user-initiated session) to assign the appropriate pre-emption capability and the pre-emption vulnerability setting.
The ARP pre-emption vulnerability of the default bearer should be set appropriately to minimize the risk of unnecessary release of the default bearer.

​

3GPP TS 23.203 "Policy and Charging Control Architecture" (V17.1.0 (2021-06)) (23203-h10) (applicable to 2G GSM, 3G UMTS, 4G LTE) §6.1.7.1 "Functional description - Overall description - Standardized QoS characteristics - General": The service level (i.e., per SDF (Service Data Flow) or per SDF aggregate) QoS parameters are QCI, ARP, GBR, and MBR. [...] For the same IP-CAN (IP-Connectivity Access Network) session multiple SDFs with the same QCI and ARP can be treated as a single traffic aggregate which is referred to as an SDF aggregate. An SDF is a special case of an SDF aggregate. [...]

​

3GPP TS 23.203 "Policy and Charging Control Architecture" (V17.1.0 (2021-06)) (23203-h10) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 6.1.7.3 "Functional description - Overall description - Standardized QoS characteristics - Allocation and Retention Priority characteristics":
The QoS parameter ARP contains information about the priority level, the pre-emption capability and the pre-emption vulnerability.
The priority level defines the relative importance of a resource request. This allows deciding whether a bearer establishment or modification request can be accepted or needs to be rejected in case of resource limitations (typically used for admission control of GBR traffic). It can also be used to decide which existing bearers to pre-empt during resource limitations.
  NOTE 1:    The ARP priority level can be used in addition to the QCI to determine the transport level packet marking, e.g. to set the DiffServ Code Point of the associated EPS bearer, as described in TS 23.401.
  NOTE 2:    When required by operator policy, the eNodeB can be configured to use the ARP priority level in addition to QCI priority level to control the packet forwarding treatment for SDFs [Service Data Flows] having high-priority ARPs.
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 resources 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 resources that are authorized by the home network and thus applicable when a UE is roaming.
  NOTE 3:    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 case appropriate roaming agreements exist that ensure a compatible use of these priority levels.

The pre-emption capability information defines whether a service data flow can get resources that were already assigned to another service data flow with a lower priority level.
The pre-emption vulnerability information defines whether a service data flow can lose the resources assigned to it in order to admit a service data flow with higher priority level.
The pre-emption capability and the pre-emption vulnerability can be either set to 'yes' or 'no'.

​

3GPP System Scheduling Controls

​

TCCA White Paper "Public Safety Prioritisation on Commercial Networks" June 2019 §5.3 "Available Prioritisation Mechanisms in 4G on shared network -​ Traffic scheduling":

Every default and dedicated EPS bearer has a QoS Class Identifier (QCI), which defines the resource type (GBR or non-GBR), latency target, packet loss rate and priority level for scheduling.
The original 3GPP Release 8 specified standard GBR QCIs 1-4 and non-GBR QCIs 5-9.
3GPP Release 12 added additional QCIs for Public-Safety applications. GBR QCIs 65 and 66 are respectively for mission-critical PTT and non-mission-critical PTT. Non-GBR QCI 69 is for mission-critical signaling and non-GBR QCI 70 is for mission-critical data. MCPTT service will use QCI 69 bearer for signaling and QCI 65 for voice media. This is similar to VoLTE service, which uses QCI 5 for Session Initiation Protocol (SIP) signaling and QCI 1 for voice media. With these new QCIs PS users get priority scheduling for MCPTT even over the VoLTE service.
3GPP Release 15 added QCI 67 for MCVideo.

3GPP TS 23.401 "GPRS enhancements for E-UTRAN access" (V17.5.0 (2022-06)) (23401-h50) clause 4.7.3 "Architecture model and concepts - Overall QoS concept - Bearer level QoS parameters":
The EPS bearer QoS profile includes the parameters QCI (QoS Class Identifier), ARP, GBR (Guaranteed Bit Rate) and MBR (Maximum Bit Rate), described in this clause. This clause also describes QoS parameters which are applied to an aggregated set of EPS Bearers: APN(Access Point Name)-AMBR(Aggregate Maximum Bit Rate) and UE-AMBR.
Each EPS bearer (GBR and Non-GBR) is associated with the following bearer-level QoS parameters:
  - QoS Class Identifier (QCI);
  - Allocation and Retention Priority (ARP).
A QCI is a scalar that is used as a reference to access node-specific parameters that control bearer level packet forwarding treatment (e.g. scheduling weights, admission thresholds, queue management thresholds, link layer protocol configuration, etc.), and that have been pre-configured by the operator owning the access node (e.g. eNodeB). A one-to-one mapping of standardized QCI values to standardized characteristics is captured in TS 23.203.
  NOTE 1: On the radio interface and on S1, each PDU [Protocol Data Unit] (e.g. RLC [Radio Link Control] PDU or GTP-U [GPRS Tunnelling Protocol for User Plane] PDU) is indirectly associated with one QCI via the bearer identifier carried in the PDU header. The same applies to the S5 and S8 interfaces if they are based on GTP.
  NOTE 2: When required by operator policy, the eNodeB can be configured to also use the ARP priority level in addition to the QCI to control bearer level packet forwarding treatment in the eNodeB for SDFs [Service Data Flows] having high priority ARPs.
[...]
Once a bearer has been successfully established, the packet handling (e.g. scheduling and rate control) within the eNodeB, PDN GW, and Serving GW should be solely determined by the following EPS bearer QoS parameters: QCI, GBR and MBR, and by the AMBR parameters. However, when required by operator policy, the eNodeB can be configured to also use a bearer's ARP priority level in addition to the QCI to determine the relative priority of the SDFs [Service Data Flows] for packet handling (e.g. scheduling and rate control) in the eNodeB as defined in TS 23.203 clause 6.1.7.2. This configuration applies only for bearers with high-priority ARPs as defined in TS 23.203 clause 6.1.7.3.
[...]
The HSS [Home Subscriber Server] defines, for each PDN subscription context, the 'EPS subscribed QoS profile' which contains the bearer level QoS parameter values for the default bearer (QCI and ARP) and the subscribed APN-AMBR value.
[...]

​

3GPP TS 23.203 "Policy and Charging Control Architecture" (V17.1.0 (2021-06)) (23203-h10) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 6.1.7.1 "Functional description - Overall description - Standardized QoS characteristics - General":

The service level (i.e., per SDF (Service Data Flow) or per SDF aggregate) QoS parameters are QCI, ARP, GBR, and MBR. [...] For the same IP-CAN (IP-Connectivity Access Network) session multiple SDFs with the same QCI and ARP can be treated as a single traffic aggregate which is referred to as an SDF aggregate. An SDF is a special case of an SDF aggregate. [...]

3GPP TS 23.203 "Policy and Charging Control Architecture" (V17.1.0 (2021-06)) (23203-h10) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 6.1.7.2 "Functional description - Overall description - Standardized QoS characteristics - Standardized QCI characteristics":
Standardized characteristics, associated with standardized QCI values, describe the packet forwarding treatment that an SDF aggregate receives edge-to-edge between the UE and the PCEF (Policy and Charging Enforcement Function) in terms of the following performance characteristics:
1  Resource Type (GBR or Non-GBR);
2  Priority;
3  Packet Delay Budget;
4  Packet Error Loss Rate;
5 [...];
6 [...].
The standardized characteristics are not signalled on any interface. They should be understood as guidelines for the pre-configuration of node specific parameters for each QCI. The goal of standardizing a QCI with corresponding characteristics is to ensure that applications / services mapped to that QCI receive the same minimum level of QoS in multi-vendor network deployments and in case of roaming. [...]
Table 6.1.7-A "Standardized QCI characteristics"

[...]

QCI: 65 - Resource Type: GBR - Priority Level: 0.7 - Packet Delay Budget: 75 ms - Packet Error Loss Rate: 10^(-2) - Example Services: Mission Critical Push To Talk voice (MCPTT)  user plane;

[...]

QCI: 67 - Resource Type: GBR - Priority Level: 1.5 - Packet Delay Budget: 100 ms - Packet Error Loss Rate: 10^(-3) - Example Services: Mission Critical Video (MCVideo) user plane;

[...]

QCI: 69 - Resource Type: Non-GBR - Priority Level: 0.5 - Packet Delay Budget: 60 ms - Packet Error Loss Rate: 10^(-6) - Example Services: Mission Critical delay sensitive signalling (e.g., MCPTT signalling, MCVideo signalling);
QCI: 70 - Resource Type: Non-GBR - Priority Level: 5.5 - Packet Delay Budget: 200 ms - Packet Error Loss Rate: 10^(-6) - Example Services: Mission Critical Data (MCData) (e.g. Video (Buffered Streaming) TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.))
[...]
The Resource Type determines if dedicated network resources related to a service or bearer level Guaranteed Bit Rate (GBR) value are permanently allocated (e.g. by an admission control function in a radio base station). GBR SDF aggregates are therefore typically authorized "on demand" which requires dynamic policy and charging control. A Non GBR SDF aggregate may be pre-authorized through static policy and charging control.
[...]
The Packet Delay Budget (PDB) defines an upper bound for the time that a packet may be delayed between the UE and the PCEF. For a certain QCI the value of the PDB is the same in uplink and downlink. The purpose of the PDB is to support the configuration of scheduling and link layer functions (e.g. the setting of scheduling priority weights and HARQ (Hybrid Automatic Repeat ReQuest) target operating points). Except for QCIs 82 and 83, the PDB shall be interpreted as a maximum delay with a confidence level of 98 percent. [...]
  NOTE 1:    The PDB denotes a "soft upper bound" in the sense that an "expired" packet, e.g. a link layer SDU that has exceeded the PDB, does not need to be discarded (e.g. by RLC (Radio Link Control) in E-UTRAN). The discarding (dropping) of packets is expected to be controlled by a queue management function, e.g. based on pre-configured dropping thresholds.
[...]
Services using a Non-GBR QCI should be prepared to experience congestion-related packet drops, and, except for QCI 80, 98 percent of the packets that have not been dropped due to congestion should not experience a delay exceeding the QCI's PDB. This may for example occur during traffic load peaks or when the UE becomes coverage limited. See Annex J for details. Packets that have not been dropped due to congestion may still be subject to non-congestion-related packet losses (see PELR [Packet Error Loss Rate] below). [...]
Except for services using QCI 82 or 83 services using a GBR QCI and sending at a rate smaller than or equal to GBR can in general assume that congestion-related packet drops will not occur, and 98 percent of the packets shall not experience a delay exceeding the QCI's PDB. Exceptions (e.g. transient link outages) can always occur in a radio access system which may then lead to congestion-related packet drops even for services using a GBR QCI and sending at a rate smaller than or equal to GBR. Packets that have not been dropped due to congestion may still be subject to non-congestion-related packet losses (see PELR [Packet Error Loss Rate] below). [...]
Every QCI (GBR and Non-GBR) is associated with a Priority level (see Table 6.1.7). The lowest Priority level value corresponds to the highest Priority. The Priority levels shall be used to differentiate between SDF aggregates of the same UE, and it shall also be used to differentiate between SDF aggregates from different UEs. Via its QCI an SDF aggregate is associated with a Priority level and a PDB. Scheduling between different SDF aggregates shall primarily be based on the PDB. If the target set by the PDB can no longer be met for one or more SDF aggregate(s) across all UEs that have sufficient radio channel quality then the QCI Priority level shall be used as follows: in this case a scheduler shall meet the PDB of an SDF aggregate on QCI Priority level N in preference to meeting the PDB of SDF aggregates on next QCI Priority level greater than N, until the priority N SDF aggregate's GBR (in case of a GBR SDF aggregate) has been satisfied.
Other aspects related to the treatment of traffic exceeding an SDF aggregate's GBR are out of scope of this specification.
When required by operator policy, the eNodeB can be configured to use the ARP priority level in addition to the QCI priority level to determine the relative priority of the SDFs in meeting the PDB of an SDF aggregate. This configuration applies only for high-priority ARPs as defined in clause 6.1.7.3.
  NOTE 4:    The definition (or quantification) of "sufficient radio channel quality" is out of the scope of 3GPP specifications.
  NOTE 5:    In case of E-UTRAN a QCI's Priority level, and when required by operator policy, the ARP priority level may be used as the basis for assigning the uplink priority per Radio Bearer (see TS 36.300 for details).
The Packet Error Loss Rate (PELR) defines an upper bound for the rate of SDUs (Service Data Units) (e.g. IP packets) that have been processed by the sender of a link layer protocol (e.g. RLC (Radio Link Control) in E-UTRAN) but that are not successfully delivered by the corresponding receiver to the upper layer (e.g. PDCP [Packet Data Convergence Protocol] in E-UTRAN). Thus, the PELR defines an upper bound for a rate of non-congestion-related packet losses. The purpose of the PELR is to allow for appropriate link layer protocol configurations (e.g. RLC [Radio Link Control] and HARQ [Hybrid Automatic Repeat ReQuest] in E-UTRAN). For a certain QCI the value of the PELR is the same in uplink and downlink.
  NOTE 6:    The characteristics PDB and PELR are specified only based on application / service level requirements, i.e., those characteristics should be regarded as being access agnostic, independent from the roaming scenario (roaming or non-roaming), and independent from operator policies.

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QoS Dynamic modification

TCCA White Paper "Public Safety Prioritisation on Commercial Networks" June 2019 §5.4 "Available Prioritisation Mechanisms in 4G on shared network -​ QoS Dynamic modification":

Default EPS bearers have QoS defined in HSS [Home Subscriber Server] (QCI, ARP, Maximum Bit Rate (MBR) plus Aggregated Maximum Bit Rate (AMBR)). It is possible to dynamically modify the QoS of EPS bearers including default bearers. This can be achieved by having a PS application (e.g. a dispatcher application in a PS control room) that triggers policy change via PCRF. A less sophisticated option is also possible where predefined rules per traffic type are defined for example.
So, the scenario for dynamic priority level for PS users is possible with bearer QoS modification. PS users could for example have QCI 6 with ARP priority 8 for generic data connection normally and in the case of an emergency mission the data connection QoS could be modified to QCI 70 and ARP priority 6.

3GPP TS 23.401 "GPRS enhancements for E-UTRAN access" (V17.5.0 (2022-06)) (23401-h50) clause 4.7.3 "Architecture model and concepts - Overall QoS concept - Bearer level QoS parameters": As above.

3GPP TS 23.203 "Policy and Charging Control Architecture" (V17.1.0 (2021-06)) (23203-h10) (applicable to 2G GSM, 3G UMTS, 4G LTE) clause 6.1.7.1 "Functional description - Overall description - Standardized QoS characteristics - General":

The service level (i.e., per SDF (Service Data Flow) or per SDF aggregate) QoS parameters are QCI, ARP, GBR, and MBR. [...] For the same IP-CAN (IP-Connectivity Access Network) session multiple SDFs with the same QCI and ARP can be treated as a single traffic aggregate which is referred to as an SDF aggregate. An SDF is a special case of an SDF aggregate. [...]