Glossary

5G QoS Identifier

5QI is a standardized scalar identifier that maps to specific QoS characteristics in 5G networks. It defines packet delay budget, packet error rate, priority level, and default averaging window for data flows. This enables consistent QoS handling across network functions and efficient resource allocation for diverse services.

Aggregate BSS QoS Profile

Aggregate BSS QoS Profile (ABQP) is a concept defined in 3GPP TS 48.018 for GSM/EDGE Radio Access Network (GERAN). It represents a composite QoS profile for a set of Packet Flow Contexts (PFCs) associated with a mobile station within a Base Station System (BSS). It enables the BSS to manage radio resources efficiently by applying a single, aggregated QoS policy for multiple concurrent data flows, simplifying resource allocation and prioritization.

Aggregated Maximum Bit Rate

AMBR is a QoS parameter that defines the maximum total bit rate allowed across all non-GBR bearers for a UE or APN. It ensures fair resource sharing and prevents a single user or application from monopolizing network capacity, which is crucial for managing best-effort traffic in mobile broadband networks.

Access Network Bit rate Recommendation

ANBR is a QoS mechanism in 3GPP networks that provides the application layer with a recommended maximum bit rate for media flows over the access network. It enables dynamic adaptation of media encoding to match available access network capacity, preventing congestion and optimizing user experience for real-time services like VoLTE and video streaming.

Access Point Name Aggregate Maximum Bit Rate

APN-AMBR is a QoS parameter that limits the total maximum bit rate across all non-GBR bearers associated with a specific APN for a UE. It ensures fair resource allocation among multiple data flows and prevents any single APN from monopolizing network capacity, which is crucial for managing user experience and network efficiency.

Area Traffic Capacity

Area traffic capacity is a key performance indicator that measures the total traffic throughput served per geographic area or per kilometer along a rail line. It is used to specify and evaluate the capacity requirements of 5G networks in different deployment scenarios.

Allocation and Retention Priority

ARP is a 3GPP QoS parameter used to prioritize the allocation and retention of network resources for bearers during admission control and congestion scenarios. It determines which bearers are established or maintained when resources are limited, ensuring critical services like emergency calls receive precedence over less important traffic. This mechanism is fundamental for network efficiency and service reliability.

Access Service Class

Access Service Class (ASC) is a QoS parameter in UMTS that prioritizes random access attempts from the UE to the NodeB. It maps logical channels to specific access service classes, managing contention and ensuring critical services like emergency calls get prioritized access to the radio network.

Associated QoS Flow

A unicast QoS Flow in the associated PDU Session used for 5GC Individual MBS traffic delivery. It is mapped from a multicast QoS Flow in a multicast MBS session, enabling seamless delivery of MBS data to individual UEs.

Authorised Quality of Service

The maximum QoS authorised for a service data flow, containing the QoS class identifier and data rate. It defines the upper limit of QoS that the network permits for a given flow, ensuring policy control and resource management.

Bearer Binding Function

The Bearer Binding Function (BBF) is a core component in 3GPP Policy and Charging Control (PCC) architecture. It is responsible for associating IP flows within a service data flow to a specific bearer that provides the required QoS. This binding ensures that user traffic receives the appropriate quality of service treatment across the access network.

Bearer Service

A telecommunications service that provides the capability for transmitting signals between user-network interfaces. It forms the fundamental transport layer upon which teleservices and applications are built, defining the QoS characteristics of the underlying connection.

Backward Explicit Congestion Notification

BECN is a congestion notification mechanism in 3GPP's Gb interface that informs the SGSN about network congestion in the downlink direction. It allows the network to proactively manage traffic flow and prevent packet loss by signaling congestion from the BSS back to the SGSN. This mechanism is crucial for maintaining QoS and optimizing network resource utilization in 2G/3G packet-switched networks.

Best Effort Quality of Service

The lowest of all QoS traffic classes, where the network delivers service without guarantees on throughput, delay, or reliability. It is the default QoS for many internet services and is used when guaranteed QoS cannot be provided.

Best Effort Service

A service model providing minimal performance guarantees with unspecified variance in measured performance criteria. It represents the simplest form of packet delivery where the network makes no commitments about throughput, delay, or reliability.

Binding

In 3GPP, Binding refers to the association between a service data flow and the IP-CAN bearer (or QoS Flow in 5G) that transports that service data flow. It ensures that the appropriate QoS treatment is applied to each service data flow.

Binding mechanism

The Binding mechanism is the method for creating, modifying, and deleting bindings between service data flows and the bearers or QoS Flows that transport them. It is a key part of 3GPP policy and charging control.

Bit rate

Bit rate is the number of bits conveyed or processed per unit of time, typically expressed in bits per second (bit/s) or with SI prefixes like kbit/s and Mbit/s. It is a key parameter for specifying data rates in 3GPP networks.

Communication Admission Control

Communication Admission Control (CAC) is a network mechanism that determines whether to accept or reject new communication requests based on available resources and QoS requirements. It ensures network stability by preventing congestion and maintaining service quality for existing connections. CAC is essential for managing network load and guaranteeing performance for critical services.

Congestion Experienced

Congestion Experienced (CE) is a signaling mechanism in 3GPP networks that indicates network congestion to endpoints. It enables explicit congestion notification (ECN) for IP traffic, allowing transport protocols to react before packet loss occurs. This improves network efficiency and user experience by reducing latency and retransmissions during congestion.

Charging control

The process of associating packets of a service data flow to a charging key and applying online and/or offline charging. It is a key function in policy and charging control (PCC) for differentiated charging.

Data Burst

A set of multiple PDUs generated and sent by an application in a short period of time, as defined in 3GPP TS 23.501. It is a key concept for optimizing 5G networks for bursty traffic patterns.

Delay Budget Information

Delay Budget Information (DBI) is a QoS parameter introduced in 3GPP Release 16 that quantifies the maximum permissible packet delay for a data flow. It is a critical component for enabling deterministic communication and ultra-reliable low-latency communication (URLLC) services. DBI allows the network to make informed resource allocation and scheduling decisions to meet stringent end-to-end latency requirements.

Dedicated EPS Bearer

An EPS bearer linked to specific uplink and downlink packet filters that match only certain traffic flows. It provides differentiated QoS treatment for selected services on top of the always-on default bearer in LTE/EPC networks.

Default EPS Bearer

The EPS bearer established with every new PDN connection that provides always-on IP connectivity to the UE. It remains active for the lifetime of the PDN connection and is always a non-GBR bearer.

Drop Eligible Indicator

A 1-bit field in packet headers that indicates whether a packet can be dropped during network congestion. It enables selective packet discarding to maintain QoS for critical traffic while managing network resources efficiently during overload conditions.

Delivered Quality of Service

The actual QoS parameter values achieved over the lifetime of a QoS session, reflecting what was truly delivered rather than what was requested. It is used for monitoring, charging, and verifying service level agreements.

Detected Application Traffic

An aggregate set of packet flows generated by a given application and detected by an application detection filter. It enables policy control and charging based on application awareness in 3GPP networks.

Differentiated Services Code Point

A 6-bit field in the IP packet header (IPv4 and IPv6) used to classify and manage network traffic according to Differentiated Services (DiffServ) architecture. In 3GPP systems, it's used to map QoS flows and bearers to IP-level service classes for consistent treatment across transport networks.

Explicit Congestion Notification

Explicit Congestion Notification (ECN) is a network congestion management mechanism that allows routers to signal impending congestion to endpoints by marking packets, rather than dropping them. In 3GPP, it is adapted for mobile networks to improve Quality of Service (QoS) and application performance. ECN reduces packet loss and latency, enhancing user experience for real-time services like video streaming and VoIP.

ECN Congestion Experienced

ECN Congestion Experienced (ECN-CE) is a specific codepoint within the Explicit Congestion Notification (ECN) mechanism, indicating that a network node has experienced congestion and marked the packet accordingly. In 3GPP, it is used to signal congestion to endpoints, triggering rate adaptation. ECN-CE enables proactive congestion management, reducing packet loss and enhancing performance for mobile services.

End-to-end latency

The time taken to transfer a piece of information unidirectionally from a source to a destination, measured at the communication interface. It is a critical QoS metric for real-time and industrial applications.

Expected Residual Time

A predictive metric used in multimedia streaming, particularly for Dynamic Adaptive Streaming over HTTP (DASH), to estimate the remaining playback time of media content in a client's buffer. It enables intelligent adaptation logic to prevent buffer underflow and maintain smooth playback quality.

Extra Service Data Unit Delivery Probability

A QoS metric defined as the ratio of total unrequested extra SDUs to total SDUs received by a destination user in a specified sample, based on ITU-T X.140.

Frame Loss Ratio

Frame Loss Ratio (FLR) is a key Quality of Service (QoS) metric defined by 3GPP to measure the proportion of lost or unsuccessfully delivered data frames in a multimedia session. It is crucial for assessing and guaranteeing the quality of real-time services like voice and video over packet-switched networks. Accurate FLR measurement enables operators to monitor performance, troubleshoot issues, and ensure user experience meets service level agreements.

Fixed Network User Rate

A standardized quality of service (QoS) parameter in 3GPP that defines a guaranteed, constant bit rate for user data transmission over a fixed network segment. It ensures predictable performance for applications requiring steady bandwidth, such as voice or video streaming, by reserving network resources.

Gating Control

The process of blocking or allowing packets belonging to a service data flow or detected application's traffic to pass through to the desired endpoint. It is a key policy enforcement mechanism in 3GPP networks, used to control access to services based on policy decisions.

Guaranteed Bit Rate

A Quality of Service (QoS) parameter that guarantees a minimum constant bit rate for a bearer or flow. The network commits resources to ensure this rate is continuously available, making it essential for real-time services like voice and video streaming.

Guaranteed Bit Rate Bearer

An EPS bearer that uses dedicated network resources related to a guaranteed bit rate value, permanently allocated at bearer establishment or modification.

Guaranteed Flow Bit Rate

The minimum bit rate guaranteed for a QoS flow in 5G networks. It ensures that certain traffic receives at least a specified data rate, critical for services like VoNR and real-time applications.

Global Quality

A comprehensive, end-to-end quality metric for a voice or video conversation, defined in 3GPP. It represents the overall user-perceived quality by integrating various impairment factors across the entire transmission path, not just individual network segments.

Hyper Reliable and Low Latency Communication

HRLLC (Hyper Reliable and Low Latency Communication) is a Rel-20 service class studied in 3GPP TR 38.914. It targets extreme combinations of ultra-high reliability and very low latency, beyond the URLLC baseline, for demanding industrial and mission-critical applications.

Interactive / Background

A standardized QoS class for packet-switched services in 3GPP networks. It defines two traffic handling priorities for non-real-time data services, enabling differentiated resource allocation and scheduling between interactive applications (like web browsing) and background transfers (like file downloads).

Information Data Rate

The rate of user information transmitted over the air interface, such as the output rate of a voice codec. It is a key parameter for QoS and radio resource management.

Internet Protocol Flow

A unidirectional stream of IP packets sharing the same source/destination IP addresses, port numbers, and transport protocol. It is the fundamental unit for traffic classification, policy control, and QoS enforcement in 3GPP networks.

Low Latency, Low Loss, and Scalable Throughput

L4S is a framework for achieving ultra-low latency and minimal packet loss in IP networks, enabling scalable throughput for applications like real-time communication and AR/VR. It allows latency-sensitive traffic to coexist with standard traffic without requiring separate queues, improving network efficiency and user experience.

Least Acceptable Value

A QoS parameter defining the minimum acceptable value for a specific performance metric, such as throughput or delay. It is used in network selection and policy decisions to ensure user experience meets a baseline threshold. This concept is crucial for maintaining service quality and enabling efficient resource utilization.

Multi-Access Rule

A policy rule defined in the 5G Core Network (5GC) that governs how User Equipment (UE) traffic is distributed across multiple simultaneous access networks (like 3GPP and non-3GPP). It is part of the Policy and Charging Control (PCC) framework and enables intelligent, dynamic steering of IP flows or QoS Flows based on conditions like access availability, load, and application requirements.

Maximum Data Burst Volume

A 5G Quality of Service (QoS) parameter that defines the largest amount of data that the 5G system is required to serve within a 5G QoS Identifier's associated Maximum Burst Duration. It is critical for guaranteeing the low latency and reliability of services like URLLC.

Maximum Flow Bit Rate

A QoS parameter that defines the maximum sustained bit rate allowed for a data flow within a PDU session. It is a key metric for enforcing traffic policing and ensuring fair resource allocation among users, directly impacting user experience and network efficiency.

MCVideo Emergency Private Priority

A specific QoS priority level and associated procedures within the MCVideo service that ensures emergency private video calls receive the highest possible network resource allocation and pre-emption capabilities. It is the mechanism that enforces the preferential treatment for MVEPC sessions.

Non-3GPP QoS Assistance Information

N3QAI is a set of parameters provided by the UE to the network to assist in QoS flow mapping and policy enforcement for traffic routed over non-3GPP access (e.g., Wi-Fi). It conveys application-level QoS requirements from the UE side, helping the 5G Core apply appropriate QoS policies when the non-3GPP access lacks native 5G QoS awareness. This ensures consistent QoS experience across different access types.

Negotiated Quality of Service

Negotiated QoS is the process by which a network adjusts requested QoS attributes to match available resources, ensuring feasible service levels. It is fundamental to bearer resource management in 3GPP networks.

Non-Guaranteed Bit Rate Bearer

An EPS bearer that uses network resources not tied to a guaranteed bit rate value. It is used for best-effort and delay-tolerant traffic such as web browsing and file downloads, where throughput can fluctuate based on network load.

Operator-Controlled Service

A service for which complete PCC rule information, including service data flow filter information, is available in the PCRF through configuration and/or dynamic interaction with an AF. It enables the operator to control QoS and charging for specific services.

Packet Flow

A packet flow is a specific user data flow carried through the Policy and Charging Enforcement Function (PCEF). It represents the granular unit of traffic that policy and charging rules are applied to, typically identified as an IP flow or a set of IP flows.

Priority Based Transmission Scheduling

Priority Based Transmission Scheduling (PBTS) is a scheduling mechanism in LTE and 5G that prioritizes data transmissions based on QoS Class Identifier (QCI) or 5QI. It ensures critical traffic like voice or emergency services receives resources before best-effort data, optimizing network performance under congestion.

Priority Code Point

A field in Ethernet frames used to indicate the priority level of traffic for QoS handling. In 5G systems, it's used within the N6 interface between the UPF and the data network to align Ethernet-based transport prioritization with 5G QoS flows, ensuring consistent quality of service across network segments.

Packet Delay Budget

A 5G QoS parameter defining the upper bound for the packet delay between the UE and the UPF (or N6 reference point). It is a key component of the 5QI (5G QoS Identifier) and is used for scheduling and admission control to guarantee latency-sensitive services.

Protocol Data Unit Set

A set of one or more PDUs carrying the payload of a single application-level unit, such as an XR video frame, all transmitted within the same QoS Flow to enable coordinated QoS treatment.

Packet Delay Variation

Packet Delay Variation (PDV) is a key Quality of Service metric that measures the variation in latency between packets in a data flow. It is critical for time-sensitive applications like real-time communications, industrial automation, and cloud gaming, where consistent packet arrival is essential for performance and user experience.

Peak Bit Rate

A measure of throughput representing the maximum bit rate offered to a user for a given time period for the transfer of a bursty signal, often used for network dimensioning and QoS guarantees.

Per Hop Behaviour

A DiffServ model component defining the forwarding treatment (e.g., scheduling, dropping priority) applied to a packet at a single network node. It is a building block for end-to-end Quality of Service, where packets are marked with a DSCP to receive a specific PHB along their path.

Priority Information Element

The Priority Information Element (PIE) is a fundamental data field within 3GPP signaling protocols used to indicate the relative importance or urgency of a session, bearer, or message. It governs network resource allocation, admission control, and scheduling decisions, ensuring critical services like emergency calls, Mission Critical Services (MCPTT), and high-priority network signaling receive preferential treatment.

Packet Loss Ratio

A key performance metric that measures the ratio of packets lost in transmission to the total number of packets sent over a network path during a specific time interval. It is critical for assessing the quality and reliability of real-time services like voice (VoIP) and video streaming.

Policy Counter Status

A non-standardized label indicating a subscriber's spending status relative to policy counter thresholds. It enables dynamic policy control based on real-time usage from OCS/CHF to PCRF/PCF.

PC5 QoS Flow Identifier

The PC5 QoS Flow Identifier (PQFI) is a unique identifier assigned to a specific QoS flow established over the PC5 reference point for direct device-to-device communication. It enables the precise mapping and enforcement of QoS requirements for individual data flows in sidelink communications, such as those used in V2X services. This granular identification is crucial for supporting differentiated service levels and ensuring reliable, low-latency communication between vehicles, pedestrians, and infrastructure.

PC5 QoS Identifier

The PC5 QoS Identifier (PQI) is a standardized index that references a predefined set of QoS characteristics (like priority, delay, reliability) for communication over the PC5 sidelink interface. It provides a simple, scalable mechanism to request and apply consistent QoS treatment for direct device-to-device data flows, such as in V2X or public safety scenarios. By using a common reference, it ensures interoperable QoS management across different vendors' equipment.

Predefined PCC Rule

A Policy and Charging Control rule provisioned directly into the SMF by the operator. It enables pre-configured QoS and charging policies to be applied without dynamic signaling from the PCF.

Predictive Service

A service model providing reliable performance with a specified variance in measured performance criteria, enabling predictable QoS for applications requiring consistent but not strictly deterministic behavior.

Packet Set Delay Budget

Packet Set Delay Budget (PSDB) is a 5G QoS parameter introduced for deterministic communication services. It defines the maximum allowed end-to-end latency for a set (or group) of packets that have a temporal dependency, rather than for individual packets. This is crucial for applications like industrial control where the synchronized arrival of a packet set is more important than the latency of any single packet.

Packet Set Error Rate

Packet Set Error Rate (PSER) is a Quality of Service (QoS) metric introduced in 3GPP Release 18 for advanced services like XR and industrial IoT. It measures the proportion of packet sets that are not delivered successfully within a required latency bound. PSER is critical for applications with stringent reliability and latency requirements, enabling more precise service level agreements.

PDU Set Importance

PDU Set Importance (PSI) is a QoS parameter introduced in 3GPP Release 18 to indicate the relative importance of a set of Protocol Data Units (PDUs) within a data flow. It enables the network to apply differentiated handling, such as prioritization for transmission or selective discarding under congestion, based on the semantic importance of data chunks. This is crucial for optimizing the delivery of segmented or layered media content, like video tiles in XR applications.

Quality of Service Class Identifier

A scalar identifier used to specify a standardized set of QoS characteristics for a bearer in 3GPP networks. It defines packet forwarding treatment parameters like priority, packet delay budget, and packet error loss rate. This enables network operators to manage and differentiate traffic for various services.

Quality Estimate

Quality Estimate (QE) is a parameter used in 3GPP specifications to represent an estimated quality level for user data flows, particularly in the context of transport channels. It is employed within the Radio Access Network (RAN) to support quality-aware scheduling and resource management decisions. The QE helps in optimizing the trade-off between data throughput and transmission reliability.

QoS Enforcement Rule

QoS Enforcement Rule (QER) is a policy rule defined in the 5G System to enforce specific QoS requirements on user plane traffic. It is a fundamental component of the Policy and Charging Control (PCC) framework, enabling dynamic and granular QoS management per application flow. QERs are provisioned by the Policy Control Function (PCF) and enforced by the User Plane Function (UPF) to ensure service quality.

QoS Flow Identifier

QoS Flow Identifier (QFI) is a scalar used in the 5G System to uniquely identify a QoS Flow within a Protocol Data Unit (PDU) Session. It is a fundamental construct for granular QoS differentiation, enabling the network to apply specific forwarding treatments (e.g., scheduling, admission control) to packets belonging to the same flow. The QFI is carried in packet headers over the N3 and N9 interfaces.

QoS Notification Control

QoS Notification Control (QNC) is a 5G core network capability that allows the network to notify a User Equipment (UE) about changes to its authorized QoS parameters. It enables dynamic QoS adaptation, such as modifying bitrate guarantees, based on network policies or conditions. This is essential for efficient resource utilization and supporting advanced services like network slicing.

Quality of Service

Quality of Service (QoS) is a set of technologies and mechanisms that manage network traffic to guarantee performance levels for specific data flows. It ensures applications receive the necessary bandwidth, latency, jitter, and packet loss characteristics. This is fundamental for supporting diverse services like voice, video, and real-time gaming over shared network resources.

Quality of Service profile

A set of QoS parameters associated with a QoS session, defining performance expectations on the bearer network. It is fundamental for ensuring service quality and resource allocation in mobile networks.

Quality of Service Session

The lifetime of a PDP context, spanning from the opening to the closing of a network connection whose characteristics are defined by a QoS profile. Multiple QoS sessions with different profiles may coexist for a single user.

QoS Rule Identifier

A unique identifier assigned to a QoS Rule in the 5G System (5GS) to manage packet flow treatment. It allows the network and UE to unambiguously reference specific QoS rules for enforcement, enabling dynamic QoS control and efficient handling of diverse service data flows.

Reflective QoS flow to DRB mapping Indication

A mechanism in 5G and later systems where the UE autonomously maps uplink QoS flows to Data Radio Bearers (DRBs) by mirroring the downlink mapping signaled by the network. It reduces signaling overhead by enabling the UE to infer uplink QoS handling without explicit configuration.

Requested Quality of Service

A QoS profile requested at the beginning of a QoS session, with possible modifications during the session. It represents the quality level desired by the application or user, which the network attempts to satisfy based on available resources and policy.

Residual Error Rate

A QoS parameter measuring the frequency of lost, corrupted, or duplicated SDUs delivered at the user-network interface. It quantifies the accuracy of a bearer service by capturing undetected errors that remain after all error correction mechanisms have been applied.

Reflective QoS Attribute

A QoS attribute used in 5G to enable Reflective QoS. It is carried within the PDU Session Establishment Accept message from the SMF to the UE. It signals that a QoS Flow is subject to reflective QoS, allowing the UE to derive uplink QoS rules from downlink traffic.

Reflective QoS Indication

A marker set in the user-plane packet header to trigger Reflective QoS at the UE. When the UE, which has an authorized QoS Flow (RQA), receives a downlink packet with RQI set, it derives an uplink QoS rule. This enables dynamic, signaling-efficient QoS management.

Reflective QoS Indication

A legacy QoS indication used in pre-5G 3GPP systems, specifically for IMS-based services. It was a parameter in SIP/SDP signaling to indicate that a media flow should use network-initiated QoS (e.g., PCC). It is a precursor concept to the 5G RQI/RQA mechanism.

Round Trip Time

The total time taken for a signal or packet to travel from a source to a destination and back again, measured in milliseconds. In 3GPP networks, RTT is a critical metric for assessing latency, influencing performance in applications like voice calls, gaming, and real-time control, and is optimized across radio and core network components.

Service Data Flow

A Service Data Flow (SDF) is a fundamental concept in 3GPP policy and charging control (PCC). It defines a set of IP packet flows matching specific filters, used to apply uniform QoS and charging policies. It is crucial for enabling granular service differentiation and monetization in mobile networks.

Service Data Unit Error Probability

The ratio of total incorrect Service Data Units (SDUs) to the total of successfully transferred plus incorrect SDUs in a specified sample. It is a fundamental QoS metric used to quantify residual errors remaining after all error correction and retransmission mechanisms have been applied.

Service Data Unit Loss Probability

The ratio of total lost Service Data Units (SDUs) to total transmitted SDUs in a specified sample. It quantifies the fraction of data units that fail to reach their destination, serving as a key QoS metric for packet loss performance in 3GPP networks.

Service Data Unit Misdelivery Probability

The ratio of total misdelivered Service Data Units (SDUs) to total SDUs transferred between a specified source and destination user in a specified sample. It measures the probability that data is delivered to the wrong destination, a critical integrity metric for network reliability.

Service Data Unit Transfer Delay

The elapsed time between the start of transfer and successful delivery of a specified Service Data Unit. It is a fundamental QoS performance metric used to characterise the delay experienced by user data across a 3GPP bearer or QoS flow.

Service Data Unit Transfer Rate

The number of successfully transferred SDUs within a transfer sample divided by the sample's input/output time. It is a throughput-oriented QoS metric quantifying how effectively a bearer or QoS flow delivers user data.

Service data flow filter

A set of packet flow header parameter values/ranges used to identify one or more packet flows constituting a service data flow, enabling differentiated QoS and charging treatment.

Service Data Flow Template

A set of packet filters or an application identifier within a PCC rule that defines a Service Data Flow (SDF) for policy enforcement and charging. It enables the network to classify and treat specific traffic streams with appropriate QoS and charging rules.

Service Delay

The time elapsed from the invocation of a service request to the corresponding service request indication at the Service Receiver, indicating the arrival of application data. It is a key performance metric for real-time services.

Service Model

A general characterisation of services based upon a QoS paradigm, without specifying actual performance targets. It defines the qualitative behaviour classes that a bearer or service must satisfy.

Session Management Congestion Control Experience

A 3GPP framework for managing network congestion at the session management level to ensure consistent user experience. It introduces mechanisms to detect, report, and mitigate congestion, prioritizing critical services and preventing service degradation during high load.

Spending Limit

A spending limit is the usage limit of a policy counter (e.g., monetary, volume, duration) that a subscriber is allowed to consume. It is a key concept in policy and charging control, enabling operators to enforce usage caps and prevent bill shock.

Spending Limit Report

A spending limit report is a notification containing the current policy counter status, generated from the OCS to the PCRF via the Sy reference point. It enables real-time policy adjustments based on subscriber usage.

Source Statistics Descriptor

A parameter in 5G QoS that characterizes the traffic pattern of a data flow, such as its burstiness or regularity. It helps the network optimize resource allocation, scheduling, and admission control for improved efficiency and QoS.

Subscribed Quality of Service

The maximum QoS level a user is allowed to receive based on their subscription profile stored in the HLR/HSS/UDM. It ensures the network does not grant higher QoS than the user is entitled to, preventing resource abuse.

Subscriber category

Subscriber category is a means to group subscribers into different classes, such as gold, silver, and bronze users, for differentiated QoS treatment and policy control.

Survival Time

Survival time is the time an application can continue without an anticipated message, a key QoS parameter for time-sensitive and industrial applications in 5G networks.

Traffic Aggregate Description

A Traffic Aggregate Description (TAD) is a template or rule set used within the Policy and Charging Control (PCC) architecture to identify and classify a group of IP flows belonging to a service data flow. It enables the network to apply consistent QoS and charging policies to aggregated traffic, simplifying policy management for complex services with multiple simultaneous flows.

Token Bucket Counter

A traffic policing algorithm used to enforce Quality of Service (QoS) parameters by measuring and controlling the data rate and burst size of a flow. It conceptually uses tokens, added at a steady rate to a bucket, which must be spent to transmit data, ensuring traffic conforms to a defined profile.

Throughput Advice

The maximum rate indicated by an intermediate network element (UPF) as specified in the IETF SCONE Protocol.

Type of Service

TOS is a field in the IPv4 packet header used to indicate the desired quality of service (QoS) treatment for the packet, such as priority, delay, throughput, and reliability. It is a precursor to modern QoS mechanisms like DiffServ Code Points (DSCP) in IP networks, including those used within 3GPP packet core.

Transit delay

Transit delay is a QoS parameter measuring the time for a protocol data unit (PDU) to cross between two designated reference points in a network. It quantifies service speed and is critical for real-time and delay-sensitive applications.

Traffic Specification

A set of parameters that quantitatively describe the traffic characteristics and QoS requirements of a data flow. It is used by the network to allocate appropriate resources, perform admission control, and ensure service quality. TSPEC is fundamental to QoS management across 3GPP systems.

Unconstrained Delay Data

A QoS class for data traffic with no specific delay requirements, such as background downloads or email. It allows the network to schedule transmission opportunistically, optimizing resource utilization without guaranteeing latency. This is fundamental for non-real-time, best-effort services in 3GPP systems.

UE Aggregate Maximum Bit Rate

UE-AMBR is a QoS parameter that limits the total maximum bit rate a User Equipment can consume across all its Non-GBR bearers. It is enforced by the base station (eNB/gNB) in the uplink and downlink to prevent a single UE from monopolizing shared radio resources.

Usage Parameter Control (UPC)

Usage Parameter Control is a set of network actions that monitor and police offered traffic on a connection, verifying that it complies with the negotiated traffic contract so that one user cannot degrade the QoS of others.

User Plane Congestion management

A framework of mechanisms defined by 3GPP to detect, mitigate, and control congestion specifically in the user data plane of mobile networks. It aims to maintain service quality during periods of high traffic load by dynamically managing resource usage.

User Radio Bearer

A logical channel established over the radio interface to carry user plane data for a specific service with defined Quality of Service (QoS) characteristics. It maps application data flows to radio resources, ensuring the required bit rate, delay, and reliability.

User experienced data rate

User experienced data rate is the minimum data rate required to achieve a sufficient quality experience, except for broadcast-like services where it is the maximum needed. It is a key QoS metric for evaluating network performance from the user's perspective.

User Requested Application Priority

A priority level requested by the user for a specific application, as defined in 3GPP TS 23.280. It is used by the MCVideo server to determine the priority of the requested communication, combined with other factors.

Variable Bit Rate

Variable Bit Rate (VBR) is a class of service where the data transmission rate is not constant but varies over time based on the instantaneous demands of the traffic source, such as video or audio encoding. In 3GPP, it is referenced in specs like TS 25.222 and TS 26.253 for radio and codec aspects. VBR is essential for efficiently transmitting compressed multimedia content, optimizing bandwidth usage while maintaining quality, and is a key attribute in QoS definitions for conversational and streaming services.

Visible Interruption Length

VIL (Visible Interruption Length) is a QoS metric introduced in 3GPP Release 19 to quantify the duration of visible interruptions in video or data services. It is specified in TS 31.122 and TS 38.133 for evaluating user-perceived quality.

Voice Quality

A set of metrics and methodologies defined by 3GPP to objectively and subjectively assess the perceived quality of a voice call from the listener's perspective. It is crucial for network operators to monitor, troubleshoot, and optimize voice services, ensuring customer satisfaction and meeting regulatory requirements for service quality.

Wanted Air Interface User Rate

Wanted Air Interface User Rate (WAIUR) is a QoS parameter that specifies the desired data rate for a user's application over the radio air interface. It is used by the network during bearer establishment or modification to understand application requirements and allocate appropriate radio resources. This parameter helps optimize radio resource management and meet user experience expectations.

Wi-Fi Multimedia

WMM is a Wi-Fi Alliance certification based on IEEE 802.11e that provides Quality of Service (QoS) for Wi-Fi networks. It prioritizes traffic into four access categories (voice, video, best effort, background) to improve performance for latency-sensitive applications like voice and video over Wi-Fi.