Quality of Service profile

Description

A QoS profile is a collection of Quality of Service (QoS) parameters that define the performance expectations placed on the bearer network for a particular QoS session. It is associated with each QoS session and comprises a number of parameters that specify characteristics such as maximum bit rate, guaranteed bit rate, delay, jitter, and packet loss. The QoS profile is used by the network to allocate resources and enforce policies to meet the required service quality. The term was introduced in 3GPP Release 4 and is specified in TS 21.905 and TS 23.057.

In 3GPP networks, QoS profiles are essential for differentiating services and ensuring that each service receives the appropriate treatment. For example, voice over IP (VoIP) requires low delay and jitter, while file downloads can tolerate higher delay but need high throughput. The QoS profile allows the network to prioritize traffic and allocate resources accordingly. The profile is typically negotiated during session establishment, such as when a PDP context is activated in GPRS or when a bearer is set up in LTE/5G. The network elements, such as the GGSN, SGSN, PGW, SMF, and UPF, use the QoS profile to enforce QoS policies.

The QoS profile includes parameters such as QoS Class Identifier (QCI) in LTE, which maps to specific characteristics like resource type (GBR or non-GBR), priority, packet delay budget, and packet error loss rate. In 5G, the 5G QoS Identifier (5QI) serves a similar purpose. The profile may also include parameters like Allocation and Retention Priority (ARP), Guaranteed Bit Rate (GBR), Maximum Bit Rate (MBR), and Aggregate Maximum Bit Rate (AMBR). These parameters are used by the network to manage congestion, admission control, and resource scheduling.

The QoS profile is associated with a QoS session, which is a logical connection between the UE and the network that provides a specific level of QoS. Each QoS session may have its own QoS profile, allowing multiple services with different requirements to coexist. The network ensures that the QoS profile is maintained throughout the session, even during handovers or changes in network conditions. If the network cannot meet the QoS requirements, it may reject the session establishment or modify the profile.

Over the releases, the definition of QoS profile has remained largely unchanged, reflecting its fundamental role in QoS management. However, the specific parameters and mechanisms have evolved significantly. In early releases, QoS was primarily based on PDP context parameters. With the introduction of LTE, the concept of EPS bearers and QCI was introduced. In 5G, the QoS framework was further enhanced with 5QI, QoS flows, and reflective QoS. Despite these changes, the core idea of a QoS profile as a set of parameters defining performance expectations remains constant.

Purpose & Motivation

The QoS profile was created to provide a standardized way to specify and enforce quality of service in mobile networks. Before its introduction, QoS was often handled in an ad-hoc manner, with limited ability to differentiate between different types of traffic. As mobile networks evolved to support multiple services with varying requirements, the need for a structured approach to QoS became apparent. The QoS profile addresses this by defining a set of parameters that can be used to describe the desired performance characteristics of a session.

The primary motivation for QoS profiles is to enable service differentiation and efficient resource allocation. In a shared network, resources such as bandwidth and buffer space are limited. Without a mechanism to prioritize traffic, all packets would be treated equally, leading to poor performance for delay-sensitive applications. The QoS profile allows the network to identify and prioritize critical traffic, ensuring that services like voice and video receive the necessary resources. It also enables operators to offer different service tiers and charge accordingly.

Historically, the concept of QoS in mobile networks dates back to early packet-switched networks like GPRS. However, it was with the introduction of UMTS in Release 4 that QoS profiles became more formalized. The 3GPP defined a set of QoS classes (conversational, streaming, interactive, background) and associated parameters. This was further refined in LTE with the introduction of QCI and EPS bearers, and in 5G with 5QI and QoS flows. The QoS profile provides a common language for describing QoS requirements across different network technologies, facilitating interoperability and consistent service delivery. It solves the problem of how to translate application requirements into network-level parameters, ensuring that the network can meet the expectations of both users and service providers.