Wanted Air Interface User Rate

Description

The Wanted Air Interface User Rate (WAIUR) is a Quality of Service (QoS) parameter defined within the 3GPP specifications for packet-switched conversational and streaming traffic classes. It represents the data rate desired by the user application for transmitting or receiving information over the radio air interface (Uu interface). Technically, WAIUR is signaled during the PDP (Packet Data Protocol) context activation procedure or bearer establishment/modification, typically as part of the QoS profile negotiated between the User Equipment (UE) and the network. The network elements, including the Radio Access Network (RAN) and the core network, use this parameter as an input for admission control and resource allocation decisions.

The parameter works in conjunction with other QoS attributes like Traffic Class, Maximum Bit Rate (MBR), Guaranteed Bit Rate (GBR), and Transfer Delay. While GBR and MBR define the network's commitment and upper limits, WAIUR expresses the application's preference or requirement from the user's perspective. For example, a video streaming application might signal a WAIUR corresponding to the bitrate of the selected video stream. The Radio Network Controller (RNC) in UMTS or the eNodeB in LTE receives this parameter and uses it, along with current cell load and radio conditions, to determine if a radio bearer with suitable characteristics can be established. It influences the allocation of dedicated channel resources, power control settings, and scheduling priorities.

WAIUR is particularly relevant for real-time services where a consistent data rate is crucial for quality. The network may not always be able to grant the exact WAIUR due to congestion or policy, but it serves as a key guideline. The parameter's inclusion in QoS signaling ensures that the application's needs are communicated to the radio layer, enabling more intelligent and service-aware resource management. This contributes to maintaining the perceived quality of experience (QoE) for end-users by aligning network resource provisioning with application demands.

Purpose & Motivation

WAIUR was introduced to provide a more nuanced mechanism for conveying application data rate requirements to the radio access network, beyond simple minimum/maximum guarantees. Early packet data services lacked a standardized way for the user application to express its desired throughput to the network's resource management systems. This could lead to inefficient resource allocation—either over-provisioning (wasting capacity) or under-provisioning (degrading user experience).

The parameter solves the problem of asymmetric information between the application and the network scheduler. By signaling WAIUR, the application informs the network of its ideal operating point. This allows the RAN to make more informed admission control decisions; for instance, it can reject a new bearer if it cannot support the wanted rate without impacting existing sessions, or it can schedule resources more efficiently to meet the collective WAIURs of active users. It was motivated by the need to support diverse real-time multimedia services (like video telephony and streaming) in 3G networks, which have strict and variable rate requirements.

Its creation addressed limitations of earlier, more static QoS models. It added a layer of user-centric signaling that complements network-centric parameters like GBR. This enables better optimization for conversational and streaming services, where the user-perceived quality is directly tied to sustained data rate. WAIUR helps bridge the gap between application-layer requirements and physical-layer resource allocation, a fundamental challenge in wireless QoS management.

Key Features

• Signaled as part of the QoS profile during bearer establishment
• Expresses the user application's desired data rate over the air interface
• Used by RAN for admission control and radio resource management
• Applies primarily to conversational and streaming traffic classes
• Works alongside Guaranteed Bit Rate (GBR) and Maximum Bit Rate (MBR)
• Helps optimize user experience for real-time multimedia services

Evolution Across Releases

Defining Specifications