NR Reduced Capability RAT Type

Description

NR RedCap (NR Reduced Capability) is a 3GPP RAT type identifier introduced in Release 19, defined in 3GPP TS 23.501 and TS 29.061. It is used exclusively within the Core Network (CN) to identify NR when used by a UE that indicates NR Reduced Capability. This identifier is a sub-type of the generic NR RAT type, meaning that while the UE is technically connected via NR, the CN can distinguish it as a RedCap device for policy, charging, and mobility management purposes.

The NR RedCap identifier is not a radio access technology in itself; rather, it is a classification that allows the 5G Core Network (5GC) to apply specific treatments to RedCap UEs. RedCap devices are designed to be lower complexity, lower power, and lower cost compared to full-fledged NR devices, targeting use cases such as industrial wireless sensors, video surveillance, and wearables. By identifying these devices at the CN level, operators can optimize network resources, enforce appropriate QoS policies, and manage mobility and session management differently.

In the 5G architecture, the RAT type is reported by the Radio Access Network (RAN) to the Access and Mobility Management Function (AMF) during UE registration and session establishment. The AMF then uses this information to select appropriate Session Management Functions (SMFs) and to apply policies. With NR RedCap, the RAN indicates that the UE is a RedCap device, and the AMF forwards this RAT type to other CN functions such as the Policy Control Function (PCF) and the Unified Data Management (UDM). This allows the network to enforce specific policies, such as restricted mobility or lower maximum bit rates, tailored for RedCap devices.

The identifier is defined in TS 23.501, which specifies the overall 5G system architecture, and TS 29.061, which covers interworking between the Public Land Mobile Network (PLMN) and Packet Data Networks (PDNs). The NR RedCap RAT type is used in signaling messages such as the N2 interface between the RAN and AMF, and in charging records generated by the SMF. It enables operators to differentiate charging and billing for RedCap devices, which may have different subscription models.

Overall, NR RedCap is a key enabler for the 5G ecosystem to support massive IoT and low-cost devices without compromising the performance of enhanced Mobile Broadband (eMBB) services. It allows the network to treat RedCap UEs as a distinct class, ensuring efficient resource utilization and service differentiation.

Purpose & Motivation

The NR RedCap identifier was created to address the growing need for a unified 5G network that can efficiently serve diverse device types, including low-power, low-complexity IoT devices. Prior to Release 19, the Core Network could not distinguish between standard NR UEs and RedCap UEs based solely on the RAT type, leading to suboptimal policy enforcement and resource allocation. RedCap devices, defined in Release 17, required a way to be identified in the CN so that operators could apply appropriate QoS, charging, and mobility policies.

The introduction of NR RedCap as a RAT type sub-identifier solves this problem by providing a standardized mechanism for the RAN to signal the RedCap capability of a UE to the CN. This allows the CN to apply differentiated treatment without requiring changes to the radio interface or UE procedures. It also enables operators to offer tailored services and pricing for RedCap devices, which is essential for the commercial success of massive IoT deployments.

Furthermore, NR RedCap supports network slicing and edge computing scenarios by allowing the CN to route RedCap traffic to specific network slices or edge applications. This flexibility is crucial for industrial and enterprise use cases where RedCap devices may require dedicated network resources. The identifier thus plays a vital role in the 5G vision of connecting everything, from high-speed broadband to low-power sensors.