What are 5G RedCap and eRedCap, and what comes next?

Reduced Capability (RedCap) is a technology developed for 5G New Radio (NR) by the 3rd Generation Partnership Project (3GPP) to bridge the gap between full-capability 5G NR and LTE-based IoT technologies like LTE Cat-1 and LTE-M. Engineers exploring RedCap for IoT product development may come across terms such as Enhanced RedCap (eRedCap), feRedCap, and efeRedCap. Among these, only eRedCap is officially recognized as a 3GPP device type.

This article examines the standardized capabilities of RedCap and the current status of related terms. It also delves into the reasons behind the introduction of eRedCap in Release 18, the differences between eRedCap and baseline RedCap, and the absence of technical definitions or 3GPP work items for feRedCap and efeRedCap.

Why Release 17 RedCap left a gap

RedCap, introduced in Release 17, simplifies user equipment (UE) complexity associated with full-capability 5G NR by reducing bandwidth and antenna chains. Also known as NR-Light, RedCap enables half-duplex operation in frequency division duplexing (FDD) mode and eliminates carrier aggregation and dual connectivity. As depicted in Figure 1, these modifications result in a more straightforward FR1 radio architecture.

RedCap can handle transmission and reception bandwidths up to 20 MHz in Frequency Range 1 (FR1) and up to 100 MHz in Frequency Range 2 (FR2). It serves as a middle-ground technology between low-rate sensing applications and full-capability 5G use cases. For instance, an industrial camera might transmit a compressed clip after detecting a defect, resulting in short bursts exceeding 10 Mb/s.

On the other hand, cost-effective endpoints deployed at scale, like point-of-sale terminals and utility meters, may not require the performance levels of baseline RedCap. For such devices, module cost and standby power consumption are more critical than peak data rates. To address this gap, 3GPP initiated the Release 18 work item “Enhanced Support of Reduced Capability NR Devices.”

What Release 18 eRedCap changes

Contrary to its name, Enhanced RedCap (eRedCap) is not a higher-performing version of RedCap. Instead, Release 18 refines the RedCap feature set further to lower device costs and power consumption. It limits peak rates to 10 Mb/s in both uplink and downlink and confines operations to FR1, eliminating the need for FR2 radio and mmWave beamforming.

Release 18 also specifies an optional reduction in downlink and uplink data-channel baseband processing to around 5 MHz. This narrower processing path reduces buffering and thermal design requirements, while single-receive-antenna operation simplifies hardware design. These enhancements enable eRedCap to target device costs comparable to LTE Cat-1bis.

To conserve power during extended idle periods, Release 18 extends the maximum extended discontinuous reception (eDRX) cycle in Radio Resource Control (RRC) Inactive from approximately 10.24 seconds for baseline RedCap to 10,485.76 seconds, equivalent to about 2.9 hours. This longer cycle reduces paging-related wakeups for devices that infrequently transmit data.

Positioning eRedCap against LTE Cat-1 and Cat-1bis

While Baseline RedCap caters to high-throughput applications, eRedCap is designed for lower-cost Cat-1-class devices. In this performance tier, LTE Cat-1 and Cat-1bis are the closest alternatives to eRedCap. As illustrated in Figure 2, RedCap and eRedCap occupy distinct positions within the broader 4G and 5G device landscape.

Both LTE categories already support point-of-sale terminals and smart meters, with Cat-1bis delivering Cat-1-class speeds using a single receive antenna. eRedCap aims to strike a balance between performance and cost in the 5G NR realm, positioning it as a viable successor to Cat-1 and Cat-1bis.

Design consideration	LTE Cat-1	LTE Cat-1bis	eRedCap
Network	LTE	LTE	5G NR standalone
Peak rate, DL/UL	10/5 Mb/s	10/5 Mb/s	10/10 Mb/s
Receive configuration	2 Rx	1 Rx	1 Rx
Ecosystem availability	Mature LTE ecosystem	Mature LTE ecosystem	Dependent on operator support and module certification

Table 1. Comparison of LTE Cat-1, LTE Cat-1bis, and eRedCap. Peak rates are standardized maxima; actual throughput varies based on network and device setup.

The choice between Cat-1bis and eRedCap often hinges on the availability of required networks and modules at product launch. Cat-1bis operates on well-established LTE infrastructure, while eRedCap necessitates confirmed 5G standalone (SA) support from the operator and certified modules in the target region. Engineers should opt for Cat-1bis for immediate deployment and eRedCap for products slated for launch once 5G SA and certified modules are accessible in the target market.

feRedCap is only a proposed direction

Sequans Communications has introduced the term “feRedCap” to hint at a possible progression beyond eRedCap towards low-rate, deep-coverage applications currently served by LTE-M and NB-IoT.

In an article titled “Preparing for 5G NR: What IoT Manufacturers Need to Know” on IoT For All, Sequans speculates that eRedCap might evolve into what they refer to as feRedCap. The EU’s Hexa-X-II 6G research consortium also mentions a more advanced RedCap variant in their 6G massive machine-type communications (mMTC) roadmap.

However, neither source provides technical specifics or a release designation for feRedCap, and 3GPP has not initiated any work item under that name. Therefore, feRedCap remains a theoretical concept with no practical basis for product development.

efeRedCap and what Release 19 adds

It’s important to note that efeRedCap is not a feature of 3GPP Release 19. Despite its name suggesting a progression beyond feRedCap, the term lacks a defined industry standard and is not part of any 3GPP work item. Engineers should exclude it from their design considerations. Noteworthy RedCap developments in 3GPP Release 19 include:

• NR NTN operation: Expands non-terrestrial network (NTN) support to RedCap and eRedCap devices in FR1, enabling satellite connectivity for remote monitoring applications.
• Power Class 2 RedCap: Specifies Power Class 2 operation for RedCap UEs in FR1, increasing available uplink transmit power.
• RedCap network management: Introduces operations, administration, and maintenance (OAM) support for configuring RedCap features and monitoring performance.

Summary

RedCap and eRedCap provide a standardized foundation for product design and certification in the realm of 5G NR. To transition a product from planning to production and ensure broad interoperability, engineers should anchor their requirements in deployable 3GPP capabilities and steer clear of speculative technology roadmaps.

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