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Would NR-Light (RedCap) succeed LTE Cat-1bis and Cat-4 for Internet of Things Devices?

LTE UE Categories were a popular topic once upon a time. I have various blog posts on the topic, the earliest one being in 2009, then in 2011 and 2015. Most of the smartphones started with Category 3 (Cat-3), going on to Cat-6, Cat-9, etc. Cat-2 was never used as far as I know. Cat-1 and Cat-4 gained popularity in various IoT applications.

The picture above from this press release, nicely summarises the evolution of various 3GPP technologies, including IoT. As you will notice, an updated version of LTE Cat-1 known as Cat-1bis was in 3GPP Release-13. You will also notice that LTE Cat-0 was introduced in Release-12 that evolved into eMTC or LTE-M (Cat-M1). A blog on Ericsson has a nice summary here.

In Release-13, LTE Cat-1bis was introduced. This article explains what Cat-1bis is and how's it different from Cat-1:

LTE Cat 1, sometimes also refers as 4G Cat 1, is specifically designed for more feature-rich Machine-to-Machine (M2M) IoT applications. The technology was initially introduced in 3GPP Release 8 in 2009 and has become standardized LTE IoT communication technology since then. With maximum speeds of 10 Mb/s downlink and 5 Mb/s uplinks, LTE Cat 1 is believed the ideal solution for scenarios that are not dependent on high-speed data transmission but still require the reliability of the 4G network. LTE Cat 1, which also supports voice and mobile IoT applications, also offers a good migration path for 2G and 3G applications, such as asset tracking, smart meters, and other remote sensors. This has pushed the IoT companies to return their attention to the already-available LTE Cat 1 technology. This can well explain why in the era of 4G, LTE Cat 1 has maintained quiet in the market for quite a long time, but only re-gains technology companies’ attention until recent years.

In nowadays, when people talk about LTE Cat 1, it is no longer the same meaning as which defined in 3GPP’S Release 8, the term also refers to the newer LTE Cat 1 bis standard that introduced in the later Release 13. The LTE Cat-1bis is a wireless communication standard that allows IoT devices to adopt single antenna designs while reserving the same level of network capability.

The older LTE Cat 1 standard, like other higher-speed cellular technology, requires 2Rx antennas to support data transmission, making it difficult to be fit into space constraint applications. Before the emergence of LTE Cat 1 bis, the only technologies that support single-antennas designs are Cat 0/Cat M1/Cat NB1, but even with their maximum throughput rate, they are not capable of satisfying the speed requirement of real-time data acquisition devices. Additionally, using single antenna design will also help manufacturers save product costs.

A new whitepaper by Heavy Reading and Qualcomm, explains the main drivers to the new 5G NR device type called NR-Light or RedCap. I have covered a tutorial on that topic here. The article on Light Reading explains: 

Many mid-tier cellular IoT use cases can be handled by LTE technologies — for example, LTE Cat-1bis and LTE Cat-4. So why, then, is there a need for a 5G-native solution? The paper outlines the compelling reasons why a 5G-native IoT solution is needed for mid-tier devices:

5G needs IoT support to become a true platform technology. In public and private networks, a large part of the investment case for 5G is about connected devices and machine communications; yet, today, the market is dominated by smartphones. 5G-native IoT solutions will expand the market for 5G by enabling it to support diverse consumer and industrial IoT use cases.

To enable a long-term migration path for LTE Cat-1bis and LTE Cat-4 services. This is important to operators seeking to refarm 2G/3G and 4G spectrum for 5G. Spectrum refarming is a long-term project for most operators, but one with significant benefits. Cat1.bis and Cat-4 represent about half the market for cellular IoT today.

The second image explains the differences between LTE Cat-1bis, Cat-4 and RedCap (NR-Light). It will be interesting to see how quickly IoT device manufacturers adopt it once the chipsets are available and networks are ready to support it. 

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