RedCap: The Advanced IoT for 5G network

RedCap stands for reduced capability. RedCap is the 3GPP IoT wireless specification designed to address several generic and specific use cases for 5G NR. The current state of RedCap can be traced back to several requirements in the industry that culminated due to multiple and overlapping requirements from use cases and IoT verticals.

There are several reasons why RedCap is needed from an infrastructure and operator’s point of view. It is important to note that while 5G networks are being deployed globally, they are not all the same 5G network types. There are two distinct 5G network types – stand alone (SA) and non-stand alone (NSA). The SA networks rely completely on 3GPP 5G specifications for all device and infrastructure equipment. NSA networks rely on both 3GPP 4G and 5G specifications. This means that SA-only devices are specifically designed for 5G networks, and do not support 4G technologies, such as LTE-M and NB-IoT. This can be a problem for operators of pure green-field 5G networks (no legacy 4G installations) and regional mandates for devices to support SA, if they want to satisfy IoT requirements.

RedCap offers a migration path from 4G to 5G as spectrum is migrated to new bands. The number of 5G NR bands is expected to grow just as they did between legacy technologies 2G→3G and 3G→4G. In fact, RedCap can operate in the FR2 bands offering entirely new spectrum that would otherwise not be available for 4G devices.

RedCap bridges the gap between 4G IoT and 5G NR technologies. Finally, IoT service providers will eventually need to sunset legacy technologies and need a migration path forward. Many 2G/3G devices and services are nearing end of life as it makes economic sense to move to more efficient technologies. RedCap will offer the most longevity of them all as 5G technologies are expected to be around even further than 4G by taking us into the next 1–2 decades.

The primary benefit of RedCap is the new use cases that RedCap addresses by enabling cost-effective devices. There are three initial IoT 3GPP Rel-17 use case requirements by the industry needed to be solved – industrial wireless sensors, video surveillance, and wearables. Each of them has slightly different requirements across data rate, latency, reliability, and battery life.

Lower-complexity wireless hardware in the devices means simpler modem and RF front-end architectures. Lower number of antennas and less MIMO allow for lower device costs. No or less duplexers (depending on the band), less amplifiers, and filters can greatly simplify the components of RedCap devices, so the form factor can be designed around specific use cases. This reduction of hardware also directly benefits the costs of the devices. In addition, RedCap devices are not required to support as many frequency bands as 5G smart phones, further lowering costs typically seen in 5G smart phones. These hardware reductions will also allow for smaller devices, which are critical in the wearables RedCap use cases. Due to these hardware and cost reductions, we should expect to see many new 5G devices and use cases develop in the coming years. We may even see much lower-cost 5G smart phones based on RedCap. Additionally, we would expect the number of use cases to grow as 3GPP continues further development of RedCap specifications.

RedCap specifications were included in 3GPP Rel-17 and finalized in June of 2022. It will take around a year for modems and RF front ends to arrive. Eventually modules and end-devices will take another year or less. So, we should expect to see some of the first RedCap devices to appear around the end of 2023 on to middle of 2024, depending on the level of complexity and integration of the RedCap devices. This will be the appropriate time as global operators will continually be deploying 5G SA networks over the next several years.

NR and RedCap devices especially need the RRC_Inactive state for reduced latency and to send small amounts of data while not requiring the extra overhead of RRC connection establishment from RRC_Idle state. RRC_Inactive is not available in 5G NSA. Measurements are still performed for the serving cell, intra-frequency, inter-frequency as well as interRat for e-Utran cells. This means all the robustness of NR mobility allows device engineers to re-use much of the core NR software. In addition, a RedCap device can have the ability to move to LTE networks, if desired. Of course, the LTE capability must be designed into devices, but it is an option. Link recovery functionality is also specified for RedCap just as NR.

Rel-17 RedCap has only begun the reduction of complexity to lower cost and increase battery life. There is still much to be done for RedCap. 3GPP has already been working on RedCap Rel-18 (NR Advanced) items for study. This RedCap Phase-2 is planned for initial release in early 2024. Some of the features under study include:

• Sidelink – direct 5G device to device communication
• Positioning – better location for accuracy applications
• Unlicensed band – availability of shared spectrum
• Multicast and broadcast (MBS) – point to multi-point services
• RedCap device types – classification of RedCap devices.

We can expect additional use cases to be defined that will address challenges in the world, such as drones, power grids, robotics, industrial, transportation, asset tracking, AGV, wearables (e.g. smart watches, wearable medical devices, AR/VR goggles, etc.), industrial wireless sensors, and video surveillance etc. Therefore, RedCap technology will change industrial and consumer arena totally which leads to energy conservation and reducing carbon footprint.

Anritsu provides cutting-edge solutions for upcoming telecommunications technologies, ranging including RedCap from indoor coverage mapping in small wireless systems to over-the-air testing in large wireless networks. Our complete solutions are designed to meet your ever-changing market needs. Anritsu has accumulated key strengths in various technologies and know-how, including signaling, protocol, conformance, and RF measurement. Anritsu uses these strengths built over many years to offer customers optimized 5G measurement solutions, supporting the fastest time to market (TTM).