5G Reduced Capability (RedCap)

Cellular IoT evolution with 5G RedCap

Cellular IoT is a fast-growing use case.

While 4G IoT technology is on the rise, the market is already preparing for the next generation of IoT technologies within 5G. Various categories have been specified to facilitate a smooth transition from LTE to 5G, e.g.

• 5G RedCap, specified in Release 17, will replace LTE Cat 4 devices
• 5G Release 18 introduces a RedCap device with lower bandwidth (5 MHz) to replace the LTE Cat 1 device

RedCap devices have a power consumption comparable to LTE Cat 4 devices and offer features which are not supported by LTE IoT technologies, such as network slicing. This 5G feature enables more use cases, as well as optimized services with quality of service (QoS) features.

Moreover, 5G RedCap devices support:

• 5G LAN or Ethernet PDU capabilities, simplifying routing and connectivity between enterprises (e.g. on factory floors)
• Voice over NR (VoNR) for enhanced voice quality
• Non-Terrestrial Networks (NTN) to ensure continuous global coverage, depending on the use case

Power saving with 5G RedCap devices

Power saving is crucial for IoT devices. The mechanisms defined in 3GPP Releases 15 and 16 are complemented by the logic of Release 17, ensuring that RedCap devices can utilize a power-saving cluster based on three pillars:

• Enhanced mechanisms and innovations, e.g. wake-up signals, relaxed measurements and adaptive bandwidth
• Hardware restrictions and reduced capabilities, e.g. lower power class, single antenna, half-duplex operation, and bandwidth restrictions
• Operational enhancements, e.g. discontinuous reception (DRX), sleep mode, power saving mode (PSM), signaling reduction and cross-slot scheduling

5G RedCap Device Testing Challenges

The compact design of RedCap devices demands rigorous testing to address key challenges: How does the device handle limited bandwidth, fewer antennas, and various modulation schemes? Can the network efficiently identify and manage devices to provide precise access control tailored to their capabilities?

A 5G RedCap device needs protocol efficiency requiring a detailed evaluation of optimized signaling flow, shorter sequence numbering, and power-efficient transmission strategies.

Even seemingly small details require careful consideration, e.g. disabled frequency hopping and multi-band connectivity. By effectively addressing these signaling challenges, we unleash the full potential of RedCap devices, ensuring their seamless integration into the 5G ecosystem while maintaining overall network efficiency.

The performance of RedCap devices is also essential. Throughput measurements are necessary in different deployment scenarios – including dense urban areas, nomadic / mobile settings, industrial environments, and rural locations – to ensure compliance with performance standards.

Early RedCap devices will use LTE fallback when a 5G standalone (SA) network is unavailable. Therefore, to ensure reliability, LTE fallback must be considered into all test setups. Test solutions should replicate customer scenarios as closely as possible to simulate real-world usage.

The Rohde & Schwarz solution for 5G RedCap testing and measurement

The R&S®CMX500 one box signaling tester (OBT) is designed with a simplified setup, specifically tailored to meet the needs of customers conducting RedCap device testing during research and development (R&D) phases and type approval processes.

It is the perfect solution for testing and measuring 5G RedCap. The OBT facilitates the verification of various RedCap aspects as defined in 3GPP 5G Release 17 during the R&D phase, including network access restrictions, bandwidth parts (BWP), BWP switching, energy efficiency/power consumption, and other RedCap-specific protocol signaling procedures.

Moreover, the R&S®CMX500 OBT reduces time to market and supports all early R&D design phases – from RF parameter testing to end-to-end application testing (including throughput testing and signaling protocol testing), and from conformity tests for type approval to sample production testing.