How The 5G Standards Stack Fits Together for Cellular IoT

The teams that build cellular IoT products know that choosing the best-fit cellular communications standard is critical to success—but the soup of acronyms that make up the 5G stack doesn’t make it easy.

How the 3GPP Standards For 5G Evolved

5G is a huge jump over 4G, and at first glance it looks like a single standard, but it’s more complex than that. Just like 4G, 5G evolved into an ecosystem of standards, each with different benefits—and different constraints.

From a consumer viewpoint, 5G is simply a welcome speed upgrade above 4G. But for product innovators, fifth-generation technology has matured into a versatile stack that supports everything from high-bandwidth applications to ultra-low-power requirements.

5G standards revolution is a step-by-step process, though, all anchored to the 3GPP (3rd Generation Partnership Project) release timeline. It’s worth looking at the 3GPP timeline to understand which 5G standards evolved, and when:

• 3GPP Releases 15 and 16: The basic standard that defines 5G, also called the “New Radio” (NR) architecture. The focus was first and foremost on speed (eMBB), alongside far lower latency than 4G—which is the URLLC or “ultra-reliable low latency” standard you may have heard about.
• 3GPP R17: This release introduces two other familiar standards: RedCap, a reduced-capability version of 5G that lowers device requirements, opening 5G to more IoT applications. R17 also includes NTN, the non-terrestrial network standard that enables 5G devices to communicate directly with satellites.
• 3GPP R18: The next, and arguably final, step in the evolution of 5G standards, integrating AI into the standard, boosting energy efficiency, and enabling 5G for accurate positioning.

So, one can see how R15 through R18 layer 5G standards. Nothing is discarded in the process, but each release injected either more flexibility or greater capabilities into 5G.

Untangling the acronyms: NR, eMBB and URLLC

Right off the bat, things got a bit complicated, as 3GPP Release 15 alone introduced three standards when it rolled out in 2018:

• NR: “New radio” is a foundational specification that’s intended to eventually replace 4G LTE altogether. NR is the new rulebook, the baseline radio access tech which defines how 5G-capable devices, including IoT devices, send and receive data over cellular networks.
• eMBB: Bandwidth is at the core of 5G, and eMBB or “enhanced mobile broadband” enables the bandwidth for applications such as 4K/8K streaming. It also provides the bandwidth for dense urban applications where lots of devices access the network simultaneously.
• URLLC: The 5G component that makes things really interesting for latency-sensitive IoT applications, URLLC, or “ultra-reliable low-latency communications,” targets 1ms latency and 99.999% uptime. That enables IoT applications such as autonomous driving, remote surgery, and critical monitoring.

URLLC was included in 3GPP R15 but expanded in R16 with a focus on mission-critical applications.

Every 5G-capable device is automatically capable of “NR” signals because it’s the defining 5G standard. However, eMBB and URLLC describe, to a degree, what the network and device are designed to optimize for.

Filling IoT gaps with 5G RedCap (NR-Light)

The trio of acronyms in the baseline 5G standard enables many applications beyond 4G, but still imposes substantial demands on devices. That doesn’t always work for cellular IoT, where devices can be tiny, making it difficult to meet the power and antenna requirements of 5G NR.

3GPP R17 aims to address these concerns with RedCap, short for “reduced capability”. Yes, NB-IoT and LTE-M are intended to support lightweight IoT apps such as sensors but won’t work well if the IoT device needs to send, say, HD video. RedCap was formerly known as NR-Light.

RedCap reduces the demands 5G cellular networks make on the device, removing a few high-end features a lot of devices won’t need:

• A normal 5G device requires at least four antennas to meet NR requirements, but RedCap reduces this to one or two. It helps IoT innovators produce smaller devices while still enjoying many of the benefits of 5G.
• RedCap also reduces the device modem's processing power requirements by operating on a 20 MHz channel rather than the 100 MHz NR requires.

All in all, RedCap enables smaller devices and reduces the cost of producing the device—which can really matter for massive IoT eSIM deployments.

It’s not entirely surprising, then, that RedCap network modules are steadily replacing LTE Cat-1 and Cat-4 hardware. RedCap has also evolved into eRedCap, with 5G Advanced.

The Next Major Step: 5G Advanced

As 5G matures, the 3GPP standards body continues to add capabilities. Next up—not so much a generational leap as a big step forward—is 5G Advanced.

Defined in R18, R19, and R20, 5G Advanced is essentially about making 5G faster, more efficient, and smarter. It includes AI-assisted network optimization, better energy use and stronger performance in crowded areas.

• AI built-in: 5G Advanced applies AI capabilities to network performance aspects including beam management, channel estimation and positioning. It’s particularly pertinent in very dense or variable radio-frequency environments, where network management can struggle with resource allocation. It aims to avoid the need for constant manual tuning of the network.
• Uplink boost: 5G NR optimized for download throughput, which, yes, does account for the majority of use cases, e.g., streaming. But sacrificing uplink bandwidth can impact devices such as cameras that upload data, so 5G Advanced boosts uplink speeds, including through more flexible slot allocations.
• Improved device location: R18 also aims to reduce the need for GNSS for indoor positioning and dense urban environments by supporting sub-100 ms positioning.
• Energy efficiency: The evolved standard better supports devices that do not need to be constantly online by introducing improvements to extended discontinuous reception (eDRX).

5G Advanced also introduces eRedCap. If RedCap is the successor to LTE Cat-4, eRedCap is the successor to LTE Cat-1. It further reduces the peak data rate to ~10 Mbps and narrows the bandwidth requirement to just 5 MHz. It aims at enabling truly mass-market cellular IoT.

Wait, Aren’t NB-IoT And LTE-M 5G Standards?

No, as much as these are modern standards that support many IoT use cases, NB-IoT and LTE-M are both wrapped within the 4G standard. Here’s a quick recap:

• NB-IoT (Narrowband IoT): Introduced in 3GPP Release 13, NB-IoT is engineered for one thing above all else: reach. It penetrates deep into basements, underground infrastructure, and remote locations where no other cellular standard reliably operates.
• LTE-M (LTE for Machines): A step above NB-IoT with more bandwidth and higher peak speeds. It offers support for voice (VoLTE) and enhanced device mobility, which is good for moving assets, connected vehicles, and healthcare wearables where devices roam across cells.

There’s a slight wrinkle, though, in that the ITU (International Telecommunications Union) classified both NB-IoT and LTE-M as massive 5G IoT technologies under the IMT-2020 framework. One way to look at it is that these two standards are 5G by classification, but not by radio stack.

Steady progress to 6G

As always in tech, progress is relentless. The next leap in cellular communication is 6G, which, while not yet commercially available, is steadily stepping through the standardization process.

The ITU is actively working on the 6G framework and, in 2023, ratified the IMT-2030 document as the formal blueprint for 6G. It’s a vision for terabit speeds and extremely low latency – less than 100 microseconds. Plus, 6G is set to integrate networking, sensing, AI, and comms into a single interface.

The 3GPP R21 standard is expected around 2028. As for commercial deployments? We may well be looking at 2030 and beyond.

So, if you’re working on a cellular IoT product, remain aware of 6G to help you envision future capabilities—but it’s not a standard you can currently integrate into a developing project in any meaningful sense.

Fitting It All Together

So, what should you consider when developing a cellular IoT project? First, 5G is not a progressive hierarchy where more is always better. RedCap, for example, demonstrates how 5G evolved to offer less—to better fit specific IoT applications.

Your challenge is to match the right standard to the device requirements where you’re deploying the device, and to the device's lifetime. Think about:

• What’s transmitted, and when: A camera uploading 4K video streams has different bandwidth requirements to a utility meter sending 100 bytes every second. The utility meter will benefit from eRedCap, which enables a simpler design with lower power requirements.
• Does the device move, and where does it usually operate? Indoor, remote, or underground deployments will work better with NB-IoT’s high-decibel coverage. In dense urban or industrial environments, 5G RedCap makes more sense.

Overspecify, and you needlessly add module complexity and cost – making your IoT product less competitive.

So, understanding how the 3GPP releases built up to the 5G standards we know now—and how these fit together, can help you make key product development decisions over the next five to ten years.