What is 5G RedCap, and will it save cellular IoT? The skinny on the (skinny) new 5G tech
The latest release of the 5G New Radio (NR) standard has, at last, fixed a problem for cellular-based sensor comms with the emergence of a cut-down version of 5G for massive-scale IoT deployments. On paper, anyway; in reality, the news only confirms a waypoint on the horizon, pointing to a commercial pathway in 2024, for existing LTE-based massive machine-type communications (mMTC) to migrate onto single 5G-based networks.
The bigger question is whether it will save cellular-based IoT, as a commercially viable technology to deliver massive-scale industrial change? Because (if one thing is clear), of all the huff and puff about planet-saving future tech, none has been longer-promised or bigger-hyped than IoT – and the cellular market has so far made a hash of it, while more disjointed, more resourceful non-cellular operatives have swooped in, as well as they have been able.
But before we editorialise any more, and before we get squinty about the small print, we should recap; the Release 17 standard, frozen in June, includes a provision for IoT sensors to connect to 5G with significantly reduced network – and therefore hardware, and therefore cost-linked – capabilities. This new specification, called Reduced Capability (RedCap; previously ‘NR-Light’, and variations-thereof, in 3GPP work items), sits provisionally between mMTC and eMBB in the 5G NR power hierarchy.
To add context; it sits two rungs below URLLC, affording the headiest view of IoT comms, in this 3GPP ladder – which is most commonly presented, actually, as three points in a 5G NR family triangle. The thing about these three specification-types, however, is that only two are 5G-native. The twin low-power wide-area (LPWA) technologies underpinning mMTC, the massive (machine-type) IoT segment, are LTE-based, albeit compatible with 5G NR radios.
And only these technologies, ultra low-power NB-IoT and 2G/3G-like LTE-M, offer support for stripped-back, dirt-cheap, long-life, mega-scale IoT. So, as it stands, and going forward, cellular IoT needs LTE to make a fist of traditional IoT, at all – and it has a fight on its hands with well-entrenched non-cellular standards like LoRaWAN in unlicensed bands. But RedCap promises to fix that – somewhere down the line, as always with cellular.
RedCap is designed, ostensibly, to make this familiar triangle of 5G NR family-tech into a venn diagram (see above), where it overlaps with the other three operating scenarios. This is actually Ericsson’s diagram, taken from a full-blooded writeup about the new NR release. In terms of capabilities, it is supposed to plug a hole. Ericsson comments: “RedCap is positioned to address use cases that are today not best served using eMBB, URLLC, or LPWA (LTE-based mMTC) solutions.”
RedCap is positioned “as a lower segment than eMBB… but higher than LPWA,” it writes in a blog post. Huawei says the same (exactly, word-for-word, perhaps lifting from the same 3GPP messaging). Elsewhere, Qualcomm slots RedCap in between (see image below) mission-critical IoT, served currently by consumer-like NR-based eMBB, but shortly by developing URLLC provisions, and massive-scale IoT, served by non-NR NB-IoT or LTE-M (or non-cellular LPWA tech like LoRaWAN).
Analyst house Omdia calls RedCap the ”big missing piece of the 5G IoT puzzle”. But operationally, it is closest to LTE-M (see Qualcomm graphic below), described as “the most popular and widely used cellular IoT standard” by Omdia – and therefore to 2G/3G, still being used for legacy cellular M2M devices. Certainly, many of the use cases sound the same: the standard 3GPP line is about industrial sensing, video surveillance, and wearable technology.
Telit writes in a blog post: “In some ways, 5G RedCap seeks to cover the needs currently met by LTE-M [Cat 1 through Cat 4]. It’s a light version of the 5G standard. 5G RedCap is designed for use cases in which ultra-low latency isn’t essential, but reasonable throughput is needed to ensure data flows for next-generation applications can be supported. It’s expected to be useful for wireless industrial sensors, video surveillance and smart wearable technology.”
Omdia suggests LTE-M-level pricing for NR-based IoT gadetry, to serve similar mid-level IoT use cases, is just the ticket for the cellular industry to make a sustained go of massive-scale sensor networks. It notes a 10-time (1000%) delta between LTE-M and eMBB module costs, as it stands, going from $30 to $300 per unit, respectively; there is no NR-provision, until now, for such “mid-speed (IoT) applications”, it says.
It writes: “The price gap between the 4G and 5G modules is one of the essential factors – if not the most crucial factor – that will continue to limit 5G adoption in IoT applications… To reduce the price gap… there is a need to develop a 5G standard with fewer features and reduced hardware complexity.” RedCap is the answer, it says. “Without RedCap, 5G NR is missing a key technology piece for IoT.”
Qualcomm talks, as well, about “applications in smart grids, environmental sensors, predictive maintenance, utility meters, high-resolution surveillance, and more”. Which sounds very LPWA actually – and probably more NB-IoT and LoRaWAN, even, than LTE-M. Nevertheless, the talk about its near-term (post 2024) usage is all about plugging a tech/app gap; Huawei, say, references “mid-tier applications… with capabilities between these extremes”.
Ericsson is good on the technical achievement, around what has been jettisoned with RedCap: bandwidth requirements, say, are reduced to 20 MHz and 100 MHz in frequency range 1 (FR1; 4.1 GHz to 7.125 GHz) and FR2 (24.25 GHz to 52.6 GHz); the number of ‘receive branches’ is reduced, also, meaning a reduction in receive antennas; the max number of downlink MIMO layers, equal to the number of receive branches, is also reduced.
There are other innovations, too, to make 5G viable for low-power IoT sensors apps, notably with more flex around modulation order, duplex operation / support. Ericsson writes: “Substantial cost and complexity reduction can be achieved… [to] establish RedCap as a distinct device segment from eMBB or [URLLC].” The upshot is lower device complexity, which results in lower cost, longer life, and enough grunt to get most IoT jobs done.
But the message about hole-filling might be considered a smokescreen; most of the industrial IoT applications linked with RedCap are variously quite-well served, from a technical point of view, by LPWA network solutions using NB-IoT, LTE-M, or LoRaWAN – or Sigfox or MIOTY (TS-UNB), or whatever else. And the 2024 time-frame for Release 17 level RedCap-equipped IoT devices to appear gives the rest of the market room to manoeuvre, also.
And with key RedCap advancements – including higher transmission rates, advanced positioning, ‘sidelink’ near-field comms, and even support for unlicensed spectrum – only defined in Release 18 (see Qualcomm graphic below), coming out in the second half of the decade, the IoT game for the cellular crowd remains a long haul. The big short-term (2024) boost is industrial enterprises, including those deploying private 5G, will be able to get two-for-one on IoT networks.
Omdia explains: “Enterprises looking to deploy a mix of… high-performance and mid-speed devices must deploy two [5G and 4G/LTE] separate networks… [which] creates extra cost and complexity. There is no upgrade path for existing… [LTE-M] devices to migrate to 5G NR. Since most operators do not have immediate plans to phase out 4G networks, this issue is not a primary concern. However, this issue will become a more critical factor in a few years.”
So really the motivation with RedCap, as Omdia indicates above, is to migrate new and legacy M2M/IoT contracts to 5G NR in time for sun-setting LTE and, with it, NB-IoT and LTE-M. Qualcomm states: “As the 5G evolution continues, there will come a time in the future when communications service providers start to migrate away from 4G toward 5G. With this in mind, 5G NR-Light becomes the platform of choice for future-proofing new mid-tier IoT designs.”
Or does it? It still sounds like a long way off – like another future cellular tech without an ecosystem, or an easy way to sell, and a track record that does not bring much optimism.