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Friday, October 06, 2023

Indoor wireless & the need for unlicensed 6GHz

This post originally appeared on October 2 on my LinkedIn newsletter, which is now my main platform for both short posts and longer-form articles. It can be found here, along with the comment stream. Please subscribe / connect to me on LinkedIn, to receive regular updates (about 1-3 / week)


Note: This article has been commissioned by the Dynamic Spectrum Alliance, based on my existing well-known analysis and positions, which I have been discussing for many years both publicly and privately. I believe that in-building wireless - irrespective of technology - receives far too little attention from policymakers and regulators. 6GHz should be indoor-primary spectrum.

Abstract & summary: The vast bulk of wireless data traffic today is for indoor applications. In future, in-building wireless will become even more important. It is ideally-suited to 6GHz spectrum, made available on an unlicensed basis. A licensed model for 5G mobile in 6GHz would be unable to deliver coverage consistently for more than a small number of sites.

Indoor wireless is already critical & often overlooked

Industry estimates suggest that 60-80% of cellular data is delivered to indoor users, predominantly on smartphones. Additional statistics shows that smartphones also typically consume another 2-5x the cellular data volume on Wi-Fi, almost all of which is indoors or in vehicles. In other words, 90%+ of total smartphone data is consumed inside buildings.

In addition, residential fixed broadband traffic volumes are roughly 10-20x that of mobile broadband, with final delivery mostly over Wi-Fi, often to non-smartphone devices such as smart TVs, laptops, game consoles and voice assistants.

Outside the consumer market, a great deal of non-residential wireless connectivity is also indoors – healthcare, education, manufacturing, conventions, hospitality and office environments are all increasingly dependent on wireless, especially with the rise of industrial automation systems, IoT, robots, connected cameras and displays. These map to the rise in cloud- and video-based business processes.

Most wireless uses & devices are indoor-centric

This does not imply that outdoor wireless use is either trivial or unimportant. Most obviously, everyone uses their phones for calling, messaging, mapping and various transport and other apps while on-the-move. Vehicle connectivity is becoming essential, as well as wireless use for safety, utilities and smart-city infrastructure. Some sectors such as agriculture, logistics and construction are predominantly outdoor-oriented, albeit often at specific locations and sites.

But to a rough approximation, if 80%+ of wireless use is indoors, then 80%+ of economic and social benefit of wireless will accrue indoors as well. This applies irrespective of the technology involved – Wi-Fi, 4G/5G cellular, or even Bluetooth.

Future growth of indoor wireless

The demands for indoor connectivity are likely to grow in both scale and scope in coming years. There will be huge demand for high-throughput, low-latency access for both consumer and enterprise use-cases.

  • Gigabit broadband, especially delivered with fibre, is becoming the default for both residential and business premises. In the medium term, we can expect 10Gig services to become more common as well. In many cases, the bottleneck is now inside the building, and local wireless systems need to keep pace with the access network.
  • There is a growing array of demanding devices and applications connected inside homes and enterprises premises. 4K and 8K screens, automation systems, healthcare products, AR/VR systems, cameras for security and industrial purposes, robots and much more.
  • Wireless devices will increasingly be located in any room or space inside a building, including bedrooms, garages, basements, meeting rooms, factory-floors and hospital operating theatres.
  • The density of devices per-building or per-room will increase exponentially. While some will be low-traffic products such as sensors, ever more appliances and systems will feature screens, cameras and cloud/AI capabilities demanding greater network performance.
  • There will be growing emphasis on the efficiency of networks, in terms of both energy and spectrum usage. “Blasting through walls” with wireless signals will be viewed negatively on both counts.

Yet only some policymakers and regulators have explicit focus on indoor wireless in their broadband and spectrum policies. There has been some positive movement recently, with regulators in markets such as the UK, Germany, Canada and Saudi  Arabia addressing the requirements. But it is now time for all governments and regulators to specifically address indoor wireless needs – and acknowledge the need for more spectrum, especially if they eventually want to achieve “gigabit to each room” as a policy goal.

Wi-Fi can satisfy indoor requirements, but needs 6GHz

Almost all indoor devices discussed here have Wi-Fi capabilities. A subset have 5G cellular radios as well. Very few are 5G-only. This situation is unlikely to change much, especially with a 5-10 year view.

Yet Wi-Fi faces a significant limit to its performance, if it just has access to traditional 2.4GHz and 5GHz bands. Not only are these limited in frequency range, but they also have a wide variety of legacy devices, using multiple technologies, that must coexist with any new systems.

While mesh systems have helped extend the reach to all rooms in a home, and Wi-Fi 6 brings new techniques to improve performance and device density in consumer and enterprise settings, much more will be required in future.

Now, Wi-Fi 6E and 7 generations are able to use the 6GHz band. This adds up to 1.2GHz of extra spectrum, with almost no sources of interference indoors, and almost no risk of indoor use creating extra interference to incumbent outdoor users, especially at lower power levels.

6GHz Wi-Fi would be able to address all the future requirements discussed in the previous section, as well as reducing system latency, improving indoor mobility and providing greater guarantees of QoS / reliability.

6GHz 5G is unsuitable for indoor use, and of limited use outdoors

By contrast, 6GHz is a poor fit for indoor 5G. Most buildings will be unable to use outdoor-to-indoor propagation reliably, given huge propagation challenges through walls. This would be hugely wasteful of both energy and spectrum resource anyway. This situation will worsen in future as well, with greater use of insulated construction materials and glass.

That leaves dedicated indoor systems such as small cells or distributed antenna or radio systems. Current DAS systems cannot support 6GHz radios – most struggle even with 3.5GHz. It may be possible to upgrade some of the more advanced systems with new radio heads, but few building owners would be willing to pay, and almost no MNOs would. In any case, only a fraction of buildings have indoor cellular systems, especially beyond the top tier of shopping malls, airports and other large venues.

The industry lacks the human and financial resources to implement new 6GHz-capble indoor systems in more than a tiny proportion of the millions of buildings worldwide, especially residential homes and small businesses.

Enabling public 5G services to work reliably indoors with 6GHz is therefore a decade-long project, at least. It would likely be the mid-2030s before 5G (or 6G) devices could routinely use 6GHz inside buildings. Lobbyist estimations of the notional GDP uplift from IMT use of the band ignore both the timing and the practical challenges for indoor applications. A very heavy discount % should be applied to any such calculations, even if the baseline assumptions are seen as credible.

Private 5G systems in factories or warehouses could theoretically use 6GHz licensed cellular, but most developed countries now have alternative bands being made available on a localised basis, such as CBRS, 3.8-4.2GHz or 4.9GHz. Many countries also have (unused) mmWave options for indoor private 5G networks. In theory, 5G systems could also use an unlicensed 6GHz band for private networks, although previous unlicensed 4G variants in 5GHz never gained much market traction.

It is worth noting that there are also very few obvious use-cases for outdoor, exclusive-licensed 6GHz for 5G either, beyond a generic increment in capacity, which could also be provided by network densification or other alternative bands. Most markets still have significant headroom in midband 3-5GHz spectrum for 5G, especially if small cells are deployed. The most-dense environments in urban areas could also exploit the large amount of mmWave spectrum made available for cellular use, typically in the 24-28GHz range, which is already in some handsets and is still mostly unused.


Regulators and policymakers need to specifically analyse the use and supply/demand for indoor wireless, and consider the best spectrum and technology options for such applications and devices. Analysis will show that in-building wireless accounts for the vast bulk of economic and social benefits from connectivity.

This is best delivered by using Wi-Fi, which is already supported by almost all relevant device types. With the addition of 6GHz, it can address the future expected growth delivered by FTTX broadband, as well as video, cloud and AR/VR applications.

The ultra-demanding uses that specifically require cellular indoors can use existing bands with enhanced small cells and distributed radios, neutral-host networks, or private 5G networks in the 3-5GHz range. There is also the ample mmWave allocations for 5G.

A final fundamental element here is timing. 6 GHz Wi-Fi chipsets and user devices are already shipping in their 100s of millions. Access points are widely available today and becoming more sophisticated with Wi-Fi 7 and future 8+ versions. By contrast, 5G/6G use of the band for indoor use is unlikely until well into the next decade, if at all.

Indoor wireless is critically important, growing, and needs Wi-Fi.

And Wi-Fi needs 6GHz.


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