Thinking Smaller

Providers are interested in the easier-to-license shared access spectrum that Ofcom offers but barriers to deployment remain, as Simon Fletcher and Caroline Gabriel explain.

SMALL CELLS ARE A GREAT way to reach the parts that other networks don’t. This can be indoors and underground, in crowded cities where the networks are congested or in rural villages, university campuses and large factory sites where the mobile networks find it uneconomic to roll out coverage in their top-down approach. There is good reason to suppose that the future of coverage lies in a network of networks, with those that have the need taking the problem into their own hands. And small cells are a crucial technology in making this happen.

To be able to install a private mobile network you need a spectrum licence, mains power and an internet connection, ideally fibre. And the big one is spectrum. If that’s available the other two can usually be found.

Ofcom has pioneered licensing of the upper n77 band, from 3.8 GHz to 4.2 GHz, potentially a valuable piece of 5G spectrum, providing additional capacity and bandwidth when combined with the widely used 3.3-3.6 GHz spectrum for which the major mobile operators have licences, or supporting expansion of enterprise and private networks based on small cells.

While Ofcom has been good with this, there is limited harmonisation of allocations or target use cases between countries. In addition, some enterprise sectors have very specific device and network requirements. These factors risk making upper n77 a fragmented market for small cell equipment makers and their chip suppliers, which could deter them from developing products. That, in turn, would reduce availability of equipment and increase costs. Suppliers have therefore been cautious. We’ve been waiting a while but progress is being made as the industry moves to address the upper n77 band and the availability and capabilities of equipment Spectrum at 3.3 GHz to 4.2 GHz has been widely adopted by major operators for the first phase of 5G macro network deployment with a few big cells covering a large area. These typically use a large dedicated tower. Band 77 is used for small cell densification and some private networks with the small cells mounted on buildings and bus stops. There are several ways to split this band in regulatory terms. Most European and Asian countries use a subset of n77 known as n78 in 3.3-3.8 GHz, while in the USA the operators can combine spectrum to use the whole n77 range via three allocations (CBRS, 3.45 GHz and C-band). Japan also uses the n77 band.

Immature Ecosystem

When the upper n77 band is used by large enterprises, the deployments will be naturally focused on small cells because of the limited geography (such as a factory or campus), and the limitations on range and power. The UK’s shared access licensing scheme targets a low power scheme at private networks, which stipulates 50 metres range with power limits based on it being an urban or rural location.

The chief barriers to deployment of small cell networks in the upper n77 band, however, relate to the scale of the ecosystem. The use of a large portion of the band in the USA and Japan will drive chipset and device makers to extend support up to 4.2 GHz, but specific components and devices for the upper band, and for non-handset applications, are regarded as a niche opportunity.

In the absence of international harmonisation, there are also challenges of creating a common product that can be sold, unmodified, in a large number of countries. Yet there will be demand for a diversity of equipment and devices including small cells, routers and radio units that are ruggedised or can be deployed in difficult locations.

During the Testbeds and Trials programme concerns were raised about affordable device availability. It was found that some device manufacturers advertised support for n77 but testing revealed they were supporting only the lower band. Projects fell afoul of general immaturity in early equipment with a number of problems including unstable firmware, poor support for 5G Standalone and limited interoperability.

Chip Support Critical

In a recent study for DCMS by Real Wireless, a survey of equipment, semiconductor and device manufacturers was conducted by Rethink Technology Research to assess appetite to target the upper n77 band, especially in the UK, and the barriers to doing so. That survey has been further developed since the publication, though the broad conclusions have not changed significantly.

The survey, and in-depth conversations with the vendors, show that chip manufacturers see little technical difficulty in adapting their full-band n77 products to target just the upper band. But large chip providers whose first priority is the mass market consumer devices such as handsets were clear that they would rarely prioritise engineering or go-to-market resources for “niche” industrial products.

A common definition of “niche” by the chip providers is a product with an addressable market below 10 per cent in unit terms, of the handset market in a country, or below 15 per cent in dollar terms. That creates challenges, since many industrial 5G devices either have a low dollar value (so large quantities would be required to attract the chipmakers) or are highly specialised with low volumes.

The value calculation chip providers are making is less daunting on the small cell equipment side, where products typically have higher value. The expectation, in a survey of private network operators conducted by Rethink in May 2022, was that small cells would cost between $1,000 and $4,500 each (including software but excluding backhaul and services) depending on specifications. If devices are hard to find, however, that will be a deterrent to deployment of enterprise networks in the upper n77 band, especially those that will require specialised devices rather than standard handsets.

The leading large-scale chip provider to offer a system-on-chip for small cell equipment, Qualcomm, has been stepping up its activities in network infrastructure in the past two years. Nokia is the largest customer for Qualcomm’s FSM100xx 5G RAN family of small cell chipsets, but other users include Samsung, Airspan, Baicells, Corning and Sercomm. Support for the upper n77 band has added.

Otherwise, the ecosystem will rely on more specialised chip providers that target industrial equipment and so are less sensitive to the challenges of a niche market. Figure 2 shows a finding from the Real Wireless survey indicating that 20 per cent of specialist industrial wireless chip providers with UK activities will provide specific upper n77 products by 2024. The figure for general purpose wireless chipmakers is only 11 per cent. In addition, 60 per cent of specialist chip providers intend to support the whole n77 band, which will be important for handsets and other devices that need to work across public and private networks.

Harmonisation Needed

Fewer than one third of device makers sell products for the 3.8-4.2 GHz band in any part of the world while a similar percentage are planning to launch such products, in at least one global market, by the end of 2024. For the UK there is a far higher level of indecision since the scale of the market is not yet clear.

Blueprint level Document proposed Description

Component/product Minimum viable product Optimal features needed to package a (MVP) blueprint for initial proof of concept or trials

Product/reference design System and product requirements to meet (PRD) the engineering product development needs

Module Reference design Baseline subsystem design (HW+FW+SW) as a building block for a complete platform

Use case Individual blueprints Use case description and blueprint for one or more service offerings (e.g. IaaS). Each blueprint consists of E2E functional and protocol stack architecture and links to reference designs (as above)

About one third of device makers expect to extend midband support to 3.8-4.2 GHz by the end of 2024, but across the whole sample, 60 per cent are undecided.

But products are starting to appear, progress will be accelerated by the development of the ecosystem and if the enterprise requirements are clear and consistent. The use cases and deployment environments for private networks are diverse, but it is important that there are as many common features as possible to enable scale. This is an important element of Small Cell Forum’s work to establish blueprints –common sets of technical and rollout requirements to drive scale into private network platforms.

Clearer Requirements

Surveys of private and enterprise network deployers indicate some of the key requirements for industrial small cells suited to the upper n77 band. Of course, the requirements differ from those for a public outdoor network, even one based on small cells, which is why a specialised ecosystem is likely to develop around industrial small cells. This is illustrated in a study conducted in 2021 by Small Cell Forum. This enterprise ecosystem is likely to be divided between providers of relatively small quantities of specialised equipment tailored to the need of

Price range per cell in small quantities (<30) Up to $2,000 for fully configured cell, up to $400 for small radio unit or repeater Power consumption

Bandwidth and data rate 45 per cent require 100 MHz, others 60 MHz

Form factor

68 per cent want small dimensions and standard shape (typically box of less than 20cm² footprint); 35 per cent want ruggedised options

Simon Fletcher Chief Strategy Officer Small Cell Forum

C hief Strategy Officer of Small Cell Forum (SCF), the organisation which supports infrastructure through small cells, Simon helps set the priorities of SCF, drive work programs and engage partners in projects. He has more than 20 years’ experience working in the mobile, beginning his career at Racal Radar Defence Systems, he moved to NEC in 1999 to play a key role in the development of technology in 3G and 4G, working in Joint Ventures, establishing open interfaces and commercialisation of ecosystems. Today he is CTO at the independent consultancy Real Wireless. He holds an MEng in Electrical and Electronics Engineering and an MBA, both from the University of Surrey.

Caroline Gabriel

Co-founder, Rethink Technology an anchor customer (a large industrial player such as Bosch, or commonly agreed requirements from a whole sector such as utilities); and providers of standardised equipment based on common specifications, tailored to the most generic requirements of indoor enterprise networks. Others told our interviewers that they expect to introduce such products but do not yet have a firm timeline

Conclusion

There is a growing ecosystem supporting the whole n77 band, and interest in enterprise or private network equipment for upper n77. Product plans may be delayed or re-prioritised if barriers are not lowered. In particular, firmer demand; large anchor customers; and a clear set of common requirements would improve confidence and move the upper n77 further up the priority list for small cell developers.

Caroline has been engaged in technology analysis, research and consulting for 30 years. and has developed a significant research base and forecast methodology, based around deep contacts with mobile and converged operators round the world. This addresses issues and trends in wireless infrastructure, and particularly operator intentions for 4G, 5G, small cells, CloudRAN and other technologies. She serves as Content Director for Small Cell Forum. Organisations looking to help develop the small cell ecosystem should join the Small Cells Forum. www.smallcellforum.org/

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Ace Axis

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Airspan

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Benetel

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CableFree

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Stephen Patrick

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Casa Systems

 www.casa-systems.com/ product-categories/4g-5g-ran/ Nav Mudhar

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 +44 7867385 893

Celona

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Robert Harlow

 rob@celona.io

 07810 755565

Comba Telecom

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 sales@comba-ctnsl.com

 +852 2635 8610

DDense Air

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Jonathan Eaton

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EEricsson

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Fujitsu

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Paul King

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Kaleidoscope Service Solutions International Ltd (KSSI)

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Shaun Blagdon

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Lions Concord

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Mavenir

 www.mavenir.com/portfolio/ mavair/radio-access/small-cellsolutions/ Tushar Dhar

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NNEC

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Nokia

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Phil Cottom

 phil.cottom@nokia.com

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Parallel

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Jonathan Adams

 jadams@parallelwireless.com

 +44 7747 470388

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Samsung

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Barry Walsh

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Sunwave

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Karl Yu

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ZZyxel networks

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