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5G indoor coverage poses problems for office buildings and operators

The millimeter waves of 5G have trouble penetrating walls and other structures, which presents significant challenges for carriers as they plan 5G indoor coverage.

Without a doubt, 5G cellular is coming. But mobile operators have been focused mostly on the consumer market. However, 5G will generate some important developments that will affect enterprise technology buyers. Business customers, at this point, should start introducing those developments into their cellular planning process now.

The one 5G feature that everyone seems to acknowledge is higher transmission rates. All mobile users will certainly benefit from higher transmission rates as they become available. However, other issues and decisions could be more important for enterprise managers. In other words, don't get bogged down in what the carriers say about speeds.

Business 5G still has work to do. Apple, for instance, has not yet introduced a 5G iPhone. As a result, enterprise users -- many of whom are iPhone users -- won't be joining the 5G party anytime soon.

The 3rd Generation Partnership Project, the body that develops cellular standards -- like 5G -- has also promised ultra-reliable, low-latency communication services and support for denser deployments of IoT devices. But those capabilities have yet to appear.

One big issue for enterprise users that's not getting enough attention is what it will take to bring 5G indoors.

5G indoor coverage issues

The operators have talked about 5G indoor coverage in their ads, but they're mostly talking about venues such as stadiums and malls -- places with lots of open space and that are under a roof. But, when enterprises address 5G indoor coverage, they're usually thinking about office space.

Offices can have many walls and solid building cores that can leave plenty of radio dead spots. Wireless LAN (WLAN) experts know about dead spots. And, as builders adopt energy-efficient designs, we're finding specially coated windowpanes often block radio signals as effectively as heat loss.

So, if users in your building want to talk on their cellphones, you may need a cellular signal source inside your building.

Small cells' big potential

Traditionally, carriers install a distributed antenna system (DAS) in buildings to improve indoor signal coverage. These systems have a signal source -- either an outside donor antenna or a dedicated cell site in the basement. A network of cables, amplifiers and antenna heads distribute the cellular signal throughout the building. Often, the DAS is installed by one carrier, and the others pay for access to it, an arrangement called neutral host.

However, traditional DAS has a big problem with 5G's multiple input, multiple output transmission technology that is key to high transmission rates, so the industry is proposing an idea called small cells.

5G small cells
Carriers have installed small cells outdoors to provide denser coverage in high-traffic areas.

The coverage of a small cell is comparable to a Wi-Fi access point and even less if walls are in the way. The operators have already installed thousands of small cells in outdoor applications to provide denser coverage in high-traffic areas. Now, operators are proposing small cells for indoor applications.

Carriers may also use new higher frequency millimeter wave -- 24 GHz to 36 GHz -- for their outdoor small cells. But those frequencies are highly linear, meaning they don't turn corners. Plus, they can't penetrate walls easily, so they have to be used in open spaces. For indoor use, you'd need small cells operating at lower frequencies more suitable for indoor applications.

Cellular voice especially problematic

Ultimately, a small cell installation in an office building will look like an enterprise WLAN. However, we haven't seen neutral host small cell services that support multiple carriers. So, unless something changes on that front, we might have to deploy a separate small cell network for each carrier we use.

Interestingly, this scenario poses a problem primarily for cellular voice. Your data traffic, on the other hand, could be just fine. The reason data is not a problem is we have a WLAN, and virtually all smartphones default to Wi-Fi as their primary choice for sending data traffic. The default choice for voice calls, however, is cellular. Tests have shown that roughly 75% of cellular data traffic is sent over Wi-Fi. So, as long as your WLAN is up to snuff, your data is covered.

Finally, 5G might be an interesting conversation topic for the general public. But, for networking professionals, it's a critical responsibility. Enterprise IT departments need to get up to speed on 5G issues. They should talk with their mobile operator sales reps and start planning to support 5G within their facilities.

Or you can skip this advice, but then I'll have to call you on your landline.

This was last published in February 2020

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