In-Building Cellular For Mid-Sized Facilities

Small and mid-sized facilities have traditionally faced the same upfront costs for wireless networks with longer ROI.

By Joe Schmelzer

The importance of in-building cellular coverage has never been greater as reliance on mobile devices in the workplace grows. Building occupants are increasingly using mobile devices to conduct business, and are less tolerant than ever of poor quality signals or spotty coverage within their office environments. Plus, increasingly more “things” (as in Internet of Things) are relying on cellular data to “phone home”.

While good indoor cellular coverage may sound simple to achieve given the ubiquitous nature of available cellular networks, there are often dead zones within buildings where users experience poor reception, poor voice quality, and dropped calls. This is quite common in elevator shafts, basements, corners of an office area, or even within highly insulated areas of a building. The trend towards greater energy efficiency in building construction and facility maintenance cause further problems for indoor cellular service, as techniques used to keep out the sun’s rays also keep out wireless cellular

Surprising as it may sound, cellular service can actually be negatively affected by too much signal. If there are overlapping signals generated from multiple network sources, they can create confusion at the handset, which will then hop from one source to another causing service irregularities. This is common in taller buildings that can “see” many network cell towers.

Extending quality cellular coverage throughout an entire building has always been a challenge. While there are technologies that have helped, until now available solutions have been either too complex or costly to install; limited in their capability; or, in the case of smaller spaces, over-engineered for the need. This has made it difficult to achieve ROI.

The cost and complexity of indoor cellular coverage solutions are less of an issue for large-scale enterprises or industrial venues. It is easier to amortize fixed costs over a larger building space, yielding lower costs per square foot. But small-to-medium-sized commercial buildings — 10,000 to 200,000 square feet — have had the same upfront costs with less return. At the same time, affordably priced residential solutions are simply not robust enough for business.

Cellular service is increasingly seen as the “4th utility.” Poor cellular coverage creates tension between the venue owners, tenants and occupants, and network service providers. Cellular subscribers become dissatisfied, churn to a different provider, frequently only to suffer the same poor service conditions.

This is frustrating for many facilities given the fact that small-to-medium-sized enterprises account for the highest percentage of businesses. U.S. census information shows that the vast majority of U.S. businesses employ less than 100 people; and that 97.8% of all commercial buildings are less than 100,000 square feet.

There is, however, a silver lining thanks to recent technology developed specifically to meet the cellular coverage and budget needs of small-to-medium-sized enterprises. The variety of solutions now available each emphasize different features and capabilities, with differences in cost and performance. Timing is also a key consideration, as it can take months before certain types of equipment can be delivered.

So where do facility managers begins? In understanding the best approach, let’s first take a look at some of the available options.

In-Building Cellular: Considering The Options

Wi-Fi Calling. This can be an effective way to extend coverage in pockets of a building or small office environments where there is no available cellular signal as calls are made over the internet.

Wi-Fi Calling comes with some limitations. Perhaps the biggest issue with Wi-Fi Calling is that it relies on unlicensed, unsecure, and unmanaged networks, unlike the much more reliable and secure cellular networks the wireless carriers provide. With Wi-Fi Calling, the quality and reliability of service is variable and unplanned “outage” periods can bring business to a grinding halt.

Wi-Fi Calling only works if the cell phone supports Wi-Fi Calling (a large number of devices do not). A Wi-Fi hot spot only enables a limited number of simultaneous users and may not support the higher data volumes common to an enterprise environment. Lastly, Wi-Fi doesn’t do handover well. Calls drop when a person moves in or out of the limited Wi-Fi calling zone.

Small Cells/Femtocells. Small cells function as mini cell towers to help deliver a greater capacity of wireless signal indoors. Residential femtocells are more or less plug and play, but provide a relatively small amount of coverage, enough for a family and guests.

For spaces in the 30,000 square foot range or smaller, some carriers now offer “self-installable” small cells. Note: “self-installable” in the cellular context means that an IT-type person — with some level of understanding of networking, Ethernet cabling, and Internet access — could install the unit. For those who prefer professional help, it is offered from both the carrier and third-parties.

For buildings that are too large, not an open plan, or suffer from other internal signal blocking factors (enclosures, walls, impenetrable materials, multiple levels), one small cell may not be enough. If multiple small cells are required, some professional RF planning may be the best route. There are many technical issues that an RF planner can help to minimize, while maximizing system performance.

DAS (Distributed Antenna System). A DAS is most commonly used in large spaces (500,000 square feet and above) with a large number of users. DAS typically uses fiber optic or coax cables to distribute cellular signals from a base station installed in the building. DAS requires considerable preparation through RF surveys and designs, planning, and approvals, as well as significant installation time and cost, so is not often considered for mid-sized or smaller enterprise environments. In a typical DAS project, multiple carriers are involved, which can create delays based on contract execution. Facility management should budget eight to12 months from start to finish for a DAS installation, and $2 to $3 per square foot of coverage.

Smart Signal Booster. A smart signal booster can be used in an office space up to 15,000 square feet. This should not be confused with repeaters or antennas that merely amplify an existing cellular signal and often cause poor quality cellular service by creating interference on the wireless network. Rather, a smart signal booster is approved by a specific carrier for use on its network, and does not cause interference. It is self-configuring and provides a higher signal gain (up to 100dB) than analog repeaters (60-70 dB), which means it will provide a better quality signal over a larger footprint.

A smart signal booster can be installed quickly drawing cellular signal directly from the outside cell tower. It costs significantly less than the investment required for DAS or small cell solutions, and is ideal for smaller office spaces.

in-building cellular
New hybrid solutions for in-building cellular coverage leverage both small cell and distributed antenna system (DAS) technologies. (Image: Nextivity)

Smart Signal Booster/Active DAS Hybrid. There is a newer product category offering the footprint of DAS and the ease of use and install of the smart signal booster. This is a carrier-approved in-building cellular system that solves coverage and capacity issues for 3G/4G/LTE, can be installed by IT professionals, and is scalable up to 200,000 square feet. This system operates in two configurations, depending on the needs of the facility:

Off-Air mode: Off-air to maximize coverage and performance up to 50,000 square feet per system in sparsely populated venues (donor signal enhanced with MIMO (multiple input, multiple output) Panel Antenna)

Supercell: Supercell architecture tethers a smart signal booster/active DAS hybrid to a small cell for increased capacity and coverage up to 200,000 square feet or in densely populated venues.

Planning In-Building Cellular Coverage: Questions To Ask

So how does one decide the best approach? Following are some of the basic questions that facility executives should ask to determine the most appropriate in-building solution for their sites:

How much space needs to be covered? Indoor cellular coverage solutions are tailored to specific sizes.

How many users? The amount of network traffic has a direct impact on whether or not a small cell is needed.

How dynamic is the environment where coverage is needed? The number of users in different areas of the building may vary throughout the day; some areas may have only one cellular call daily, while others have hundreds. This also impacts the type and configuration of the system installed.

What cellular carrier is used by building occupants for their mobile devices? Single tenant buildings often have a corporate account with one carrier; multi-tenant buildings may have multiple carriers in use by occupants. A public space will have many carriers.

What is the building layout and construction? Open floor plans versus walled-in plans, metals walls, elevator shafts, and LEED green building construction can all affect the type, placement, and number of devices needed.

How complicated is the solution to install, and who will be installing? Some solutions require extensive engineering and specialized technical expertise to ensure they are installed and functioning optimally. Some solutions are self-installing, self-configuring, and self-optimizing which is usually the best and least costly choice if available.

What is the timeline? Some solutions require several months for contract negotiations, equipment delivery, and installation. Others can be installed in less than a week.

Is seamless coverage throughout the building necessary for business operations? One challenge that is often overlooked is whether calls can be handed over from one space within the building to the next without getting dropped or impacting voice quality.

What is the budget and business model? Understanding both capital and operating expenditures of any solution is critical. Upfront equipment and installation costs need to be considered along with any ongoing maintenance costs, as well as outsourcing expenses if required instead of internal IT resources.

Using these questions, a facility manager is armed with a checklist for a solid apples-to-apples comparison between the different available solutions to resolve the specific indoor cellular coverage problems experienced by the occupants of that venue.

In today’s always-on, always-connected world, ubiquitous in-building cellular coverage is as much of a day-to-day necessity as lighting or heating. The need will only increase as connectivity extends to an increasing number of devices, from appliances and wearables to building management and security systems. However, there are now affordable, flexible and scalable solutions that can address cellular coverage needs within facilities of any size today and into the future.

in-building cellularSchmelzer is senior director at Nextivity, Inc., a San Diego, CA-based developer of Cel-Fi Smart Signal Boosters. A veteran of the wireless industry, with 20 years’ experience driving the creation of products and solutions for the global market, he has played a critical role in developing devices for chipset vendors, device OEMs, and service providers, including products for Sony, Qualcomm, Google, Verizon Wireless, AT&T, Dell, and HP. Schmelzer has held product management positions at Wavecom, Sierra Wireless, and Novatel Wireless, and was a founding member of CTIA’s Wireless Internet Caucus.


  1. I’m planning to erect a building in the future that will be rented by many commercial businesses, and it would seem like a good idea to add an in-building cellular communication system to make sure that it’s ready for 5G connections. It’s interesting to know that I have to consider the amount of traffic that will be expected on every floor if I’m planning to have that installed. I think I’ll talk to a professional regarding this once I have my building finished so that I’ll know how many systems are needed to be installed on every floor.

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