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A Guide for Building Owners to Select the Best Technology Cellular networks were originally designed for outdoor use, with mobility as a focus since we all had desk phones and home

phones, and businesses used PBX. Twenty five years later, those things no longer exist or are fading quickly, and reliable

indoor cellular coverage can no longer be considered as simply nice to have. Up to 80% of mobile sessions are indoors. In a

connected world, applications like Uber, YouTube, Salesforce, Yahoo, Zoom, Whatsapp, and thousands more have made the

mobile device mission-critical (not to mention voice calls and messaging).

When it comes to Wi-Fi, it’s great to use as a primary low-cost, low-expectation network for carrying pure IP data traffic –

although Wi-Fi 6 is another step forward for the technology. If latency doesn’t matter, best effort service is okay, and dropped

packets, jitter, and warble are acceptable, Wi-Fi is great to use – as long as you have a fallback when the unlicensed, unmanaged

2.4/5 GHz Wi-Fi network is unavailable, which is a common occurrence.

Whether your tenants, customers, or employees use their phones for business, pleasure, or both, it’s probable that they’ve

experienced dropped calls or poor-quality sessions when inside a building, or simply can’t properly connect a call despite

numerous cell towers in proximity. That’s because topography, such as mountains or trees, and interference caused by

building materials like concrete walls and Low-E glass can block signals from getting inside.

Given the industry efforts over the past 10+ years, and the continuing improvements in both cost and performance, many

buildings, in particular Class A structures or high-need spaces, have already taken steps to fix coverage issues. But research

shows that as much as 90% of buildings have no cellular coverage solution in place.

Beyond getting the external signals from the macro network through the building to the inside, a major challenge with cellular

is the uplink connection, from the handset to the tower. Most modern cellphones are rated for 250 mW, or one-quarter watt.

These power levels are substantially reduced from the early days of cellular when it was common for a phone, terminal, bag

By Joe Schmelzer, Senior Director of Products at Nextivity Sept 2019

Indoor Cellular Coverage Solutions 2019: Hype vs. Reality

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phone, portable phone, or car phone to be powered with one or two watts. Today’s lower-power devices, while designed to fall

well below human safety standards as issued by the regulatory agencies, often “lack the power to hit the tower.”

A variety of solutions and technologies are available to facilitate communications by helping to get the outside signal in and

the inside signal out. But not all solutions to this problem are created equally. In addition, some technologies are marketed as a

panacea while the actual, rational application may be somewhat narrower. By separating fact from fiction, you can determine

which indoor cellular coverage solution and supporting technologies are best for your specific requirements and budget,

especially if your building lands in the middleprise category (buildings up to 500,000 square feet).

There are a variety of solutions being marketed today. We’ll attempt to address the most prominent.

Mature Technologies

The Hype: Not much, as this aging solution is well known.

The Reality: This is a mature technology that is useful under certain conditions. Competent technicians can quickly evaluate the RF environment and a project’s goals to determine whether or not passive distributed antenna systems (DAS) will work in that environment.

PASSIVE DAS

Passive DAS solutions can be a very cost-effective way to improve in-building cellular

coverage, but they do have their limits – and can cost more than most people think.

A passive DAS based on a bi-directional amplifier (BDA), or “repeater,” is less

expensive than an active DAS, and typically the solutions are simpler, with less gear.

However, it can be quite difficult to deliver consistent and great user experiences

if external network conditions are not ideal, or if the building is large (greater than

30,000 square feet), or user density is high.

Perhaps the greatest benefit of the passive DAS is that it does not necessarily require

any contracts or retransmission agreements with wireless carriers. (Some passive

DAS solutions do require a contract, but not all.) The process of getting contracts

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signed with the carriers can be quite onerous, depending on the carrier, region, loading, and many other factors – some

physical and some business related.

Traditional passive DAS solutions rely heavily on the quality of signal received from existing carrier towers. The power levels

of passive equipment are restricted because of the inherently noisy technology platform upon which they are built. In poor

or mediocre conditions, a BDA-based passive DAS simply can’t support a large number of users at the service levels they’ve

come to expect.

Passive DAS solutions rely on cellular signal distribution over coaxial (coax) cable. This adds to installation costs and time

compared to the Ethernet cable used in some digital systems. Coax loses power and signal quality over distance, and is

therefore restricted in application.

ACTIVE DASThe Hype: Active DAS is the best way to deliver good wireless service in all buildings and conditions. In particular, fiber-enabled active DAS solutions are marketed as a panacea for wireless service.

The Reality: In scenarios that require signal to be transported long distances, or for extremely dense use cases such as large sporting events, active DAS is great. In small to mid-size buildings, active DAS is usually overkill and unnecessary.

An active DAS normally consists of a “head end” which drives a series of remotes. The head end connects to the carrier’s

signal source. The signal source can take many forms, from small cell to base transceiver station (BTS), to CPRI-based fiber

connection. (A detailed discussion of CPRI isn’t important for this document.) Often, an active DAS is modular and able to add

carrier and band support through the addition of cards into the head end.

In an active DAS the remote normally connects to the head end over fiber. Fiber is an excellent distribution method in this

context as it can carry nearly unlimited bandwidth over long distances. But the cost is high. The remote will output the RF

signal, and normally distribute from that point over coax cable.

Although expensive, if the space to be covered is larger than 500,000 square feet, an active DAS solution should be considered.

High-demand, high-density environments, like stadia, are also good candidates for active DAS, as the capacity from the carrier

signal source is delivered over high-bandwidth fiber.

But if your building (or a portion of it) is less than 500,000 square feet with several hundred to a few thousand occupants, you

may not need the spend of an active DAS.

Even cellular-based IoT applications – such as a more reliable connection for point-of-sale or payment processors, video

feed from security sensors, or vending machines with remote management – don’t require the bandwidth and distance that a

traditional active DAS with fiber provides.

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SMALL CELLThe Hype: Small cells are the next big thing.

The Reality: There are several realities with small cells. One, they have been coined ‘the next big thing’ for five years, and every year the forecasts get pushed out. Two, they can be very useful as a single-carrier signal source as long as the distribution method is well-designed and efficient. Three, in mmWave 5G, small cells are going to be a very important part of the network, initially outside, but eventually everywhere.

“Small cell” is a sort of catch-phrase for a variety of device types with similar features. A small cell typically has a physical connection

to the carrier network through a dedicated or virtual data link via broadband. Small cells come in a variety of power levels, ranging from

100 milliwatts (“femtocell”) to five watts. Small cells can be used indoors and outdoors. For many carriers, small cells are an important

part of their network plan, helping to meet the increasing demand for mobile device connectivity. They are relatively expensive, ranging

from $3,000 to $5,000 each, and the delivery and installation wait time can be long, depending on a variety of factors.

One strong benefit of a small cell is that it adds network capacity. Whereas a repeater-based system draws from the existing

external macro network, a small cell relies on an additional broadband connection to the network core, and delivers its own

network signal. The downside is that the user has to pay for that data feed. Many users are uncomfortable with that fact

because they have already paid for the cellular service once, via their phone bill, and now have to pay the operational cost

for the data feeding the small cells. Carriers are however beginning to roll out more cost-friendly small cell programs for

businesses. T-Mobile, for example, has a program called Bring Your Own Coverage where they make it easier and more cost-

effective for building owners to cover their buildings.

WEAKER: small cell distribution method is not ideal, leaving coverage issues.

LEGEND

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Centrally locatedsmall cell

Service Blind Spots

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WEAKERSmall Cell Signals at Perimeter

The layout of the indoor space requiring coverage dictates the coverage footprint of a small cell, taking into consideration

building material and other factors that may stand in the way of providing a strong signal. Small cells require the skills of an IT

professional to configure specific and detailed IP settings, as well as to maintain them on an ongoing basis.

Not all small cells are created equally, nor are the implementations equal across all carriers. Some small cells suffer from

interference issues, or have extremely limited functionality and technology capabilities. For example, some carriers only

provide 3G small cells. Small cells may use a “white list” (only specific users can join) or “blacklist” (example, no public users

allowed), which can limit their usefulness.

Another significant challenge with a small cell is that it is a single-point solution. Coverage is great around the small cell but

once beyond that proximity, the effects diminish. In a multi-story building, or in a space that isn’t open (i.e., most spaces), a

small cell struggles to provide uniformly reliable service.

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So, despite the hype around small cells, the reality is that they can take a while to deploy, have significant operational costs,

require specialized skills to set up and maintain, and their performance is not always guaranteed. This is different from a

Supercell though, which is covered below.

ACTIVE DAS HYBRID AND THE SUPERCELLThe Hype: An Active DAS hybrid combines the digital distribution performance benefits of active DAS, at the price points of passive DAS. And the Active DAS hybrid can deliver on the promise of the Small Cell, with the Supercell Configuration.

The Reality: Active DAS hybrid does a great job delivering quality cellular service up to the 500,000 square foot range.

An active DAS hybrid is flexible enough to support numerous configurations that can deliver service quality at a cost-effective

price point for the middleprise market. It can also be installed in a matter of weeks. That flexibility includes using either Off-Air

antennas or Small Cell as a donor source.

There is actually no fiction to be dispelled in the statement above. The unique strength of a hybrid, such as Cel-Fi QUATRA,

is the ability to support different coverage needs, signal source availability, and building layouts. For example, a single Cel-Fi

QUATRA coverage unit (CU) can provide coverage for a large, open setting with high ceilings and low (or no) interior walls. It

can also be mounted quickly, and uses Cat 5e cable for power and signal.

Likewise, in an area with obstacles or other signal blockers, an installer can use a single Cel-Fi QUATRA CU as a remote source

to power a passive DAS instead of using multiple CUs. Using coax cable to distribute coverage between the CU’s external

antenna ports and antennas, Cel-Fi QUATRA can amplify each carrier independently up to 100 dB, versus the traditional

passive DAS application of one gain value for all operators. In addition to the higher gain, each of the four internal amplifiers is

independently gain-controlled, allowing each band to reach maximum downlink power regardless of the input signal strength.

Cel-Fi QUATRA tethered

to a small cell

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STRONGERSmall Cell Signals at Perimeter

STRONGER: Supercell distributes signal, delivering on promise of small cell.

And there is finally a solution to deliver on the promise of the small cell, which is called the Supercell. If the environment has

no available signal or struggles with capacity challenges, the Cel-Fi QUATRA Supercell configuration is a perfect solution. The

Supercell combines the strength of a small cell as a donor source with the superior distribution capability of the Active DAS

Hybrid. The Supercell is an ideal solution for larger venues where it would be cost prohibitive to install multiple small cells and

difficult to plan.

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New Technologies

FIBERThe Hype: If you’re not using fiber you are not future-proof.

The Reality: Fiber is great for distances and high-bandwidth applications. At approximately 10 times the cost of copper, it’s an unnecessary expense in many applications.

Fiber on its own does not provide coverage, but it can be an essential part of the coverage solution and the decision-making

process. That being the case, it’s worth discussing.

So-called “wireless” networks are actually mostly wired until the point of signal distribution. Fiber is the backbone of today’s modern

high-speed high-capacity networks. Sales teams and marketers in the industry often promote the use of fiber in all applications. But

in facilities less than 500,000 square feet, or without a high-density of users, it can be an unnecessary hassle and expense.

Cost per linear foot varies widely, and is dependent on the number of drops and topology of the building, and the number of

terminations. That said, the cost of fiber normally ranges from $3.00 to $5.00 per linear foot. Ethernet cable (copper, CAT5e,

and above) is typically an order of magnitude less, running between $0.30 to $0.35 per linear foot, is fast and easy to install,

provides excellent quality of service, and can be used in the installation of an active DAS hybrid solution (more on that later.)

Finding technicians trained and equipped to properly install fiber can be a challenge, whereas finding technicians to run

category cable (Ethernet) is relatively easy.

WI-FI 6The Hype: Wi-Fi 6 is four times faster than Wi-Fi 5, and has some other improvements.

The Reality: Wi-Fi 6 is four times faster than Wi-Fi 5 (if all of the equipment has been upgraded), and has some other improvements. But it’s still Wi-Fi.

Wi-Fi 6 is the name for the next generation of the wireless standard, following the current 802.11ac protocol. Wi-Fi 6 is

technically called 802.11ax, but in addition to new wireless technology, it’s also bringing with it a new naming scheme: it’ll be

known simply as Wi-Fi 6, while 802.11ac will be referred to as Wi-Fi 5.

Wi-Fi 6 is expected to be approximately four times faster than Wi-Fi 5, and will continue along the trajectory previous versions

of Wi-Fi have established in terms of scale, cost, and coverage.

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While this new version of Wi-Fi promises to improve many aspects of the user experience, nothing has changed regarding the

spectrum upon which it runs, which is unlicensed, overloaded, and hotly contended for.

5GThe Hype: 5G is here and has added some completely new and radical capabilities and use cases to cellular. Throughput, latency, and reliability are going to take a quantum leap forward. It’s going to replace Wi-Fi.

The Reality: Initial 5G variants, for the next few years, are going to represent a marginal improvement over 4G. There are several unanswered questions. There are significant physics and subsequent cost issues that need to be addressed before 5G can achieve mass adoption. Optimistically speaking, assuming those issues get solved over the next five years, 5G will enable many new product and service platforms. Cisco alone, a key Wi-Fi technology provider, has committed $5 billion dollars to 5G. Data also indicates that 5G will replace many Wi-Fi use cases.

5G is perhaps the hottest topic in cellular in 2019. 5G offers a variety of new use cases. There are, depending on where you

look, approximately eight performance indicators that separate 5G from the preceding generations. The three most commonly

referred to are (1) throughput, 1 Gb or more; and (2) latency, ultra-low latency, less than 1 millisecond, well below thresholds

a human could perceive; and (3) ultra-reliability. The first two are relatively easy to understand. The third item is somewhat

technical in its implementation, but it’s essentially based on many improvements inside the network that provide for nearly

100% uptime and ultra-consistent service.

One other point to make is that 5G is not one thing, as it is commonly marketed. Current-generation 5G mostly represents

slight improvements over 4G, whereas the amazing features marketed with 5G – such as ultra-low latency and substantial

throughput improvements – will become available in three to five years’ time with future iterations of 5G.

For our purposes here, we will divide 5G into Sub-6 GHz and mmWave. Globally, 3.5 GHz is a popular frequency range for sub-

6GHz 5G. T-Mobile has stated it will deploy 5G in 600 MHz. Other U.S. carriers are deploying mmWave 5G in 28 GHz and 39 GHz.

Today, 5G has been deployed exclusively outdoors thus far. In the sub-6 GHz context, in-building coverage solutions should

come from a basic iteration of existing technologies. Fundamental changes are not needed to support sub-6 GHz 5G.

However, the physics are completely different above 6 GHz: propagation is extremely poor, and there are no cost-effective in-

building 5G systems available.

Qualcomm, one of the great wireless technology innovators, is a key player in 5G. The company has produced research that

shows a requirement for 20 access point-like (small cell) nodes in a 27,000 square foot building. The capex and opex costs for

this kind of solution would be so exorbitant that there’s little point in trying to estimate them. This would work in only the most

demanding building use cases – a speciality hospital room, real-time remote drone operation, etc.

Not only is it a costly and time-consuming process for carriers to migrate spectrum to 5G bands, but much of the global

marketing around 5G to date actually relates to 5G mmWAVE technology. mmWave 5G delivers extremely high data rates to

support advanced IoT applications – think driverless cars, remote surgical equipment, and robotics – that are simply not in

the purview of most building owners at this time.

That said, you can still get 5G ready. For most building owners, this simply means selecting infrastructure that can transition

seamlessly to this next-generation technology.

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CITIZEN BROADBAND RADIO SERVICE (CBRS)The Hype: CBRS is going to take over as the in-building cellular coverage technology in the Neutral Host Network (NHN) scenario. CBRS is going to replace Wi-Fi as the wireless network technology of choice for large enterprise.

The Reality: There is no supporting business model for CBRS-based NHN and no commercial provider of a solution, as of this writing, although CBRS industry insiders claimed it would be available long before now. CBRS as a Private LTE solution for large enterprise makes a bit more sense, and may gain traction in corporate environments soon.

Citizen Broadband Radio Service (CBRS) has been touted as the next big thing in in-building cellular coverage, particularly in

the middleprise. Like 5G, CBRS is an extremely generic term, which actually refers to a frequency band as designated by the

FCC, covering 150MHz between 3550 and 3700 MHz.

The spectrum’s primary use until now has been for U.S. government radar systems. The spectrum is managed by a three

tiered-access system. Lessees check into a Spectrum Access Server to determine spectrum availability on site and ensure

non-interference. While NHN is 100% hype, Private LTE solutions to replace Wi-Fi should gain ground as a more secure network

environment for business; not to be confused with cellular for voice and data.

CELLULAR-BASED IOTThe Hype: Cellular-based IoT is going to represent billions of connections for use cases that require mobility or have other specifications that prohibit the use of some of the less expensive solutions.

The Reality: Cellular-based IoT is the path of least resistance for cellular operators. Existing networks more or less support the technology already, so new networks or expensive upgrades are unnecessary. Cellular-based IoT will take a percentage of the global total, but less expensive solutions will remain attractive and take the lion’s share over time.

According to Ericsson (2018), by 2023 there will be more than 3.5 billion cellular IoT devices on the market, making cellular

technology a major communication enabler of IoT. And while it’s true that some legacy technologies can support IoT

applications, they have battery life and latency issues that negatively impact mission-critical business operations and cost.

Less costly alternatives are LTE-based devices, which have extended battery life and are easier to reach from the network

infrastructure. LTE-based IoT systems, offered by companies such as Sierra Wireless, CalAmp, and Digi, can be incorporated

into existing LTE networks, making them easier and more cost-effective to deploy.

CONCLUSION: WHAT IS THE BEST SOLUTION?In short, each of the solutions above has its place in the market, but not all are built to meet the unique needs of the middleprise.

There is no one size fits all solution for all in-building cellular coverage, but specific building categories do have natural leaders.

Total project cost (labor and hardware), installation time, and remote management / maintenance requirements must all be

factored in when determining the ROI for the system being installed. That’s why an Active DAS Hybrid approach is the most likely

to give you the flexibility and quality of service required at a reasonable price point for the majority of the buildings in the market

(classified between SMB to middleprise, ranging up to 500,000 square feet).

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CEL-FI QUATRA• Built for Installers with Signal Quality Maximized by AntennaBoost™• Best Signal by 1000x• Scalable for Middleprise Buildings• SingleorMulti-CarrierSolutionsAvailableinOff-AirorSupercellConfigurations• Remote Monitoring and Management via Cel-Fi WAVE Platform• Lowest Costs per ft2/m2

About the AuthorJoe Schmelzer has 20 years of experience driving the creation of products and solutions for chipset

vendors, device OEMs, and service providers, including Sony, Qualcomm, Google, Verizon Wireless, AT&T,

Dell, and HP. Mr. Schmelzer has previously held positions with Wavecom, Sierra Wireless, and Novatel

Wireless. He was also a founding member of CTIA’s Wireless Internet Caucus. For more information,

contact hello@cel-fi.com or visit www.cel-fi.com.

cel-fi.comU.S. Headquarters: Nextivity Inc.16550 West Bernardo Drive, Bldg 5, Suite 550, San Diego, CA 92127, USA+1 858.485.9442 tel • +1 858.485.9445 fax

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SmallCell

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Scalable: Each Cel-Fi QUATRA Network Unit distributes RF to up to four Coverage Units, via Cat5e ethernet cabling.