In-Building Wireless Systems (DAS and ERRCS)–Myth, Fact, Fiction and Reality

In-Building Wireless Systems (DAS and ERRCS)–Myth, Fact, Fiction and Reality

If ever there was a realm of building technology systems, and a point in time, where more confusion, hype and wasted dollars have been strewn about, it’s got to be today in the area of in-building wireless systems.

While the category of “in-building wireless” does include wireless LAN, better known as WiFi, this article will principally address the more confusing and dynamic technologies of cellular distributed antenna systems (DAS) and public safety DAS, which, as per the code book, is more accurately labeled Emergency Responder Radio Coverage Systems (ERRCS). WLAN technologies are routinely handled well by client IT departments, and while they can be challenging to design and manage, especially with the surfeit of devices in this bring-your-own-device (BYOD) world, they are in general well-defined in terms of their costs and benefits.

With cellular DAS (or for the sake of brevity in this article just “DAS”) and ERRCS, mystery and the potential for costly mistakes abound. Because of the complexities, we’re going to generate a series of three articles. This first one will tackle the current state of DAS, and the related cellular booster technologies, which enhance cell coverage inside buildings.

  • What technologies exist today?
  • What sort of cost expectations are realistic?
  • What potential jeopardies exist if I, the building owner, choose not to spend my money on one of these systems?

Also, we’ll spend some time reviewing the pros and cons of DAS versus boosters, both from the perspective of the cost and features of each as well as how the wireless service provider (WSPs), also known as carriers, (AT&T, Verizon, T-Mobile and Sprint) view the different technologies. There have been some exciting developments in making DAS more affordable to the enterprise building owner, and we see these trends developing rapidly in this (what some people are calling the) “fourth utility.”

The second article will take on ERRCS, especially in light of changing jurisdictional requirements and the related concerns of risk mitigation—it does, after all, concern life safety. We’ll explain FirstNet, the nationwide broadband first responder network. The federal government just awarded the buildout contract for FirstNet to AT&T, after much delay, so it’s a coming reality. We’ll also Identify ERRCS trends as they relate to the requirements being imposed by particular states and cities. Both in the first and second article we’ll make sure that the commonalities and differences of DAS versus ERRCS are clear—because there’s just that much confusion. One obvious one that often is overlooked: DAS is used by cellular device consumers, while ERRCS is only used by first responders, i.e., firefighters, paramedics, and police.

The final article peers into the future, to the cellular 4G+ and 5G technologies, which are not nearly as far down the road as most people believe.  For example, I have a friend who participated in a 5G trial with a major wireless carrier almost two years ago. He downloaded an HD copy of the movie “Interstellar” in 3 seconds while driving 60 mph. We’ll start seeing commercial 5G deployments in select markets next year.  The last article shall address how to prepare for 4G & 5G technologies wisely without being sucked into incurring massive costs that don’t provide real benefit today.


Some people are surprised to learn that DAS deployments in commercial buildings have been taking place for almost twenty years. Phil Ziegler, CTO for Whoop Wireless, recalls efforts during his tenure at Verizon Wireless when VzW, Qualcomm, University of Colorado professors, and Lucent technologists collaboratively developed functional and test requirements for 4G DAS and OTAR product performance objectives.  “Those requirements had venues such as airports, stadiums, convention centers and other places where large crowds gathered in mind.  Now we are faced with the realization that increased data demand is being felt throughout the ecosystem and not only in the largest facilities.  So, just as small cells are reduced power and capability base stations, affordable commercial grade DAS platforms are needed in the enterprise space to accommodate the small cell paradigm.“

A number of large and respectable neutral host companies, such as American Tower, Crown Castle, Boingo and Extenet, have built a profitable business model on deploying DAS. These companies serve as liaisons between venue owners and the WSPs and attempt to generate as much participation on the DAS as is possible.  It must be understood that the priorities of the WSPs are as different as are their budgets across vertical markets, and so there are many cases where neutral host and carrier-owned DAS have less than full participation from the four major cellular carriers.

In today’s BYOD world, perhaps the first lesson in deciding on implementing any in-building cellular enhancement system—whether it’s DAS or a simple booster technology—is: Does it offer access to all the major players? The trend is veering away from corporate environments where a carrier obtained a contract to provide cell phone to all the users and agreed to implement a one-carrier DAS in return. The modus operandi for today’s consumer, be she an employee, visitor or guest, ischoice. We’re seeing this sharp turnabout in all market verticals, but perhaps most vigorously where the building houses numerous non-employees. These types of buildings include hotels, apartments and condos, higher education, and, perhaps surprisingly, medical centers. As many as 85% of the people who work in a hospital can be contractors. The hospital IT staff struggles against overwhelming odds to overcome obstacles around giving WLAN access to these non-employees while complying with HIPA requirements. They would much rather see the BYOD contractor workers fulfill their broadband needs through the cellular networks.

Common questions about DAS

  • What about cost?
  • Aren’t DAS implementations ridiculously expensive?
  • Can’t I just put in a low-cost booster that works just as well as DAS?
  • Won’t one of the carriers pay for a DAS in my building if I just wait long enough?
  • And finally, shouldn’t the carrier’s broad, tower-based cellular network (industry jargon—they call it the “macro network”)  pump enough signal into my building so that I don’t need an in-building cellular enhancement system?

Let’s peel these layers back in reverse order:


The answer to that question boils down to a cost/benefit analysis, as you decide whether to rely exclusively on what AT&T, Verizon, T-Mobile and Sprint do to make your building a desirable destination or you determine to supplement their buildout efforts. Do you, as a building owner, gain enough of a competitive, and therefore revenue, advantage to justify the cost of a DAS or booster? And to answer that question, there are three factors to consider.  They are interference, capacity and demand.

First, building construction technologies increasingly create radio frequency (RF) interference that limits the signal strength within a building. Triple pane, low –E glass, for example, has a 40 dB impact on RF signal strength. Doesn’t sound like much? In case you’ve forgotten your logarithms, a 40 dB loss in signal strength means the signal inside the building is only 1/10,000 as strong as the signal outside the building. Honestly. Building iron, hurricane shutters, other buildings, even furnishings can significantly impact the signal strength within a building, creating dead zones or even an entirely “dark” building. With or without triple pane glass, we routinely see a 30 -50 dB drop in signal strength, making what was a fine cell experience outside the building excruciating once you step inside.

The second factor in considering whether you will supplement the macro network with an in-building wireless system involves capacity. What once was an empty lot on a carrier’s macro network map transforms into a 32-story high rise hotel. Even if you can walk throughout your high-rise hotel at 5AM and obtain excellent cell signal everywhere, you may well encounter the circle of death when the building is fully occupied and active as you attempt to download critical content. The reason? Hundreds of other building occupants are attempting the very same thing, at the same time, and the macro network wasn’t built to handle all of you occupying the same dot on a map. Thus, excellent cell coverage, that is, signal strength, often does not always translate into excellent cell performance, due to the lack of capacity.

Along with this second factor of capacity is the related third factor of the increasing user demand for more bandwidth—broader and deeper Internet experiences by each and every one of us. We are like a pack of ravenous wolves when it comes to expecting HD, 3D, VR and more and more high information content on our cell devices. How will that increasing demand be delivered to users? Nearly everyone assumes that the carriers will just take care of it. But Verizon, and the other carriers, too, have gone on record as stating it will be impossible for their macro network to accommodate the increasing bandwidth demand. As a hypothetical, Verizon asked how many additional cell towers it would take, if that were the only means utilized, to cover usage demands in the US in seven years. The answer? Three million. There are only 300,000 cell towers today. Does anyone in his right mind believe the citizens of the United States will accept increasing the number of cell towers tenfold? Verizon has a plan to meet the demand, which includes a few more towers, a lot of technology advancements, and for the vast majority of that increased demand, “in-building wireless systems” (IBTUF 10 Conference general session, January, 2016). Yes, Verizon expects that you, the building owner, will install a system to “densify” its network. So do AT&T, T-Mobile and Sprint. They won’t thank you; in fact, they’ve historically made it difficult and expensive for you to do so. But they expect it nonetheless. And they won’t pay for it in most cases.


Carriers do still pay for DAS. If you’re building a stadium, arena, high-end and sizable mall, massive hotel and conference center (as in something over a million square feet), Wynn-like casino, or a major medical complex, the chances are fair that you can attract a benevolent carrier or neutral host company (who are largely funding their buildouts with carrier funding). Since most buildings in the enterprise space do not fall into those categories, the reality is that carriers do not have the capital budget, and even if they do they do not intend to pay for your 300,000’ building DAS.

We’ve seen the ROI models the carriers use in determining to pay for DAS; there must be enough foot traffic to justify their investment. And they measure foot traffic in the thousands, not hundreds, when they generate their payback models. Even then, they will often still fight to make it a single carrier DAS, if not forever then at least for an extended period in order to recoup their investment.

There are exceptions. We’ve seen a few cases in recent years where a carrier has agreed to cover DAS costs for a smaller facility—a recent corporate headquarters, for example, that was only 550,000’. But, that carrier is angling for a 4000-line mobility contract and wants access to that corporation’s many other facilities and mobility contracts. It’s a carrot on a stick, though; they won’t foot the DAS bill for the remaining buildings.


If I as a building owner am persuaded that sooner or later I’m going to have to foot the bill for enhancing the cell coverage in my building, why would not just put in a booster and some antennas instead of a full blown DAS? My low voltage contractor told me that I don’t need DAS.

In case it isn’t clear, we do endorse boosters—In the right application. We also endorse several different DAS product sets—in the right application. There is no A-Z solution for any type of product, no one type of boat or clothing or food that satisfies every situation. The same goes for cellular enhancement.

Boosters are best suited in smaller environments. We generally recommend to clients to use boosters in facilities under 50,000’. The FCC has approved the use of these boosters, and as long as your contractor properly registers these booster installations on your behalf with all four carriers, you should experience a much better cell environment with relatively little cost and no risk.

The disadvantages with boosters are why they’re so low in cost. Unlike a DAS, a booster is akin to a massive firehose of cell signal that is sprayed throughout a building. There is no intelligent distribution, no constant measuring of cell activity and adjustment of signal strength and quality between multiple active remote nodes. A DAS is more like a very smart sprinkler system, with valves and meters, that delivers the precise amount of water to the exact area needing it.

To overcome the passive nature of the signal distribution with boosters, contractors will often attempt to install multiple boosters in larger buildings. This situation could not be worse, because these multiple, unintelligent boosters create oscillation—standing RF waves that cause massive noise to flow back into the macro network. To a cell carrier Radio Access Network (RAN) engineer, it sounds like a microphone stuck in front of a speaker. The carriers will find that system, and they will shut it down. Because they paid billions for the spectrum, they have the right to do so and can have the FCC levy the building owner (not the contractor) with fines in the tens of thousands of dollars per day range.

If a booster system has been registered with the carriers, they will cordially instruct the building owner to shut it down if they detect any backflow of noise into the macro network—without generally threatening fines. If they find a rogue, unregistered noisy booster(s), all bets are off, however. Depending upon the trouble your rogue system has caused, they might decide to make an example of you.

Finally, boosters do not accommodate RF source inputs from carriers across broadband landlines. They cannot, in other words, increase capacity, only coverage. They can only take what signal is in the air (over the air or OTA) and amplify it. They increase coverage (along with some noise) but they don’t do anything to increase the density of the cellular capacity. The lack of additional capacity may be OK, for a while. We’ve had customers with small areas of poor coverage and no budget, and we’ve not denounced their decision to install a booster as a temporary coverage-only solution. We have advised them, however, that sooner or later they will want to upgrade to an intelligent, capacity increasing system, i.e., a DAS, for all the reasons mentioned above.

In contradistinction to boosters, therefore, a DAS is an intelligent, actively monitored, often self-optimizing system that, done right, will actually reduce RF noise in the facility while significantly increasing cell coverage and capacity. It has a headend and multiple remote nodes distributed throughout the building. It will make your building occupants very happy. But it costs more—and you get what you pay for.


Five years ago, when we had (a very few) enterprise clients with a conviction they needed a DAS, we were seeing all-in DAS costs averaging $3-4/foot—sometimes more, depending upon what requirements the carriers imposed. It’s asking a whole lot of any building owner to swallow that kind of cost impact, even for a putative fourth utility. Thankfully, two significant changes have taken place in the interim to make the costs much more palatable.

First, all the traditional DAS OEMs and spate of new ones are bringing new, enterprise-centric products to market. These new products do not have the sophistication and layers of Bellcore engineering as the technologies that are needed in complex RF environments such as stadiums. But those additional features are completely unnecessary in enterprise environments, where there may be only hundreds of users in a very simple, stacked building RF environment. Corning Mobile Access and Commscope, the two major DAS industry OEMs, have released new products recently to address the need for a lower cost, enterprise grade solution. In fact, Commscope’s system is termed Ion-E—“E” for enterprise. Along with them are products from SOLiD, ADRF, JMA, and scores of others.

Even better cost savings can be had with some of the non-traditional, new DAS OEMs who are making their mark with increasing wins. Some examples include Zinwave, and especially Whoop Wireless, whose total, turnkey installations including RF sources from the carriers often come in at close to $1/foot. These new OEMS are employing non-traditional approaches to providing an intelligent DAS, for example Whoop’s two-stage gain, modular design and upgradable (through flash) 5G roadmap.

The second important advancement in reducing costs has been due to the carriers themselves. Whereas for prior DAS implementations carriers routinely required a full base terminal station (BTS) buildout, typically costing $100,000 or more per carrier per sector, they are now offering small cell devices that increase capacity at a cost of only a few thousand dollars. Plus, these small cells have vastly lower real estate, power and cooling needs. An entire DAS headend, with all the carrier small cells, can often fit inside one 19” rack.


So what’s an owner to do in light of this fluid environment where the only constant is the insatiable bandwidth demand of the consumer?

Our recommendation if fairly simple and falls into four categories:

  • New construction, more than 500 occupants at peak: Swallow your medicine and plan for a DAS. Thank your personal deity that costs have dropped dramatically. Make sure you engage a quality technology partner who knows you’ve read this article and are expecting all-in costs to be less than $2/foot and closer to $1/foot.
  • New construction, fewer than 500 occupants or less than 150,000’: Engage a quality technology partner to prepare a preliminary design (using an industry tool known as iBwave) to identify antenna and equipment locations, and pay the cabling contractor to install the cable during construction. The cost will be quite low—at most in the tens of thousands of dollars total. Wait until your building opens, then test for cell quality and strength. If it’s good, thank that same personal deity and wait to install the DAS (which has been cabled already so that you’ll have no construction mess in public areas) whenever demand demonstrates that you need it. Or, if signal is not so great, install that DAS that you’ve already had designed and for which you’ve gotten all the construction mess resolved.
  • Existing construction, more than 50,000’: If it ain’t broke, don’t fix it. But if you have problems, engage a quality technology partner who will address coverage, signal quality, and capacity issues instead of just offering an immediate coverage bandage. In other word, put in a DAS that works now and has a smooth technology roadmap to 5G. Don’t cheat yourself, or worse, incur potential fines, with a low cost booster.
  • Existing construction, less than 50,000’: Install a high-quality booster to address coverage needs, and wait and see what DAS or small cell technologies might emerge in the future to address capacity needs you’ll have later.

We haven’t addressed ERRCS much at all in this article.  That’s for next time. But do note that some manufacturers offer integrated systems that combine DAS and ERRCS. There’s some potential viability there, and very high-end, sophisticated systems such as the one at Atlanta’s Hartsfield Airport deploy just such a system. However, we have found these integrated systems, so far, to cost more than the new technology platforms that separate the two. Plus, there are very real life safety concerns that argue for separation. Even at Hartsfield, although the system is integrated, the DAS and ERRCS antennas are separated by a minimum of 15’. That separation is critical to eliminate the “skirting” effect of contiguous frequencies. That last thing anyone would want to have happen would be for a firefighter, in a critical life safety situation, to have bleed from a cellphone conversation on his radio. More on this and other aspects of ERRCS to come . . . .

[Featured on Network Technologies, Inc.’s website:]

[For more info on Public Safety DAS, read Eric Fichtner’s article HERE ]