An Insider’s Guide to Distributed Antenna Systems

It’s no longer news that connectivity is the future. What more businesses and users are discovering, however, is that the type of connectivity you use is key to success.

WiFi dominates indoor connectivity. But as a consumer-grade solution, its bandwidth, interference, security and latency issues leave much to be desired.

By contrast, LTE-based cellular signal is the ideal solution, particularly as lightning-fast, high-capacity 5G networks emerge. It’s the gold standard of secure, encrypted connectivity. Unfortunately, cellular signal struggles to penetrate buildings — unless you have the right technology in place.

Distributed antenna systems (DAS) ensure that 4G LTE or 5G signal is distributed throughout a given building, eliminating dead zones and providing secure, reliable, fast connectivity.

The potential of this technology is staggering.

By employing a DAS, organizations could:

  • Create dedicated networks rather than sharing bandwidth
  • Eliminate server farms and their inherent latency issues
  • Receive mobile calls anywhere without dropped calls
  • Provide coverage in locations they previously couldn’t
  • Increase team mobility without connectivity concerns
  • Attract more clients with standout connectivity
  • Deploy and operate on 5G as soon as it’s available
  • Control their infrastructure and connectivity solution

Perhaps most importantly, DAS allows organizations to dictate where the network traffic is hosted: transactions or confidential information routed via the DAS, guest calls and web surfing via the WiFi. In hospitals, for instance, healthcare providers and staff can share files and operate equipment on the LTE, while patients watch movies or video call family members via WiFi.

However, not all DAS systems are built equal.

DAS comprises numerous solution families, only some of which are active, 5G-ready, and future-proof.

With a slew of DAS solutions on the market, it’s vital to find the right option for your business — or a partner that will design the right option. A mediocre DAS will fail to deliver benefits or only leave you with moderate indoor coverage. DAS that’s optimized for your needs, however, will leverage the right technology to deliver the best possible signal per space in your building.

To help you navigate the solutions in the market, this guide walks you through:

  1. How the technology works
  2. Which types of DAS to consider
  3. What to look for in a DAS partnership

How Does DAS Technology Work?

Active, 5G-ready DAS is comprised of small antennas installed strategically throughout a venue to maximize the reception of mobile networks. These antennas are connected to radios via fiber optic and coaxial cables, which are in turn connected to a central signal source.

Together, this system creates a dedicated LTE network that connects users to major cellular carriers in your area.

Essentially, you’re building telecommunications infrastructure into the walls and ceiling of your building.

This type of true DAS is a standalone system that provides a dedicated service for the given building or company. It doesn’t boost an existing mobile network; instead, it generates a new private network leveraging signal from mobile carriers.

It’s scaled to guarantee the best mobile connectivity experience for the venue by accounting for characteristics unique to each enterprise, such as the architectural characteristics, flow of people and user profiles.

The mechanics of this type of active DAS include:

  1. A signal source, responsible for generating the signal produced by carriers/operators and received by mobile devices
  2. An interface system that spreads the signal through the coverage area
  3. Irradiation points, or antennas, that sends the signal into a particular location

Essentially, the signal source captures various LTE signals from multiple carriers. Those signals then need to be cleaned up and distributed throughout the venue, which is where the other two systems come in.

The interface system combines those signals via a single transmission path from the source to the antennas; this is a key step to ensure that LTE signal level is homogenous across different technologies and frequencies throughout the building. Last, antennas distribute the combined signal at set points.

Which Types of DAS Should You Consider?

To find a DAS that meets your needs, you need to optimize for each aspect of DAS technology, from signal capture to distribution. Perhaps most important of all is the signal source: the best distribution system can only supply the quality of signal provided by that source.

Different types of DAS vary dramatically in signal source technology, with significant consequences for signal quality, interference and network capacity. It’s more than just 4G or 5G — it’s the difference between slow, unreliable networks and lightning-fast private ones.

Passive DAS

The benefits of DAS technology, particularly those of uninterrupted signal and a high-quality private network, are only guaranteed on an active DAS system. Passive DAS falls far short of that promise.

Passive DAS systems are known by several names:

  • Off-air
  • Booster
  • Repeater
  • Donor antenna
  • BDA

Passive DAS technology appeals to unknowing customers because it’s quick to install, cheap and readily available — some units can even be purchased on Amazon. These systems seem to deliver the same service as active DAS because they pick up the LTE signal of carriers and redistribute it indoors. However, the technological approach is drastically different.

Passive DAS systems do not generate an LTE signal the way an active DAS signal source does. Instead, think of them like the WiFi booster plugs you might buy for your back room: they simply latch on to an existing signal and amplify it, including any flaws that exist within that original signal.

Imagine your building is located near restaurants and shops. During the lunch hour, when pedestrians pack the neighborhood and use mobile data, your signal speed will drop dramatically because it’s shared will all those users — the same shared-bandwidth issue you sought to escape by leaving WiFi.

Similarly, if the signal is poor and provides low-quality service for cell phone calls, there’s nothing you can do about it because it’s not your own network. It’s simply borrowed and echoed from an existing one.

Worst of all, the carriers themselves don’t approve of passive DAS. Donor antennas transmit this reflected signal back to them full of noise, so they receive a “dirty” signal; in extreme cases, carriers are known to send out teams to investigate these signals and turn them off by order of the FCC.

CBRS

Citizens Broadband Radio Service, or CBRS, is included in this list because it’s often compared to DAS services, but it’s technically not a DAS. Instead, it’s a radio frequency band made available by the U.S. government. Using an AP-like structure similar to WiFi — instead of small, distributed antennas — it also provides private LTE networks.

However, the technology has a few major drawbacks: it’s still in its early stages, it’s less scalable and it doesn’t deliver the same high-speed 5G access as active DAS.

Active DAS

Active DAS systems create a scalable, 5G-ready private network free of flaws and designed for your building. However, nuances exist within those systems.

Makes and models of DAS are often distinguished by the types of cabling used, or whether the system is digital or analog. Each type was created to address a slightly different design problem, and each of the ones listed below are investment-worthy and carrier-approved.

Here are just some of the types of active DAS on the market:

  • Enterprise C-RAN
  • CAT5e or POE-based
  • FTTE (Fiber to the Edge), using only fiber optic cables to connect the antennas
  • HFC (Hybrid Fiber-Coax), a mix of both cable type

For instance, in a typical active DAS system, the signal source and distribution systems are typically connected by fiber optic or coaxial cables, while the antennas themselves are micro mobile phone antennas hidden within the structure of the building.

Some DAS solutions also leverage small cells, which are small antennas that transmit a carrier-specific signal. A bespoke network can mix and match cabled antennas and small cells to create optimal coverage.

Designing for 5G

Truly future-proof active DAS systems are designed with 5G in mind. That doesn’t necessarily mean they’re 5G-ready immediately, as not all regions have 5G available and carriers are rolling it out on their own timelines.

Instead, DAS should be built to be easily upgradable to 5G, like a multi-layer cake with lots of features baked in, rather than a flat, “bare minimum” design. More specifically, it should be modular, fiber-based and MIMO-capable.

MIMO stands for multiple-input, multiple-output. Many DAS systems are SISO, or single-input, single-output, with only one signal path. High-quality 4G DAS uses a setup of 2×2 antennas, or 2×2 MIMO, whereas 5G will require 4×4 or 6×6 MIMO with more data streams running and more bandwidth available.

This is a dramatic increase in throughput and extra capacity — and it’s absolutely necessary for 5G. A SISO DAS will never be able to upgrade to MIMO, requiring a wholesale replacement instead. A MIMO-capable setup, even if it’s using fewer antennas, is much easier to transition.

A great way to tell if your setup is truly 5G capable is whether your signal source works with both LTE and NR. LTE signal is 4G signal, while NR or New Radio signal comprises 5G; a 5G DAS will provide both services.

What Should You Look for in a Partner?

The right technology is only half the equation. Just as important is the right partner to deploy that technology. Otherwise, your DAS may not deliver the full potential of the technology due to challenges like cost or suboptimal system design.

Here are key factors to consider when choosing a DAS partnership:

Multiple DAS Options

Avoid prospective partners that only work with one or two types of active DAS, such as only fiber-based. Otherwise, you run the risk that they’ll shoehorn the wrong type of DAS into your building.

Above all, be wary of partners that recommend passive DAS boosters as an option. Though these solutions are cheaper, they’re heavily flawed for the reasons discussed above, and partners that work with passive DAS are likely either inexperienced or overpromising.

From design shops to third-party operators to carrier, high-quality partners will be able to work with and provide several active DAS options. These providers can ensure an optimal solution that’s tailored to the needs of your building and ecosystem by considering all available options.

References and Tenure

Proven experience is important in every industry, but in DAS deployment, it’s critical. Inexperienced companies can cost significant time and money, and harm vendor or carrier relationships.

Look for companies that have been working explicitly in the DAS field for a while, not just similar telecommunications operations. General telecom companies that are new to DAS may not understand how to properly dimension and test DAS during installation.

Similarly, check whether the business has done DAS work for the wireless carriers themselves. This is a true test of experience and a major indicator of credibility.

System Warranty

High-quality partners with significant DAS experience also tend to be more willing to stand behind the quality of their work for a long period of time, where newer companies might have an abbreviated warranty.

For instance, at QMC, we monitor our DAS systems 24/7 and maintain them for the lifetime of the partnership, through every modification driven by the venue or the carrier.

Accurate Bids

Be wary of bids loaded with assumptions. Some partners will lowball, assuming that they’ll complete projects and make profits via change orders. Scrutinize the scope of work to understand whether the project as designed will actually accomplish what it needs to.

For instance, a bid that comes in significantly lower may include the assumption that a wire would go across the hallway floor, rather than through a closet. Moving that wire would add cost to the scope — but without digging into the bid, you wouldn’t realize that until everything was partly installed.

Venue Control and Financing

Until recently, active DAS was only available to larger venues, whose heavy traffic appealed to carriers. Neutral host partners broadened access, but the associated costs can be prohibitive and projects can stall. Securing funding can delay project start dates dramatically.

Ideally, aim for a partner that streamlines the funding process and puts you, the venue owner and client, in control rather than the carrier.

That’s been our goal at QMC: we’ve pioneered a venue-led model that truly democratizes DAS solution delivery. Check out this piece to learn more about this approach, based on long-term partnership and flexible financing.

Want to learn more about DAS and find the right solution for your building? Get in touch with one of our experts today.

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An Insider's Guide to Distributed Antenna Systems

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