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Understanding Distributed Antenna Systems

Selecting The Optimal DAS Solution

What is Distributed Antenna System (DAS)?

A Distributed Antenna System (DAS) is a network of antennas across your buildings and facilities that enhance your ability to transmit radio and cellular signals within outdoor and indoor environments. Most often these systems are used to amplify in-building wireless coverage, though there are numerous outdoor applications as well.

Signals travel from exterior antennas along various cable types to specialized equipment like bi-directional amplifiers (BDA), remote radio units (RRU), head-end units (HEU), baseband units (BBU), backup batteries, and ceiling or wall mounted antennas. The quantity and types of cables and equipment utilized in your DAS will vary based on the type of DAS system you select to suit your facilities needs and your organizations budgetary requirements.

Public Safety vs. Cellular DAS Solutions

Public Safety DAS

Unlike Cellular DAS options, having a properly configured Public Safety DAS (PSR/PSC) installed inside your buildings is a legal requirement in most jurisdictions. These systems boost radio and cellular frequencies in the 700 to 800MHz range. The 700 to 800Mhz range is used exclusively by first responder agencies (EMS, Police, Fire) and building codes refer to the DAS solutions that boost them as emergency responder radio coverage systems (ERRCS).

Cellular DAS

Unlike Public Safety DAS systems, which are only built to enhance signal coverage for a singular specific frequency range, Cellular DAS can be configured and designed to boost signal coverage for multiple frequency bands, like those used by major cellular carriers (like Verizon, T-Mobile, AT&T) and those used in private cellular networking (like CBRS). The greater the number of frequencies your system supports the more complex it will be to design and install.

Can you upgrade a Public Safety DAS to be a Cellular DAS?

Yes. But doing so can be cost prohibitive. Part of the process of installing a DAS system is evaluating your coverage needs and designing a system that meets or exceeds them. Designing a Public Safety DAS is considerably less complex than designing a Cellular DAS system. For starters, Cellular DAS systems require antenna patterns to be tighter in order to provide ubiquitous coverage for those additional frequencies. It makes the system more expensive because there is more to the system – more antennas, cabling, tappers, splitters, connectors, and additional associated labor. But the real additional expense comes from not planning for an upgrade ahead of time. If you see a future need to upgrade your Public Safety DAS to a Cellular DAS, it can make the process more affordable if you include this goal in the initial planning and design phases. Doing so allows your systems integrator to survey your site for not only the system you need today, but also for the one you need tomorrow. This lets them properly map out your installation so that it leaves room for future upgrades. Otherwise, your site will need to be surveyed again, and your system redesigned to accommodate the systems expansion. Its always best to plan ahead.

Expandable Public Safety DAS Solutions

As mentioned earlier, if your organization determines that there will be a future need for Cellular DAS within your facility it generally makes the installation of your Public Safety DAS more expensive. This is especially true for buildings and facilities that do not utilize drop ceilings. If your facility has drywall ceilings (or those of another solid material), it becomes impractical to plan to cut into those materials later to install all the components necessary to add the additional antennas.

Those extra components we mentioned before — cables, tappers, splitters, connectors — all need to be in place ahead of time to optimize their placement in anticipation of the later upgrade. At the same time, this minimizes the future expense of upgrading, because everything is optimized and where it needs to be allowing for a much faster installation process.

Future-Proof DAS Installations

Typical Cellular DAS installations include frequency ranges up to near 2200 MHz. To include a greater range of frequencies in preparation for a 5G future, requires an even more complex installation, with even greater costs. While many may shy away from the idea of extending their budget even further, it is important to note once again that planning for the future is always the better investment.

Major carriers 3G networks are already going on-line and while 4G has no anticipated sunset date, it is a certainty that in time, it will also make the move towards obsolesce. Planning for 5G sets your buildings up to have a reliable communications infrastructure for the next 20 years or more.

Antenna Density by DAS Solution

Lower frequencies travel farther than higher frequencies, as such Public Safety DAS installations require the fewest number of antennas. A standard Cellular DAS installation requires more antennas configured to higher 4G LTE frequencies. While a “future-proof” Cellular DAS requires even more antennas to cover PLTE, CBRS, and 5G frequencies.

To loosely illustrate the concept, we’ve provided three drawings below.*

Is there a difference between an indoor and outdoor DAS?

Yes and no. Indoor DAS (iDAS) and Outdoor DAS (oDAS) systems generally use the same components. The major difierence is in the design of the system and its installation. Outdoor environments have additional considerations – specifically things like the environment. The antennas and other components used in an oDAS must be hardened against weather extremes like heat, cold, and rain. iDAS systems are generally shielded from such extremes, as they are located within your facility.

What types of DAS systems do you offer?

As already mentioned, we can install Public Safety or Cellular DAS systems for indoor and outdoor environments. But those designations only specify the types of frequencies the system is meant to enhance. There are four types of DAS systems with varying equipment requirements and associated costs — Passive DAS, Active DAS, Hybrid DAS, and Digital DAS. Of those four, we currently offer the first three as options to our clients.

Passive DAS

Passive DAS solutions are typically the most affordable. They have the lowest maintenance needs and are relatively easy to install. However, they are not the strongest or most effective. Passive generally means that the system isn’t powered and utilizes primarily coaxial cables to function, which can produce weaker connections as signal strength is lost over significant distances. Passive systems are best for Public Safety DAS installations at small to medium sized buildings and facilities.

Active DAS

Passive DAS solutions are typically the most affordable. They have the lowest maintenance needs and are relatively easy to install. However, they are not the strongest or most effective. Passive generally means that the system isn’t powered and utilizes primarily coaxial cables to function, which can produce weaker connections as signal strength is lost over significant distances. Passive systems are best for Public Safety DAS installations at small to medium sized buildings and facilities.

Hybrid DAS

A Hybrid DAS is a mix of Passive and Active DAS. With a Hybrid DAS, some components are separated from the main antenna, which allows our team to use a blend of fiber optic and coaxial cables and powered and unpowered equipment. This system type is more powerful than a Passive DAS but less powerful than an Active DAS – as such is more middle of the road cost-wise. But only a site survey can determine if a Hybrid DAS will meet your needs and budgetary requirements

 

How can MCA help us with our cellular coverage enhancement needs?

Mobile Communications America is a Tier 1 National Integrator of Carrier-Grade DAS Solutions. We provide services every step of the way — including consultation, site surveys, iBwave design, solution engineering, system testing, and on-site installation. And with our equipment service agreements you can hire us to perform ongoing system monitoring and maintenance to ensure your signal levels stay consistent and strong

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