Five Considerations for Defining DAS Requirements

by Matthew Schwartz, Director of Technology and Engineering

Unreliable mobile communications is a growing problem for today’s businesses.  Whether it’s our mobile devices or the IoT devices that gather data and operate the machines that surround us, we are dependent on connectivity.  Dropped calls and no availability to data services including email and other communications platforms results in decreased productivity and lost revenue.  Compounding this issue, new construction practices, including low-e glass and super-insulated structures are making it more difficult for signal to penetrate into buildings.

The solution to this challenge is a Distributed Antenna System (or DAS) which allows occupants and devices located in a building to connect to their wireless carrier of choice at all locations in the building.

Any organization in the market for a DAS should purchase the system needed to fulfill the requirements of the business’s objectives.  A DAS can be designed to support differing carriers, varying occupancy loads, any size of building, and different bandwidth requirements.

So how to determine what you need?

Generally, a fully-featured DAS that supports all carriers on all frequencies is likely beyond the requirements for most organizations.  Arguably, the most important requirement is which carriers are required to safely operate equipment in the facility and allow staff to effectively communicate.

1.      Identify carrier requirements.

A survey of cellular connected devices in the facility should be performed to catalog the communications vendor for all equipment.  This should be all-inclusive, from vending machines to IoT devices.  An investigation of corporate cellular plans is also necessary to understand the mobile dependencies of staff.

2.      Determine peak load.

A DAS, properly designed and implemented, should be minimally constructed to handle peak load.  Defined as the maximum quantity of end users simultaneously connected to the DAS, this includes not only staff and equipment but also visitors to the building.  It is important to understand that voice calls, although absolutely critical, represent only a small portion of the traffic on a DAS.  Data usage dominates bandwidth requirements.

3.      Assess carrier “macro” signal strength.

DAS deployments should begin with an assessment of the carrier signal, both in and out of the facility.  A measurement of “macro” or tower signal both inside and outside the building is necessary to understand what signal is available to rebroadcast inside the building.  DAS contractors, and their RF engineering teams, are unable to produce a valid recommendation without first measuring the existing “macro.”

4.      Recognize coverage areas.  

It may not be important to equally weight all areas of the building when considering DAS.  Likewise, cellular coverage in some auxiliary areas may be critical to the business that operate in them.  For instance, businesses that cater to on-site clients should consider waiting rooms and conference spaces as areas of primary concern.  Parking structures are notoriously poor areas of cellular coverage making it impossible to transact business during transit.

5.      Repurpose legacy DAS systems and retransmission agreements.

During a survey of the facility, an existing legacy DAS may be discovered.  Generally, these systems were financed and installed by a carrier, and deployed to support only their services.  Part of the discovery phase of the project should consider legacy cabling for reuse.  If an existing system is found, there will almost certainly be a complementary retransmission agreement in place.  This legal document notifies the FCC that the carrier is rebroadcasting signal from the “macro” tower from the local DAS; it is required to operate a DAS.

These five considerations inform the Owner’s Project Requirements, and ultimately the success of the project as a whole.  Parallel’s approach to any engagement is to solve the point problem presented by the client.  In the case of unreliable mobile communications, a scalable DAS architecture is certainly the solution.

As Director of Technology and Engineering Matthew leads the company’s new Emerging Business unit which focuses on the integration of building technology platforms including distributed antenna systems (DAS), network infrastructure, physical security, building automation, and energy management. Schwartz joined Parallel Technologies in 2013 after owning Zephyr Controls, where he contracted, designed, installed and serviced technology infrastructure for commercial and residential buildings. Earlier in his career, he worked as a research associate at the University of New Mexico in the Robotics Lab and was an engineer with Hypertect, which specializes in HVAC for data centers. Schwartz holds a bachelor of science degree in mechanical engineering from Carnegie-Mellon University and a master’s degree in mechanical engineering from University of New Mexico. He can be reached at mschwartz@ptnet.com

Eva Keiser