Building information:
• Two building project
• Mixed-use buildings
• 295 units, ~700 occupants, and retail elements

Scope of work: Design, engineer, and install an ERRCS
Project duration: 6 months (2017-2018)

Two in one ERRCS solution

Executive Summary:

Completed in 2018, The Mountain View Greystar property features two buildings on two separate plots separated by a public alley that housed 295 units, 700 occupants, and a variety of retail spaces.

The scope of intervention required DAS Systems to design and install an ERRCS system – which accounted for two separate systems – one for each building.

While the initial assessment suggested passing an underground cable to connect both structures, the client was adamant the City of Mountain View, CA would not approve, as it involved disturbing a public road.

As such, DAS Systems leveraged its expertise to explore options with city officials and stakeholders, to solicit an ease of encroachment, allowing both buildings to run on one system.

Background:

The initial ERRCS design rendered two separate systems as a street separated both buildings.
Since all underground electrical works between the two buildings had been completed months before the intervention, receiving a permit to uncover the streetway would have been impossible without the correct arguments.

Case Evaluation:

This project presented a peculiar challenge since both buildings are considered separate plots, yet under the same project.
As such, designing a system that would work for both buildings to improve on initial and upkeep costs was paramount.
For that, ease of encroachment had to be solicited and granted by the City, which required well-founded arguments.
The case needed to serve the public interest and help ensure the safety and integrity of occupants and first responders.

Proposed Solutions:

With all the facts, documents, and extensive research, DAS Systems reached out to the City of Mountain View, CA and submitted a request to receive an ease of public encroachment. The City was presented with the current design schematics, which had a provision for a tri-wave signal (VHF 150, UHF 450, 700-800 Digital System) to provide signals for Police, Fire, and EMT agencies.
And while both buildings were separated, two donor antennas would be within 100ft of each other. These antennas are programmed to send and receive the actual signal from the City’s first response agencies, which created a problem.

“There is a potential that this proximity can cause oscillation or looping.”

This effectively meant that the signal could be potentially sent and received from one building to another within that 100ft range.

This reproduces the signal effectively, creating a loop that would prevent the signal from reaching the respective agency’s radio receivers.

The arguments were compelling enough for the City to grant the easement encroachment, which ended up saving the up-front client costs on the system itself and maintenance costs over the life of the ERRCS.

Once approved, DAS System moved forward and proceeded to install all of the equipment in the first building. A fiber optic cable was funneled through the alleyway under the joint trench conduit, into a fiber-fed remote optical unit (repeater) that reproduced the signal inside the building two.

Other challenges:

Among the challenges faced during the intervention, track, logistics, and time constraints
had to be met. As there was a delivery date that had to be honored, and track slowed
operations while supply chain delays became a concern, a fast solution had to be reached.
The system chosen was also a three-frequency system which brings its own set of unique challenges:

• Only one manufacturer, Comprod, at the time produced a tri-band antenna.
  There were manufacturing delays due to a backlog, and DAS Systems had an existing order for an ongoing project.

The team decided to use the antennas from the ongoing project to meet the upcoming deadline,
particularly as the antennas were hard to get, including the passive antennas.

• The company also produced the BDA, or repeater, which is the most expensive component, as well as duplexers and diplexers that combined multiple frequencies (700-800, 150, 450) that met the specifications, albeit at 10x the price of a conventional unit.

This would effectively solve the three-frequency issue as it relates to the passive components of combining those signals into one cable, which was distributed through nearly 100 antennas over both buildings.

 As the construction happens, DAS Systems assesses the accuracy of their predictive model on the heatmap. Engineers then interface back with IBWAVE and correct for weaker areas based on the finding of each phase vs. the predictive model.

More value was eventually driven out, given that testing revealed the need for fewer antennas, which essentially decreased the cost of the Annual Testing and Recertification, or ATR. Since there are fewer antennas that need to be tested, reduced chances for RF leaking, and a more negligible risk of components failing

This is pivotal, as the idea of an ERRCS is to propagate an external signal into the building. However, that signal cannot go back outside. If it does, it will create another oscillation loop, which means that the signal should not permeate and must stay inside.

Since the system is also smaller, components do not require as much amplification, which improves the system’s energy efficiency. This also ensures a longer lifespan of components, particularly BDAs, as they are not being utilized at full power.

Conclusions:

Leveraging experience and know-how can go a long way, particularly in an industry where going the extra mile can reflect on lifelong safety and cost efficiency.

As such, we always encourage our partners to reach out to us, to get in early and often, whether in pre-construction consulting or during official talks with the city.

Communication is key. So, communicate, coordinate, and cooperate with all stakeholders, by asking questions and avoiding assumptions.

Most importantly, engage DAS Systems early in the conceptual drawings and design to let us understand the needs and allow us to assess elements of public interest.