Distributed antenna systems (DAS)

A distributed antenna system (DAS) brings radio signals inside a building that the building itself blocks, by feeding them through cabling to a network of small antennas. We design and build DAS for cellular coverage and for the in-building public safety radio coverage that many fire authorities now require, starting with a survey of what signal you have and why you need more.

Modern buildings are hard on radio. Low-emissivity glass, concrete, steel framing and below-grade levels all weaken signals from outside, so tenants lose calls in the core, parking levels go dead and firefighters' radios may not reach the street from a stairwell. A DAS solves this by capturing a signal at one point and redistributing it where it is needed. It is a different system from WiFi: a DAS carries carrier cellular and public safety radio, while WiFi carries your own data network, and many buildings need both.

What we design and build

Cellular DAS for tenant and visitor coverage, fed from an off-air donor antenna or from a signal source provided by the carriers.
Public safety DAS and bi-directional amplifier (BDA) systems for emergency responder radio coverage, including the monitoring and backup power that fire authorities typically expect.
Passive, active and hybrid architectures, chosen for the building's size, the number of services and the budget.
Donor antenna locations and alignment, head-end rooms, fibre and coaxial risers and horizontal cabling.
Antenna layouts for each floor, stairwells, elevators, parking levels and other critical areas.
Pathways, fire stopping, grounding and power coordinated with the electrical and structured cabling design.

Every DAS has the same basic parts. A signal source, either a donor antenna on the roof pointed at a carrier or radio site, or equipment the carrier installs on site, feeds a head end. The head end amplifies and conditions the signal and sends it out through a riser, as radio frequency over coaxial cable or converted to light over fibre, to remote units and antennas on each floor. Signals from handsets and radios travel the same path in reverse.

How a DAS is put together. The donor antenna captures the signal from outside and sends it down to the head end, which distributes it up a fibre riser to a remote unit on each floor. Short coaxial runs connect each remote unit to ceiling antennas. Handset and radio signals return along the same path.

Carriers and fire authorities have a say. A cellular DAS retransmits the carriers' licensed spectrum, so each carrier must agree before it is connected, and equipment must be certified for use in Canada. Public safety systems are reviewed and accepted by the local fire authority, whose requirements vary. We build that coordination into the schedule from the start.

How it works

Why and what. We find out what problem you are solving: tenant complaints, a lease requirement, a fire authority order or a new building where the requirement is known in advance. That decides which services and frequencies the system has to carry.
Survey. We measure existing signal levels and quality through the building, including stairwells, elevators, parking and mechanical spaces, check potential donor locations on the roof and look at riser, ceiling and room space.
Design. We prepare a predictive coverage model, a link budget, the antenna layout for each floor, the riser and head-end design, and power, grounding and pathway details. Drawings for permit are sealed by a licensed professional engineer where required.
Approvals. We coordinate with the carriers for cellular service and with the fire authority for public safety coverage, and prepare the submissions they ask for.
Build. Cabling, antennas and head-end equipment are installed by licensed electrical contractors and qualified low-voltage installers under permit, with fire stopping and labelling checked as the work goes in.
Verify and hand over. We test coverage across the building against the design criteria and any acceptance test the fire authority requires, then hand over test results, as-built drawings and a maintenance and annual testing plan.

Antenna placement is where coverage is won or lost. Antennas usually sit in the ceiling, spaced so their coverage areas overlap, with extra attention to the core, stairwells and the edges of the floor plate, where the inside signal must dominate any leakage from outside.

Overlapping coverage on a typical floor. Ceiling antennas fed from a remote unit in the core are spaced so their coverage areas overlap, leaving no gaps between them. Stairwells often need their own antennas, because public safety coverage there is usually treated as critical.

What to have ready

Floor plans and reflected ceiling plans, ideally in CAD, and riser diagrams.
Any fire authority correspondence or orders about radio coverage.
Tenant complaints or carrier coverage reports that describe where service fails.
Access to the roof, risers, electrical and telecom rooms, stairwells and parking levels.
Your plans for the building: renovations, new tenants or envelope work that could change coverage.

What you get

For a design, a drawing and specification package including the coverage model, antenna layouts, riser and head-end design and a bill of materials that contractors can price. For a build, a working system with coverage test results, as-built drawings, equipment and cabling records, and an annual testing and maintenance plan. Where public safety coverage is involved, the documents are prepared with the fire authority's acceptance process in mind.

Who it's for

Owners and developers of office towers, hospitals, campuses, residential high-rises and buildings with below-grade parking.
Property managers dealing with tenant complaints about cellular service.
Owners who have received a requirement or order from the fire authority about responder radio coverage.
Design and construction teams who want DAS coordinated with the electrical, cabling and fire alarm design.

For background, read what is a distributed antenna system?, in-building public safety radio coverage and passive, active and hybrid DAS. If your problem is the building's own data network rather than carrier service, see our WiFi design and build service.

Common questions

Can we just install a signal booster?

Small consumer boosters exist, but in a commercial building a booster that is not properly designed, certified and authorised can interfere with the carrier network and with public safety radio. A designed system, agreed with the carriers, avoids those problems.

Will one DAS carry both cellular and public safety radio?

Sometimes. Some designs share antennas and cabling, but many fire authorities expect public safety equipment to meet requirements for survivability, backup power and monitoring that a commercial system does not, so they are often built separately or with dedicated components.

Does a DAS need maintenance after it is accepted?

Yes. Equipment fails, batteries age, and renovations, new partitions or a change of tenant can move the coverage. Public safety systems are commonly retested on a regular schedule set by the fire authority, and cellular systems benefit from periodic checks and monitoring alarms that someone actually watches.

Who pays for a cellular DAS?

It varies. Arrangements between building owners and carriers differ by building and by carrier, so it is worth raising early. We can help you understand the options before design starts.