When contractors encounter RFPs that include requirements for Emergency Responder Communications Enhancement Systems with a Distributed Antenna System (DAS) for public safety, it is crucial for them to collaborate with experienced DAS integrators such as MCA's In-Building Wireless Solutions (IWS) team. These integrators possess comprehensive knowledge of project requirements and have the capability to meet budget and service-level expectations.
What Is Public Safety DAS?
Public safety DAS, like cellular distributed antenna systems, enhances and expands RF coverage within a building. However, it differs from cellular DAS as it is specifically intended for first responders' use. When firefighters, police officers, and EMTs are on-site for emergencies, public safety DAS guarantees robust and dependable coverage for their communication devices throughout the entire area.
Requirements, Costs, and Testing
Design Requirements: MCA's IWS team ensures that the system design meets both the property owners' requirements and the Authority Having Jurisdiction (AHJ) regulations. Our team's expertise lies in using industry-standard iBwave software, which requires certification and training for accurate DAS designs.
Estimated Cost: By leveraging iBwave software, contractors can provide precise cost estimates instead of relying solely on square footage. MCA's team can generate comprehensive quotes that include material, equipment, and labor costs based on the completed design.
Coverage Testing: To ensure accuracy, coverage testing is crucial. This pretesting stage allows for more precise designs based on actual signal strength variations within the building. Ideally conducted when construction reaches around 80% completion, coverage testing involves physically inspecting each floor and using frequency testers to measure signal strength. Depending on local requirements, each floor may be divided into grids. If more than two signal failures occur per floor, remedial measures may be necessary. Additionally, structures like basements, parking garages, or buildings with LEED high-efficiency glass often require a DAS.
Key Terms
Authority Having Jurisdiction
Authority Having Jurisdiction (AHJ) refers to the responsible agency, office, or individual, such as the fire marshal, tasked with enforcing compliance with various IFC and NFPA codes. While most jurisdictions align their requirements with these codes, there may be variations at the city, county, and state levels.
Examples of discrepancies across jurisdictions include:
- First Responder Frequencies: In certain municipalities, first responders operate on distinct frequency bands, necessitating a DAS configuration that amplifies multiple bands accordingly.
- Backup Battery Life: Requirements for backup battery duration range from 12 to 24 hours, and the need for backup batteries may differ if a 24-hour generator is already in place.
- Amplifiers and Cable: Equipment must be housed in NEMA 4-rated cabinets to withstand damage from liquids and corrosive substances. Vertical cables must be routed through a two-hour fire-resistant space, and in some regions, horizontal cables may also require a two-hour fire-resistant space, which can significantly impact installation costs.
To ensure compliance with AHJ regulations and mitigate the need for future renovations or remediations, MCA's IWS team strictly adheres to the entire fire code rather than solely relying on the local fire marshal's interpretation.
Radio System Owner
During DAS implementation, authorization from Radio System Owners (RSO) is necessary to inform them of any DAS rebroadcasting of their signals. In case signal interference needs to be resolved, the RSOs must be aware of the location of every system within the building.
Backbone Infrastructure
DAS installations require specific half-inch coaxial cables that differ from standard electrical or Wi-Fi coax cables. These rigid cables demand careful handling. Even minor oversights like cable bends or kinks can significantly degrade DAS performance, requiring additional labor for remediation. These seemingly insignificant issues could lead to system failure during emergencies, rendering it ineffective and potentially endangering lives.
Design for Specific Building Needs
Meeting the needs of First Responders and ensuring compliance with IFC and NFPA codes requires deploying the appropriate type of DAS based on the building structure and size.
Bi-directional Amplifiers (BDA)
BDAs serve as the interface for signal transmission in and out of the DAS. However, not all BDAs can handle all requirements and frequencies. Our IWS team selects the suitable equipment to meet the system's needs and requirements.
Channelized System
For public safety DAS, channelized systems are typically the preferred choice. They amplify only the necessary channels, resulting in stronger, reliable signals with superior sound quality and less interference. While it may be a slightly more expensive option, it provides greater reliability.
Fiber DAS and Active Systems
For buildings over 250,000 square feet or campus environments, fiber optic cable is recommended over coaxial cable due to its lower signal loss. Fiber backbones are used throughout the DAS to ensure optimal signal strength. At the end of the run, the signal is converted back into radio frequency and transmitted through the antenna network via the fiber remote unit.
Separate Cellular DAS
If a building requires both a cellular DAS and a public safety DAS, it is crucial to keep these systems separate. This separation avoids the risk of competing or interfering signal sources on the first responder system, ensuring its proper functionality during emergencies.
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