Mission Critical - Public Safety In-Building Communication Systems | Blog

Mission Critical - Public Safety In-Building Communication Systems

Posted 01/11/2021 by Bird RF Engineer

When we talk about public safety, we often use the term “Mission Critical.”  An application or system is defined as mission critical if operation cannot continue without it.  In the commercial world, when operations stop, business is lost.  However, in public safety, if operations stop, it means someone could get injured, or worse.

First responders rely heavily on the use of their radios to communicate – it is imperative that they can communicate clearly and reliably to do their job, making it “Mission Critical.”  First responders can find themselves in a number of different environments that might make radio communications difficult – basements, tunnels, and high rises, just to name a few.

The Challenge
Emergencies can happen anywhere at any time.  The challenge is to find a solution for maintaining communication in these difficult environments.  To add complexity to the problem, these solutions need to work for any agency that could possibly enter the building and needs to be able to communicate inside.  And each of these agencies uses different frequencies for communication and may even operate on different frequency bands.   A local fire department may be operating on an analog VHF network, while the Police Department may be operating on an 800MHz digital system.  But they all need to be confident in their ability to communicate.

In-Building Technology for Public Safety
The solution to the challenge is to find a way to bring in the signals from outside the building, and vice versa.  And in cases of buildings with coverage holes, we need to bring the signals to the hard-to-reach places.  All the while, we need to make sure that we’re not impacting the communications outside of the building.  With this in mind, most applications can benefit from a Bi-Directional Amplifier (BDA) and a Distributed Antenna System (DAS.) 

Bi-Directional Amplifiers
Signal boosters or BDAs are amplifier systems that are designed to boost downlink into the building and uplink back to a remote base station, while filtering out undesired signals for optimal performance. These BDAs can either pass a large band of frequencies (FCC Class B) or can pass individual channels (FCC Class A). 

Unlike their consumer-grade relatives, public safety signal boosters must be designed for the extreme conditions common in times of emergency. They are available in a variety of enclosures designed to handle these conditions (such as watertight NEMA 4 enclosures) and are designed to not shut down in the event of high temperatures or power surges and interruptions.

Since mis-configured amplifiers can cause interference for other forms of communication, the FCC limits the use of BDA’s to frequencies in which a licensee is authorized for use. The public safety agencies approve a company to operate a signal booster on public access channels through the enactment of an ordinance or via site visit to inspect their specific requirements.

*National Electrical Manufacturers Association

Distributed Antenna Systems (DAS)
A Distributed Antenna System is a network of cables and antennas configured to distribute the signals from the BDA evenly throughout the building. This is usually accomplished through the use of multiple antennas or radiating cable (also known as leaky coaxial cable.) When combined with a BDA, DAS is the best option for enabling capacity and coverage inside dense infrastructures, such as shopping malls, medical centers, and high rise buildings. In addition to the standard coaxial cable distribution, DAS can also use a fiber-optic backbone to distribute signals.  This fiber-optic option provides a lower loss solution for larger venues or more complex systems like college campuses, as fiber-optics can extend out to over 10 miles before it impacts system performance.

Ordinances and Codes
Many local governments have enacted or are considering the enactment of ordinances and building codes which require a mandatory level of public safety in-building communications coverage and reliability.  In recent years the National Fire Protection Association (NFPA) and the International Code Council (ICC) have developed national building codes focused on ensuring this coverage and reliability. As these national codes are adopted across the country by different local governments, they drive a growing mandate for emergency responder radio coverage. This mandate will further necessitate the use of public safety BDAs and DAS. 

To Summarize… In an emergency situation, it is imperative that first responders be able to communicate quickly and clearly - the safety of the public, as well as the men and women who serve, lie in the balance.  BDAs and DAS ensure that they’re heard, loud and clear.