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BDA or DAS Public Safety 700 800 900 MHz SMR Signal Enhancement

Feb 27, 2018

BDA or DAS Public Safety 700 800 900 MHz SMR Signal Enhancement

Public Safety 700 800 900 MHz SMR Signal Boosting with In-Building Bi-Directional Amplifier System (BDA) or Signal Enhancement with Distributed Antenna System (DAS).

Public Safety 700, 800, 900 MHz SMR
Bi-Directional Amplifier (BDA):

Public Safety 700, 800, 900 MHz SMR Bi-Directional Amplifier (BDA)

Public Safety 700, 800, 900 MHz SMR
Distributed Antenna System (DAS):

Public Safety 700, 800, 900 MHz SMR Distributed Antenna System (DAS)

Specialized Mobile Radio (SMR) may be an analog or digital trunked two-way radio system, operated by a service in the VHF, 220, UHF, 700, 800 or 900 MHz bands. In-building public safety radio enhancement system is becoming more crucial for many reasons. For one, major changes have occurred in land mobile radio over the last 20 years-or-so, with users migrating from UHF and VHF systems to 700, 800, and 900 MHz systems. These changes have created a different set of problems because signals with low frequency deliver better in-building penetration, meaning they are able to pass through walls and other objects with less attenuation. To combat the issue of higher frequency signals delivering poor building penetration, the use of bi-directional amplifier systems (BDA) or signal boosters and distributed antenna systems (DAS) have now become a widely used and accepted means of providing improved coverage within stadiums, tunnels, buildings, and parking garages.

Both indoor and underground amplifier systems or public safety das systems are employed by the cellular radio industry, although for different reasons. As a frequency reuse network, a cellular radio network has ability to improve both capacity and coverage by reusing frequencies. Adjacent cells are required to use different frequencies. However, when two cells are far apart it is acceptable for two cells to operate on the same frequency, providing of course that the network users' equipment and masts don't transmit with too much power.

In order to increase the number of users per square mile per megahertz, and without introducing damaging co-channel interference, the cellular operator is now required to bring cell sites closer together. The result of this close spacing is short towers, which ultimately means poor building penetration. Public safety radio amplification systems or public service BDA's cover these gaps or lapses in cellular coverage areas indoors within buildings.

Distributed Antenna Systems (DAS).

Enter the DAS cellular network enhancement technology. DAS stands for Distributed Antenna System. DAS, usually meaning "active DAS" with its more complex technology, is a viable (but more expensive) alternative to a signal booster (also referred to, as "passive DAS"). Active DAS has been developed specifically to provide full-strength signal reception in areas otherwise prone to receiving poor or even no cell phone signal. Today, DAS tech is used extensively in hospitals, hotels, and other large commercial buildings and areas like subterranean subway platforms. Emergency responder radio distributed antenna system (DAS) is a necessity in locations referred to, as congested "concrete jungles" that have wireless dead zones for public safety bands due to obstructions such as concrete and metal buildings.

Bi-Directional Amplifiers (BDA).

Emergency responder radio coverage in buildings with under 500,000 sq. ft can be effectively enhanced using bidirectional amplifier systems (BDAs) as long as there's good signal outside to inject into the building using donor antenna, then amplify with bi-directional amplifier, and then broadcast indoors using interior antennas. Bi-directional booster amplifiers are permitted by the FCC in the 700MHz, 800MHz, 900MHz and other bands, on the proviso that coverage gaps are filled by the amplifier within the FCC-licensed service contour. However, when outside the service contour, coverage cannot be extended using the amplifier. The two main categories of signal booster amplifiers are:

  • Class A: Narrowband (Channelized) Amplifiers; which the FCC has limited to output power of 37 dBm, 5 watts ERP per channel, and which have been designed to amplify just a single 25 kHz or 12.5 kHz channel.
  • Class B: Broadband Amplifiers; which are also limited to 5 watts per channel but have been designed specifically to amplify either large portions of the band – or the entire band.

In addition, the FCC governs broadband amplifiers, with Part 90.219(d) stating that broadband (Class B) signal boosters may only be used in remote areas or indoor or confined areas like underground areas, buildings, tunnels, and-so-on where interference to other users is minimal or non-existent. Because it is highly unlikely that an outdoor broadband booster amplifier would be isolated enough to not interfere with other users, you would rarely find a broadband booster amplifier being used outdoors.

Because booster amplifiers are generally installed with low antenna heights and operate at low output power they are usually used to cover either small outdoor areas of perhaps a few blocks, or indoor areas. Booster amplifiers must typically be high gain, between 70 dB and 90 dB, to be useful. Also challenging is the fact that, to avoid harmful feedback, there must be a certain degree of isolation between the donor and coverage antennas, which must be installed on the same tower or building. In order to achieve this isolation, building blockage, horizontal antenna separation, vertical antenna separation, and directional antennas are used.

A donor signal is required by booster amplifiers, and this is typically captured using a directional antenna straight from the main transmitter. But, 800 MHz interference is often caused by over-the-air boosters, and this interference can be time-consuming and difficult to track because booster amplifiers are not licensed separately.

Greater isolation can be achieved by feeding the booster amplifier with microwave radio or fibre-optic cable and, ideally, all booster amplifiers would have dedicated donor systems utilizing these technologies. However, Active DAS, which is what this dedicated donor system is known as, does cost a lot more.

Public Safety DAS Solutions.

Public safety is the key requirement during emergencies and natural disasters, and this entails enabling effective and efficient voice and data services. Lives can only be saved when first responders and victims can depend on reliable communication. Today, broadband technologies have evolved whereby wideband data transmission has been enabled and we now have the potential to dramatically improve the capabilities of communication technologies to ensure public safety.

Emergency Organizations Must be Able to Share Critical Information.

Public Safety organizations are tasked with planning for and responding to emergencies, with their job being to protect the public's well-being in cases of man-made and natural disasters. These emergency agencies include fire departments, law enforcement agencies, emergency medical services, rescue squads, and other entities which are typically the first to arrive at emergency scenes. As you can imagine, it is vitally important that emergency first responders have the ability to communicate not only amongst themselves, but also be able to share critical information which directly affects their responsibility to save lives.

The Federal Communications Commission (FCC) Is Your Communication Regulatory Body.

In United States, the FCC is the regulatory body controlling communication by satellite, wire, television, radios, and cable. It is the FCC's responsibility to ensure that, when disaster strikes, both 911 and other life-saving communication facilities remain operational. One of their major goals is to ensure an operable and interoperable PSC (Public Safety Communications) system for users of 700, 800, 900 MHz and UHF/VHF narrowband including the new FirstNet network. Due to man-made obstructions (building materials) and natural obstructions (hills, valleys, bad weather, etc.), public safety band radio signal enhancement may be required to enhance public safety band signals so first responder radios and communication devices operate properly when in the building to combat an emergency situation such as a fire.

Changing Legislation for Public Safety.

Due to ever-increasing federal, state, and local legislation requirements, Public Safety DAS has now become a priority when budgeting for major renovations and new buildings. That is why our DAS solutions have been specifically designed for public safety, ensuring they adequately fulfil the needs of any location or size.

It can be a daunting task for building operators to keep up to code because requirements and regulations are constantly being updated. In addition, these requirements can vary by location and they’re not always enforced. The IFC (International Fire Code) and NFPA (National Fire Protection Association) are the regulatory bodies who establish code for public safety wireless.

National Fire Alarm and Signalling Code (NFPA 72).

In order to meet continuously-changing emergency communications, signalling, and fire detection demands, United States trade organization known as the NFPA drafted the National Fire Alarm and Signalling Code (NFPA 72) which produces the latest safety code. This code contains requirements pertaining to mass notification systems used for terrorist events, weather emergencies, chemical, biological, and nuclear emergencies, in addition to fire alarms and other threats.

A New Benchmark for Fire Alarm Systems.

Today, we're seeing a dramatic change in the benchmark for fire alarm systems, giving designers, contractors, engineers, installers, and inspectors, rules that clearly show things as they stand today. NFPA 72 provides the most advanced requirements ever established for MNS (Mass Notification Systems), including the application, location, installation, performance, inspection, testing, and maintenance of emergency communications systems, including fire alarms.

Public Safety DAS Systems for First Responders.

Today it is a requirement of the NFPA 72 code that a Public Safety DAS system be used by first responders. DAS is still important for the day-to-day effective communication of personnel or tenants within a building. However, Public Safety DAS allows first responders to communicate effectively and efficiently during an emergency. And, in case of an outage, Public Safety DAS must have a backup. Covering areas not specifically requiring commercial wireless, like basements and stairwells, Public Service DAS must cover the entire building and be on a different spectrum than commercial wireless.

Current NFPA 72 Code Covers the Following:


    All Critical Areas: Fire pump rooms, fire command centres, elevator lobbies, exit passageways and stairs, sprinkler sectional valve locations, standpipe cabinets, and any other areas charged by the appropriate authority with jurisdiction to be areas deemed critical, must receive radio coverage over 99% floor area.


    Throughout the coverage area a minimum incoming signal strength of -95 dBm shall be provided; or alternatively, a signal strength as determined by the appropriate authority with jurisdiction.


    -95 dBm from the coverage area shall be the lowest outbound signal strength at the donor site; or alternatively, a signal strength to be determined by the appropriate authority with jurisdiction.


    In order to achieve the required coverage, structures and buildings that are unable to support the necessary coverage level must be prepared with a DAS (Distributed Antenna System) with a signal booster that is FCC-certified, or a radiating cable system, or both; or alternatively with a system that is otherwise approved.

Enterprises Now More Determined to Provide First Responders with Good Coverage.

Unfortunately, complications arise when different versions of the NFPA code are passed each year. States can endorse whichever version they feel best suits their needs, but it is not always enforced. The result is that not only does the code vary from location to location, there's no strict adherence to the code. Today, however, with the increasing incidence of emergencies, enterprises are now more determined than ever to ensure that first responders have adequate coverage. Both techniques are used - BDAs as well as DAS.

A BDA system uses donor antenna to catch outside public safety band signals and amplify those signals indoors inside buildings. If exterior signal is too weak, a DAS can also use respective cell service carrier feed for the needed carrier(s) public safety band signals to amplify their signals in large buildings so it meets the wireless signal requirements per the fire codes of the city, county, state, and federal regulations.

Today, legislation at federal, state, and local levels is increasing requirements to ensure that Public Safety DAS is taken into consideration when budgeting for major renovations or new buildings. Local code may now demand that wireless coverage be provided throughout buildings to assist first-aid responders.

Today's Public Safety DAS Solutions are Custom-Made for Your Building.

Our public safety DAS solutions for public safety band signal enhancement - both active (DAS) and passive (BDA or signal booster system) are customized specifically to meet the requirements of any location and any size. Our wireless signal enhancing system experts stay abreast of the very latest regulations and, together with our complete range of up-to-date products to enhance signals, we can meet the requirements of all authorities having jurisdiction over your building by tailoring the ideal solution for your renovation or new build.

Using our supply chain solutions and technical expertise, we can provide an efficient, effective, and quick installation of your required in-building wireless network. Meeting public safety requirements does not need to become a complex challenge, because we're here to help you find an effective solution.

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  • While I’ve heard of public safety signal boosters, I’ve never seen a diagram of how they’re set up in a building. I had an idea how they might be arranged and this confirms it for me. Looks like things are built to arrange a strong signal no matter where EMS personnel go to.

    Zach Jindrak on
  • “Just imagine If I brought a person from 1956 to 2018. What would he think?”
    I think you bring up a good point—science fiction. If a person read a lot of science fiction, they’d probably recall things like wall-size TV’s from “Fahrenheit 451” and automated cars from “Caves of Steel” (or was it “I, Robot”?). They would want to know what happened to flying cars though. I think most people would be blown away by the advances due to the Information Age. Personally, I see the Internet as being as big (or bigger) than the printing press. And picture this, computers were building size and now our cell phones are more powerful than desktops and laptops used to be not long ago. Worldwide communication made easy, unbelievable amounts of information at our fingertips (and readily available), and all of this affordable. And if your phones aren’t fast enough or you’re in a rural area, you can get cell phone boosters to power them up.

    Terry K. Simmons on
  • As for the question, “By the way, why do 4G phones consume more battery?” the answer is “more data means more problems.” 4G phones are obviously great thanks to their extra power, but the power doesn’t come from out of the ether (unless Tesla’s ideas really did work). That’s one possible reason. Another is which type of phone you have. Some 4G’s are better at conserving power than others. You can try wi-fi if you need to save power, but that’s not always an option or the best one.

    Mitch Peterson on
  • What is the difference between WiFi and MiFi connections?
    It’s a little tricky. Wi-Fi refers to the wireless standard where phones can piggyback on wireless signals from wireless routers. Mi-Fi is a trade term for an electronic device which has an internal modem and wi-fi capabilities. This device not only provides a wireless signal, but supports 3G, 4G, and LTE technology. Where a Wi-Fi signal is limited to a certain area, Mi-Fi travels with you (since the signal comes from a portable device). Does that make sense?

    Paul J. Hudson on
  • This picture shows you why these public safety devices are so important. By the way, why do 4G phones consume more battery? They seem like battery hogs.

    Elwood Thompson on
  • If you’ve read more than a couple blogs here (which provide a lot of helpful information on how to improve cell phone reception, data speeds, and reduce or eliminate dropped calls), you’ve probably heard of DAS. It’s a system found in buildings, malls, stadiums, etc. to increase cell phone signals. However, first responders need to have strong signals too, which is why BDA or DAS Public Safety systems are a must. They allow first responders to communicate with each other, even when they’re in areas of a building that normally might not get good reception. Based on what I’ve read, you not only want to have such a system in your building, but you want it installed by an expert. Don’t leave this to some fly-by-night outfit because lives could be at stake. It may sound melodramatic, but it’s true.

    Kelly Forrester on

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