Basic Emergency Responder Radio Coverage Systems Principles
By Josh Helling
Tuesday, March 29, 2022 | Comments
The various codes and guidelines for ERRCS came as a direct result of the tragedy of September 11. The complexity of the building systems and type of construction affected first responder communication efforts. Firefighters and police could not communicate with each other or dispatch, directly resulting in loss of life.

Radio telecommunications networks are vital to first responder operations. Radio frequencies are transmitted from a source (mobile or fixed) over fiber optic and coax to antennas at donor sites at various locations around a geographic area. Different frequency bands like VHF/ UHF/700 MHz/800 MHz have various capabilities and propagation characteristics.

Suppose you are in your car listening to your favorite radio station. As it starts to fade out, you pull forward a short distance, and the radio gets better reception. That is a wave signal, which travels in the atmosphere and can be deflected or absorbed by structures resulting in poor communication. Signal wavelengths have a high impact on propagation characteristics when penetrating buildings.

Buildings new and old of significant size vary in construction type. Wood frame structures (type III type V), concrete (type I), stone and brick all have different fire burn ratings (the time it takes fire to burn through a wall) and all materials have a varying effect on propagation factors of signal in a building. For example, modern double pane glass (lowE) can seal a building off from the outside world, making it a dangerous situation for first responders.

Emergency responder radio coverage systems (ERRCS) provide communication radio to radio in a building and radio to dispatch. ERRCS engineering designers augment coverage in buildings by using sophisticated software to design in a 2D and 3D environment. Engineers assign RF loss values to walls and ceilings of the building utilizing PDF images of construction drawings. They can place coverage antennas at locations through the virtual floor plan before it's ever constructed.

An RF coverage study should be obtained by using a spectrum analyzer that measures the signal strength of the construction site. Not every property needs to have a system installed. The signal strength value found is inputted into the software. The engineering software shows projected signal strengths in the building to find coverage gaps and adjust.

The job of the ERRCS designer is to interpret the collected baseline reading data and understand RF behavior in a building. They must have ERRCS code knowledge and strong RF knowledge/architecture and construction base to ensure proper function and integration.

ERRCS architecture looks like illustrations A and B above. A directional antenna is pointed at a donor site. The signal is brought down the building into a head-end bidirectional amplifier (BDA). The amplifier repeats the signal over coax into coverage antennas in a building.

Code knowledge of ERRCS varies from jurisdiction to jurisdiction. Some authorities having jurisdiction (AHJ) are well versed; some may be new. The AHJ can require coverage in buildings new and old. New building construction has several codes and standards, each with its own year cycle, providing AHJs guidelines they can enforce for ERRCS. AHJs can create a technical services bulletin from the various codes and standards to suit how they see best fits their community operation needs.

The codes and standards stipulate requirements for technical design criteria, including frequency strength and delivered audio quality (DAQ) requirements, battery backup run times, alarm annunciation with fire panel and pathway survivability. The codes stipulate that coverage must be provided in buildings to emergency responders. It is the responsibility of the building owner to pay for the cost and provide coverage.

Some of the things that AHJs look at in new buildings include:
• Frequency required: All jurisdictions should consult with the FCC frequency license holder as required by federal regulations. Permission to rebroadcast licensed frequency must be obtained. BDAs must be registered with the FCC per article 90 guidelines.
• Permitting required to ensure proper installation and inspection: Since there are many code cycles and options for AHJs to choose from, enforced codes must be obtained by request from the AHJ. Specified testing can be required.
• Pathway survivability: Key portions of a system should be protected in the event of fire. If infrastructure is destroyed in one area, it should not have an adverse effect on the entire system. Different levels of pathway survivability are outlined in code. There exist products by multiple manufactures that meet UL 2196 burn criteria, which mandates the ability to withstand 1,850 degrees for two hours. In these protected areas a fire can burn directly under a cable run for a period of up to no less than two hours and still function.
• Battery backup: Each active component in an ERRCS is required to have a battery backup to keep equipment operational for a period of 12 to 24 hours (this is up to the AHJ). In the event of a fire, most fire departments practice removal of electrical meters to prevent added electrical hazards from fire and fire hoses. Once power is disconnected, these systems will continue to function by use of batteries in rated enclosures.
• Interface with fire panel: Equipment should be tied into a fire alarm system to annunciate supervisory signals from the distributed antenna system (DAS) equipment. This lets firefighters know what the operational status of an ERRCS is upon entry of a building. A dedicated annunciator can also be required to allow for facilities that do not have fire alarm systems installed.
• NEMA 4 enclosures: All active system components are housed within NEMA 4 or 4X or UL type 5 enclosures. In an active fire situation, the equipment can take the water from a sprinkler system or fire hose and still function.
• Rated rooms for vital equipment: Head end (HE) and remote locations are required to be in rooms rated no less than two hours fire protection. This is to ensure function at a minimum of two hours in a major fire event.

• Acceptance: Buildings are tested by use of a spectrum analyzer and readings are collected in the form of a 20 parcel grid and recorded in decibels (dB). Each floor of a structure is broken into 20 even parcels. Readings are taken from the center of this general area and recorded on the floorplan. Code stipulates that radio coverage must meet -95 dB in 95% of the building. -95 dB is the minimum signal strength required. Discernable audio quality readings must be collected that illustrate the clearness of radio speech. Technicians talk in and out of the building and back to dispatch. Readings are given a value of one to five, with one being poor and five being excellent. Readings of 3.4 or less constitute a failure. See the chart below. Areas of egress and vital areas as determined by the AHJ must have zero failures to have a building pass acceptance. Fire pump rooms/fire command centers and stairwells are examples of these areas.

Existing Buildings
Existing buildings can be augmented as well. This is important to some of the older critical public buildings made of stone. As historic and beautiful as they are, these facilities present a challenge of their own. Stone and concrete structures absorb RF, causing coverage issues.

Existing buildings of a certain age have wired phone communications for firefighters. Modern emergency breathing apparatus have radio microphones built in. Firefighters will not remove their masks to use conventional phones in a smoke-filled environment.

A coverage study should be collected to see native coverage. This collection is used to identify and engineer solutions for adequate coverage. Once the code criteria is ascertained, a custom-designed system can be engineered to accommodate its unique characteristics. Cost of surveys is nominal, with the cost varying slightly due to size of a structure and geographic area. Survey cost can be deducted from contract cost should a system need to be installed.

The cost of these systems ranges significantly based on the frequencies involved and the size of the building. Loss factors require the use of fiber optic cables and remotes in some designs to augment coverage. Remotes that require AC power convert light signals into RF to cover larger areas.

Every system installed in a jurisdiction has the chance of raising a network's noise floor. The increase, however small, will be felt increasingly over time and can affect communications in a jurisdiction. ERRCS must be degraded to barely passing to lessen the impact of the volume of systems being installed.

ERRCS codes and engineering can be challenging to navigate without the experience of a well-integrated team. It is crucial to partner with a team that has knowledge of the codes, RF engineering experts, and an installation team well versed in troubleshooting for the various types of construction and survivability. Without proper testing and understanding of what is required before a system is designed, building owners risk overdoing it. Most buildings do not need full coverage; they need only partial coverage of certain areas to meet the code.


Josh Helling is executive senior vice president and general manager of LEAF Communications.



 
 
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Comments
On 4/16/22, Tom Warfield said:
Very nicely written. I do have a a couple of suggestions
1. Signal strength is measured in dBm not dB
2. ERRCS must be degraded to barely passing I don t like the word degraded as actually the system is being optimized to the minimum power and gain values to lessen .....

On 4/1/22, Chris Woodworth said:
Great article Josh this tells the story in a very informative and easy to understand fashion. Thanks.


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