In-Building Public Safety Radio Coverage Testing

Cleaned Lesson Transcript / Study Notes

This lesson explains the major concerns, testing stages, code expectations, network technologies, channel grouping, floor plan setup, measurements, and best practices for in-building Emergency Responder Radio Coverage Systems, also known as ERCES.

1. Testing Concerns for Organizations

Where an in-building ERCES is used, the system design must be approved by:

• AHJ — Authority Having Jurisdiction
• Frequency license holder — also known as the donor agency or radio shop

There are two primary concerns:

AHJ Concern

The AHJ, typically the fire marshal, is mainly concerned with first responder safety.

Their primary question is:

Can first responders communicate reliably inside the building?

Coverage inside the building is normally the AHJ’s focus.

Frequency License Holder Concern

The donor agency or frequency license holder is mainly concerned with the use of their licensed frequencies.

Their primary questions are:

• Does the system work properly on their frequencies?
• Is the in-building system causing harm to the macro network?
• Is the system creating uplink noise?
• Has the system been approved for retransmission?

Under FCC 90.219, a signal booster cannot be operated without the express consent of the licensee.

These approvals are commonly handled through written retransmission agreements.

2. When to Test

Testing can occur at multiple stages of the project.

Each stage serves a different purpose.

Baseline Coverage Test

The baseline test is usually submitted to the AHJ to determine whether an in-building system is needed.

It can show either:

• Coverage is adequate without an enhancement system, or
• Coverage is not adequate and an ERCES/BDA system is required

A baseline test can be performed during different construction stages, but it is most meaningful at substantial completion.

Early testing may provide guidance, but it may not represent final conditions.

Early Construction Testing

Testing can be done before construction is complete to estimate whether the building may need a system.

This may include testing during:

• Greenfield stage
• Before windows are installed
• Before walls are complete
• Before interior materials are installed

Modern materials, especially low-E glass and dense construction materials, can significantly affect radio signal penetration.

Early testing can help avoid the higher cost of installing an ERCES after the building is complete.

System Design and Approval

If the baseline test fails, the enhancement system must be designed and submitted for approval.

This includes review by:

• AHJ
• Radio system owner
• Frequency license holder

The design review confirms code compliance and verifies that the system will not negatively affect the macro network.

Phase One Testing

During installation, much of the system can be tested using test channels.

This may include:

• Cable installation
• Antenna installation
• BDA mounting
• Cable sweeps
• CW testing
• Signal generator testing
• Other installation verification

These test channels are not the live public safety radio system channels.

They are used to verify the system before live operation.

Turn-On Coordination

After installation and phase one testing are complete, the system can be coordinated for turn-on.

At this stage, the radio shop or frequency license holder monitors their infrastructure while the BDA is activated.

The purpose is to confirm that the system is not creating harmful noise or interference.

Post-Commissioning Coverage Test

After the BDA is fully commissioned and no more changes will be made, the post-commissioning test is performed.

This is the final acceptance-style coverage test.

Ideally, the building should be complete and operating under normal day-to-day conditions.

This test creates the acceptance test package.

The acceptance test becomes the baseline that annual inspections will be compared against.

Annual / Periodic Testing

After occupancy and retransmission approval, the system moves into annual or periodic testing.

Annual tests determine whether:

• Building conditions have changed
• Antennas or cables have been damaged
• The BDA is still functioning properly
• Coverage has degraded
• Signal quality problems have developed

3. Determining Good Coverage

Seahawk Touch uses several measurement indicators to determine indoor radio coverage quality.

Common downlink indicators include:

Common uplink indicators include:

Delivered audio quality fields are manual entry fields.

They require radio communication and subjective scoring.

Uplink data can be imported from Seahawk Monitor, which sits at the radio tower and measures uplink signal quality in a similar way to how the scanner measures downlink signal quality.

4. Testing Stages Summary

Testing can be grouped into four major stages:

For new construction, a test before construction begins can provide guidance, but it is not enough for final acceptance.

The final test should be performed after the building is mostly complete or fully complete.

For buildings such as warehouses, the difference between an empty building and an occupied building with racks, products, and equipment can be significant.

Whenever possible, the final test should reflect normal operating conditions.

5. Code and Test Requirements

The AHJ typically provides the required:

• Channels
• Frequencies
• Technologies
• Pass/fail thresholds
• Accepted test method
• Report format

Testing may include:

• Public safety radio systems
• LTE or cellular systems
• FirstNet
• Wi-Fi
• Private occupant radio systems

General requirements often include:

• Divide each floor into 20 equal grid areas
• Test each grid area near the center
• Test critical areas separately
• Use signal strength, delivered audio quality, SINR/SONAR, or bit error rate
• Test both uplink and downlink
• Grade each area as pass/fail
• Grade the building by percentage
• Submit a report signed or accepted by the AHJ or approved person

Annual retests are compared to the original acceptance test.

6. Frequencies and Channels

Frequencies and channels vary by jurisdiction.

A building may require testing of several overlapping systems.

Examples include:

• County fire system in UHF
• Law enforcement system in 800 MHz
• City fire control channel in 700 MHz
• Cellular or FirstNet bands
• Private business radio system

Seahawk can test multiple systems, channels, and technologies at the same time when properly configured.

7. Network Technologies

Different network technologies affect how the test should be configured.

Common technologies include:

• Analog FM LMR
• P25
• DMR
• TETRA
• NXDN
• EDACS
• Cellular
• FirstNet

Analog FM systems are older but still widely used.

Digital LMR systems such as P25, DMR, TETRA, NXDN, and EDACS behave differently and may require different test methods.

Cellular and FirstNet systems continue to expand and may also be included in testing requirements.

8. Conventional vs. Trunked Systems

Conventional Systems

In a conventional system, the radio must be keyed to create a signal.

The signal goes to the repeater at the tower site and is then retransmitted on the downlink channel.

Because conventional systems may not have an always-on control channel, the technician may need to key the radio to make the downlink measurable.

Trunked Systems

In a trunked system, a control channel is always broadcasting.

The control channel is measured and averaged continuously.

When a user keys a radio:

1. The radio talks to the control channel.
2. The system assigns a traffic channel.
3. The voice transmission occurs on the traffic channel.
4. After the transmission ends, radios return to listening to the control channel.

Trunked systems are generally easier to test because the control channel is always available.

9. Public Safety Bands

Common public safety bands include:

The AHJ or radio system owner should provide the required channel assignments.

10. Simulcast vs. Multicast

Simulcast Systems

In a simulcast system, multiple tower sites transmit the same control channel frequency.

These systems use high-stability timing to prevent destructive interference and maintain proper overlap between sites.

Multicast Systems

In a multicast system, different towers may use different frequencies.

One tower may cover one side of a building well while another tower covers the opposite side better.

Grouping these channels allows the system to test all relevant control channels together.

When a BDA is installed, a directional donor antenna is usually aimed at one selected tower site, and that is the site being enhanced.

11. Channel Groups

Channel groups are important when one radio system may use multiple channels.

A group should be used within the same system, not across unrelated systems.

Why Use Channel Groups?

Channel groups are useful for:

• Multicast systems with multiple control channels
• Simulcast systems with multiple control channel candidates
• Systems where the control channel may roll
• Conventional systems with no always-on control channel
• DMR systems where active channels may move

If one channel in the group passes, the group passes.

This allows the test to reflect how the radio actually works in the field.

Control Channel Roll

In some systems, the control channel can change during the test.

If only one control channel is tested and it rolls to another frequency, the remaining test points could appear to fail incorrectly.

By grouping all control channel candidates, the test can still capture valid results even if the active control channel changes.

Conventional Traffic Channel Groups

For conventional systems with no control channel, all voice channels may be placed into one group.

This allows the scanner to capture whichever channel becomes active during the test.

This is useful when the tester does not know which voice channel will be active at a given time.

12. Noise Channels

Noise channels are frequencies between licensed channels that are not part of the actual radio network.

They are selected as noise channels and are not graded.

Noise channels are power-only measurements.

Their purpose is to document the noise environment in the building.

Noise channels can help identify possible interference sources such as:

• High-inductive motors
• Refrigeration equipment
• Grocery store equipment
• Other electrical or RF noise sources

When a system is later installed and noise appears on the DAS, the noise channel data can help identify where that noise may be coming from.

13. Floor Plans and Grids

Use approved floor plans whenever possible.

The floor plan should be:

• Readable
• High-quality
• Accurate
• Easy to navigate
• Large enough to place reference points outside the building

Level one should include space outside the building so exterior reference points can be documented.

These exterior points help show what signal is coming into the building and what signal may be leaking out.

Leakage Reference

In-building systems are intended to stay inside the building, but some leakage can occur.

NFPA guidance states that at 3 feet outside the building, the macro network should be 15 dB stronger than the building system.

This helps reduce interference outside the building.

Floor Plan Integrations

Seahawk tools can integrate with floor plan formats from:

• Ranplan
• iBwave

These native file formats can be used to build floor plans and later upload data back into the tools.

14. Grid Requirements

Each floor should generally be divided into 20 grid areas.

Grid size is important.

Typical grid guidance:

If the floor is larger than what 20 grids can reasonably cover, add another set of 20 grids as a new sector.

The grid should fit the building and remain a grid shape.

It should not be a circle, ellipse, or odd shape.

15. Test Point Placement

The test point should represent where the technician actually stands during the test.

The point should not be placed somewhere impractical, such as:

• On top of a table
• Inside a wall
• In an inaccessible area
• Behind locked equipment
• Somewhere the tester cannot physically stand

The test point should make sense and be repeatable for future testing.

16. Critical Areas

Critical areas have more stringent requirements than normal grid areas.

In this example:

Critical areas may include:

• Fire command centers
• Fire pump rooms
• Exit stairs
• Exit passageways
• Elevators
• Elevator lobbies
• Standpipe cabinets
• Sprinkler sectional valve locations
• Areas of refuge
• Rescue areas
• Other areas identified by the AHJ

In schools, restrooms or other refuge/rescue areas may be considered critical points depending on the AHJ.

Not every exterior door is automatically an exit passageway.

Exit passageways are typically marked by exit signage and include features such as crash bars or other keyless egress hardware.

17. Measurements

Code may allow several types of measurements to determine whether coverage is acceptable.

Common measurements include:

• Delivered Audio Quality
• RSSI / signal strength
• SINR / SONAR
• Bit Error Rate

These measurements help answer the basic question:

Can the radio communicate clearly and reliably?

18. Delivered Audio Quality

Delivered Audio Quality, or DAQ, is a subjective measure of how understandable the voice transmission is.

General DAQ scale:

A DAQ of 3.0 is generally considered the minimum requirement in many public safety applications.

DAQ 3.4 is more stringent because speech must be understandable without repetition.

19. P25 Equivalency Metrics

TSB-88.1 provides equivalency values for P25 Phase 1 and P25 Phase 2.

Example values discussed in the lesson:

For DAQ 3.4, the BER and SINR requirements become more stringent.

20. BER vs. FBER

There are two bit error rate concepts discussed:

For normal in-building testing, FBER is used most of the time.

Out-of-service BER is less common and is generally used for special test-pattern-based work.

21. Limitations of DAQ Testing

Delivered Audio Quality testing has limitations.

It:

• Requires two people
• Can take 3 to 5 times longer
• Is subjective
• Depends on hearing ability
• Can be affected by accents
• Can be affected by radio tuning
• Can vary between testers
• Should be performed for both uplink and downlink

People with long-term exposure to loud environments, such as fire alarm testing, may have different hearing ability than newer personnel.

Because DAQ is subjective, objective metrics such as SINR and BER are often preferred where available.

22. Uplink vs. Downlink

Coverage testing should consider both directions.

The radio must work:

• From the tower to the portable radio — downlink
• From the portable radio back to the tower — uplink

Uplink is especially important because a portable radio may transmit only around 3 to 4 watts, while a tower site may transmit anywhere from 30 to 200 watts.

If the uplink works properly, the downlink often has a stronger source, but both directions still need to be verified according to the test requirements.

23. Best Practices

Service companies should work with the AHJ and radio shops to create clear requirements for test companies.

Best practices include:

• Add noise frequencies to the test plan.
• Do not grade noise channels, but use them as a record of in-building noise.
• Capture spectrum analyzer screenshots when issues are found.
• Add exterior reference points at ground level and on the roof.
• Add clear comments for reference points and critical points.
• Explain why a point is critical or why a reference point was used.
• Make reports easy for another reviewer to understand.
• Average measurements meaningfully.
• Rotate in a circle or walk an X pattern to reduce body-loss effects.
• Test all control channel candidates for trunked systems.
• Use max hold for traffic channel power.
• Use SINR and BER where available.
• Measure the signal at each antenna for a good record.

24. Body Loss

The technician’s body can affect RF measurements.

Body loss can cause an 8 to 10 dB difference depending on whether the technician’s body is blocking the path between the radio and the tower site.

To reduce this effect, the technician should:

• Turn in a circle during the measurement, or
• Walk an X pattern within the test area

This provides a more meaningful average reading.

Final Summary

In-building public safety radio coverage testing verifies whether emergency responders can communicate reliably inside a building.

The major responsibilities are split between:

• AHJ — focused on first responder safety and in-building coverage
• Frequency license holder / radio shop — focused on frequency use and protecting the macro network

Testing should occur at the right stages:

1. Baseline / initial test
2. Intermediate construction testing
3. Phase one test-channel verification
4. Coordinated system turn-on
5. Post-commissioning acceptance test
6. Annual or periodic retesting

A good test plan should include approved floor plans, proper grids, critical areas, reference points, noise channels, and the required technologies and frequencies provided by the AHJ or radio system owner.

Objective metrics such as SINR and FBER are preferred when available because they are accurate, repeatable, and directly tied to radio system performance.