NIST Technical Note 1792

Performance Analysis of RF-Based 

Electronic Safety Equipment in a 

Subway Station and the Empire State 

Building

William F. Young

Kate A. Remley

Galen Koepke

Dennis Camell

Jacob Healy

http://dx.doi.org/10.6028/NIST.TN.1792

NIST Technical Note 1792 

Performance Analysis of RF-Based 

Electronic Safety Equipment in a 

Subway Station and the Empire State 

Building 

William F. Young

Kate A. Remley

Galen Koepke

Dennis Camell

Jacob Healy

Electromagnetics Division 

Physical Measurement Laboratory 

http://dx.doi.org/10.6028/NIST.TN.1792

March 2013

U.S. Department of Commerce 

Rebecca Blank, Acting Secretary

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director
Certain commercial entities, equipment, or materials may be identified in this

document in order to describe an experimental procedure or concept adequately.

Such identification is not intended to imply recommendation or endorsement by the

National Institute of Standards and Technology, nor is it intended to imply that the

entities, materials, or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Technical Note 1792 

Natl. Inst. Stand. Technol. Tech. Note 1792, 70 pages (March, 2013) 

http://dx.doi.org/10.6028/NIST.TN.1792

Article I. CODEN: NTNOEF
iii

Contents

Executive Summary................................................................................................................. iv

1. Introduction........................................................................................................................... 1

2. Test Environments................................................................................................................ 3

2.1 Subway station, New York City ....................................................................................... 4

2.2 Empire State Building, New York City .......................................................................... 11

3. RF PASS System Performance in the Structures ............................................................ 16

3.1 Subway station................................................................................................................ 16

3.2 Empire State Building..................................................................................................... 24

3.3 PASS system results versus path loss............................................................................. 29

4. Path-Loss Measurement..................................................................................................... 38

4.1 Transmitters for Path-Loss Measurements ..................................................................... 38

4.2 Receiver for Path Loss Measurements............................................................................ 39

4.3 Data Normalization......................................................................................................... 41

5. Path-Loss Behavior for Various Floors of the Structures............................................... 42

5.1. Empirical cumulative distribution functions.................................................................. 43

5.2. Box plots........................................................................................................................ 44

6. Estimated Received Power on Several Floors or Levels of the Structure ..................... 44

6.1. Estimating path-loss in the subway................................................................................ 45

6.2. Estimating path-loss in the Empire State Building........................................................ 46

6.3. ECDF and log-normal results ........................................................................................ 46

7. Contributions to Uncertainty in Path Loss Estimates..................................................... 56

7.1 Small-scale fading........................................................................................................... 56

7.2 Type A uncertainties of the measurement instrumentation ............................................ 56

7.3 Type B uncertainties of the measurement instrumentation............................................. 57

7.4 Combined uncertainty of the measurements................................................................... 58

8. Summary and Conclusion.................................................................................................. 59

Acknowledgements ................................................................................................................. 59

References................................................................................................................................ 60

Appendix A: RF PASS Performance and Path Loss Data.................................................. 62
iv

Executive Summary

The National Institute of Standards and Technology (NIST) has participated in a 

multi-year project to support the development of performance metrics and test methods 

for radio-frequency (RF)-based electronic safety equipment used by the public-safety 

community. The work reported here focuses on side-by-side measurements of radiopropagation environment characteristics and actual wireless device performance in two 

key representative emergency responder environments, a subway station and a highrise building. Identifying the impacts of path loss on wireless device performance in 

various environments enables the development of standardized laboratory-based test 

methods that simulate the conditions under which electronic safety equipment will be 

used in the field. The test methods can then be incorporated into consensus standards 

for this equipment.

The analysis presented here has been funded by the U.S. Department of 

Homeland Security Standards Branch. The work reported here focuses on RF-based 

personal alert safety systems (PASS), used by firefighters to indicate when a firefighter 

is motionless or in distress. However, the methodology, analysis, and RF propagation 

results presented here could easily be extended to other types of wireless devices that 

operate in similar environments. 

In previous propagation-channel studies, NIST engineers measured path loss

(“attenuation”) and the level of reflectivity (or “multipath,” quantified by the root-meansquare delay spread) in large public structures and environments where radio 

communications could be challenging. (See NIST Technical Notes 1545, 1456, 1550, 

1552, 1557, and 1559.) These environments included multi-story buildings; buildings 

with subterranean floors and tunnels; buildings with deep interior spaces; those with few 

windows; and outdoor “urban canyons,” consisting of city streets surrounded by tall 

buildings. The NIST Public-Safety Communications Research Lab funded those 

measurements of the propagation channel. Current work focuses on the subterranean 

environment presented by subways, and a 100-story high-rise, the Empire State 

Building. The tests were completed in New York City with the help of the Fire 

Department of New York and several firefighters from the Research and Development 

Division. Access to the subway station was provided by the New York City Transit 

Authority. The building owners, management, and maintenance personnel provided 

access and support for testing the Empire State Building. 

To support standards development in public-safety applications, the NIST studies 

focus on the penetration of radio signals from outside to inside a given structure (and 

vice versa), as opposed to outdoor-to-outdoor or within-building tests. To simulate an 

incident command post in the propagation-channel studies, a receive antenna was 

positioned outside of each structure at a location representative of a fireground 

configuration. Portable RF PASS units were carried through the environment and 

success or failure in receipt of various alarms was noted. A continuous-wave radio 

transmitter was then carried through the structures with a spectrum-analyzer-based 

receiver system continually measuring the received signal power. Key locations in the 

walked path were “marked” in the collected data. These key location “markers” enable 

the correlation between path loss and RF PASS performance at specific locations within 
v

the structure. The markers also allow parsing of the data among different floors or 

platform levels, which supports path-loss analysis on a per-floor or level basis. 

The RF-based PASS systems are capable of two-way communications, and 

these measurements determined whether or not the alarm from the portable RF PASS 

device was received by the base station and if the portable device received an alarm

signal from the base station. The portable RF PASS device generally transmits with a 

lower power than the base station in order to conserve battery life and, in some cases, 

to meet “intrinsic safety” standards for electronic equipment. Consequently, the signal 

emitted from the RF-based PASS device is typically weaker, and testing the reception of 

this alarm by the base station represented a worst-case scenario. 

A second aspect of these tests was the collection of path-loss data for these two 

high-attenuation RF propagation-environments at 430 MHz, 750 MHz, 905 MHz, 

1834 MHz, and 2405 MHz. With the simulated incident command post located outside,

but near an entrance to the structure, the maximum measured path-loss values ranged 

from 140 dB to 175 dB for the Empire State Building and 210 dB to 240 dB for the 

subway station. The 140 dB path-loss value suggests that a point-to-point system could 

provide coverage over much, though not necessarily all, of this RF propagationenvironment. The range of success with one of the point-to-point systems during the 

RF PASS systems testing verified that good, but not complete, coverage was indeed 

possible. If an RF PASS system is deployed with the incident command post outside a 

large structure, even without subterranean elements, the encountered path-loss should 

be expected to be at least 140 dB to 175 dB. A large, subterranean structure will likely 

exhibit path-loss values greater than 200 dB.

We tested four different commercially available RF-based PASS systems, one 

that operates on a licensed frequency in the 450 MHz public-safety narrowband 

frequency allocation, two that operate in the unlicensed spectrum between 902 MHz 

and 928 MHz, and one that operates in the unlicensed spectrum of 2.4 GHz. In the case 

of the subway environment, one 900 MHz and the 2.4 GHz systems were tested with 

and without a repeater unit. We expect that use of repeater technology will continue to 

increase in RF-based systems. The tests demonstrated that the repeater approach 

added significant improvement coverage for those two systems.

The data and corresponding discussion presented below are intended to aid in 

the development of laboratory-based test methods for RF-based emergency safety 

equipment such as RF-based PASS devices. Test methods developed to date focus on 

inserting a controllable amount of attenuation (i.e., 100 dB of path-loss) between the 

portable PASS device and the PASS base station and inserting a specified level of RF 

interference between the portable and base station units. These current tests have been 

adopted in the 2013 revision of NFPA 1982: Personal Alert Safety Systems. We 

anticipate that additional test methods and standards covering multi-hop networks and 

medium-to-high attenuation environments will be forthcoming in the near future as well.

The data and test results provided here directly support the development of these future 

tests and standards.
1

Performance Analysis of RF-Based Electronic 

Safety Equipment in a Subway Station and the 

Empire State Building

William F. Young, Kate A. Remley, Galen Koepke, Dennis Camell, and Jacob Healy

Electromagnetics Division

National Institute of Standards and Technology

325 Broadway, Boulder, CO 80305

Abstract: We analyze data from NIST field tests in which radio-propagation channel 

path-loss values were measured at approximately the same physical locations where 

the performance of various RF-based firefighter distress beacons were tested. These 

side-by-side tests were made in two key representative emergency responder 

environments: a New York subway station and the Empire State Building. These 

environments contain propagation features that may impair radio communications, 

including stairwells, tunnels, and rooms deep within buildings. The goal of this work is 

to determine appropriate performance metrics for use in the development of laboratorybased test methods for RF-based electronic safety equipment. The analysis supports 

the classification of building structures into categories of attenuation values that can be 

used in laboratory-based test methods to verify the performance of the RF-based alarm 

systems. The environments, tests, and measured data are discussed in detail. The RF 

propagation-channel data also provide insight into the expected attenuation in high-rise 

buildings and below-ground structures.

Key words: attenuation; emergency responders; firefighter communications; publicsafety radio communications; radio propagation-channel measurements; wireless 

communications.

1. Introduction

Emergency responders count on reliable radio communications between 

responders, who are often inside a structure, and the incident command station outside. 

New wireless technology is being developed that can further increase responders’ 

safety and efficiency by remotely monitoring their position, status, and situational 

awareness. The responder community would like to take advantage of this technology. 

Because lives may depend on its performance, wireless technology used in emergency 

response scenarios must generally satisfy higher levels of reliability than technology 

used in the commercial sector. Even though standards currently exist for commercial 

wireless devices such as cell phones, wireless local-area-networks and handheld 

radios, few standards currently exist for wireless electronic safety equipment. Unlike 

commercial-sector applications, the performance requirements for electronic safety 
2

equipment typically focus on communication reliability and availability rather than the 

amount of data throughput, and thus any applicable standards should reflect these key

performance metrics. 

The U.S. Department of Homeland Security (DHS) Standards Branch has tasked

researchers at the National Institute of Standards and Technology (NIST) with providing

technical support for the development of consensus standards for these new products. 

As examples, DHS, through NIST, has determined gaps in existing standards and 

developed appropriate test methods for RF identification (RFID) systems used in publicsafety and government applications such as tracking or inventory control [1-3]. A 

second project is working with the urban search and rescue community to support 

development of standards for the wireless control of robots through ASTM International

[4], [5]. 

Here we describe DHS-sponsored work carried out to support the National Fire 

Protection Association (NFPA) in the revision of NFPA 1982: Standard on Personal 

Alert Safety Systems (PASS) [6] to include RF-based PASS (RF PASS). A PASS is 

essentially a “firefighter-down” alarm that emits a loud audible alarm when the wearer is 

motionless for 30 seconds. Some PASS manufacturers are now including an RF 

transceiver in the portable, body-worn PASS device to alert the incident command 

station. The transceiver is also capable of receiving a signal from the incident command 

station to evacuate. The work presented here is expected to apply to other types of RFbased electronic safety equipment as these become available.

The technical approach taken here involves two main measurement activities. 

First, we collect RF propagation-channel data by walking over a predetermined path in a

structure with a transmitter emitting a continuous-wave (CW) signal, as done in our 

previous RF propagation-channel studies [7-9] A spectrum analyzer at a location that 

simulates an incident command station measures the received-signal strength. The 

measured values are recorded, and subsequently processed, to estimate the path at

distinct locations, such as the location of a portable RF PASS, and general sections of 

the structure, such as different floors.

In the second part of the experiment, several RF PASS technologies are tested 

at specific locations along the same path covered in the CW transmitter walk. The base 

stations of these PASS systems are co-located with the spectrum analyzer 

measurement equipment; i.e., the simulated incident command station. At the specific 

test locations on the path walked, the RF PASS devices are tested for their ability to 

successfully send a firefighter-down alarm to the base station, and to successfully 

receive an evacuation alarm from the base station. In post-processing, the RF 

propagation-channel data provide path-loss information that is correlated with the RF 

PASS test locations. This analysis supports the refinement of laboratory tests for RF 

PASS devices as well as RF-based emergency equipment, in general.

While the aforementioned testing offers insight into real-world RF PASS 

performance, there are limitations and challenges with the direct use of such 

environments as test beds. Laboratory-based test methods of RF-based emergency 

safety equipment provide the advantages of accuracy, repeatability, efficiency, and, 

often, reduced cost, when compared to the use of building structures and/or structurebased test beds. This is because it is possible to carefully control the test environment 

and conditions in a laboratory while covering propagation-channel parameters 
3

measured over a wide range of building types. For the testing of RF-based equipment, 

we can expose the system under test to specific and reproducible levels of attenuation, 

interference, or multipath, and with known uncertainties.

It has been necessary for NIST to perform the RF propagation measurements as 

part of this project because much of the data that have been previously published in the 

literature describe tests made to support commercial applications such as cellular 

telephone communications, where a cellular base station provides coverage to a wide 

area, rather than the point-to-point, pedestrian-height scenarios utilized in many RFbased emergency scenarios. In addition, one important goal of the study presented here

was to analyze the performance of the RF PASS systems under the same conditions 

under which the channel characterization tests were conducted. 

In the following sections, we discuss various aspects of our measurements and 

provide insights that support RF-based testing for similar technologies. We also discuss 

factors that contribute to the uncertainty in the measurement comparison. For instance, 

since the locations of the measurements were not identical, the performance of the RF

PASS system does not, in some cases, agree with what is expected theoretically. 

However, certain trends are clearly indicated from the data allowing us to identify

representative values of attenuation for the development of laboratory-based test 

methods.

In Section 2, we describe the various environments in which the measurements 

were performed, and include sketches of the two structures. Section 3 contains the RF 

PASS systems’ performance results and analysis, including a discussion of the 

relationship between RF PASS performance and RF propagation-channel 

characteristics. We purposely provide RF PASS performance results before describing 

the RF propagation-channel measurements so that the reader is exposed to the system 

level performance first. This is because we anticipate most readers are interested in 

these system level performance results, with a smaller subset interested in the details of

the RF propagation-channel itself. In Section 4, we describe the measurement system 

and data-processing algorithms used in the RF propagation-channel measurements. 

Section 5 describes the statistical methods used in representing the data, and Section 6

contains channel measurement results for the two environments. In Section 7, we 

discuss the assumptions and approximations that were made in measuring and 

analyzing the data and how they affect the uncertainty in relating RF-based PASS 

performance to propagation-channel characteristics. Finally, in Section 8, we provide 

conclusions based on these measurements and subsequent analysis. 

2. Test Environments

We provide a brief description of the environments and conditions in which radio 

propagation-channel measurements were made and RF PASS systems were tested.

Pictures of the general environment are included, along with basic diagrams of the 

subway station and Empire State building. Positions are marked on the diagrams of 

each structure where the tests of the RF PASS systems were conducted. Markers are 

also included for positions that delineate key sections of the structures such as floors, 

stairwells, and elevators. These sketches of the two structures are provided to give the 
4

reader a perspective on the relative locations of the RF PASS test points within the 

structures.

2.1 Subway station, New York City

The West 4th Street Station, with the entrance shown in Figure 1, was the 

subway station used for these RF PASS tests. An external receive site, Receive Site 1,

was setup next to the entrance, with measurement equipment and the RF PASS base 

stations. Figures 2 and 3 show the Receive Site 1 setup along with some of the 

equipment used for the RF PASS tests. These pictures illustrate the close proximity of 

the site to the stairway entrance into the subway. The stairwell leading down to the pay 

turnstile level is shown in Figure 4. As shown in Figure 5, the stairwell is located down a 

narrow walkway from the pay turnstile. Inside the station, there are passenger platforms 

as shown in Figure 6.

Figure 1. The subway station where the RF PASS systems were tested.
5

Figure 2. FDNY and NIST personnel setting up Receive Site 1, located outside the subway entrance.
6

Figure 3. Receive Site 1 at the subway station. Some of the equipment in the picture includes spectrum 

analyzers and RF PASS base stations.

Figure 4. Subway station stairwell entrance.
7

Exit to street

Figure 5. Token booth turnstile. The stairwell that exits to the street is located at the end of the walkway.
8

Figure 6. Passenger platforms and stairwell between two of the platforms.
9

For the purposes of understanding the RF PASS tests and results, a general 

description of the subway layout is useful. The subway station consisted of three 

passenger platforms below ground, with a length of approximately three city blocks. A 

fare station located at an elevation between the street stairwell entrance and the first 

passenger platform connects the entrance via stairwells to the first platform. Thus, there 

are four distinct levels considered here, starting with the subterranean token booth

(Level 1), the first subterranean passenger platform (Level 2), the middle, subterranean 

passenger platform or “Mezzanine Level” (Level 3), and the deepest subterranean

passenger platform (Level 4). Figure 7 shows the basic layout, along with markers 

indicating the path walked with the radio used in the path-loss measurements. The 

order of the numbers indicates the progression in the walk. Points that are labeled with 

two numbers, such as point 7/19, indicate that the point was crossed both entering and 

exiting the subway station. 

For RF PASS system testing, the base stations were located outside near the 

stairwell entrance at Receive Site 1. The second receive site, Receive Site 2, was used

only for RF propagation-channel analysis. The RF PASS system results, mapped to the 

locations within the subway, are found in Section 3.
10

Figure 7. Layout of the four-level subway station. Receive Site 1 is located at the street level and Receive Site 2 is located on Level 3. The numbers indicate the 

marker locations corresponding to the propagation-channel measurement path. These locations are used to estimate the path loss at RF PASS test locations. Note 

that the figure is not to scale. RF PASS base stations were located at Receive Site 1.

0/26 Receive Site 1

3/23 1/25

2/24

4/22

5/21

6/20

10 9 8 7/19

11 12

13 14 15

16

Receive Site 2

17

18
11

2.2 Empire State Building, New York City

Tests were also conducted in the Empire State Building in New York. We provide 

a few pictures here of the building and receive site locations. Figure 8 shows FDNY and 

NIST personnel setting up the radio receive site and RF PASS base stations outside of 

the Empire State Building. In Figure 9, the main lobby and Receive Site 2 are shown. 

Figure 10 includes pictures from several floors with the building where the RF PASS 

tests were conducted. The floors were typically being remodeled or at least contained 

minimal furnishings. 

Figure 11 shows a sketch of the Empire State Building with markers that indicate 

the progression of the radio walk-through used for path-loss measurements. As in the 

case of the subway, the walk begins on the sidewalk at Point 0, enters the building, and 

proceeds in a path that follows the increasing numbers. From Point 30 on the 83rd floor, 

the path returns to Point 0 in as direct of manner as possible, i.e., through a series of 

elevators and through the first floor. The transitions between different floors occurred 

largely via freight elevators; the entering and exiting locations were in the interior portion 

of the floors because the main elevator shaft is located in the core of the building.

The portable RF PASS devices were tested in specific locations where the RF 

propagation-channel was measured on several floors of the building. This supported the 

goal of obtaining correlated path-loss values and RF PASS performance. It also allowed 

comparison of path-loss behavior between floors in the building.
12

Empire State Building

Empire State Building

Receive Site 1

Figure 8. Setting up Receive Site 1 outside the Empire State Building.
13

Receive Site 2

Figure 9. First floor lobby of the Empire State Building. Receive Site 2 was set up in the lobby.
14

Figure 10. Several of the floors and areas covered in RF PASS tests.
15

Figure 11. Empire State Building with receive/ base station sites depicted; Receive Site 1 is a parked van on 

the side of the road opposite the Empire State Building and Receive Site 2 is inside the building lobby. Marker 

numbers indicate the path walked with radio used for path-loss measurements. RF PASS base stations were 

located at Receive Site 1.
16

3. RF PASS System Performance in the Structures

This section describes results from RF PASS tests. First, we provide illustrations 

that show where a given RF PASS system either successfully or unsuccessfully 

executed a firefighter-down alarm. Second, we provide illustrations that show either the 

success or failure of RF PASS base-station initiated evacuation signals. Third, we 

include bar graphs that correlate the success/failure of the both alarm signals against 

the path loss in Section 4. For path-loss values at specific RF PASS test points in the 

subway station and Empire State Building, see Tables 7 and 8, respectively, in 

Appendix A.

The results in this section precede the RF propagation-channel results so that 

the reader is exposed to the system-level performance results before delving into the 

detailed analysis necessary to obtain RF propagation-channel values. We chose this 

order because we expect readers to range from those interested primarily in systemlevel performance, with minimal interest in the detail behind the RF propagation-channel 

measurements, to those interested in both system-level performance and detailed 

explanations of the RF propagation-channel measurement results. The former group of 

readers can concentrate on the results presented in this section, while the latter group 

will want to explore the entire document.

3.1 Subway station

Our results cover all four RF PASS systems tested for point-to-point 

communication. In addition, the built-in repeater capability of Systems 2 and 4 was 

tested with a single repeater. (Systems 1 and 3 did not have repeater capabilities).

Figures 12 to 17 depict the success or failure in receiving a “firefighter-down” alarm at 

the base station or an evacuation signal at the portable PASS unit at specific locations 

in the subway station. The figures show the results overlaid on the sketch of the subway

station, along with a marker number that corresponds to the RF propagation-channel 

test point location. The marker numbers are used to correlate the RF PASS results with 

path-loss measurements described in Section 4. If the system was tested with a 

repeater, two results at a test point are indicated, separated by a forward slash, “/”.

These “firefighter down” and evacuation test results are labeled “Alarm” and 

“Evacuation,” respectively. A measured success, denoted by a circle or “○” inside a 

rectangle, is indicated if the signal is received within 30 seconds; otherwise, the test

was considered a failure, denoted by an “X” inside a rectangle. Due to the limited time 

available for field testing, some points were not tested. However, predicted results are 

indicated for some of the test points based upon the path-loss measurements, 

observations from these and previous field tests, and laboratory tests. A circle or “○”

inside a hexagon is a predicted success, while an “X” inside a hexagon is a predicted 

failure. In addition, darker shading of a green “○” or red “X” indicates field-test or 

measured results, and the lighter shading a green “○” or red “X ”indicates predicted 

results. This coloring scheme is used in the associated bar charts presented in Section 

3.3.

Figure 12 shows the results for System 1. The first observation is that the Alarm 

and Evacuation signals both fail at Point 5. Failure for both signals is predicted starting 

at Point 6 and beyond because the measured path-loss is great than 125 dB. (For path-
17

loss values at specific RF PASS test points in the subway station, see Table 7 in 

Appendix A.)

In Figures 13 and 14, results are shown for a point-to-point and a repeater 

configuration of System 2, respectively. Failure occurs starting at Point 2 for the pointto-point configuration, but the use of a repeater extends the range to Points 7, for the 

Alarm and Evacuation signals. At Point 8, both the Alarm and Evacuation signal fail. 

Clearly, System 2 experienced significant improvement in range when a repeater was 

used.

The System 3 results in Figure 15 indicate failure of the Alarm signal at Point 3 

and beyond, and failure of the Evacuation signal at Point 4 and beyond. System 4 Alarm 

and Evacuation signal results in Figures 16 and 17, respectively, show a failure at Point 

2 and beyond for both the Alarm and Evacuation signal if no repeater is used. When a

repeater is placed at Point 1, both the Alarm and Evacuation signals are successful up 

to Point 6. Similar to System 2, the use of a repeater provides a significant improvement 

in range.
18

Figure 12. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal for RF PASS System 1. System 1 did 

not have a repeater option.

(a)

(b)
19

(a)

(b)

Figure 13. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal for RF PASS System 2. These are 

results without the repeater. 
20

Figure 14. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal for RF PASS System 2, with the 

repeater unit located at point 1.

(a)

(b)
21

Figure 15. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal for RF PASS System 3. System 3 did 

not have a repeater option.

(a)

(b)
22

(a)

(b)

Figure 16. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal results for RF PASS System 4. These 

results are without a repeater.
23

Figure 17. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal results for RF PASS System 4, with the 

repeater unit located at Point 1.

(a)

(b)
24

3.2 Empire State Building

The second set of results covers the four RF PASS systems tested in a point-topoint configuration in the Empire State Building. The base station was located outside 

the building at NIST Site 1. Due to time restrictions for conducting the tests, the repeater 

capabilities of Systems 2 and 4 were not tested. As in the previous four figures, 

Figures 18 to 21 depict the success or failure in receiving a firefighter-down alarm signal 

at the base station or an evacuation alarm signal at the PASS unit. A success is 

indicated if the signal is received within 30 seconds; otherwise, the test was considered 

a failure.

Figure 18 shows test results for System 1. Here, the Alarm signal is successful 

up to the 29th floor, but fails at the 61st floor and above. The Evacuation signal shows 

success on Point 24 of the 61st floor and success at Point 29 of the 83rd floor. The 

difference in range for the Alarm and Evacuation signals may be due to the fact that the 

Evacuation signal is sent from the base station, while the Alarm signal is sent by the 

portable RF PASS device, which is typically at lower power. 

Results for System 2 are depicted in Figure 19, which indicate that the Alarm 

signal fails starting at Point 4 on the first floor, and the Evacuation signal at Point 10 on 

the 5th floor. There was some concern with these Alarm results for System 2, as the 

software was not resetting properly, and thus, the Alarm results may be indicating a 

performance less than expected. However, based on the subway performance for the 

point-to-point configuration of System 2 along with the Evacuation signal results here, 

the Alarm signal would not be expected to exceed the range of the Evacuation signal. 

Thus, at best, the range of the Alarm signal would likely extend to parts of the 5th floor.

Figure 20 shows the test results for System 3, where there was demonstrated 

success on the 20th floor for the Alarm signal at Point 17, but failure at Points 13 and 16. 

While the RF PASS worked in some parts of the 20th floor, other areas were out-ofrange. Although the Evacuation signal failed at Point 13 as well, the Evacuation signal is 

predicted to work at Point 17. In general, the 20th floor behavior is indicative of a RF 

PASS system operating at the edge of its coverage limit, where the signal is successful 

approximately half of the time, but fails the other half of the time.

Finally, Figure 21 shows that System 4 has a very limited coverage capability for 

this building when operating in a point-to-point configuration. Unfortunately, time 

restrictions did not allow testing with a repeater because, as demonstrated in the 

subway tests, the coverage range of System 4 can be significantly improved with use of

a repeater.

In the next section of results, bar plots are used to relate the RF PASS 

success/fail tests to the measured RF path loss. Those plots provide greater insight into 

this key RF propagation problem that the RF PASS systems must overcome. 
25

Figure 18. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal results for RF PASS System 1 in the 

Empire State Building.

(a) (b)
26

Figure 19. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal results for RF PASS System 2 in the 

Empire State Building.

(a) (b)
27

Figure 20. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal results for RF PASS System 3 in the 

Empire State Building.

(a) (b)
28

Figure 21. (a) Firefighter-down “Alarm” signal and (b) “Evacuation” signal results for RF PASS System 4 in the 

Empire State Building.

(a) (b)
29

3.3 PASS system results versus path loss

In this section, we plot the RF PASS test results in Figures 12 to 21 versus the 

estimated path loss at the test location. The basic approach was to measure the pathloss experienced by a radio operating in the same frequency band as the RF PASS at 

the same test points. The RF PASS success/failure results for the test point were then 

associated with estimated path loss value. Sections 4 and 5 discuss the measurement 

method and data processing used for determining the path-loss. Correlation between 

the PASS system performances and the path loss at the frequency of radio operations 

supports the development of laboratory test methods by allowing the accurate recreation of field-test conditions.

Figures 22 to 28 provide histograms of RF PASS test results versus the 

measured path-loss at the test location. The success/failure results are placed in bins, 

5 dB in width, based on the associated path-loss value. Lines that correspond to an 

attenuation test threshold of 100 dB (i.e., the NFPA 1982 low-attenuation test) and the 

effective noise floor of the path-loss measurement system are also shown on the plots.

Note that the noise floor limit depends on frequency and, thus, the noise floor lines in 

the plots correspond to the frequency of operation specific to that RF PASS.

Figure 22 shows the Alarm (or firefighter-down) signal results in the subway for 

all four systems in a point-to-point configuration. Figure 23 shows the Evacuation signal 

results for the same configuration. All four systems are able to successfully transmit 

signals when the path loss is less than the 100 dB threshold. However, between 100 dB

and 140 dB of path loss, all systems experience at least one failure in both the Alarm 

and Evacuation signal tests.

When a repeater is located at Point 1, Systems 2 and 4 exhibit a much better 

coverage range. Figure 24 shows both the Alarm and Evacuation signal test results for 

these two systems, where both systems successfully transmit signals with up to 

approximately 140 dB of path loss. System 4 does not fail until the path loss exceeds 

150 dB. There are two failures indicated for System 2 at just over 140 dB, but the pathloss number might actually be closer to 150 dB at that location. This is due to the fact 

that all of the path-loss numbers are subject to measurement uncertainty and channel 

variability; these factors will be discussed in Section 7. Also, since the path-loss 

estimate is near the noise-floor limit of the measurement equipment, distinguishing the 

signal power from the noise power is difficult. This can cause a lower path-loss 

estimate than when a sufficient signal-to-noise margin exists. Overall, these single-hop 

repeater results demonstrate the benefits of the use of repeaters to overcome

significant path loss in the communication link.

In Figures 25 and 26, the Alarm and Evacuation results are shown for the test 

carried out in the Empire State Building. Systems 1 and 3 both successfully transmit 

Alarm and Evacuation signals with more than 100 dB of path loss. System 1 

demonstrates the ability to successfully transmit most signals near the 130 dB noise 

floor of the measurement system, while System 3 transmits with success up to 

approximately 105 dB to 110 dB of path loss. 

System 2 generally transmits successfully beyond the 100 dB threshold, and 

exhibits better performance for the Evacuation signal than the Alarm signal. To some 

extent, the difference between the two signals for System 2 is consistent with the 

subway results. However, as mentioned previously, there appeared to be some reset 
30

issues with the software when performing the Alarm tests, so those results should be 

viewed with some skepticism. The Evacuation results, along with the previous subway 

results, indicate that the system can overcome a 100 dB of path loss without a repeater.

System 4 indicates a failure of both the Alarm and Evacuation signals for 100 dB 

of path-loss. However, the estimated path loss value bin is 5 dB wide, and thus 

represents a 97.5 dB to 102.5 dB range. Thus, the actual path-loss value may be 

higher than 100 dB, which is likely the case at this test point; e.g., the path-loss could be 

102 dB at this test point, but the result falls in the 97.5 to 102.5 dB bin. Again, as 

mentioned before, there is uncertainty is the measurement of the path-loss values as 

well. These uncertainties will be discussed in Section 7.

Figures 27 and 28 contain the aggregate results (without repeaters) from the 

subway station and the Empire State Building. One of the important factors to notice is 

that the path-loss values are lowest for System 1 and highest for System 4. This is due 

to a difference in operating frequency as the systems were tested at the same points in 

the buildings. The frequencies of operation for the tested RF PASS systems ranged 

from the 400 MHz to the 2.4 GHz bands. As will be discussed in Section 4, the path-loss 

values are based on continuous-wave transmitters, and provide a good estimate across 

the operational bands of the RF PASS.

Except for a few cases, the Alarm and Evacuation signals for System 1 are 

successful up to 120 dB of path loss. System 2 successfully communicates the 

Evacuation signal with 100 dB of path loss, and as mentioned previously, the failure of 

the Alarm signal around the 100 dB threshold is likely attributed to a software reset 

issue. System 3 successfully communicates Alarm and Evacuation signals up to 105 dB 

in all except a few cases around 105 dB. In the case of System 4, a majority of the test 

points exceed 100 dB of path loss, with many test points experiencing greater than 125 

dB of path loss. Without a repeater, System 4 is not able to overcome path loss-values 

of this magnitude. Note that none of the other point-to-point systems consistently and

successfully communicated Alarm and Evacuation signals when the path-loss level was 

close to 125 dB.

Finally, the estimated path-loss values associated each test point, along with the 

success/failure results are presented in Appendix A. Tables 7 and 8 provide the results 

for the Alarm and Evacuation for the subway station and the Empire State Building, 

respectively. The path-loss values listed in these two tables are determined as 

described in Section 4 below. 
31

Figure 22. Subway firefighter-down signal results without a repeater. Plots are based on data contained in Table 7.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8Number of test points

Firefighter down: System One Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB)

System Three Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
32

Figure 23. Subway evacuation signal results without a repeater. The Attenuation Test threshold is 100 dB for all 

systems, and represents the NFPA Standard. The noise limit depends on the test equipment and is frequency 

dependent. Plots are based on data contained in Table 7.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Evacuation: System One Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB) Number of test points

System Three Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
33

Figure 24. Subway firefighter-down and evacuation results with a single-hop repeater. Only Systems Two and Four 

were tested with a repeater node. Plots are based on data contained in Table 7.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Firefighter Down: System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB) Number of test points System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Evacuation: System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
34

Figure 25. Empire State Building firefighter-down results without a repeater. Note that the software for System 2 

did not appear to be resetting properly during the test. Thus, the results for firefighter-down alarm for the Empire 

State Building should be viewed with skepticism. The cause of the problem was not identified, but the software 

for System 2 had not previously shown a reset problem over the last several years of our testing in the field. (RF 

interference did not appear to cause the problem.) The evacuation signal did not appear to be impacted. Plots are 

based on data contained in Table 8.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Firefighter down: System One Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB) Number of test points System Three Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
35

Figure 26. Empire State Building evacuation signal results without a repeater. Plots are based on data contained in 

Table 8.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Evacuation: System One Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB) Number of test points System Three Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
36

Figure 27. Aggregate firefighter-down results for the subway and Empire State Building tests without a repeater.

Plots are based on data contained in Table 7 and 8.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Firefighter down: System One Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB) Number of test points System Three Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
37

Figure 28. Aggregate evacuation signal results for the subway and Empire State Building tests without a repeater.

Plots are based on data contained in Table 7 and 8.

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Evacuation: System One Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Two Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

Total path loss (dB) Number of test points System Three Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)

50 60 70 80 90 100 110 120 130 140 150 160

0

1

2

3

4

5

6

7

8

System Four Attenuation Test threshold Noise limit of test equipment Success(meas)

Fail(meas)

Success(expct)

Fail(expct)
38

4. Path-Loss Measurement

The path-loss, or reduction in signal strength experienced by a signal as it 

penetrates and travels through a structure, will directly impact the ability of an 

emergency responder to receive a signal from the incident command post, or vice 

versa. The primary goal of the measurements was to determine representative values of 

this key impairment to successful transmission of alarm signals from RF PASS systems. 

The basic approach taken to obtain these path-loss measurements used a radiomapping technique, where a continuous-wave (CW) transmitter is carried throughout 

the building while a receiver located elsewhere captures the signal. Typically, as is the 

case here, at least one receive location corresponds to location that simulates the 

incident command station. Additional receive locations within the two structures also 

provide measurement of the signal propagation as the transmitter is carried throughout 

the various tunnel levels or building floors. The combination of data from the external 

and internal receive sites enables us to estimate the path loss from the street level to 

the lower levels of the subway station. In order to correlate the RF PASS results with

the propagation measurements, the transmitter is held at each RF PASS test location 

for a short period of time. Details on the transmitters, receivers, and data-capture 

process used in determining the path-loss values are discussed below.

4.1 Transmitters for Path-Loss Measurements

The transmitters used in the path-loss measurements were chosen to meet the 

following criteria: (1) transmit at the frequencies used for the various RF PASS systems 

and other frequencies of interest in Table 1, (2) operate continuously for several hours, 

and (3) be portable in a manner similar to the RF PASS devices (i.e., a single person 

could easily carry the device while walking through the building.) Commercial 

transmitters in plastic protective cases, such as depicted in Figure 29, were available for 

all of the frequency bands. These transmitters allow for the external connection of 

antennas. The antennas were electrically short monopoles or “rubber duck” types for 

the frequency bands of 430 MHz and 1834 MHz, loaded monopoles for the 750 MHz 

and 905 MHz bands, and a linear dipole-array antenna for 2.4 GHz. All of these 

antennas generate an omnidirectional pattern, with nominal gains ranging from 0 dBi for 

the rubber duck to 5 dBi for the linear dipole-array. 

Table 1. Public-safety communication frequencies and cellular bands, including nominal frequencies used 

in the measurements.

Frequency 

Band (MHz)

Nominal frequency 

used in 

measurements

“Transmit” antenna 

Description

406-470 430

electrically short monopole 

or “rubber duck”

Used by public-safety and others, 

including RF PASS technology

700-800 745,750 loaded monopole Includes the new public-safety band

902-928 905 loaded monopole Unlicensed band; used in RF PASS 

technology 

1850-1990 1834 electrically short monopole 

or “rubber duck” PCS or digital systems

2400-2500 2405 linear dipole array Unlicensed band; wireless LANs; used in 

RF PASS technology 
39

The 430, 750, 905, and 1850 MHz radios had nominal output powers of 1 W 

(30 dBm), and the nominal output power of the 2405 MHz radio was 5 W (37 dBm).

However, rather than work with nominal transmitter power levels, we opted to measure 

the total radiated power (TRP) of the various transmitter/antenna combinations so as to 

calibrate the transmitted power in the path-loss calculations. The measured TRP values 

were based on reverberation chamber measurements. The benefit to this approach is 

evident by the fact that the TRP values never reach the nominal values due to factors 

such as antenna efficiencies, cable losses (the cable connecting the antenna to the 

transmitter), and connector losses. Measured TRP values also account for antenna-toradio impedance mismatches, which can significantly impact the actual radiated power.

These measured TRP values are incorporated into the calibration process discussed in 

Section 4.3.

4.2 Receiver for Path Loss Measurements

As shown in Figure 30, the receiver consisted of a spectrum analyzer controlled 

by a graphical programming language. The software ran parallel processes of 

collecting, processing, and saving the data for post-collection processing. The data 

were continuously read from the spectrum analyzer and stored in data buffers. The 

software processed these buffers by searching for the power level of the desired CW 

signal, which was subsequently displayed for the operator. These processed data were 

then saved (along with the original raw data) on the laptop containing the control

software.

Figure 29. Typical transmitter with a “rubber duck” antenna used to generate the CW signal
40

The sampling rate of the complete measurement process and the walking speed 

determined the spatial resolution during radio-mapping experiments and the time 

resolution for recording the signals. A narrow frequency band (called the capture 

bandwidth) around the desired CW signal was measured during each walk, resulting in 

sampling period of between 0.15 s and 0.3 s. Continuous-wave sources (i.e., the radios) 

were carried through the buildings and the receiver recorded the capture bandwidth 

around the CW frequency. The capture bandwidth was typically less than 20 kHz, but 

wide enough to ensure that the CW signal was measured even if the CW source 

experienced frequency drift.

Linear dipole arrays with gains ranging from 3 dBi to 5 dBi were used as the 

receive antenna in Figure 30 for the 2.4 GHz frequency band. A discone antenna was 

used for the frequency bands below 1 GHz, with a gain of 2 dBi and a beamwidth of 

approximately 45 degrees. Finally, a conical antenna was used for the 1.8 GHz receive 

antenna, with a gain of approximately 3 dBi. When the receive site was outside the 

structure, the receive antenna was mounted with a short tripod on the top of a van or a 

fire-emergency medical vehicle for a total height of approximately 4 m above the 

ground. At receive sites inside the structure, the receive antennas were located on a 

tripod at a height of approximately 2 m above the ground. Figure 31 depicts the 

complete transmitter and receiver setup, and indicates the typical orientation of the CW 

transmitter (Figure 31(a)) and the receive antenna location (Figure 31(b)) for an external 

receive site. 

(a) (b)

(c)

Figure 30. Receiver equipment and setup. The choice of receive antenna depends on the frequency band: (a) 

conical antenna for 1.8 GHz or a linear dipole-array antenna for 2.4 GHz, and (b) 50 MHz to 1 GHz discone 

antenna. (c) The spectrum analyzer was connected to a laptop via a GPIB interface.
41

Figure 31. Transmitter and receiver details, (a) a CW transmitter carried through the building and (b) the receive 

antenna location on an emergency vehicle.

4.3 Data Normalization

A number of post-processing steps were necessary to “normalize” the receivedpower level of the measured data. These normalized data were then used to obtain

path-loss values corresponding to RF PASS test positions and the path-loss for various 

floors and levels of the structures. These steps are detailed below. 

The first step began with a refined power-level search, where the software 

searched for the maximum signal within the capture bandwidth (between 10 to 20 kHz)

by use of a smaller search bandwidth (less than 10 kHz). This search bandwidth was 

set even smaller, less than 5 kHz, if an interference source lay within the original 

capture bandwidth, and the CW source did not experience significant frequency drift. 

The maximum value was obtained over a given time interval. The use of narrower 

search bandwidth allowed us the flexibility to remove nearby (in frequency) interference 

in the measured data.

As stated earlier, the radios from 430 MHz to 1.8 GHz nominally transmitted 1 W,

while the 2.4 GHz radio transmitted 5 W. To compare received signals, the measured 

signal power was reduced by the difference in transmit power, approximately 7 dB 

between 1 W and 5 W, by subtracting 7 dB from the measured 2.4 GHz path-loss data. 

These path-loss data were also corrected for the measured total radiated power (TRP) 

of the transmitter/antenna combination to allow comparison across the range of 

frequencies (see Figure 32). The TRP measurements provide a correction factor that 

ranges from 1.7 dB to 8.5 dB for the transmitter/antenna combinations used here. 

(b)
42

The normalized power is then given by

 

 ( )  ( ) ( ) ( ) ( ) ( ) (1)

where 

 is the normalized received power,  is the measured received power 

before any normalization, is the difference from the nominal transmitted power,

 is the nominal transmitted power, and is the gain of the receive antenna. The 

gain of the transmit antenna is not included because the electromagnetic scattering 

environment of the interior of the building reduces the benefits of antenna directivity; the 

transmit antenna efficiency and mismatch are included in the term. The 30 dB 

subtraction in the square bracket converts the received power from dBm to dBW. Note 

that the transmit power is given relative to 1 watt, which is 0 dBW and 7 dBW for the 

1 W and 5 W transmitters, respectively. To a first approximation, the receive system 

(i.e., spectrum analyzer, cables, and receive antenna) and the antennas on the 

transmitting radios are assumed to impact the measured power in a manner roughly 

equivalent to an actual deployed public-safety radio network or other wireless system.

5. Path-Loss Behavior for Various Floors of the Structures

In this section, we discuss methods to visualize and analyze the collected data

on several of the floors in the Empire State Building and the four levels within the 

Figure 32. Total radiated power measurements of the CW radios used in the measurement of the path loss. The μ 

and σ values refer to the mean and the standard deviation as measure in a reverberation chamber at NIST.

5

10

15

20

25

30

35

Power (dBm)

TRP for several devices with their respective antennas

430 MHz, "Rubber Duck" 751 MHz, Monopole 751 MHz, "Rubber Duck" 751 MHz, Sig. Gen., Monopole 905 MHz, Monopole 905, "Rubber Duck" 1834 MHz, "Rubber Duck" 2400 MHz, Lin. Dipole-Array 4900 MHz, Lin. Dipole-Array

Measured results, 

Error bars = (   2) / 

Nominal device output power

Uncertainty bars = (μ±σ)/μ
43

subway station. (All of the data considered in this section are the normalized data 

described in the previous section.) In the first representation, the data are presented as 

empirical cumulative distribution functions (ECDFs) with corresponding log-normal 

distribution curve fits to data measured at individual floors or levels. Parameters for the 

log-normal curves are provided as well. The ECDF is a direct representation of the data 

that shows what percentage of the data is below a particular power level. No 

assumptions about the underlying distribution are required to interpret the ECDF. A lognormal fit provides the parametric values for generating representative distributions that 

can be used in channel simulations. The log-normal distribution represents the typical 

power distribution associated with the large-scale fading that is anticipated in office 

building and urban environments [11]. In addition, as discussed in [12], the log-normal 

distribution is well-suited for a variety of data analysis problems, several of which exhibit 

behaviors similar to the data sets collected here. In general, the log-normal distribution 

provides a good representation of these data, as the data cannot be less than zero and 

have only a few relatively large values [13]. 

 In the second data presentation, path-loss information derived from the data is 

displayed in the form of box plots, including the 25, 50, and 75 % quartiles. Box plots 

are a non-parametric method of displaying data that illustrate the basic symmetry and 

spread of the data [14]. A key benefit to use of a box plot is that data are not assumed 

to follow an underlying distribution; e.g., Gaussian or Rayleigh. The values at the 25, 50, 

and 75 % quartiles are also listed in accompanying tables.

These data representations provide insight into the propagation behavior of the 

individual floors. Additional details on the formation and analysis associated with the 

ECDFs and the box plots are discussed below. Analysis of the collected data follows in 

Section 6.

5.1. Empirical cumulative distribution functions (ECDFs)

The normalized received-power data 

 captured at all of the receive sites 

were combined for each frequency, and a Kaplan-Meier estimate of the ECDF was 

computed on this aggregate data set with a commercial software package. This ECDF

was then used to obtain the parameters for the log-normal CDF. We include some 

fundamental properties provided in [12] that are relevant to the data analysis. 

The log-normal probability density function is given by 

 ( ) 

 

√ 

exp [ 

( )

 

 

 

] (2)

Integrating (2) over ( ) by use of the substitution 

 

√ 

 and (7.1.2) in [15], 

yields 

 ( ) 

 

 

erfc [ 

ln 

 √ 

] (3)
44

where erfc(·) is the complementary error function, and and are the mean and 

standard deviation, respectively, of the natural logarithm of the random variable . 

Then, the expected value is found from

 

 

 

 

 

 

 

(4)

the median value is given by

median 

 

 (5)

and the standard deviation is found from

standard deviation 

 

 

 

 

 

√ 

 

(6)

5.2. Box plots

The “box” in a box plot contains the median value of the data, and the edges of 

the box correspond to the range of data between two percentiles, typically the 25th ( ) 

and 75th ( ) percentiles. A dashed or broken line called a whisker is attached at each 

end of the box, where the maximum length is typically given by

 ( 

) (7)

where ( ) is called the interquartile range, or IQR. If the maximum data value is 

less than ( ) , then the whisker extends only to the maximum data value, 

which is called the “upper adjacent.” Likewise, if the minimum data value is greater than 

 ( ), then the whisker extends only to the minimum data value, called the 

“lower adjacent.” Any data that fall beyond the whiskers are called outliers and are 

plotted as individual points. The 50th percentile is the median of the data, the 25th

percentile is the midpoint of the data below the median, and the 75th percentile is the 

midpoint of the data above the median. Thus, the symmetry (or asymmetry) of the box 

provides insight into the symmetrical properties of the data. For example, if the data fit 

well to a Gaussian distribution, the 50th percentile would equal both the median and the 

mean, and the box edges and whiskers would be symmetric about that median.

6. Estimated Received Power on Several Floors or Levels of the 

Structure

Here, we estimate the cumulative distribution of the received signal on several

floors or levels within each structure. The point-of-reference is Receive Site 1 for both 

the subway station and the Empire State Building. These power levels were determined 

from normalized data with (1), and represent the power received at the external receive 

site when a 1 W radio transmitter is carried through the building. By normalizing the 

data to 1 W with a 1 W transmitter as the source, the path loss (PL) results are easily 

found from

 ( ) 

 ( ). (8)
45

These data provide insight on the expected path-loss and variability that the signal will 

experience as a function of floor or level. 

6.1. Estimating path-loss in the subway

As the transmitter was carried to levels three and four of the subway station, the 

signal was not discernible at Receive Site 1. That is, the signal-to-noise ratio was less 

than 0 dB. Thus, to obtain an estimate of the received signal level and corresponding 

path-loss relative to Receive Site 1, we combined the measured results from Receive 

Sites 1 and 2. Because Receive Site 2 was located within the subway, we were able to 

estimate the received mean power on each level in the subway. We then renormalize 

the data from Receive Site 1 based on knowledge of the path-loss between various 

levels as determined at Receive Site 2. The steps below explain the process.

1) Normalize the data from Receive Sites 1 and 2 as given in (1).

2) Parse the data into subsets representing the different levels. For the subway, the 

subsets are

a. normalized data for Level 1 as measured at Receive Site 1,

b. normalized data for Level 1 as measured at Receive Site 2,

c. normalized data for Level 2 as measured at Receive Site 2,

d. normalized data for Level 3 as measured at Receive Site 2,

e. normalized data for Level 4 as measured at Receive Site 2.

The stairwell data were not included in the data for the four levels because the 

stairwell represents a transition between levels rather than a particular level.

3) Estimate the difference in path-loss between adjacent levels. This is 

accomplished by computing the absolute difference in the means of the subsets 

of data for two adjacent levels of data measured at Receive Site 2.

 ( ) 

 |   

| (9)

Here, 

 

is the mean of the subset of data from Receive Site 2 for the i

th level.

4) Estimate the mean for Level 1 by use of normalized data measured at Receive 

Site 1. This is the mean value 

 

for Level 1, as measured at Receive Site 1.

5) Subtract the difference in path-loss between levels found in Step 3 from the 

mean path-loss found in Step 4:

 ̂ 

 

 ∑ ( ) 

 

 

 (10)

The difference in path-loss between all of the levels that are necessary to reach 

the desired level must be included, as indicated by the summation in (10). This 
46

provides an estimate of the mean for each level if the receiver location was at 

Receive Site 1. The three values provide an estimate of the mean path-loss with 

respect to Receive Site 1 for Levels 2, 3, and 4.

6) Renormalize the data for Levels 2, 3, and 4 from Step 2 by subtracting the mean

of each parsed, normalized data set. This renormalizes the data for Levels 2, 3, 

and 4 to a 0 dB mean. The parsed, normalized data from Step 2 has a mean with 

respect to Receive Site 2, and thus needs to be set to a 0 dB mean before 

adding the mean path-loss computed in Step 5. 

7) Finally, add the path-loss means computed in Step 5 to the renormalized data 

from Step 6 to obtain data that can be used to estimate the ECDFs and path-loss 

values.

6.2. Estimating path-loss in the Empire State Building

For the Empire State Building, the normalized data from Receive Site 1 provided

sufficient coverage to obtain path-loss estimates for the areas covered in the walkthroughs. In this case, Steps 1 and 2 from the process above were carried out, where 

“levels” now refers to the “Street,” and Floors 1, 5, 20, 29, 61, 80, 83. The normalized

data were parsed into subsets corresponding to the different floors of the building, which 

then were used to create the corresponding ECDF and path-loss estimates.

6.3. ECDF and log-normal results

Based on the process described above, the ECDFs are plotted in Figures 33 and

34 for the various platform levels of the subway station and floors of the Empire State 

Building. The subplots with the figures correspond to the frequencies used in the 

measurements, including two frequencies, 750 MHz and 1834 MHz, not utilized by the 

four RF PASS systems tested. These additional frequencies were included to provide 

better insight in the frequency dependence of the structures as well as in anticipation of 

future public-safety usage of those bands, 750 MHz in particular. 

Parameters that can be used to generate representative log-normal distributions

are found by curve-fitting the data. Table 2 below lists the parameter values for the 

associated fitted curves in Figures 33 and 34. These values can then be used with 

equations (2) and (3) to obtain representative PDFs and CDFs for the propagation 

environments.

Associated with the ECDF plots are box plots shown in Figures 35 and 36. The 

data are presented as path-loss information in the box plots. These plots provide insight 

into the symmetry aspects of the data as well at the spread of the data. Table 3 and 4

contain the 25th, 50th, and 75th percentile values for the path-loss results of the subway 

station and Empire State Building, respectively. Recall that by normalizing the data to 

1 W, the path loss and measured power results are simply the inverse of each other. 

In Figure 33, the ECDF results fit a log-normal distribution well for Levels 1 and 4 

for all five frequencies. ECDF results for the other two levels generally follow a lognormal distribution, but not as well as Levels 1 and 4. This is likely due to the fact that 
47

the areas covered on Levels 2 and 3 represented a larger physical distance, with more 

coverage of the widely separated areas of the platform. The marker numbers and

walked-path shown in Figure 7 shows the difference in coverage between the four 

levels. These coverage differences are also reflected in the spread or range of the 

received power for each level. For example, at 905 MHz, the Level 1 results range from 

approximately -140 dBW to -100 dBW, or a 40 dB spread. For Level 2, the range is from 

-200 dBW to -120 dBW, or an 80 dB spread. 

Another interesting feature shown in Figure 33 is that at the frequencies of 

905 MHz and lower, the Level 3 and 4 results overlap in the 0.2 to 0.7 probability 

regions. The 1834 MHz and 2405 MHz results overlap only below the 0.1 probability 

region. Looking at Figure 35, the impact of the overlap effect becomes more obvious as 

the box for Level 4, depicting the 25th to 75th percentile coverage, fits within the box 

boundaries for Level 3 of the three lower frequencies. Figure 35 also shows that the 

median values decrease for the 1834 MHz and 2405 MHz frequencies as the radio 

transmitter is carried to the lower levels.

The Empire State Building ECDF results in Figure 34 and associated box plots in 

Figure 36 show how the signal is attenuated as the radio is carried to ever higher floor 

levels. In Figure 34, the ECDFs generally follow a log-normal distribution, as is evident 

by the differences between the measured data and the log-normal fit curves. The 

largest differences occur for the data collected on the street and are likely due to a 

combination of a limited number of points and a strong line-of-sight contribution. 

Another important observation occurs in the significant attenuation that occurs 

between the data collected on the street and data within the building on the first floor. 

For the four frequencies other than 430 MHz, the median path loss is between 20 dB 

and 30 dB. More interestingly, the median path loss for 430 MHz is nearly 50 dB, even 

though there is just a 17 dB range in the median attenuation over all of the floors within 

the building at 430 MHz. This is easily seen in the median path loss values in Table 4. 

During these measurements, aluminum scaffolding covered the side of the Empire State 

Building facing Receive Site 1. We hypothesize that the scaffolding caused significant 

attenuation at 430 MHz, but had much less impact at the higher frequencies. The freespace wavelength at 430 MHz is 0.7 m, and the scaffolding, with all the accompanying 

supports and safety railings had many features on the same order as this dimension.

The performance of the RF PASS appeared not to be impacted because the path-loss 

was still less than 115 dB for most of the test locations, and the system operating in the 

450 MHz band has demonstrated the ability to successfully operate with path-loss 

values of around 115 dB.

A third observation is that the box plots for the Empire State Building, Figure 36, 

indicate several outliers for the frequencies of 905 MHz, 1834 MHz, and 2045 MHz. 

Those path-loss estimates are measured near the noise-floor limit of the measurement 

system, so they likely represent a limitation of the measurement equipment, and not a 

true path-loss value. This same behavior, shown in Figure 35, is observed across all 

frequencies in the Level 1 results for the subway station. However, if the signal cannot 

be distinguished from the noise, this implies that the signal has experienced a path-loss 

sufficient to attenuate the signal to at least the noise level, if not greater. (Note that 

although the noise floor is indicated as a single value, it actually fluctuates. The noise 
48

floor limit shown in Figures 12 22 to 28 actually represents a slight margin, 

approximately 2 dB, above the upper limit of the fluctuation.) 
49

Figure 33. Empirical CDFs and corresponding log-normal-fit curves for the estimated received power across the 

five frequencies and for the four levels within the subway. Each frequency subplot shows results for the four levels, 

with the right-most curves representing the first level (and least amount of path loss). 

0

0.2

0.4

0.6

0.8

1

430 MHz

0

0.2

0.4

0.6

0.8

1

745 MHz

0

0.2

0.4

0.6

0.8

1 Pr[received power  abscissa]

905 MHz

0

0.2

0.4

0.6

0.8

1

1834 MHz

-250 -230 -210 -190 -170 -150 -130 -110 -90 -70 -50

0

0.2

0.4

0.6

0.8

1

Estimated received power level, (dBW)

2405 MHz

Level 1, eF(x)

 lnN (,

2

)

Level 2, eF(x)

 lnN (,

2

)

Level 3, eF(x)

 lnN (,

2

)

Level 4, eF(x)

 lnN (,

2

)
50

Figure 34. ECDFs representing the estimated received power at the street outside and on the various floors within 

the Empire State Building.

0

0.2

0.4

0.6

0.8

1

430 MHz

0

0.2

0.4

0.6

0.8

1

750 MHz

0

0.2

0.4

0.6

0.8

1

905 MHz

0

0.2

0.4

0.6

0.8

1

1834 MHz

-180 -170 -160 -150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50

0

0.2

0.4

0.6

0.8

1

2405 MHz Pr[received power  abscissa]

Estimated received power level, (dBW)

Street, eF(x)

 lnN (,

2

)

Floor 1, eF(x)

 lnN (,

2

)

 Floor 5, eF(x)

 lnN (,

2

)

Floor 20, eF(x)

 lnN (,

2

)

Floor 29, eF(x)

 lnN (,

2

)

Floor 61, eF(x)

 lnN (,

2

)

 Floor 81, eF(x)

 lnN (,

2

)

Floor 83, eF(x)

 lnN (,

2

)
51

Table 2. Parameter values to compute the log-normal fit to the empirical CDF data results for the various floors and 

levels of the subway station and the Empire State Building.

Parameter Values (dB)

Frequency

(MHz)

μ σ μ σ μ σ μ σ

Subway

Level 1 Level 2 Level 3 Level 4

430 -23.3 1.7 -32.1 4.9 -43.4 5.6 -50.7 3.4

745 -24.7 1.4 -32.8 4.5 -45.0 4.8 -51.1 3.1

905 -25.5 1.4 -32.3 4.2 -44.9 5.1 -53.1 3.1

1834 -29.1 2.2 -34.7 4.0 -45.6 3.9 -54.3 3.4

2405 -27.5 2.0 -35.4 3.5 -49.3 4.6 -59.1 2.7

Empire State Building

Street Floor 1 Floor 5 Floor 20

430 -14.8 0.6 -26.1 2.8 -25.7 2.1 -26.4 2.3

750 -15.8 1.1 -21.1 2.8 -24.0 2.2 -25.0 2.0

905 -17.0 1.2 -23.1 2.5 -24.1 2.1 -25.0 1.9

1834 -19.0 1.1 -24.5 2.5 -25.5 2.4 -27.2 2.3

2405 -19.9 1.4 -26.8 2.5 -30.1 2.1 -31.8 1.9

Floor 29 Floor 61 Floor 80 Floor 83

430 -26.8 1.7 -28.5 1.5 -30.3 1.0 -30.1 1.4

750 -26.0 1.6 -26.0 1.5 -27.6 1.1 -28.1 1.2

905 -25.6 1.8 -28.2 1.5 -31.0 1.1 -29.6 1.6

1834 -28.0 2.0 -30.7 2.0 -34.5 1.0 -31.8 1.6

2405 -32.4 1.9 -34.6 1.6 -35.9 1.7 -34.5 1.4
52

Figure 35. Boxplot of subway path-loss estimates at the four levels. The indent in the box represents the median 

values, the edges of the box represent the 25th and 75th percentiles, the edges of the whiskers represent the lower and 

upper adjacent values, and the red crosses are the outliers. 

Level 1 

Level 2 

Level 3 

Level 4 

430 MHz

Level 1 

Level 2 

Level 3 

Level 4 

745 MHz

Level 1 

Level 2 

Level 3 

Level 4 

905 MHz

Level 1 

Level 2 

Level 3 

Level 4 

1834 MHz

50 70 90 110 130 150 170 190 210 230 250

Level 1 

Level 2 

Level 3 

Level 4 

Path loss(dB)

2405 MHz
53

Figure 36. Boxplots of path loss estimates for the Empire State Building. The indent in the box represents the 

median values, the edges of the box represent the 25th and 75th percentiles, the edges of the whiskers represent the 

lower and upper adjacent values, and the red crosses are the outliers.

Street

Floor 1

Floor 5

Floor 20

Floor 29

Floor 61

Floor 80

Floor 83 

430 MHz

Street

Floor 1

Floor 5

Floor 20

Floor 29

Floor 61

Floor 80

Floor 83 

750 MHz

Street

Floor 1

Floor 5

Floor 20

Floor 29

Floor 61

Floor 80

Floor 83 

905 MHz

Street

Floor 1

Floor 5

Floor 20

Floor 29

Floor 61

Floor 80

Floor 83 

1834 MHz

60 80 100 120 140 160 180

Street

Floor 1

Floor 5

Floor 20

Floor 29

Floor 61

Floor 80

Floor 83 

Path loss (dB)

2405 MHz
54

Table 3. Quartiles and adjacents of path-loss estimates for the four levels within the subway. The quartile indicates 

the percentage of estimated path-loss data below the specified path-loss value.

Frequency

(MHz)

Subway 

Path loss estimates (dB) at quartiles (%)

Level 1 Level 2 Level 3 Level 4

Upper Adjacent

430 120.6 198.2 222.3 209.0

745 121.2 204.7 233.2 224.0

905 126.4 207.6 232.1 226.6

1834 151.7 212.2 226.8 237.5

2405 139.7 191.0 238.5 228.3

75 %

430 106.0 165.2 190.3 177.3

745 110.4 165.7 200.9 201.9

905 114.3 168.5 208.8 204.0

1834 133.4 184.6 202.6 208.6

2405 124.9 171.3 212.4 213.5

50 % (median)

430 100.8 138.3 173.4 167.3

745 106.7 142.0 185.3 188.6

905 110.1 147.9 195.7 191.7

1834 125.1 166.7 191.9 198.0

2405 117.8 160.1 200.4 205.4

25 %

430 96.1 127.2 144.3 155.8

745 103.2 131.1 162.3 177.9

905 106.1 137.7 167.2 182.9

1834 118.9 154.6 172.4 184.9

2405 113.7 145.1 177.4 195.2

Lower Adjacent

430 82.6 100.0 119.8 134.6

745 92.6 113.5 137.2 161.3

905 95.1 116.5 142.8 164.7

1834 103.6 129.5 148.2 164.2

2405 102.8 125.3 152.0 174.8
55

Table 4. Quartiles of path-loss estimates for the seven floors studied in the Empire State Building. The quartile

indicates the percentage of estimated path-loss data below the specified path-loss value.

Frequency

(MHz)

Empire State Building

Path loss estimates (dB) at quartiles (%)

Street Floor 

1

Floor 

5

Floor 

20

Floor 

29

Floor 

61

Floor 

80

Floor 

83

Upper adjacent

430 71.2 138.7 136.3 139.3 136.8 139.5 140.5 141.4

750 78.8 127.9 129.7 130.6 131.0 130.0 132.8 133.4

905 86.1 127.5 130.5 130.4 130.3 138.6 146.4 146.6

1834 93.4 135.4 139.4 147.7 145.9 158.3 159.0 156.4

2405 96.5 148.2 155.6 162.9 165.8 168.5 174.4 164.4

75 %

430 66.3 122.7 118.5 123.0 121.7 127.9 135.3 136.1

750 71.6 101.5 111.6 114.2 117.9 117.4 122.8 126.5

905 77.1 108.3 110.8 113.7 116.0 126.2 137.8 133.3

1834 86.7 113.7 119.0 125.5 127.2 139.8 153.6 142.5

2405 88.8 124.5 137.1 144.0 146.6 155.0 160.3 153.4

50 % (median)

430 64.3 114.9 110.9 113.9 116.4 123.1 130.8 131.8

750 68.7 89.3 104.2 108.4 113.0 112.2 119.5 122.2

905 73.9 100.5 104.7 108.4 111.7 121.3 134.2 127.8

1834 81.5 104.9 110.0 117.4 121.5 131.7 149.4 137.6

2405 85.9 115.7 130.7 137.7 140.5 149.6 154.9 149.4

25 %

430 62.6 104.9 104.8 106.9 110.6 119.4 128.1 127.2

750 65.5 81.5 96.4 103.1 107.9 107.9 115.8 118.3

905 70.6 92.2 97.4 102.4 106.5 117.7 131.7 123.4

1834 78.6 98.6 103.1 110.0 114.4 126.8 146.5 133.1

2405 82.6 108.3 124.2 131.5 133.7 144.9 150.9 145.7

Lower adjacent

430 57.7 85.1 92.1 93.3 100.1 109.6 121.2 114.2

750 59.4 70.3 82.8 86.9 93.8 97.1 108.9 108.7

905 63.5 74.0 80.9 87.2 92.5 108.4 123.5 111.8

1834 73.3 81.0 85.7 97.0 99.9 112.8 138.1 119.9

2405 79.1 92.1 107.4 115.8 118.5 135.2 137.5 134.4
56

7. Contributions to Uncertainty in Path Loss Estimates

In this section, we provide an estimate of the uncertainty in our path-loss 

measurements, as measured by the combination of CW transmitters and the spectrumanalyzer receiver setup. Following the convention described in [16], the uncertainties 

associated with the measurement and estimation of path loss can be broken into two 

categories: Type A (evaluated by statistical means), and Type B (evaluated by nonstatistical means). Contributions associated with the repeatability of the measurement 

instrumentation and the transmitted power estimations are described with Type A

techniques. Other, systematic effects are described with Type B methods. These 

include errors in the drift of the measurement instrumentation components not covered 

in the Type A analysis. We describe these effects below, and then calculate the 

combined expected uncertainty in our estimation of path loss due to these contributions.

This uncertain analysis covers the measurement of a single value, and is, thus, the 

measurement uncertainty. 

7.1 Small-scale fading

One potential source of uncertainty when measuring a propagation channel can 

be attributed to small-scale fading, often called channel variability in the literature. 

Small-scale fading occurs due to multiple frequency-, time-, and position-dependent 

reflections in the local area around each test point. Even though a building environment 

is fixed and measurements made there would be deterministic, small-scale fading 

occurs as cars, trucks, and pedestrians move randomly through the environment during 

measurement. However, the uncertainty analysis here does not consider the channel 

variability; a relevant discussion on uncertainties attributed to channel variability is found 

in [17]. Uncertainty estimates due to channel variability in the 434 MHz , 745 MHz and 

905 MHz bands are expected to be on the same order of magnitude as the values listed 

in [17], since the RF propagation environments are similar; i.e., large buildings and 

urban streets. 

7.2 Type A uncertainties of the measurement instrumentation 

As discussed in Section 4, CW sources were carried through the structures, and 

a spectrum analyzer connected to an antenna measured the received power for a single 

frequency. Use of narrowband filters, data processing, and a check of background 

environmental signals ensured that the signals we acquired corresponded to the ones 

we transmitted, rather than those from interfering sources. Measurements from all 

radios were normalized for nominal differences in transmit power levels (1 W or 5 W, 

depending on the frequency), as discussed in Section 4.3.

For the measurements here, we performed Type A uncertainty analyses of both 

the transmitters and the receiver setup. First, using a reverberation chamber, we 

measured the total radiated power of each radio with the specific transmit antenna 

attached. The mean results with the relative uncertainty values for the relevant 

radio/antenna pairings are listed in Table 5. (These values are also displayed in Figure 

32)
57

Table 5. Mean power and relative uncertainty for 10 total radiated measurements of the radio/antenna pairs.

Frequency (MHz) Antenna μ (dBm) (dB)

430 “rubber duck” 21.5 +1.1,-2.25

745 monopole 26.4 +0.7,-1.0

905 monopole 24.0 +0.6,-0.75

1834 “rubber duck” 24.7 +0.7,-1.1

2400 linear dipole-array 35.3 +0.7,-1.2

The uncertainty analysis of the receiver setup, namely the spectrum analyzer and 

the laptop used to control the analyzer, consisted of taking six measurements for three 

different signal level inputs, with a two-hour interval between measurements. The 

source was a signal generator connected into the spectrum analyzer through a coaxial

cable via the port connected to the antenna for the field measurements. The signal

generator emitted a CW signal at 0 dBm, and an inline attenuator of 20 dB, 50 dB or 

80 dB was included to represent different path-loss conditions. Two minutes of 

measurement data, consisting of 100 data samples, were collected for each of the 

frequency bands and attenuator values with the same software and processing as in the 

field measurements. To approximate the field experiment conditions, the spectrum 

analyzer and controlling laptop were placed on an external loading dock, which 

experienced sun in morning and shade in the afternoon. This test was performed during 

November in Boulder, CO, where the normal temperature range is -1.1° to 13.3° C (30°

to 56° F). Because we wished to study the drift of the receiver setup, the signal 

generator was located inside the building, having more stable environmental conditions.

To obtain the uncertainty value for each frequency, the data were normalized to 

the mean value of the combined results of the six different tests at each of the three 

power levels. These normalized data, which now had a nominal 0 dB mean, were then 

combined, resulting in a data set of 1800 samples. Then, the standard deviation was 

computed for each frequency set of 1800 samples. Based on the six tests and the three 

different inline attenuation levels, the relative uncertainty of the receiver setup, , 

was less than 0.1 dB for all frequencies except 1834 MHz. The 1834 MHz case had a 

standard deviation of just less than 1 dB due to more variability when the 80 dB 

attenuator was inline. This was the only combination of frequency and attenuator that 

demonstrated any significant variability between the six tests intervals.

We also include the uncertainty , for the spectrum analyzer itself, as

provided by the manufacturer and is given as typically less than 0.6 dB.

7.3 Type B uncertainties of the measurement instrumentation

We next consider the Type B uncertainties of the receiver setup for the 

measurement system. In the section above, statistical methods were used to arrive at 

uncertainties for various components of the measurement system. The main component 

not covered in that analysis was the uncertainty contribution due to the RF cables 

connecting the receive antenna to the spectrum analyzer. Factors that can contribute to 

uncertainty include items such as temperature drift, the repeatability of connecting 

cables to the equipment and antennas, and the flexing or bending of the cables. While 

the impacts due such factors are expected to be small, the uncertainties are discussed 
58

because these measurements take place in less than optimally controlled environments.

We call this uncertainty and estimate it as less than 0.2 dB, based upon 

observations over numerous field measurements.

7.4 Combined uncertainty of the measurements

Table 6 summarizes the various components of uncertainty described in the 

previous subsections. The combined uncertainty in the measured data is then

 √ 

    

. (11)

These uncertainties were combined by use of root-sum-of-squares addition on 

the linear (as opposed to logarithmic) values, and then converted back to decibels, 

giving of typically less than 1.4 dB, and less than 2.8 dB for the worst case 

(i.e., the 430 MHz radio.) This combined uncertainty in the measurement system is 

reasonable for this type of experiment, where the channel variability will be on the order 

of 7 dB or greater. In addition, the goal of this work is to provide broad classifications of 

environments whose measured path-loss values range from a few tens of decibels to 

well over 150 decibels. Thus, a measurement uncertainty of 2.8 dB is acceptable for our 

application.

Table 6. Description of the measurement uncertainties with associated values.

Type Uncertainty Description Method of Estimate Values (dB)

Type A

Accuracy in spectrum 

analyzer measurements. 

Specified by the 

manufacturer.

< 0.6

Typical

Type A

Data collection system tests, 

including laptop and spectrum 

analyzer.

Collected statistical data 

for a known source over 

a one day period, in an 

outdoor environment.

0.1

(1.0 for 1834 MHz)

Type A Transmitter reverberation 

chamber TRP 

measurements.

Standard deviation of 10 

independent 

calculations of TRP.

0.6 to 2.25 

Type B Cable changes due to 

temperature.

Observations from 

previous uncertainty 

experiments. 

< 0.2
59

8. Summary and Conclusion

RF PASS tests were performed in a New York subway station and the Empire 

State Building because these types of structures provide challenging RF propagationchannel environments. In the subway, the RF PASS systems were limited in their ability 

to communicate beyond the initial entrance level. Without the use of repeaters, most of 

the systems could communicate only a short distance beyond the bottom of the stairwell 

that connected the token booth corridor to the street. Two systems used repeaters to 

extend the coverage area. When a repeater was located at the base of the stairwell 

leading up to the street, those two systems were able to communicate the RF PASS 

alarms between the street level and the first passenger platform. However, with only a 

single repeater, neither of the two repeater systems was able to communicate between 

the external receive site and the second passenger level. This suggests that for 

structures with sizable subterranean sections, a repeater system will likely be required 

to reach an external incident command post. If the structure has multiple subterranean

levels of increasing depth, a multiple-hop relay system will likely be necessary to ensure 

the reliability of the communication channel. 

In the path-loss measurements and analysis performed at five frequencies,

ranging from 430 MHz to 2405 MHz, there are several important insights. Based on the 

upper adjacent values in the box-plot statistical representation of the path-loss data

from the Empire State Building (see Figure 36), path-loss values of 140 dB to 175 dB 

are possible for high-rises. For the subway, the path-loss values exceed 210 dB to 240 

dB at the lower two passenger platforms (see Figure 35). The frequency dependence is 

more pronounced for the Empire State Building results, but less apparent in the subway

data. Thus, while a system may function well at the lower end of the frequency 

spectrum in the above ground portions of a large building, the subway results 

demonstrate that subterranean structures can cause path-loss values greater than 

200 dB across the 430 to 2400 MHz range. 

The testing completed here focused on RF PASS system performance and RF 

propagation-channel measurements in a high-rise and subway station. While a primary 

goal of the effort was to look at the correlation between the system performance and 

path-loss behavior, a secondary goal was to gather path-loss data in two highattenuation settings. Thus, parameter values for log-normal distributions that will allow 

simulation of the measured path-loss conditions are included in this report. The authors 

hope that the data presented here, along with future sets of data, can be used to 

develop a complete suite of test methods, not only for RF-based PASS systems, but 

also for other RF-based electronic safety equipment. The path-loss values obtained 

here are general and could be used to develop standards for other equipment as the 

need arises for standards for these systems.

Acknowledgements

The analysis and development of test methods for RF-based emergency equipment has 

been funded by the Department of Homeland Security Standards Branch, Bert Coursey, 

Chief (retired 2011), Philip Mattson Acting Chief (present). 

Several organizations and many people were responsible for the success of this

in-field measurement program: The Fire Department of New York provided logistics and 
60

support for the field measurements; the New York City Transit Authority facilitated 

access to the subway station; and Empire State Building personnel provided access for 

the measurements within the building.

From the New York City Transit Authority, we thank Tom Leonard, Office of 

System Safety; Paul R. Gerardi, Manager, Fire Safety, Office of System Safety; and 

Thomas Derienzo, Jr., Superintendent, Fire Suppression, Track and Infrastructure, 

Maintenance of Way. From the Empire State Building, we thank Karl Tremmel, Chief 

Engineer; and Timothy J. Clancy, Director of Operations. And from the Fire Department 

of New York, we owe thanks to Chief Edward Kilduff, Chief of Department; Deputy 

Assistant Chief Stephen Raynis, Chief of Safety Command; Battalion Chief Robert 

Keys, Chief in Charge (retired), Research and Development Unit; and the officers and 

firefighters of FDNY's Research and Development Unit including Lt George Hough, FF 

George Grammas, FF Mario Tarquinio, and FF Ed Clancy.

Finally, we acknowledge the support received from NIST Physical Measurements 

Laboratory management, Perry Wilson, RF-Fields Group Leader, and Mike Kelley, 

Division Chief. 

References

[1] D.R. Novotny, J.R. Guerrieri, and D.G. Kuester, “Potential interference issues 

between FCC Part 15 compliant UHF ISM emitters and equipment passing 

standard immunity testing requirements,” IEEE EMC Symp. Dig., Aug. 2009, pp. 

161-165.

[2] M.R. Souryal, D.R. Novotny, J.R. Guerrieri, D.G. Kuester, and K.A. Remley, 

“Impact of RF interference between a passive RFID system and a frequency 

hopping communications system in the 900 MHz ISM band,” IEEE EMC Symp.

Dig., July 2010, pp. 495-500.

[3] K.A. Remley, M.R. Souryal, W.F. Young, D.G. Kuester, D.R. Novotny, and J.R. 

Guerrieri, “Interference tests for 900 MHz frequency-hopping public-safety 

wireless devices,” IEEE EMC Symp. Dig., Aug. 2011, pp. 497-502.

[4] National Institute of Standards and Technology, “Statement of Requirements for 

Urban Search and Rescue Robot Performance Standards-Preliminary

Report”http://www.isd.mel.nist.gov/US&R_Robot_Standards/Requirements%20R

eport%20(prelim).pdf .

[5] K.A. Remley, G. Koepke, E. Messina, A. Jacoff, and G. Hough, “Standards 

development for wireless Communications for Urban Search and Rescue robots,” 

Proc. Intl. Symp. Advanced Radio Technologies, June 2007, pp. 66-70.

[6] National Fire Protection Association, NFPA 1982: Standard on Personal Alert 

Safety Systems (PASS), document scope available at 

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=1982 , 

accessed Nov. 4, 2011.
61

[7] C.L. Holloway, W.F. Young, G. Koepke, K.A. Remley, D. Camell, and Y. 

Becquet, “Attenuation of Radio Wave Signals Coupled Into Twelve Large 

Building Structures,” NIST Technical Note 1545, Aug. 2008.

[8] W.F. Young, K.A. Remley, J. Ladbury, C.L. Holloway, C. Grosvenor, G. Koepke, 

D. Camell, S. Floris, W. Numan, and A. Garuti, "Measurements to support public 

safety communications: attenuation and variability of 750 MHz radio wave signals 

in four large building structures," NIST Technical Note 1552, Aug. 2009.

[9] W.F. Young, C.L. Holloway, G. Koepke, D. Camell, Y. Becquet, and K.A. 

Remley, "Radio-wave propagation into large building structures—part 1: CW 

signal attenuation and variability, IEEE Trans. Antennas Propagat., vol. 58, no. 4, 

Apr. 2010, pp. 1279-1289.

[10] W. F. Young, K. A. Remley, D. W. Matolak, Q. Zhang, C. L. Holloway, C. 

Grosvenor, C. Gentile, G. Koepke, and Q. Wu, “Measurements and models for 

the wireless channel in a ground-based urban setting in two public safety 

frequency bands,” NIST Technical Note 1557, Jan. 2011.

[11] A. Molisch, “Wireless Communications,” Chapter 5, pp. 96-99, John Wiley & 

Sons Ltd., Copyright 2011.

[12] E.L. Crow and K. Shimizu, (Ed.), “Lognormal Distributions: Theory and 

Applications”, Marcel Dekker, New York, 1988.

[13] C. Forbes, M. Evans, N. Hastings, and B. Peacock, “Statistical Distributions,” 

Fourth edition, pp. 131-134, John Wiley & Sons Inc., Copyright 2011.

[14] J.M. Chambers, W. S. Cleveland, B. Kleiner, and P. A. Tukey, “Graphical 

Methods for Data Analysis,” Chapter 2, pp. 21-24, Duxbury Press, Boston, 

Massachusetts, Copyright 1983 by Bell Telephone Laboratories Inc.

[15] M. Abramowitz and I. A. Stegun (Ed.), “Handbook of Mathematical Functions with 

Formulas, Graphs, and Mathematical Tables,” p. 297, Dover Publications, Inc., 

New York, 1972.

[16] B. N. Taylor, C. E. Kuyatt, “Guidelines for Evaluating and Expressing the 

Uncertainty of NIST Measurement Results,” NIST Technical Note 1297, 

September, 1994.

[17] K.A. Remley, W.F. Young, and J. Healy, “Analysis of Radio-Propagation 

Environments to Support Standards Development for RF-Based Electronic 

Safety Equipment,” NIST Technical Note 1559, Mar. 2012.
62

Appendix A: RF PASS Performance and Path Loss Data

Table 7. RF PASS system test results for the subway structure. Associated path loss values are based on the 

frequency band of operation for that particular system. Note that only Systems 2 and 4 were tested with a single-hop 

repeater.

System 1 System 2 System 3 System 4

PASS test locationFirefighter-downEvacuationPath loss (dB)

Without 

repeater

With 

repeater

Path loss (dB)Firefighter-downEvacuationPath loss (dB)

Without 

repeater

With 

repeater

Path loss (dB)

Firefighter-downEvacuationFirefighter-downEvacuationFirefighter-downEvacuationFirefighter-downEvacuation

1 67.1 66.8 66.8 79.1

2 94.3 104.7 104.7 112.3

3 104.6 108.1 108.1 120.7

4 103.9 111.9 111.9 124.7

5 102.5 124.1 124.1 132.7

6 127.4 122.7 122.7 144.3

7 125.5 138.3 138.3 153.4

8 135.0 140.7 140.7 160.7

Legend : Measured failure : Expected failure

 

 : Measured success : Expected success 

X

X

X

X

X

X

X X

X X

X

X X

X X

X X

X X

X X

X X

X X

X X

X X

X X

X

O

×

O

O

O O

O O

O O

O O

× ×

×

× ×

×

×

×

×

×

×

×

× ×

×

×

×

×

O O

O

O

O

O

O O

O O

O O

O O

O

O O O O

O

O O

O O

O

O O

O O

O O O O

O O

O O

O
63

Table 8. PASS system test results for the Empire State Building. Associated path loss values are based on the 

frequency band of operation for that particular system.

System 1 System 2 System 3 System 4

Test locationFirefighter-downEvacuationPath loss (dB)Firefighter-downEvacuationPath loss (dB)Firefighter-downEvacuationPath loss (dB)Firefighter-downEvacuationPath loss (dB)

0 58.9 61.9 61.9 69.7

4 108.3 91.4 91.4 100.4

5 117.5 99.4 99.4 113.8

8 105.2 96.6 96.6 119.6

9 97.7 93.7 93.7 110.3

10 108.1 106.4 106.4 115.8

11 112.0 106.7 106.7 127.1

12 103.4 94.6 94.6 114.5

13 113.0 107.2 107.2 123.7

14 108.3 113.2 113.2 134.2

15 109.8 100.7 100.7 121.9

16 115.6 108.4 108.4 125.9

17 116.6 106.5 106.5 122.9

18 104.3 103.0 103.0 125.8

20 112.9 116.2 116.2 126.3

21 118.1 106.4 106.4 117.4

23 110.9 103.9 103.9 135.0

26 128.9 114.1 114.1 137.2

29 136.8 129.0 129.0 146.4

Legend : Measured failure : Expected failure

 : Measured success : Expected success

X

O

×

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O O O

O

O

O

O

O

O

O

O

O

O

O

O O

O O

O

O

O

O

O

O

O

O

O

O

O

O

O O

O O

O O

O O O O

O

O O

O O

O O

O

O O

O O

O

O

×

×

×

×

×

× ×

× ×

× ×

×

× ×

× ×

× ×

× ×

× ×

× ×

× ×

× ×

X X

X X

X X

X X

X X

X X

X X

X X

X X

X X

X X

X X

X

X X

X X

X X

X X

X X

X X

X X

X

X X

X X

X X

X
64

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