May 12, 2021

AWS-3 LTE Impacts on AMT: Public Outreach Brief
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Audience Instructions

2
Context & Background

Technical Components

▫ Task 1: In-Situ Captures of AWS-1 LTE for Aeronautical Mobile Telemetry 

System Evaluation

Speaker: Eric Nelson, NTIA 

▫ Task 2: Laboratory Methods for Recording AWS-3 LTE Waveforms

Speaker: Duncan McGillivray, NIST

▫ Task 3: AWS-3 LTE Impacts on Aeronautical Mobile Telemetry

Speakers: W.F. Young, MITRE; Duncan McGillivray, NIST; Adam Wunderlich, NIST

Wrap-up

Welcome

3
National Advanced Spectrum and Communications 

Test Network (NASCTN)

Established in 2015 by NIST, the U.S. 

DoD, and NTIA. In 2018, added 

NOAA, NSF, and NASA.

Organizes a national network of 

federal, academic, and commercial 

test facilities

Provides trusted spectrum testing, 

modeling, and analysis to develop 

and deploy spectrum-sharing 

technologies and inform future 

spectrum policy and regulations.

4
NASCTN MISSION

Develop scientifically rigorous test 

plans and new methodologies with 

independent experts

Access to key test facilities, and 

commercial and federal equipment 

and capabilities

Provide validated data and models 

for use within the spectrum sharing 

community

To provide, through its members,

robust test processes and validated

measurement data necessary to

develop, evaluate and deploy

spectrum sharing technologiesthat

can increase access to the spectrum

by both federal agencies and nonfederalspectrum users.

Operates as a trusted agent and protect proprietary, sensitive, and classified information

5
Contributors

Duncan McGillivray

Adam Wunderlich

Jack Sklar

Aric Sanders

M. Keith Forsyth

Daniel Kuester

Melissa Midzor

Fabio daSilva

Matthew Briel

Irena Stevens

Kenneth Dudley

Claude (Lee) Joyce

Charmaine Franck

Steven Harrah

Eric Nelson

Frank Sanders

Kenneth Brewster

Rebecca Dorch

William Young – Test Lead

Mark Krangle Shawn Lefebre

Mark Lofquist Tim Mull

Evan Briggs Victor Haley

Ashton Knight Adam Paranay

Jacob Johnson Matt Puentes

Nevan Shattuck

Keith Hartley

6
• ABE

– adjacent band emission

• AMT– aeronautical mobile telemetry

• ARTM-CPM– Advanced Range Telemetry 

continuous phase modulation

• AWGN– additive white Gaussian noise

• AWS-1– advanced wireless services –1

• AWS-3– advanced wireless services –3

• Az– azimuth

• BER– bit error rate

• BW– bandwidth

• dBFS– decibel relative to Full Scale

• DUT– device under test

• EAFB– Edwards Air Force Base

•E

b/N0 

- energy per bit per noise density

• IRIG– Inter-Range Instrumentation Group

• LaRC– Langley Research Center

• LDPC– low density parity check

• LTE– long term evolution

• NASA– National Aeronautics and Space 

Administration

• NASCTN– National Advanced Spectrum and 

Communications Test Network 

•N

a

eff

- effective ambient noise

•N

0

– noise spectral density

• NIST– National Institute of Standards and 

Technology

• OBW– occupied bandwidth

• OOBE– out of band emission

• PL - pathloss

• PCM/FM – pulse code modulation / frequency 

modulation

• QPSK– quadrature-phase shift keying

• RB– resource block

• Rx– receive

•Save– signal average power

• SABE– AMT Signal to ABE Power ratio

• SOQPSK– shaped offset QPSK

• SOQPSK-FEC– SOQPSK with forward error 

correction

• STC– space time coding

• STC-FEC– STC with forward error correction

• Tx– transmit

• UE– user equipment

• UL– uplink

• VSA– vector signal analyzer

• VSG– vector signal generator

• WF– waveform

Acronyms Slide

7
• AWS-3 auction led to compressed operations of 

DoD range Aeronautical Mobile Telemetry 

(AMT) systems. 

• AMT infrastructure remains unchanged, and 

current IRIG protocols for mitigating 

interference do not include new waveforms 

such as LTE. 

• NASCTN Projects focused on:

▫ Out-of-band emissions measurements for LTE 

devices operating in the AWS-3 Band (2018)

▫ Coexistence metrics and compatible evaluation 

methodologies for studying LTE impacts on AMT 

receivers (2021)

▫ Developing a curated set of LTE waveforms for 

future testing of multiple range environments

 Single and multi-user, uplink only (2021)

AWS-3: Adjacent Band LTE to AMT

8
• Report jointly published by NTIA and NIST Jan 2018: 

▫ NTIA TR-18-528, NIST TN-1980

Prior NASCTN Project: Out-of-Band Emissions Measurements of LTE 

Devices Operating in the AWS-3 Band

Report presents power 

spectral densities of AWS-3 

LTE OOBE with the potential 

to impact operation of 

physically co-located AMT 

systems in adjacent bands. 

9
Test Plan Review

10
Susceptibility Study Test Plan Concept

Notional scenario • Collect radiated LTE uplink waveforms

in-situ and in-laboratory

▫ Surrogate in-situ LTE form translated to AWS-3 band

▫ In-situ waveforms captured through telemetry receiver 

antennas and at the input to the AMT receiver

• Collect multiple Key Performance Indicators

▫ Bit error rate, signal-to-noise ratio, Eb/N0, etc.

▫ Include Gaussian noise waveforms

• Process and analyze data 

▫ Compare against IRIG band edge back off 

recommendations

▫ Investigate relation of impacts to “equivalent in-band 

Gaussian noise”

• Two Laboratory Testbeds

▫ NIST/NASCTN Boulder, CO

▫ MITRE Bedford, MA

11
Overview of testing efforts Resources

1

Collect In-Situ LTE waveforms/spectrograms at AWS-1 

a. Capture LTE signals in a variety of AMT environments (EAFB, NASA Langley)

b. Informs efforts #1 and #2 on network laydown and settings

c. Use waveforms/spectrograms to playback/build interference waveforms for effort #1 & 

future tests

NTIA, NIST, NASA, 

EAFB

2

Generate Waveforms (and Library for future testing) - Radiated Tests In Lab

a. Leverage existing equipment and test benches to generate and capture LTE – UL 

waveforms

b. Develop & measure various radiated test scenarios

c. Establish a “Library of LTE – UL waveforms” that can be leveraged for this and & future 

tests

NIST

3

Sensitivity and Susceptibility Testing - Connectorized Lab bench test with AMT hardware

a. Test sensitivity to various VSG produced signals. Unidirectional Tx -> Rx AMT link, using 

predefined data-payload/streams. 

b. Test susceptibility to generated LTE waveforms based on efforts #2, #3

i. Gain insights into response & relaxation time

ii. Automate / execute tests in laboratory environment

iii. Define, track, and analyze AMT Key Performance Indicators

iv. Develop statistics required (output resultant distributions with uncertainties)

NIST, MITRE

Test Outline

12
Presented by: 

Eric Nelson, NTIA ITS

Task 1

In-Situ Captures of AWS-1 LTE for Aeronautical Mobile 

Telemetry System Evaluation
Institute for Telecommunication Sciences

In-Situ Captures of AWS-1 LTE for Aeronautical 

Mobile Telemetry System Evaluation

Eric Nelson ▪ enelson@ntia.gov ▪ (303) 497-7410

12 May 2021
Institute for Telecommunication Sciences

● Measurement support to NASCTN leveraged ITS experience measuring LTE UE 

uplink aggregate transmissions for DISA/DSO’s Spectrum Sharing Test and 

Demonstration (SST&D) program

● Carrier Coordinated Testing events have been ongoing since October 2018 in 

Longmont, Boulder, Denver and Grand Jct, CO as well as the SEC Football 

Championship game in Atlanta, GA

● Measurements of a wireless carrier’s aggregate uplink transmission in the AWS-1 

band (1710-1755 MHz) have served as proxies for future loading of the AWS-3 band 

(1755-1780 MHz)

● Given the carrier’s cell laydown, the measurement data permit system modelers to 

compare measured aggregate power at the receive location to model predictions

● In-Situ Captures of AWS-1 LTE for Aeronautical Mobile Telemetry System Evaluation 

provided a unique opportunity to examine UE emissions through a victim receiver 

Background

15
Institute for Telecommunication Sciences

● Center frequency between two 

subcarriers

● FFTs sized to band of interest

● FFT bins are 15 kHz and centered 

on LTE subcarriers

Reference NTIA Tech Memo 21-552 for more details

Tech Tip: Align to LTE Uplink Modulation 

16
Institute for Telecommunication Sciences

AWS Band Plans (uplink only)

...so evaluate 

emissions here...

... as a proxy for 

emissions here...

Note: wireless carriers often combine adjacent licenses to permit larger LTE band deployments

... to assess impacts 

on Federal systems

LTE deployments in AWS-1 

are mature but those in

AWS-3 are not...

17
Institute for Telecommunication Sciences

Standalone VSA Capture System

18

Ant

Ant

Attenuator

12 dB

Keysight 

N9030B PXA

(VSA)

CommScope HBX-3319DS-VTM, 20.5 dBi, cross polarization antenna

Instrument 

Control 

Computer

Arduino 

GPS Sync

Preselector

Bulkhead +45o output

Rx

Serial I/O

Net system gain (Ant  Rx) is 23.0 dB

Trig In

PPS out

Ethernet

Standalone system was optimized for assessing aggregate interference 

from population centers. Measurements are referenced to the antenna 

terminal and impact on victim receivers is inferred.

Aggregate UE 

emissions system 

deployed at Grand 

Mesa overlooking 

Grand Jct, CO
Institute for Telecommunication Sciences

Panel Antenna Coverage in Grand Jct, CO

azimuths and beamwidths indicated

19
Institute for Telecommunication Sciences

● ITS aggregate interference system characteristics:

Panel antenna has a 33° horizontal beamwidth and 20.5 dBi gain

Preselector has LNA preceded by 60 MHz bandpass filter, which only encompasses the 

AWS-1 uplink

 Standoff distance is typically 7-10 km and encompassed population ranges from 50,000 to 

well over 500,000

UEs are served by tens to hundreds of eNBs, so aggregate PRB occupancy during daytime 

hours is routinely 100%

● The in-situ measurements had these differentiators:

 Employed a narrow-beam dish antenna

 Front end filter is much wider—approximately 1370-2560 MHz

At EAFB assessed victim receive system with VSA tapped in adjacent to AMT receiver

As a basis for comparison...

20
Institute for Telecommunication Sciences

21

Longmont, CO

10 MHz LTE band

(center)
Institute for Telecommunication Sciences

22

Denver, CO

10 MHz LTE band

(center)
Institute for Telecommunication Sciences

23

In-building DAS 

at Mercedes 

Benz Stadium, 

Atlanta, GA 

10 MHz LTE band 

(right)

20 MHz LTE band 

(left) is an external 

macrocell
Institute for Telecommunication Sciences

24

Edwards AFB

20 MHz LTE band

(center)

Aggregate measurements of 

larger populations with wide 

beamwidth antenna permit 

AWGN assumptions

Narrow beamwidth in-situ 

AMT captures demonstrate 

need for lab testing to 

characterize and model 

emissions
Institute for Telecommunication Sciences

● Assess the characteristics of the RF chain and any presence of strong in-band 

transmissions

● Demonstrate that the AMT receiver’s front-end LNA determines the receive system 

noise figure, i.e. the VSA’s internal noise is negligible

● Examine worst case scenario with AMT antenna at 0° elevation. Slew antenna 

through all azimuths and note azimuths with stronger UE transmissions

● Revisit noted azimuths and dwell for several minutes to gauge level of activity

● Map each noted azimuth to ascertain possible sources; investigate source(s)

 Intermittent transmissions were often associated with vehicles on rural highways

Periodic transmissions were often associated with office buildings or nearby 

developments

Regular transmissions were typically from distant cities

Site Survey

25
Institute for Telecommunication Sciences

Azimuthal Scanning and Source ID

26

Real Time 

SpecAn Display

Antenna Control 

and Camera

Note: instrument noise floor is driven by front end LNA
Institute for Telecommunication Sciences

Edwards AFB

Azimuthal Scan Mapping

27

NASA LaRC
Institute for Telecommunication Sciences

● Revisit worst case azimuths noted during site survey

● Capture UE transmissions from uppermost AWS-1 LTE band

● Increase VSA span to ensure capture of upper adjacent-band emissions

● Using a test UE, generate emissions with known throughputs into antenna sidelobes

● Measure G/T using the sun as a noise source (EAFB) or net loss from the antenna to the 

VSA input (NASA/LaRC) to provide a gauge to estimate UE transmit power

In-Situ Measurement Approach

28
Institute for Telecommunication Sciences

Edwards AFB

Sample over-the-air captures

29

NASA LaRC
Institute for Telecommunication Sciences

Edwards AFB

Single UE Captures

30

NASA LaRC

* bandwidth not obtained as indicated 

by traffic monitoring tool
Institute for Telecommunication Sciences

Capture Post-Processing

● Spectrograms are optimal for observing UE activity in a band, but the LTE 

transmission time interval (TTI) of 1 ms imposes a practical limit of 100 ms per plot 

making hundreds of plots necessary.

● Spectrogram contours indicate decile power thresholds for each of the FFT bins 

and are a useful summary—especially for illustrating out of band emissions and 

peak powers.

● A single sample exceeding the VSA’s Input Range will flag an overload. The 

instrument has several dB of headroom, so Power vs. Time plots provide insights 

into overload conditions during a capture. 

31
Institute for Telecommunication Sciences

Power vs. Time and Spectrum Contour Plots

32
Institute for Telecommunication Sciences

Selection of Waveforms for Bench Testing 

Sliding Window Technique

● Start with the 3072 x (N/3072) FFT array 

which represents power in mW per 15 kHz 

bin;

● For each FFT sum linear power across the bins 

within the 18 MHz occupied bandwidth which 

in this instance was the center 18,000/15 = 

1200 bins;

● From this result which contains 15 power 

measurements per ms, compute the 

cumulative density functions (CDFs) for 

windows ranging in size from 100-1000 ms or 

1500-15000 samples, slid through the data 

sequence in 50 ms overlapping steps;

● Determine the 50th, 90th, and 99th 

percentile power for each window; and

● Plot the percentiles as a function of window 

number.

33
Institute for Telecommunication Sciences

Multi-UE (Live) Waveform Artifacts

34

One of 4 waveforms (2 each from EAFB and NASA/LaRC)
Institute for Telecommunication Sciences

Single (Test Mode) UE Waveform Artifacts

35

UE upload rate of 10 Mbps
Institute for Telecommunication Sciences

Conclusions

● Use of AWS-1 as a proxy for AWS-3 continues to foster ongoing research as wireless 

carrier LTE deployments in AWS-3 lag those in AWS-1

● In-situ captures evidence dramatically reduced band occupancy (versus wider 

beamwidth antennas) and demonstrate the need for controlled experiments with eNBs

● Mature VSA capture and post-processing techniques yield test waveforms that 

illustrate the impact of real-world UE emissions through controlled bench testing

● References

 E. D. Nelson, “LTE Uplink Aggregate Interference Measurement System,” NTIA Technical Memorandum 

TM-21-552, February 2021,

 Eric D. Nelson and Duncan A. McGillivray, “In-Situ Captures of AWS-1 LTE for Aeronautical Mobile 

Telemetry System Evaluation,” NTIA Report TR-21-553, March 2021

36
Presented by: 

Duncan A. McGillivray, NIST 

Task 2

Laboratory Methods for Recording AWS-3 LTE 

Waveforms
38

• Experimental Setup

• Experimental Design 

• Data Synchronization and Validation

• Library

Purpose

Record Radiated Waveforms for Receiver Sensitivity and Susceptibility Testing

a. Leverage existing equipment and test benches to generate and capture 

LTE – UL waveforms

b. Develop & measure various radiated test scenarios

c. Establish a “Library of LTE – UL waveforms” that can be leveraged for AWS3 LTE Impacts on AMT and future tests
39

Anechoic Chamber LTE UE Measurements

• Communications and Diagnostic

• Hybrid – cabled & over the air testbed controls test 

factors:

• Pathloss to DUT 

• RF condition of Traffic Generator

• Cellular traffic parameters

• DUT UE data rate

• Background traffic of the eNB cell

• Monitoring of LTE diagnostics at the DUT UE and 

uplink (UL) traffic close to the eNB

• Records

• UE diagnostics

• Spectrum occupancy 

• IQ recording

• Separate path

• Electronically triggered 

• Optimized for dynamic range

Communications & Diagnostic

IQ Recording

Data Sources
40

IQ Capture Scenarios

• Static Settings:

▫ IQ Recording

 61.44 M Samples/s

 Length: 5 seconds

• eNB

• P0 PUSCH -85 dBm

 P0 PUCCH -117 dBm

 alpha 0.8

• DUT UE-primary ▫ traffic type: UDP

▫ RSRP: -95 dBm

▫ DUT UE-secondary  0.5 Mbps uplink rate

 traffic type: UDP

 RSRP: -115 dBm

• Background Traffic 

• 0.5 Mbps per loading UE

• traffic type: UDP

• RSRP: -95 dBm

Factor # Levels* Settings Type Testbed 

Component

Power control 2 Open Loop / Closed 

Loop

categorical eNB

Allocation 3 5, 10 , 20 MHz numeric eNB

Resource Block (RB) 

blanking mask

4 None, Upper 6 RBs, 

Upper 10 RBs, 

Center 10% RBs

categorical eNB

DUT UL 

data rate

4 0.5, 1, 5, 10 Mbps numeric DUT UE

# loading UEs 3 3, 7, 15 numeric Traffic 

Generator

# radiating UEs 2 1, 2 numeric NBIT

*Test scenarios not fully factorial

56 unique configurations; 5 seconds recordings; each recorded twice
41

Data Synchronization and Validation

• IQ recording

• Published as

• interleaved 16 bit integer

• spectrogram (dB/RB)

• referenced to -25 dBm

• Real-time spectrum

• Not published

• Used as cross confirmation that VST and 

USRD are recording the same events

• UE Diagnostic

• Published as

• Diagnostic spectrogram (mW/RB)

• Time series of

• uplink grant size & location (Start RB, # of RBs)

• MCS index (integer)

• Total Power per TTI (dBm)

IQ Recording Real-time 

spectrum

Uplinkgrants

Time-aligned through autocorrelation 
42

IQ Library

AWS-3 Captures in 

Laboratory Setting

Configuration 1

Capture 1

Data.zip

140 millisecond snapshot of 5 second recording 
Presented by: 

William F. Young, MITRE

Adam Wunderlich, NIST 

Duncan A. McGillivray, NIST

Task 3

AWS-3 LTE Impacts on Aeronautical Mobile Telemetry
• Testbed Design & Characterization

• Experiment Design

• Waveform Processing

• Susceptibility Study

▫ Frequency Offset Experiment: IRIG-based Analysis 

▫ Selected Results from Main Characterization Experiment

▫ Equivalent Ambient Noise (Eb/N0 Loss) Analysis

• Anomalous Results

• Conclusions

Outline

44
Testbed Design & Characterization

45
• MITRE, Bedford MA

▫ Lead testbed for

 Test execution

 Automation development

Highlights

NIST, Boulder CO

MITRE, Bedford MA

Efficient traversing of test design with multiple degrees of 

freedom

Parallel acquisition of test matrix

High degree of consistency in results

Confidence in investigation of anomalous results

• NIST, Boulder CO 

▫ Lead concept development of

 Experiment Design

 Test Profiles

46
50 

Ω

Δ

Σ

1

2

TP #

TP #

AMT

TX

ABE

WFs

Noise

Diode

VSA

Power

meter

Test

Point 1

Test

Point 2

PC

Physical State Automation

Setting and Measurements

DUT State Automation

Setting and Data Recording

Verification Testpoints

12

Σ

AT1

Δ

Σ

1

2 10 dB

AT2

AMT

RX

dBm

20 dB

10 dB

AT3

10 dB

Test

Point 

3

TP #

Test Circuit AMT TX and ABE 

Referenced to input of 

AMT RX

• Shared ▫ RF circuit 

componentry

▫ Test automation 

framework 

▫ Calibration source

• Differences ▫ AMT TX ▫ ABE waveform 

generator

▫ Power meter ▫ VSA

47
Testbed characterization

• Characterized

▫ sources for power output and variability across all test design factors

▫ variable attenuator performance

• Quantified test circuit path loss

• Investigated receiver noise performance 

• Performed rigorous uncertainty estimation for: 

▫ Aeronautical Mobile Telemetry (AMT) Signal Power at the plane of the AMT receiver (RX)

▫ Adjacent band emissions (ABE) signal power at the receiver for both additive white Gaussian noise 

(AWGN), Long-term Evolution (LTE)

▫ AMT Signal to ABE Power ratio (SABE) at the plane of the AMT receiver (RX)

48
Experimental Design

49
• Pre-testing (a.k.a. sensitivity testing)

▫ Early-stage investigations to inform test procedures & test automation

• Seven designed experiments – further details in Chapter 2 of tech report

▫ Pilot Study: Baseline Experiment, Characterization Experiment

▫ Frequency Offset Experiment

▫ Main Characterization Experiment

▫ Supplemental Experiments

 Side Experiment A: Equalizer

 Side Experiment B: Space-Time Coding

 Side Experiment C: Excess Noise

Overview of Experiments 

50
Pilot Study NIST, Boulder CO

Goals: 

1) Verify testbed automation (on two testbeds)

2) Obtain preliminary data to inform subsequent experiments

• Baseline Experiment (Repeatability Assessment)

▫ 2 factors, fixed receiver settings, 33 unique test configs

▫ Repeated 7 times

• Characterization Experiment 

▫ 6 factors, 1320 unique test configs

• First NASCTN implementation of parallel testbeds

▫ Led to improvements in testbed automation software

▫ Informed selection of factors and signal levels for main 

characterization experiment (described next)

MITRE, Bedford MA

51
Frequency Offset Experiment

Id Factor Settings # Levels Easy/Hard to Change 

A Modulation Type PCM/FM, SOQPSK, SOQPSK-FEC, ARTM-CPM 4 Hard

B Bit Rate 1, 5, 10 Mbps 4 Hard

C ABE Type AWGN 20 MHz, in-situ LTE captures: single-UE (92 RB, Full, 

92 RB filtered, Full filtered), multi-UE: (EAFB Az76, EAFB 

Az198), lab LTE captures (20 MHz Full, 20 MHz upper 10 RB 

blanked, 5 MHz Full)

10 Hard

D Frequency Offset 1 MHz steps on grid including IRIG-recommended offset 12 Hard

• Only test Modulation/Bit Rate combinations shown in yellow

• Same Save/ABEpeak ratio for each LTE waveform

• Save/ABEave fixed for AWGN

• 840 unique test configurations

• Repeats/replication

 All configurations tested twice at MITRE-Bedford

 Subset tested twice at NIST-Boulder (excluding SOQPSK-FEC)

Modulation Type Bit Rate (Mbps)

PCM/FM 1 5

SOQPSK 5 10

SOQPSK- FEC 5 10

ARTM CPM 5

Objective: Characterize effect of shifting AMT center frequency relative to ABE 

52
Modulation Type Bit Rate (Mbps)

PCM/FM 1 5 10

SOQPSK 1 5 10 20

SOQPSK- FEC 1 5 10 20

ARTM CPM 5 10 20

Main Characterization Experiment

Id Factor Settings # Levels Easy/Hard to Change 

A Modulation Type PCM/FM, SOQPSK, SOQPSK-FEC, ARTM-CPM 4 Hard

B Bit Rate 1, 5, 10, 20 Mbps 4 Hard

C ABE Type None, AWGN (BW=20, 18, 16.5 MHz), in-situ LTE 

captures: single-UE (92 RB, Full), multi-UE (EAFB 

Az76, EAFB Az198, LaRC Az140, LaRC Az165)

10 Hard

D AMT Signal Level 1 dB steps on grid spanning a 

10 dB range with config-dependent shift

11 Easy

• Configurations not tested: 

 PCM/FM at 20 Mbps, ARTM-CPM at 1 Mbps 

• 1540 unique test configurations 

• Repeats/replication

 All configurations tested twice at MITRE-Bedford

 Subset tested twice at NIST-Boulder (excluding SOQPSK-FEC) First priority shown in yellow

Objective: Assess impact of different ABE types on AMT receiver performance. Cover 

transition from strong link (BER < 10-7) to a poor link (BER > 10-4)

53
• Address emerging aspects of AMT receiver operations and 

susceptibility testing – details and results in tech report

• Side Experiment A: Equalizer

Objective: Assess impact of enabling equalizer in the presence of ABE

• Side Experiment B: Space-Time Coding

Objective: Assess impact of STC option in the presence of ABE

• Side Experiment C: Excess Noise

Objective: Assess impact of in-band excess white noise on AMT performance

Supplemental Experiments

54
Waveform Processing

55
As Captured Waveforms

In Band LTE

Persistent 

noise due to 

Amplifiers/ 

Non 

persistent 

due to time 

evolved 

OOBE

Persistent 

noise due to 

Amplifiers/ 

Non 

persistent 

due to time 

evolved 

OOBE & 

adjacent 

band activity

VSA induced roll off

VSA induced roll off

Shoulder

RollOff

VSA Calibrated 

Frequency 

Range

In-Situ LTE Full

Persistence Spectrum

56
• ABE level target same peak level

• ABE waveforms filtered to 20 MHz in-band 

occupied bandwidth

• Adjacent band testing of LTE fundamental 

Band Edge and Na

eff Experiments

• ABE level set to as captured in the field

• ABE waveforms include OOBE

• ABE waveforms with extended noise floor

Frequency Offset Experiments

Adjacent Band Waveform Review

57
ABE Waveform processing for Frequency offset Experiments

• Receiver Passband can overlap 

with as captured VSA roll off 

and is dependent on: 

▫ IF Filter Selection by the receiver 

▫ IRIG Band Edge back off frequency

▫ Frequency range of the experiment

• To mitigate we present an 

approach to extend the noise floor 

of the waveforms

Band Edge

58
• Resample Original waveform • Apply a bandpass filter (based 

on VSA calibration window) to 

the resampled waveform

• Develop an AWGN signal at the 

same level as the noise shoulder 

of the original waveform

• Combine the signals

Noise “Floor” Extension 

Process

59
In-Situ Single UE from Edwards – LTE Waveforms

• Filtered for desired Resource Block (RB) activity

• Activity in all RBs of the LTE band

• No user activity in 8 RBs closest to AMT channel 

LTE Waveform 2

LTE Waveform 1

Subframes 

761 to 795

Subframes 

1863 to 1893

60
Frequency Offset Experiment: IRIG-based Analysis 

61
Frequency Offset Experiment

Id Factor Settings # Levels Easy/Hard to Change 

A Modulation Type PCM/FM, SOQPSK, SOQPSK-FEC, ARTM-CPM 4 Hard

B Bit Rate 1, 5, 10 Mbps 4 Hard

C ABE Type AWGN 20 MHz, in-situ LTE captures: single-UE (92 RB, Full, 

92 RB filtered, Full filtered), multi-UE: (EAFB Az76, EAFB 

Az198), lab LTE captures (20 MHz Full, 20 MHz upper 10 RB 

blanked, 5 MHz Full)

10 Hard

D Frequency Offset 1 MHz steps on grid including IRIG-recommended offset 12 Hard

• Only test Modulation/Bit Rate combinations shown in yellow

• Same Save/ABEpeak ratio for each LTE waveform

• Save/ABEave fixed for AWGN

• 840 unique test configurations

• Repeats/replication

 All configurations tested twice at MITRE-Bedford

 Subset tested twice at NIST-Boulder (excluding SOQPSK-FEC)

Modulation Type Bit Rate (Mbps)

PCM/FM 1 5

SOQPSK 5 10

SOQPSK- FEC 5 10

ARTM CPM 5

Objective: Characterize effect of shifting AMT center frequency relative to ABE 

62
• Calculations based on 10W transmitter

• Band Edge frequency: 1780 MHz

IRIG 106 Band Edge Back Off

Modulation

/ Bit Rate

PCM/FM SOQPSK SOQPSK 

FEC*

ARTM CPM

1 Mbps 2.5 MHz Not Tested Not Tested Not Tested

5 Mbps 10.0 MHz 5.0 MHz 7.5 MHz 4.0 MHz

10 Mbps Not Tested 9.0 MHz 14.0 MHz Not Tested

*LDPC Code Rate 2/3 Information Block Size 4096

Test configurations shown in yellow

AMT Transmitter center frequency spacing 

to the band edge

Inter-Range Instrumentation Group: Range Commanders Council Telemetry Group. 

IRIG 106-19: Telemetry Standards. 

Section A.12: Valid Center Frequencies Near Telemetry Band Edges

• Determined by:

▫ Transmitter power output

▫ Power spectral density masks

▫ Modulation 

▫ Bit rate

▫ Channelization frequency 

discretization

63
AMT Signal and ABE Waveform Levels

Configure the testbed AMT Signal pathloss and ABE pathloss such that

at the N-type connector of the receiver:

• AMT average signal targeted -80 dBm 

• ABE peak value of in-situ waveforms = ABE peak value as recorded in the field

• ABE peak value of Lab waveforms targeted in-situ single UE ABE peak value

• AWGN 20 MHz average signal targeted Single UE Full 100 RB (37 MHz Filter) 

average signal 

64
AMT Signal and ABE Levels for Frequency Offset Experiment

Waveform Average (dBm) Peak (dBm)

AWGN 20 MHz -59.6 ± 1.1 dB N/A

Single UE Full 100 RB (20 MHz Filter) -63.4 ± 1.1 dB -52.2 ± 1.1 dB

Single UE Lower 92 RB (20 MHz Filter) -63.5 ± 1.1 dB -52.7 ± 1.1 dB

Single UE Full 100 RB (37 MHz Filter) -60.5 ± 1.1 dB -52.4 ± 1.1 dB

Single UE Lower 92 RB (37 MHz Filter) -63.4 ± 1.1 dB -52.8 ± 1.1 dB

Multi-UE Az-76 100 RB (EAFB 37 MHz Filter) -70.6 ± 1.1 dB -48.0 ± 1.1 dB

Multi-UE Az-198 100 RB (EAFB 37 MHz Filter) -82.5 ± 1.1 dB -53.9 ± 1.1 dB

Lab-UE Full 100 RB (49 MHz Filter) -66.0 ± 1.1 dB -52.9 ± 1.1 dB

Lab-UE Lower 90 RB (49 MHz Filter) -65.4 ± 1.1 dB -52.9 ± 1.1 dB

Lab-UE Full 25 RB (49 MHz Filter) -70.7 ± 1.1 dB -52.9 ± 1.1 dB

Test Case AMT Signal Average (dBm)

Frequency Offset Experiments -79.9 ± 0.9 dB

Uncertainties are expanded uncertainties for the MITRE Bedford testbed 

as calculated in Appendix A of the Report

65
• AMT signal frequency is varied across the range from near band edge beyond IRIG 106

Frequency Offset Experiment Procedure

AMT Allocation

LTE RBs

TransitionTransition

AMT 

Signal

AMT 

Signal

99% OBW 

Center Frequency

IRIG 106 specified 

Center Frequency

Frequency

Band edge

Cellular Allocation

66
Frequency Offset Results: PCM/FM 1 Mbps

Lab LTE & AWGN In-situ LTE

67
Frequency Offset Results: PCM/FM 5 Mbps

Lab LTE & AWGN In-situ LTE

68
Frequency Offset Results: SOQPSK 5Mbps

Lab LTE & AWGN In-situ LTE

69
Frequency Offset Results: SOQPSK 10 Mbps

Lab LTE & AWGN In-situ LTE

70
Frequency Offset Results: SOQPSK FEC 5 Mbps

Lab LTE & AWGN In-situ LTE

71
Frequency Offset Results: SOQPSK-FEC 10 Mbps

Lab LTE & AWGN In-situ LTE

72
Frequency Offset Results: ARTM CPM 5 Mbps

Lab LTE & AWGN In-situ LTE

73
Selected Results from Main Characterization Experiment

74
Modulation Type Bit Rate (Mbps)

PCM/FM 1 5 10

SOQPSK 1 5 10 20

SOQPSK- FEC 1 5 10 20

ARTM CPM 5 10 20

Main Characterization Experiment

Id Factor Settings # Levels Easy/Hard to Change 

A Modulation Type PCM/FM, SOQPSK, SOQPSK-FEC, ARTM-CPM 4 Hard

B Bit Rate 1, 5, 10, 20 Mbps 4 Hard

C ABE Type None, AWGN (BW=20, 18, 16.5 MHz), in-situ LTE 

captures: single-UE (92 RB, Full), multi-UE (EAFB 

Az76, EAFB Az198, LaRC Az140, LaRC Az165)

10 Hard

D AMT Signal Level 1 dB steps on grid spanning a 

10 dB range with config-dependent shift

11 Easy

• Configurations not tested: 

 PCM/FM at 20 Mbps, ARTM-CPM at 1 Mbps 

• 1540 unique test configurations 

• Repeats/replication

 All configurations tested twice at MITRE-Bedford

 Subset tested twice at NIST-Boulder (excluding SOQPSK-FEC) First priority shown in yellow

Objective: Assess impact of different ABE types on AMT receiver performance. Cover 

transition from strong link (BER < 10-7) to a poor link (BER > 10-4)

Showcased

75
ABE Levels as Tested at Band Edge

Frequency Offset

Waveform Average (dBm) Peak (dBm)

AWGN 20 MHz -75.8 ± 0.9 dB N/A

AWGN 18 MHz -76.4 ± 0.9 dB N/A

AWGN 16.5 MHz -76.8 ± 0.9 dB N/A

Single UE Full 100 RB (20 MHz Filter) -69.9 ± 1.1 dB -61.8 ± 1.1 dB

Single UE Lower 92 RB (20 MHz Filter) -72.8 ± 1.1 dB -62.3 ± 1.1 dB

Multi-UE Az-76 100 RB (EAFB 20 MHz Filter) -84.6 ± 1.1 dB -62.1 ± 1.1 dB

Multi-UE Az-198 100 RB (EAFB 20 MHz Filter) -86.5 ± 1.1 dB -62.1 ± 1.1 dB

Multi-UE Az-140 100 RB (LaRC 20 MHz Filter) -80.3 ± 1.1 dB -62.1 ± 1.1 dB

Multi-UE Az-165 100 RB (LaRC 20 MHz Filter) -78.9 ± 1.1 dB -62.1 ± 1.1 dB

Uncertainties are expanded uncertainties for the MITRE Bedford testbed 

as calculated in Appendix A of the Report

Tests aligned 

to Peak Power

Tests aligned to 

consistent PSD

76
Main Experiment: PCM/FM 5 Mbps

77
Main Experiment: SOQPSK 5 Mbps

78
Main Experiment: SOQPSK-FEC 5 Mbps

79
Main Experiment: ARTM CPM 5 Mbps

80
Summary of 

BER =10

-5

Behaviors 

81
Equivalent Ambient Noise (Eb/N0 Loss) Analysis

82
1) At a fixed BER = BER*, set 

Eb/No|no ABE = Eb/Na

eff |ABE

• In other words, define Na

eff as the 

equivalent noise power density that yields 

the same BER as in the no-ABE case. 

2) Letting S*n and S*a denote the signal 

power at BER* for the no-ABE and ABE 

cases, and using Eb = S/BR, yields 

Na

eff = No(S*a/ S*n) 

Can we characterize the impact of adjacent band 

emissions in terms of an equivalent ambient noise level? 

AMT RX power

BER

No ABE With ABE

BER*

S*n S*a

83
Main Experiment: PCM/FM 5 Mbps

BER vs AMT Rx Power

BER* vs Na effective

84
Anomalous Results

85
Anomalous Result –

Frequency Offset Experiment: Az 198 Waveform 

Unexpected response 

with Az 198 waveform

Spurious out-ofband emissions in 

Az 198 waveform 

land in AMT band

No correlation between OOBE in AMT 

band and LTE transmissions. 

OOBE could be due to non-LTE emitter.

AWS-3 Band AMT Band

AWS-3 Band AMT Band

Power (dBm/15 KHz)

86
Anomalous Result – Main Experiment: PCM/FM 1 Mbps

Unexpected 

response at -98 dBm

Results from Bedford testbed;

similar unanticipated receiver behavior 

observed on both testbeds

87
• Pilot Study

Goals: Verifying testbed automation & obtain preliminary data

• Frequency Offset Experiment

Objective: Characterize effect of shifting AMT center frequency relative to ABE 

• Main Experiment

Objective: Assess impact of different ABE types on AMT receiver performance

• Side Experiment A: Equalizer

Objective: Assess impact of enabling equalizer in the presence of ABE

• Side Experiment B: Space-Time Coding

Objective: Assess impact of STC option in the presence of ABE

• Side Experiment C: Excess Noise

Objective: Assess impact of in-band excess white noise on AMT performance

Summary of Experiments

 4,723 unique test configurations, 12,571 valid tests

88
• The frequency offset experiment results suggest that the IRIG back-off 

calculations work for most of the test ABE types. 

• Careful consideration of OOBE characteristics is important

▫ Simulation or emulation of ABE does not generally reflect real-world features

▫ Two ABE waveforms with nearly equivalent average powers but with seemingly 

inconsequential differences in OOBE behavior can cause very different impacts 

on the AMT system. This is clear in the frequency offset results. 

• The concept of equivalent in-band ambient noise (Eb/No loss) is 

demonstrated and supports interpretation of impacts on receiver 

performance. 

Conclusions

89
• NASCTN Program

▫ https://www.nist.gov/ctl/nasctn

• Project Page 

▫ https://www.nist.gov/programs-projects/aws-3-lte-impacts-amt

• Reports

▫ AWS-3 LTE Impacts on Aeronautical Mobile Telemetry

 Report: https://doi.org/10.6028/NIST.TN.2140

 Data: https://data.nist.gov/od/id/mds2-2279

▫ In-Situ Captures of AWS-1 LTE for Aeronautical Mobile Telemetry System 

Evaluation 

 Report: https://www.its.bldrdoc.gov/publications/details.aspx?pub=3262

▫ Laboratory Method for Recording AWS-3 LTE Waveforms

 Report: https://doi.org/10.6028/NIST.TN.2159

 Data: https://doi.org/10.18434/mds2-2395

Publication Information

90
Contact Us

Dr. Melissa Midzor

Program Manager

NASCTN

melissa.midzor@nist.gov

91
Back Up Slides

92
Measurements and improved methodology to determine the impact of 

LTE on AMT systems. 

Project comprises three major integrated tasks: 

1. Test effects on AMT using a curated set of LTE waveforms of varying 

signaling conditions

2. Develop a Library LTE waveforms for this and future testing (captured 

from laboratory and in situ settings)

3. In situ captures using AMT infrastructure to inform scenario 

development for current and future testing (using deployed AWS-1 as 

a stand in for AWS-3)

Test Plan Review

93
PCM/FM SOQPSK ARTM CPM SOQPSK – FEC STC STC - FEC

1 Mbps 2 MHz 1.4 MHz Not Tested 2 MHz Not Tested Not Tested

5 Mpbs 10 MHz 6 MHz 6 MHz 10 MHz 6 MHz 10 MHz

10 Mbps 20 MHz 14 MHz 10 MHz 20 MHz 14 MHz 20 MHz

20 Mbps Not Tested 28 MHz 20 MHz 40 MHz 28 MHz 40 MHz

Backup Slide – IF Filter Selection by the Receiver

Priority shown in yellow

Modulation Type Data Rate (Mbps)

PCM/FM 1 5 10

SOQPSK 1 5 10 20

SOQPSK- FEC 1 5 10 20

ARTM CPM 5 10 20

Side Experiment

94
Example of Consistent Result Example of Inconsistent Result

Testbed Comparison

95
Waveforms

4G-LTE Scheduling of UL resources

96

 LTE Systems interleave/“schedule” uplink 

broadcasts within the overall allocation

 Scheduling dynamics are derived from 

several settings within a base station –

often customized by cellular operators 

Image credit: https://yatebts.com/an-introduction-to-the-lte-mac-scheduler/

 Capture of UE emissions in a 20 MHz uplink allocation 

obtained through a high gain aeronautical mobile telemetry 

– tracking antenna
Comparison of Waveforms

97

AWGN as generated in a VSG Single UE as captured in a laboratory 

environment

Multiple-UE as captured in the field 

with high directivity Antenna
NASCTN Project Timeline

98