GPS Adjacent Band Compatibility Assessment

Space-Based PNT Advisory Board Meeting

May 18, 2016

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“. . . without affecting existing and evolving uses of

space-based PNT services vital to economic, public

safety, scientific, and national security needs.”

EXCOM Co-Chair Letter to NTIA

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• DOT Study to Evaluate:

Adjacent-band power levels, as a function of

offset frequency, necessary to ensure

continued operation of all applications of

GPS services

Adjacent-band power levels to ensure

continued operation of all applications of

GPS services by future GPS receivers

utilizing modernized GPS and interoperable

Global Navigation Satellite System (GNSS)

signals

GPS Adjacent Band Compatibility Assessment

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• Certified Aviation Portion of Effort Led by FAA

• Non Aviation Certified effort (all other applications) led by DOT/OST-R Volpe Center

• DOT Extended Pos/Nav Working Group (Civil Departments and Agencies)

- GPS Directorate, Aerospace, Mitre, Zeta Associates, and Stansell Consulting

• Conduct public outreach to ensure the plan, on going work, and assumptions are vetted and an opportunity to gain feedback

- Held Many Public Workshops

- Federal Register Notice for Comments/Input on Draft Test Plan

- One-on-One Discussions with Industry

- Open and Transparent Approach

Approach to DOT GPS Adjacent Band Compatibility Assessment

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• Finalized GPS/GNSS Receiver Test Plan

• Contracted for Use of WSMR Anechoic Chamber

• Coordinated Government and Manufacturer Participation

and executed Non Disclosure Agreements (NDAs)

• Developed Test Procedures

• Developed/Validated Radiated RF Test Environment

• Conducted GPS/GNSS Receiver Testing

Activity Since October 2015 Advisory Board Meeting

Testing Overview

• GPS Receiver Testing Conducted April 25-29, 2016 at the Army Research Laboratory's (ARL) Electromagnetic Vulnerability Assessment Facility (EMVAF), White Sands Missile Range (WSMR), NM – EMVAF – 100’ x 70’ x 40’ Anechoic Chamber

• Participation included DOT’s federal partners/agencies and GPS manufacturers

• 80 receivers were tested representing six categories of GPS/GNSS receivers: General Aviation (non certified), General Location/Navigation, High Precision & Networks, Timing, Space Based, and Cellular

• Tests Conducted: – Linearity (receivers CNR’s estimators are operating in the linear region)

– 1 MHz Bandpass Noise (Type 1)

– 10 MHz LTE (Type 2)

– Intermodulation (effects of 3rd order intermodulation)

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Signal Generation Equipment

• GNSS Generation and Playback – Spirent GSS8000 GNSS signal simulators synchronously generate

signals for the GPS+WAAS, Beidou, GLONASS, and Galileo systems

– Constellations recorded using three National Instruments (NI) Vector Signal Analyzers

– Playback through three NI Vector Signal Generators (VSGs)

• Interference Signal Generation – Interference signal generation uses a VSG to generate the interference

signal of either Type 1 or Type 2

– 200 Watt High Power Amplifier used to boost the interference signal

– 22 RF filters used to sufficiently attenuate the interference out-of-band emission (OOBE), to ensure that degradation measured is not due to OOBE

• Signal Antennas – GNSS Signals: Passive GNSS Patch Antenna

– Interference Signals: Passive Horn Antenna 7

GNSS Signals Used in Testing

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Signal

GPS C/A-code

GPS L1 P(Y)-code

GPS L1C

GPS L1 M-code

GPS L2 P(Y)-code

SBAS L1

GLONASS L1 C or P

BeiDou B1I

Galileo E1 B/C

Chamber Diagram

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Data Collection

Test Grid

←Exit

K0 K2 K4 K6 K8 K10 K12

K1 K3 K5 K7 K9 K11 K13

J6

J5

I0 I2 I4 I6 I8 I10 I12

I1 I3 I5 I7 I9 I11 I13

H8

H7

G0 G2 G4 G6 G8 G10 G12

G1 G3 G5 G7 G9 G11 G13

E0 E2 E4 E6 E8 E10 E12

E1 E3 E5 E7 E9 E11 E13

D8

D7

C0 C2 C4 C6 C8 C10 C12

C1 C3 C5 C7 C9 C11 C13

B6

B5

A0 A2 A4 A6 A8 A10 A12

A1 A3 A5 A7 A9 A11 A13

Note: not drawn to scale

Mezzanine

GM

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UNAVCO

5

1211

2

4

3

USGS TRIMBLE DEERE

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106

2

NOVATEL

15

98

UBLOX

7 13

Aero_Spec_A

182

1 2

USDOTUSCG NASA NOAA

3

9

5

FAA

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Name Value Unit

𝒇𝒔𝒕𝒂𝒓𝒕 1475 MHz

𝒇𝒆𝒏𝒅 1675 MHz

[𝒑𝒎𝒊𝒏𝟏,𝒑𝒎𝒂𝒙𝟏

] (1475 to 1540 MHz) [-80,-10] dBm

[𝒑𝒎𝒊𝒏𝟐,𝒑𝒎𝒂𝒙𝟐

] (1545 to 1555 MHz) [-100,-30] dBm

[𝒑𝒎𝒊𝒏𝟑,𝒑𝒎𝒂𝒙𝟑

] (1575 and 1595 MHz) [-130,-60] dBm

[𝒑𝒎𝒊𝒏𝟒,𝒑𝒎𝒂𝒙𝟒

] (1615 to 1625 MHz) [-100,-30] dBm

[𝒑𝒎𝒊𝒏𝟓,𝒑𝒎𝒂𝒙𝟓

] (1630 to 1675 MHz) [-80,-10] dBm

𝚫𝒇𝟏(1475 to 1520 MHz) 15 MHz

𝚫𝒇𝟐(1520 to 1555 MHz) 5 MHz

𝚫𝒇𝟑(1575 and 1595 MHz) N/A MHz

𝚫𝒇𝟒(1615 to 1645 MHz) 5 MHz

𝚫𝒇𝟓(1645 to 1675 MHz) 15 MHz

𝚫𝑷 2 dB

Startup Time 15 min

𝑻𝑩𝑳 5 min

𝑻𝒔𝒕𝒆𝒑 15 s

𝑵𝒄𝒚𝒄𝒍𝒆 2 N/A

Interference Test Signal Frequencies and Power Profiles (1/2)

0 200 400 600 800 1000 1200 1400 1600 1800-100

-80

-60

-40

-20

0

X: 1680

Y: -10

Time (sec)

Receiv

ed I

nte

rfere

nce P

ow

er

(dB

m)

0 50 100 150 200 250 300 350 400-100

-90

-80

-70

-60

X: 300

Y: -80

Time (sec)

Receiv

ed I

nte

rfere

nce P

ow

er

(dB

m)

X: 315

Y: -80

Nominal receive interference power profiles at GNSS antenna location for the (1475 to 1540 MHz) and (1630 to 1675 MHz) frequency ranges.

Interference Test Signal Frequencies and Power Profiles (2/2)

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1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700-140

-120

-100

-80

-60

-40

-20

0

Frequency (MHz)

Targ

ete

d R

eceiv

e P

ow

er

(dB

m)

Type 1 & 2

Type 1

RNSS Band

Data Collected

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• Data Needed to Develop an ITM for each receiver:

− 𝐶𝑁𝑅(𝑠, 𝑖, 𝑗. Δ𝑡) (here, s identifies the GNSS, i the SV, Δ𝑡 is the reporting time

increment)

• To the extent possible, additional data to report the state of

the receiver at each time step

Number of satellites tracked for each GNSS service: 𝑁𝑆𝑉(𝑠, 𝑡𝑗)

Location: Lats(𝑗. Δ𝑡), Lons(𝑗. Δ𝑡), hs(𝑗. Δ𝑡) (relative to WGS84 or other Datum)

Pseudorange: Rs,i(𝑗. Δ𝑡)

Carrier phase

Cycle slip or loss of carrier phase lock indicator (per satellite)

Loss of code and carrier tracking indicator, or inferred loss of tracking in the

case when it is not reported by the receiver (per satellite)

Next Steps

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• Analyze test data and develop interference tolerance masks for all

receivers tested based on 1 dB CNR degradation

• Conduct lab testing on a limited number of receivers to determine

how well test results can be reproduced

• Conduct receiver acquisition testing on a limited number of receivers

• Evaluate correlation of 1-dB CNR degradation to other receiver data

collected

• Develop use-case scenarios

• Evaluate appropriate propagation models for each use-case scenario

• Develop maximum tolerable transmitter power level as a function of

frequency offset

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Questions?