signal structures for satellite-based navigation: past, present, … · 2013-07-16 ·...
TRANSCRIPT
John W. Betz 23 April 2013
Signal Structures for Satellite-Based Navigation: Past, Present, and Future*
*Approved for Public Release; Distribution Unlimited. 13-0908. The contents of this material reflect the views of the author. Neither the Global Positioning Systems Directorate nor the U.S. Air Force makes any warranty or guarantee, or promise, expressed or implied, concerning the content or accuracy of the views expressed herein.
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Early Satnav Signal Design
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Project 621B Contributions to Structure of Original GPS Signals and Receiver Processing
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Direct sequence spread spectrum/code division multiple access “Clear/Acquisition” signal Techniques for Selective Availability (SA) …and differential techniques to remove SA Poor crosscorrelation performance of short spreading
codes used for GPS C/A code signal Carrier-aided code tracking DLL tracking error model for wideband processing of
BPSK-R signals in white noise 6 dB lower tracking threshold of coherent phase locked
loop carrier tracking over Costas loop tracking “Pseudocoherent carrier tracking” and data wiping
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Powerful error correction codes, both block and convolutional Separate pilot (“unmodulated carrier component’)
and data components Phase-multiplexing and time-multiplexing of different
signals or components onto the same carrier
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© 2012 The MITRE Corporation. All rights reserved.
Project 621B Contributions Not Included in Structure of Original GPS Signals
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Two global systems: GPS and GLONASS – Fewer than 40 total operational satellites – Each satellite transmitted three signals, only one for
civil use SBAS emerging; none fully operational
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© 2012 The MITRE Corporation. All rights reserved.
Satnav Circa 10 Years Ago
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Two operating global systems: GPS and GLONASS – Almost 60 total operational satellites – Newest satellites transmit five to seven signals, three
for civil use on different carrier frequencies One operating regional system: BeiDou Two emerging global systems: BeiDou and Galileo Two emerging regional systems: QZSS and IRNSS Three operational SBASs: WAAS, EGNOS, MSAS Three emerging SBASs: GAGAN, SDCM, BeiDou
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© 2012 The MITRE Corporation. All rights reserved.
Satnav Today
Approximately 90 Operational Satellites
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Satnav Circa 10 Years from Now Open: Blue, Encrypted: Red
Frequency (MHz)
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1560 1570 1580 1590 1600 16101160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300JWBetz
?
GPS: 27 to 36 SVs
GLONASS: 24 to 30 SVs
Galileo: 26 to 30 SVs
BeiDou: 35 SVs
QZSS: 3+ SVs
IRNSS: 5+ SVs
SBAS: 14 to 20 SVs
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Satnav Circa 10 Years from Now Open: Blue, Encrypted: Red
Frequency (MHz)
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1560 1570 1580 1590 1600 16101160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300JWBetz
?
GPS: 27 to 36 SVs
GLONASS: 24 to 30 SVs
Galileo: 26 to 30 SVs
BeiDou: 35 SVs
QZSS: 3+ SVs
IRNSS: 5+ SVs
SBAS: 14 to 20 SVs
More than 160 Operational Satellites
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© 2012 The MITRE Corporation. All rights reserved.
Future Signal Occupancy in Upper L Band: GPS, GLONASS, SBAS, QZSS, Galileo, BeiDou Phase 3
1560 1565 1570 1575 1580 1585 1590 1595 1600 1605 1610Frequency (MHz)
Pow
er S
pect
ral D
ensi
ty (
dBW
/Hz)
Betz
GPSM Code
GPSM Code
GPSC/A Code
GPS L1CGalileo E1 OSBeiDou B1-CGalileo
PRSGalileoPRS
BeiDouB1-A
BeiDouB1-A
GLONASS L1OF
GLONASSL1OC
GLONASSL1SC
GPS C/A Code QZSS C/A Code and SAIF
L1 SBAS
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© 2012 The MITRE Corporation. All rights reserved.
Quantifying the Future Signal Occupancy in Upper L Band
System Number of Signal Types
Number of Satellites
Signal-Satellite Product
GPS 4 36 144 GLONASS 4 27 108
SBAS 1 19 19 Galileo 2 30 60 BeiDou 2 35 70 QZSS 3 7 21
Total signal-satellite product: 422, or 8.3 per MHz 1559 MHz to 1594 MHz, signal-satellite product: 314, or 9.0 per MHz 1594 MHz to 1610 MHz, signal-satellite product: 108, or 6.8 per MHz
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© 2012 The MITRE Corporation. All rights reserved.
Signal Characteristic Original Civil Signals
Changes In Today’s New and Modernized Signals
Possible Changes In Future Signals
Carrier Frequency L Band, One Civil
Signal Center Frequency
Two or Three Civil Signal Center Frequencies in L
Band
S Band, C Band, Diverse Carrier Frequencies in
Upper L Band Min. Received Power < −160 dBW < −154 dBW
Polarization RHCP Multiple Access CDMA and FDMA CDMA
Spreading Modulation BPSK-R BOC, Symmetrical AltBOC, TMBOC, CBOC
Spreading Code ≤1023 bits; Shift-
Register Generated
4092 to 767,250 bits; Memory and Weil-Based
Data Message Structure Fixed Flexible Message Format,
Intersystem Time Offsets
Digital Signatures or Other Authentication,
Text Messages Data Message Error
Correction and Detection
Hamming Code Parity Bits
Modern Error Control Coding621, CRC-Based
Error Detection
Data Modulation 50 bps, Biphase 25 to 2000 Bits per Second; Code Shift Keying
Pilot and Data Components Only Data Distinct Pilot and Data
Components
Overlay Codes Extensively Used
Multiplexing Carrier Phase Division
Time-Division621, Majority Voting, Interplex, Intervote, Non-Symmetrical AltBOC,
Generalized AltBOC
Optimized M-ary Constant-Envelope
Transmission
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© 2012 The MITRE Corporation. All rights reserved.
Signal Characteristic Original Civil Signals
Changes In Today’s New and Modernized Signals
Possible Changes In Future Signals
Carrier Frequency L Band, One Civil
Signal Center Frequency
Two or Three Civil Signal Center Frequencies in L
Band
S Band, C Band, Diverse Carrier Frequencies in
Upper L Band Min. Received Power < −160 dBW < −154 dBW
Polarization RHCP Multiple Access CDMA and FDMA CDMA
Spreading Modulation BPSK-R BOC, Symmetrical AltBOC, TMBOC, CBOC
Spreading Code ≤1023 bits; Shift-
Register Generated
4092 to 767,250 bits; Memory and Weil-Based
Data Message Structure Fixed Flexible Message Format,
Intersystem Time Offsets
Digital Signatures or Other Authentication,
Text Messages Data Message Error
Correction and Detection
Hamming Code Parity Bits
Modern Error Control Coding621, CRC-Based
Error Detection
Data Modulation 50 bps, Biphase 25 to 2000 Bits per Second; Code Shift Keying
Pilot and Data Components Only Data Distinct Pilot and Data
Components
Overlay Codes Meander Extensively Used
Multiplexing Carrier Phase Division
Time-Division621, Majority Voting, Interplex, Intervote, Non-Symmetrical AltBOC,
Generalized AltBOC
Optimized M-ary Constant-Envelope
Transmission
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© 2012 The MITRE Corporation. All rights reserved.
Signal Characteristic Original Civil Signals
Changes In Today’s New and Modernized Signals
Possible Changes In Future Signals
Carrier Frequency L Band, One Civil
Signal Center Frequency
Two or Three Civil Signal Center Frequencies in L
Band
S Band, C Band, Diverse Carrier Frequencies in
Upper L Band Min. Received Power < −160 dBW < −154 dBW
Polarization RHCP Multiple Access CDMA and FDMA CDMA
Spreading Modulation BPSK-R BOC, Symmetrical AltBOC, TMBOC, CBOC
Spreading Code ≤1023 bits; Shift-
Register Generated
4092 to 767,250 bits; Memory and Weil-Based
Data Message Structure Fixed Flexible Message Format,
Intersystem Time Offsets
Digital Signatures or Other Authentication,
Text Messages Data Message Error
Correction and Detection
Hamming Code Parity Bits
Modern Error Control Coding621B, CRC-Based
Error Detection
Data Modulation 50 bps, Biphase 25 to 2000 Bits per Second; Code Shift Keying
Pilot and Data Components Only Data Distinct Pilot and Data
Components
Overlay Codes Meander Capable and Extensive
Multiplexing Carrier Phase Division
Time-Division621B, Majority Voting, Interplex, Intervote,
Symmetrical AltBOC
Optimized M-ary Constant-Envelope
Transmission
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© 2012 The MITRE Corporation. All rights reserved.
Signal Characteristic Original Civil Signals
Changes In Today’s New and Modernized Signals
Possible Changes In Future Signals
Carrier Frequency L Band, One Civil
Signal Center Frequency
Two or Three Civil Signal Center Frequencies in L
Band
S Band, C Band, Diverse Carrier Frequencies in
Upper L Band Min. Received Power < −160 dBW < −154 dBW
Polarization RHCP Multiple Access CDMA and FDMA CDMA
Spreading Modulation BPSK-R BOC, Symmetrical AltBOC, TMBOC, CBOC Asymmetrical AltBOC
Spreading Code ≤1023 bits; Shift-
Register Generated
4092 to 767,250 bits; Memory and Weil-Based
Data Message Structure Fixed Flexible Message Format,
Intersystem Time Offsets
Digital Signatures or Other Authentication, Text
Messages Data Message Error
Correction and Detection
Hamming Code Parity Bits
Modern Error Control Coding621B, CRC-Based
Error Detection
Data Modulation 50 bps, Biphase 25 to 2000 Bits per Second; Code Shift Keying
Pilot and Data Components Only Data Distinct Pilot and Data
Components
Overlay Codes Meander Capable and Extensive
Multiplexing Carrier Phase Division
Time-Division621B, Majority Voting, Interplex, Intervote,
Symmetrical AltBOC
Asymmetrical & Generalized AltBOC,
Optimized M-ary Constant-Envelope
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Common signal characteristics make multisystem receivers simpler – Reference frames – Center frequencies – Spectra – Spreading modulations – Spreading code family – Data message structure and encoding
Signals with diverse frequencies also have advantages – Greater compatibility – More robust multisystem receivers
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© 2012 The MITRE Corporation. All rights reserved.
System Designers Will Select Degrees of Interoperability and Diversity
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Multiple origins of modern GNSS signal structures – Original designs – Originally identified concepts not included in original designs – More recent innovations
Improvements in receiver processing techniques and technologies
enable and drive more advanced signal designs
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© 2012 The MITRE Corporation. All rights reserved.
Parting Thoughts
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Multiple origins of modern GNSS signal structures – Original designs – Originally identified concepts not included in original designs – More recent innovations
Improvements in receiver processing techniques and technologies
enable and drive more advanced signal designs Are we approaching the limits of what new signal designs can offer,
or do more revolutionary advances lie ahead?
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© 2012 The MITRE Corporation. All rights reserved.
Parting Thoughts
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An Analysis of Combined COMPASS/BeiDou-2 and GPS Single- and Multiple-frequency RTK Positioning
Interoperability and Compatibility Analysis of GNSS L1/B1/E1 Open Signals
Semi-Coherent and Differentially Coherent Integration for GPS L1C Acquisition
Real-Time Validation of BeiDou Observations in a Stand-alone Mode
Research on GNSS Interoperable Parameters
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© 2012 The MITRE Corporation. All rights reserved.
GNSS Signal Structures Session