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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Signal Structures for Satellite-Based Navigation: Past, Present, … · 2013-07-16 · CLASSIFICATION CLASSIFICATION Multiple origins of modern GNSS signal structures – Original
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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
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
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
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
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
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,