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GPS Modernization Legacy User Equipment Compatibility Tests

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Welcome and Introductions LCDR Fontana 0900-0910 ... Improves the dynamic rage of receivers. Can receive weaker signals without self interference ... – PowerPoint PPT presentation

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Title: GPS Modernization Legacy User Equipment Compatibility Tests


1

L2 and L5 Civil Signal Industry Day 2 May
2001 LCDR Richard Fontana GPS Deputy Program
Manager, DOT
2
GPS L2 Civil Signal Industry Day Agenda
  • ITEM BRIEFER TIME
  • Welcome and Introductions LCDR Fontana 0900-0910
  • Overview of GPS Modernization Paul
    Novak 0910-0920
  • Advantages of a New L2 CS LCDR Fontana 0920-0945
  • BREAK 0945-1000
  • Technical Description of L2CS Tom
    Stansell 1000-1100
  • Laboratory and Simulation Dr Dafesh 1100-1130
  • Results
  • Almanac Karl Kovach 1130-1200
  • Question and Answer Session LCDR
    Fontana 1200-1215
  • LUNCH 1215-1330

3
GPS L5 Civil Signal Industry Day Agenda
  • ITEM BRIEFER TIME
  • Welcome and Introductions Lt Victoria 1330-1340
  • L5 Design Background Dr Hegarty 1340-1400
  • L5 Design Background Dr Van Dierendonck 1400-144
    5
  • L5 Environmental Studies Dr Hegarty 1445-1500
  • BREAK 1500-1515
  • ICD-GPS-705 Organization Dr Slattery 1515-1540
  • ICD-GPS-705 Review Process Lt Victoria 1540-1600
  • Question and Answer Lt Victoria 1600-1630

4
L2 and L5 Civil Signal Industry Day 2 May
2001 Paul Novak SMC/CZC (SAIC)
5
Civil Use of GPS
The nations reliance on GPS has become an issue
of national security -- national security in its
broadest sense, that goes beyond merely national
defense. -- Dr. James Schlesinger, March 1997
Power Grid Interfaces
Personal Navigation
Surveying Mapping
Trucking Shipping
Aviation
Communications
Railroads
Recreation
Fishing Boating
Off shore Drilling
6
GPS Space Systems
24-satellite (nominal) constellation Six orbital
planes, four satellites per plane Semi-synchronous
, circular orbits (11,000 mi)
Block IIF
7
Civil GPS, Summary of Key Events
  • 1978 - First Global Positioning System satellite
    launch
  • 1983 - President Reagan offers GPS to the world
    free of charge
  • 1993 - GPS Standard Positioning Service available
  • 1994 - FAA approves GPS for use in National
    Airspace System
  • 1996 - Presidential Decision Directive, first
    National GPS policy
  • 1998 - Two new GPS civil signals (L2 and L5)
    announced
  • 1999 - Third civil signal (L5) at 1176.45 MHz
    announced
  • 2000 - Congress funds GPS Modernization in DoD
    budget
  • 2000 - Selective Availability set to zero
  • 2000 - GPS JPO begins modifications to IIR-M and
    IIF satellites
  • 2000 - JPO awards Boeing and Lockheed Martin GPS
    III contracts

8
GPS Modernization Mission
Current Mission
Additional Modernization Mission
Anti-Jam/Anti-Spoof Protection, Civilian Safety
of Life Signals, Upgraded Redundant Control,
and demonstrate Legacy and Upgraded Military
Receivers.
Precise Continuous, 3-D Position, Velocity and
Timing Information to an unlimited number of
military and civil users
9
GPS Users Wants
Civil User
  • Accuracy
  • Availability
  • Coverage
  • Integrity
  • Robustness
  • Redundant signals
  • More power
  • More jam resistance
  • More security
  • Anti-spoof
  • User discrimination
  • Shorter time to first fix
  • Backward compatibility

Military User
  • Selective Availability (SA) to zero
  • Second civil signal
  • Ionospheric correction
  • Redundancy
  • Third civil signal
  • High accuracy
  • real-time applications
  • Spectrum protection for
  • safety of life applications

L2 Civil Signal
Military code L1 / L2
  • Higher power
  • New military signal
  • Spectral separation
  • from civil signals
  • Faster signal acquisition
  • Improved security codes

L5
10
Why Modernize GPS?The Civil GPS Perspective
  • Better support to civil GPS customers worldwide
  • New civil signals for improved accuracy,
    integrity and continuity of service robustness
  • Global utility economic enabler
  • Optimize GPS PVT and augmentation systems in a
    overall national network architecture

Presidential Decision Directive - Mar 96 Vice
Presidential Announcements - Mar 98 and Jan 99
11
GPS ModernizationBlock II Space Vehicles
Block IIR-M
Block IIF
  • L1 Enhancements
  • New developmental Military code (M-code)
  • L2 Enhancements
  • New L2 civil signal
  • New developmental M-code
  • L1 Enhancements
  • Similar to IIR-M
  • Operational M-code
  • L2 Enhancements
  • Similar to IIR-M
  • Operational M-code
  • L5
  • New civil signal at 1176MHz

12
Modernized GPS Signal Evolution
L2
L1
L5
C/A
P(Y)
P(Y)
Present Signal (Block II/IIA/IIR)
M
M
C/A
L2CS
Next Generation Of Capability (Block IIR-M)
P(Y)
P(Y)
M
M
C/A
L2CS
Civil Safety of Life Applications (Block IIF and
beyond)
P(Y)
P(Y)
1227.60 MHz
1575.42 MHz
1176.45 MHz
13
GPS III Architecture Studies
  • Military missions
  • Precision bombing
  • Mine clearing
  • Situational awareness
  • Civilian missions
  • Precision farming
  • Building/ urban canyon personnel tracking
  • Global Air Traffic Management (GATM)
  • Time synchronization for utilities/
  • telecommunications

14
GPS Modernization Program Summary
15
L2 Civil Signal
LCDR Richard Fontana GPS Deputy Program Manager,
DOT May 2, 2001
16
Overview
  • Background
  • Advantages of New Signal
  • Design Considerations

17
Background
  • Option to implement a new signal
  • Did not want to limit future GPS by what is
    implemented on IIR/IIF
  • Overcome some limitations of C/A coded signals
  • Can make significant improvements with new
    technology signal
  • C/A code designed as an acquisition signal
  • 1070s technology

18
Advantages of a New Signal
  • Improved Cross Correlation Properties
  • Improves ability to transmit more signals
    (SBAS,Pseudolytes)
  • Improves the tolerance to interference
  • Improves susceptibility to self interference
  • Improves the dynamic rage of receivers
  • Can receive weaker signals without self
    interference
  • Enables operation in more stressful environments
    (wooded area, buildings, urban canyons)
  • Enables ability for higher power signals on
    future satellites

19
Advantages of a New Signal
  • Improved Tracking capability
  • Enables operation in more stressful environments
    (wooded area, buildings, urban canyons)
  • Improved Data Demodulation
  • Want equivalent to tracking threshold
  • Again, enables operation in more stressful
    environments
  • Acquisition Capability
  • Dependent on user equipment
  • Design trade with code length
  • Not limited by code. With right UE, can acquire
    signal in more stressful environments than C/A
    code

20
Design Considerations
  • Enhance existing professional/commercial dual
    frequency applications
  • Provide more robust iono correction signal
  • Provide a more effective single frequency
    navigation signal
  • Drives need for data
  • Simple to implement in the SV and UE
  • Schedule and Cost (both SV and UE)
  • Replacement for C/A signal

21
Design Considerations (continued)
  • Compatible with L2 M-code
  • Spectral Separation
  • Ensure no detriment to Codeless/Semi Codeless L2
    P(Y) receivers
  • As a result of two earlier objectives
  • Same power level and spectral shape as C/A
    codeno additional testing required
  • Risk Mitigation
  • Design schedule short, IIR implementation
    schedule short, coordination process short
  • C/A code switch

22
Design Considerations (continued)
  • What is optimum in the future (GPS III) to
    determine the best step now.
  • Did not want to artificially constrain thinking
    due to possible IIR/IIF perceived limitations.
  • Perceived cost/schedule limitations.
  • Design for future, provide natural migration path
  • Then determine what portion could be implemented
    on IIR and IIF
  • L2 C/A code compatibility
  • Assess impact on both military and civilian
    receivers
  • Not a design driver but have C/A switch as risk
    mitigation

23
Signal Characteristics
  • Two codes one with one without data
  • Serves single and dual frequency users
  • Signal characteristics
  • Codes longer than C/A to minimize cross
    correlation
  • Separated by time Time Division Multiplexed
    (TDM)
  • Narrow band signal Spectral separation
  • Improved data structure Enhanced Data
    demodulation
  • Enhance cross correlation, tacking threshold,
    data demodulation threshold.

24
Signal Comparison
  • L2 splits power 50/50 between data and data-less
    channels
  • Medium Code with Data, Long code no data
  • Higher effective L2 channel for tracking
  • 3db higher than C/A on L2
  • Approximately 3dB better Data demodulation
    capability
  • Enhanced data structure

25
Signal Comparison
  • 24dB better cross-correlation protection.
  • C/A code cross correlation protection is 21
    dB. The L2CS signal is 45dB protection
  • Dynamic range improvement.
  • Better capability to receive both weak and strong
    signals
  • Acquisition threshold
  • Given assumptions of improved UE, not harmed
  • Under stressful conditions improved

26
L2CS Summary
  • TDM service for both single and dual frequency
  • Significant improvements in
  • Cross correlation performance
  • Tracking threshold
  • Data recovery threshold
  • Acquisition Capability
  • Modern signal for future GPS

27
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