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
2GPS 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
3GPS 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
-
4L2 and L5 Civil Signal Industry Day 2 May
2001 Paul Novak SMC/CZC (SAIC)
5Civil 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
7Civil 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
8GPS 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
9GPS 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
10Why 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
11GPS 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
12Modernized 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
13GPS 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
14GPS Modernization Program Summary
15L2 Civil Signal
LCDR Richard Fontana GPS Deputy Program Manager,
DOT May 2, 2001
16Overview
- Background
- Advantages of New Signal
- Design Considerations
17Background
- 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
18Advantages 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
19Advantages 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
20Design 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
21Design 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
22Design 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
23Signal 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. -
24Signal 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
25Signal 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
26L2CS 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
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