L2 and L5 Civil Signal
Industry Day
2 May 2001
LCDR Richard Fontana
GPS Deputy Program Manager, DOT
1
GPS L2 Civil Signal
Industry Day Agenda
ITEM
BRIEFER
Welcome and Introductions
LCDR Fontana
Overview of GPS Modernization Paul Novak
Advantages of a New L2 CS
LCDR Fontana
BREAK
Technical Description of L2CS Tom Stansell
Laboratory and Simulation
Dr Dafesh
Results
Almanac
Karl Kovach
Question and Answer Session LCDR Fontana
LUNCH
TIME
0900-0910
0910-0920
0920-0945
0945-1000
1000-1100
1100-1130
1130-1200
1200-1215
1215-1330
2
GPS L5 Civil Signal
Industry Day Agenda
ITEM
Welcome and Introductions
L5 Design Background
L5 Design Background
L5 Environmental Studies
BREAK
ICD-GPS-705 Organization
ICD-GPS-705 Review Process
Question and Answer
BRIEFER
TIME
Lt Victoria
Dr Hegarty
Dr Van Dierendonck
Dr Hegarty
1330-1340
1340-1400
1400-1445
1445-1500
1500-1515
1515-1540
1540-1600
1600-1630
Dr Slattery
Lt Victoria
Lt Victoria
3
L2 and L5 Civil Signal
Industry Day
2 May 2001
Paul Novak
SMC/CZC (SAIC)
4
Civil Use of GPS
“The nation’s 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
Trucking &
Shipping
Surveying &
Mapping
Aviation
Railroads
Recreation
Off shore
Drilling
Communications
Fishing &
Boating
GPS Space Systems
Block II/IIA
Block IIR
24-satellite (nominal)
constellation
Six orbital planes, four satellites
per plane
Semi-synchronous, circular
orbits (~11,000 mi)
Block IIF
6
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
7
GPS Modernization Mission
UHF Crosslink
S-band
NDS
Downlink
L-Band
MS
Alternate MCS
GA
MCS
Current Mission
Precise & Continuous, 3-D Position,
Velocity and Timing Information to
an unlimited number of military and
civil users
Additional Modernization Mission
Anti-Jam/Anti-Spoof Protection,
Civilian “Safety of Life” Signals,
Upgraded & Redundant Control,
and demonstrate Legacy and
Upgraded Military Receivers. 8
GPS Users “Wants”
• More jam resistance
• More security
• Anti-spoof
• User discrimination
• Shorter “time to first fix”
• Backward compatibility
Civil
• Accuracy
• Availability
• Coverage
• Integrity
• Robustness
• Redundant signals
• More power
User
Military User
Military
• Higher power
code
• New military signal L1 / L2
• Spectral separation
from civil signals
• Faster signal acquisition
• Improved security codes
• Selective Availability (SA) to zero
• Second civil signal
• Ionospheric correction L2 Civil
• Redundancy
Signal
• Third civil signal
• High accuracy
L5
real-time applications
• Spectrum protection for
“safety of life” applications
9
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
10
GPS Modernization
Block II Space Vehicles
Block IIR-M
Block IIF
 L1 Enhancements
 New developmental
Military code (M-code)
 L2 Enhancements
 New L2 civil signal
 New developmental Mcode
 L1 Enhancements
 Similar to IIR-M
 Operational M-code
 L2 Enhancements
 Similar to IIR-M
 Operational M-code
 L5
 New civil signal at
1176MHz
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Modernized GPS Signal Evolution
L5
L2
L1
C/A
P(Y)
P(Y)
Present Signal
(Block II/IIA/IIR)
M
Next Generation
Of Capability
M
L2CS
P(Y)
C/A
P(Y)
(Block IIR-M)
M
Civil Safety of Life
Applications
L2CS
P(Y)
M
C/A
P(Y)
(Block IIF and beyond)
1176.45 MHz
1227.60 MHz
1575.42 MHz
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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
13
GPS Modernization
Program Summary
CY 01
02
03
04
System
Milestones
05 06
SAASM
OA
07
08 09 10 11
L2CS&
M-Code
M-Code L2CS&
M-Code
IOC
IOC M-code
IOC
FOC
12
L5
IOC
13
14
L5
FOC
15 16 17 18 19
M+Power M+Power
IOC
FOC
Heritage Launches
Space Segment
M-Code (IIRM/IIF) Launches
1st IIR Mod
1st IIF
EMD
Control Segment
Functionality
Dev
Test
SAASM Capable
Dev
Test
Dev
M-Code Capable
Test
M-Code + Power Capable
1st LRIP RCVRs
SAASM UE Producton / Platform Installs
1st LRIP RCVRs
M-Code UE Development
Production / Platform Installs
UE Fielding
1st LRIP AE
High Power AE Development
Production / Platform Installs
Increasing Percent Fielding
User Equipment
GPS III Launches
GPS III Launches
14
L2 Civil Signal
LCDR Richard Fontana
GPS Deputy Program Manager, DOT
May 2, 2001
Overview
 Background
 Advantages of New Signal
 Design Considerations
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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
17
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
18
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
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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
20
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 code…no
additional testing required
 Risk Mitigation
 Design schedule short, IIR implementation schedule short,
coordination process short
 C/A code switch
21
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
22
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.
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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
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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
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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
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Back up
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