1. Development of Global navigation satellite system (GNSS) Receiver
Veena G Dikshit
Sc ‘E’
ADE, Bangalore
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

2. Veena G Dikshit, Sc 'E' , ADE, Bangalore
Introduction
Global Navigation Satellite Systems (GNSS) involve satellites, ground stations and user equipment to determine positions around the world and are now used across many areas of society
GNSS GPS (USA), GLONASS (Russia), Galileo(Europe), Augmentation Systems (SBAS, GBAS), IRNS (India), QuasiZenth (Japan)
Fuelling growth during the next decade will be next generation GNSS that are currently being developed.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

3. Veena G Dikshit, Sc 'E' , ADE, Bangalore
GNSS SYSTEM
GPS Modernization
Improved code on the L2 frequency of GPS (called L2C) –
ionospheric error,
more immune to RF interference and
multipath.
The first Block IIR-M during October 2005.
Under currently published plans, that is not expected to occur until 2013 or beyond.
A third civil frequency at MHz (called L5) on the Block IIF satellites. Full operational capability is unlikely until 2015.
GPS-III, (extra L2 and L5 signals of the Block IIR-M and Block IIF satellites), Thirty GPS-III satellites are planned for launch from about 2013 until 2018.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

4. Veena G Dikshit, Sc 'E' , ADE, Bangalore
GLONASS from Russia
GLONASS-M (L1 and L2 bands ) satellites with an improved 7-year design lifetime.
2007 to 2008 planned to launch GLONASS-K satellites with improved performance, also transmit a third civil signal (L3).
Stated intention is to achieve a full 24-satellite constellation transmitting two civil signals by 2010.
Full constellation is planned to be broadcasting three sets of civil signals by 2012.
Indian Government announced at the end of 2004 that it would be contributing funds to assist Russia to revitalize GLONASS.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

5. Veena G Dikshit, Sc 'E' , ADE, Bangalore
Galileo from the European Union
Constellation of 30 satellites, increased altitude (approximately 3000km higher than GPS) which will enable better signal availability at high latitudes.
Exact signal structure is still liable to change,
Galileo satellites broadcast signals compatible with the L1(E5a E5b) and L5 GPS signals. Galileo will also broadcast in a third frequency band at E6; which is not at the same frequency as L2/L2C of GPS.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

6. Veena G Dikshit, Sc 'E' , ADE, Bangalore
Current plan is to offer 5 levels of service:
Open Service uses the basic signals, free-to-air to the public with performance similar to GPS and GLONASS.
Safety of Life Service allows similar accuracy as the Open Service but with increased guarantees of the service, including improved integrity monitoring to warn users of any problems.
Public Regulated Service is aimed at public authorities providing civil protection and security (eg police), with encrypted access for users requiring a high level of performance and protection against interference or jamming.
Search and Rescue Service is designed to enhance current space-based services (such as COSPAS/SARSAT) by improving the time taken to respond to alert messages from distress beacons.
Commercial Service allows for tailored solutions for specific applications based on supplying better accuracy, improved service guarantees and higher data rates.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

7. Veena G Dikshit, Sc 'E' , ADE, Bangalore
GNSS Signal Spectrum
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

8. Veena G Dikshit, Sc 'E' , ADE, Bangalore
BENEFITS OF GNSS
Availability of Signals
Extra satellites improve continuity
Extra satellites and signals can improve accuracy
Extra satellites and signals can improve efficiency
Extra satellites and signals can improve availability (of satellites at a particular location)
Extra satellites and signals can improve reliability
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

9. GNSS RECEIVERS DESIGN APPROACHES A typical GNSS Receiver
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

10. Software Receiver (SDR) Architecture
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

11. Comparison of ASIC and SDR
Features
ASIC
SDR
Upgradability
A fixed platform.
Dictate the potential capabilities of the receiver
Re-programmable
Re-configurable
Separation of Hardware
Multi system upgrades changes in base band processing Hardware
Simple software change
Acquisition
Serial search Acquisition
Convolution in the time domain
Using correlation technique
Parallel Search Acquisition
FFT, Multiplication in the frequency domain
Buffering memory
Tracking
More efficient
Cost effective
Depends on the processor MIPS availability
Power Consumtion
Less power consumtion
More power consumption
Cost effectiveness
More Hardware, More cost
Less Hardware less cost
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

12. Development of GNSS Receiver
GPS L1 (Current)
GPS L1 & L2
GPS + GLONASS + SBAS
GPS + L5 + GLONASS + GALILEO
GPS + L5 + GLONASS + GALILEO + SBAS + GBAS
GPS + L5 + GLONASS + GALILEO + SBAS + GBAS + IRNS
BY 2015 position every where with decimeter and even centimeter accuracy will be widely available and affordable
ISSUSES
Lack of uniform compatibility
Differing Timing of Operational availability
Hybrid receiver Architecture required
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

13. Veena G Dikshit, Sc 'E' , ADE, Bangalore
architecture.
Software receiver approach is nearly ideal in terms of cost and system integration, as only a single front end is needed to process all of the signals
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

14. Challenges in the next generation receivers
Antenna Unit
Two Narrow band separated by 402 MHz
Broad band antenna covering multiple band signals
Challenge low cost satellite navigation receiver antenna requires – circular polarization with adequate axial ratio and the medium gain.
RF Front end
Challenge proper on/OFF chip filter design and component selection will improve the system performance.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

15. Demands are on the edge of currently available DSP
Digital Signal processing (A Big Challenge !?)
Multi-system receivers - Increased number of correlator channels
Dual band 2 correlator
Demand on the processing power depend on implementation
Implementation depend on the dynamics of the application
Approach either software correlator or trditional hardware correlator on FPGA
To process a single C/A code channel with one chip correlator spacing reqire a processing capacity of 4 MIPS
Increase in band width 2 t0 20 MHz wide band signals MIPS requirement increases by factor of 10
To reduce the noise level 2 bit signal sampling further MIPS requirement increases by factor 3
Finally for 48 channel 5760 MIPS are required
Demands are on the edge of currently available DSP
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore

16. Veena G Dikshit, Sc 'E' , ADE, Bangalore
Conclusion
Modernization trend, complexity, multitude of users and application,
Availability of different systems, differing time scale of availability are
Considered the development of the GNSS receiver for the defense
application offers a great challenge which need to be tackled right
from now
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore