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Fabio Dovis, Rodrigo Romero, Nicola Linty
Politecnico di TorinoDepartment of Electronics and Telecommunications
OutlineOutline
• Presentation of the team• Unit Research 2• UR2 contribution to DemoGRAPE• Introduction to software radio and GNSS• Tasks to be performed• Open questions and actions
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 22
The NavSAS Research GroupThe NavSAS Research Group
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting
NavSAS, according to a EC survey is considered one of the top 3 teams “of excellence” in the field of Navigation in Europe
NavSAS research group is a joint team of Politecnico di Torino Politecnico di Torino and ISMBISMB
Research in the areas of satellite navigation and positioning
Joint labs in the Navigation Technologies research area of ISMB
• Receiver design and implementation• Interference and spoofing detection, signal quality monitoring• Hybridization with communications and inertial navigation
• Advanced signal processing for scientific applications• Higher education – Master on Navigation and Related Applications
33
UR2 involvement in DemoGRAPEUR2 involvement in DemoGRAPE
• Empirical assessment of the polar ionosphere based on real measurements
• GNSS signals observation at high latitudes by means of multisystem and multifrequency receivers– Regular Monitoring receivers
– Fully software receivers (implementing advanced processing algorithms)
• Sharing of the data and of the results
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 44
Initial remarks on GNSS receiversInitial remarks on GNSS receivers
• GNSSs are communication systems
• GNSS receivers are processing an electromagnetic signal
• Each GNSS receiver is a suboptimal implementation of a maximum likelihood estimator of a propagation delay of the signal
• The classical acquisition + code and carrier tracking scheme is a way to implement such an estimator that exploits the features of the GNSS radio signal
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 55
What is software radioWhat is software radio
• A software-defined radio system, or SDR, is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system
• While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which used to be only theoretically possible.
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 66
SDR conceptsSDR concepts
• A basic SDR system may consist of a personal computer equipped with a sound card, or other analog-to-digital converter, preceded by some form of RF front end.
• The ideal receiver scheme would be to attach an analog-to-digital converter to an antenna.
• A digital signal processor would read the converter and do the processing (software algorithms)
• An ideal transmitter would be similar. A digital signal processor would generate a stream of numbers. These would be sent to a digital-to-analog converter connected to a radio antenna.
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 77
GNSS Receiver Functional SchemeGNSS Receiver Functional Scheme
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting
antenna
RFFront End
Acquisitionstage
Channel 1Tracking
Channel 2Tracking
Channel nTracking
NAVUnit
Position
Velocity
Carrier & Code correlator
Carrier & Code tracking
Evaluation of user position and time
External aidings
Time
88
Receiver logic
Traditional GNSS Receiver ImplementationTraditional GNSS Receiver Implementation
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting
)(, tx iRF
Antenna
SIS (Signal in Space)
Analog Front End
Digital Baseband processing (ADC-ASIC)
Micro/Signal Processor
Acquisition Tracking Navigation
User Computer & DisplayUser applications and interfaces
User Computer & DisplayUser applications and interfaces
Ser
ial
Co
mm
un
icat
ion
L
ink
Front end for analog signal conditioning, filtering and digitization
Core GNSS receiverCore GNSS receiver
High speed correlation ASIC (Application Specific Integrated Circuits)
Embedded programmable micro/signal processor
General Purpose Microprocessor
t
A/D converter
General purpose processor
Programmable hardware (FPGA) General purpose CPU
99
What is SDR forWhat is SDR for
• Software implementations are useful for:– prototyping and testing
– accessing the low level processing stages
– Implementation of new algorithms
– Specific applications where upgrading is foreseen (e.g. new signals to process)
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1010
SDR vs digital receiverSDR vs digital receiver
• Flexibility and reconfigurability: the same hardware can be reprogrammed but…– Limitations of the processing capability of the
processor wrt. the sampling rate (i.e. fc)– Capability of the front-end to be reconfigured as
central frequency and/or filter bandwidth
• Software implementations are generally less efficient than hardware dedicated receivers– Power consumption– Size of the processors– …
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1111
SDR and GNSSSDR and GNSS
• SDR became popular for the implementation of the baseband part of GNSS receivers– GNSS signals have small bandwidths compared to
other communication systems
– It is a receiver-only system
– The data rates involved allow real-time implementations
• GPS L1 and Galileo OS in fully software implementations
• GPS L5 and Galileo E5 (single sideband) in FPGA
• E6 ??
• …
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1212
GNSS software receiversGNSS software receivers
• NORDNAV receiver– A successful commercial story ?
• SX-NSR by Ifen Gmbh
• Namuru – University of New South Wales• N-GENE – Politecnico TO• Univ. of Calgary• EPFL• ….• Other non real-time implementations
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1313
Com
mer
cial
Com
mer
cial
Scie
ntifi
cSc
ient
ific
Non real-time and post-processing solutions are
usually enough for scientific research
Non real-time and post-processing solutions are
usually enough for scientific research
SDR receivers and ionosphereSDR receivers and ionosphere
• The advantage of having an SDR receiver allows to have access to the precorrelation sections of the receiver
• Reconfigurability allows for dynamic adjustments of the receiver parameters to mitigate the scintillation effect:– a new generation of “iono-corrections” or “iono-
aidings” for single frequency receivers?– easy implementation of advanced signal processing
algorithms working on the time-series of the samples of the signal at IF
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1414
Hardware componentsFully
software receiver
Post processing
GNSS data collection and processingGNSS data collection and processing
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1515
• Strong potentialities offered by fully software GNSS receivers for scientific purposes:
– flexibility– configurability– block structure: capability to test
different algorithms– Temporary and fixed installations
RF front-endRF front-end Bit grabberBit grabber
(raw samples)(raw samples)
storagestoragePCPC
L1 antenna
A powerful tool for the collection of raw data (pre-correlation), and post-processing replay
fL1 = 1575.42 MHz
-
Processing of the data: Scintillating signalsProcessing of the data: Scintillating signals
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting
A fully software receiver updated to process scintillating GPS and Galileo signals is used to post-process the IF samples and calculate the scintillation indices.
Software receivers allow to test with ease different configurations and architectures when processing of scintillating GNSS signals.
GPS PRN 23, March 14 UTC 1440
1616
Implementation in the Navis centerImplementation in the Navis center
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1717
NAVIS CentreHanoi University of Science
and Technology
International collaboration center
Monitoring station set-up in cooperation with ESA and EU-JRC
Hosting professional receivers and a data grabber system
http://navis.hust.edu.vn/http://navis.hust.edu.vn/
Data collection set-up @NavisData collection set-up @Navis
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1818
USRP
• Data collection on L1
• Raw samples collected after sunset on a daily basis
• Raw data storage on 2Tbyte hard disks
• (1 day of data amounts to 178 GB)
• Professional receiver is used for benchmarking
demoGRAPE tasksdemoGRAPE tasks• Front-end set-up and tailoring to the polar installation
– Antennas– A/D conversion stage– Clocks– Storage system
• Software Receiver tuning and refinement • Additional material procurement
• Temporary installation• Data collection campaign performed in parallel to the data
acquisition by a benchmark professional receiver
• Data processing • Sharing of raw data and results of meaningful scenarios
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 1919
Open issuesOpen issues
• Availability and interaction with instruments in location– Antennas (bandwidth, power level?)– Splitter– Interface with front-end/data grabber– Professional receiver
• Data storage (Data and Metadata) and sharing– open repository @polito /@ismb?– interface and interaction with the cloud architecture?
• Design of a resident raw data grabber (automatic data collection, or triggered by events in the professional receiver)?
• Can we see the SW RX as an application running (remotely) on a set of data (Agent)?– - scalability?
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting 2020
US-ION WG
09/10/201409/10/2014 DEMOGRAPE Kick-off meetingDEMOGRAPE Kick-off meeting
Visit: www.navsas.euwww.polito.itwww.ismb.it
Fabio Dovis
Politecnico di TorinoDept. Of Electronics and Telecommunications
2121