dgdovis

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


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


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.


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.


GNSS Receiver Functional SchemeGNSS Receiver Functional Scheme


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

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Receiver logic

Traditional GNSS Receiver ImplementationTraditional GNSS Receiver Implementation


)(, 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

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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)


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– …


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 ??

• …


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


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


Hardware componentsFully

software receiver

Post processing

GNSS data collection and processingGNSS data collection and processing


• 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


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


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


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


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?


US-ION WG


Visit: www.navsas.euwww.polito.itwww.ismb.it

Fabio Dovis

Politecnico di TorinoDept. Of Electronics and Telecommunications

[email protected]

2121

dgdovis

Science

digital converter

digital signal processor

radio antenna

analog converter

radio communication

gnss receiversgnsss

ismb research

electromagnetic signal