gnss receiver - software radio concept františek vejražka czech technical university in prague...

GNSS Receiver -

Software Radio Concept

František VejražkaCzech Technical University in Prague

Faculty of Electrical Engineering

Czech Technical University in Prague

NavSup 2006

November 14-16, 2006, Gdynia, Poland Vejražka: GNSS Receiver – SW Radio Concept ... 2

Why we have developed GNSS Receiver ?• Czech economy needs satellite

navigation

• Grant of Ministry of Transport „Implementation of Galileo System in the Czech Republic“


NavSup 2006


Receiver concept: 1. Present situation• GPS signal available only• several GLONASS satellites (14)• no Galileo signals in early future

– Giove A, Dec. 2005 - no ranging signals– Giove B, June 2007 (?)– first SV 2009 (?) [Hein, Jeju 2006]– full constellation 2011

• CR government imperative: to prepare for Galileo


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Receiver concept: 2. Requirements• 2006: prepare applications with GPS

(&GLONASS) signals use

• 2009: be able to add Galileo signals even with uncompleted constellation

• 2011: use full Galileo constellation signals and to support them by GPS &

GLONASS and by differential corrections (EGNOS)


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Receiver concept: 3. Decision

Receiver should process signals

• GPS: C/A L1, L2C, L5C

• GLONASS: L1, L2

• GALILEO: L1, E5a, E5b (~ OS service)

and later

• GPS III: L1C

• GALILEO: E1, E2, E6


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Receiver concept: How to realize it?• HW: to do basic processing only on highest frequencies where digital processing is impossible

• SW: to process signals digitally on as highest frequencies as it is possible

SOFTWARE DEFINED RADIO ARCHITECTURE


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Software Defined Radio Architecture• Processor only solution

• Processor & programmable logic

RF frontend

ADC Computer

RF frontend

ADC Programmablelogic Computer


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Architectures Comparison

Processor only solution

Processor & prog. logic

Cost + -Bandwidth ++ +++GNSS performance

GPS L1 C/A

WAAS/EGNOS

Galileo L1

GPS L1, L2, L5

WAAS/EGNOS

Galileo L1, E5

GLONASS


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Aim of the Experimental GNSS Receiver• Signal processing algorithms development tool• Algorithms validation in experiments in real

environmentRequirements• High performance• High flexibility

Processor & programmable logic

receiver architecture


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Experimental GNSS Receiver Development

20

2002 2004 2006 2008

Bandwidth[MHz]

2000

40

60

80

2nd generation

3rd generation

1st generation


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Experimental GNSS Receiver G3Features• Four RF channels • Bandwidth >80 MHz• Capability

– GPS L1 C/A– GLONASS– WAAS/EGNOS– Galileo L1– GPS L5– Galileo E5, E5A, E5B– NON GNSS signals processing

• Complex signal processing• Integration with terrestrial

navigation and communication systems

Synthetiser

Com plex m ixer

cos

sin

E5 filter LNA

E5 base bandChebyshev filter

ADC

ADC

I

Q

Galileo E5 front end


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Correlator Logic schema


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CorrelatorResults of analysis & simulations

20 25 30 35 40 45 50 55 60 6510

-2

10-1

100

101

102

Noncoherent E5 DLL Performance with Envelope Type Detector (Bn = 3Hz)

Pc/N

0 [dB-Hz]

DLL t

rackin

g e

rror

(1)

[ns]

theoretical performancetheoretical coherent perf.simul.: independent DLLsimul.: mena E5a and E5bsimul.: mean E5


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Correlator structure


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Correlator realization


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32 bits NCO and PRN generatorof GPS and EGNOS codes


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32 bits NCO and PRN generatorof GPS and EGNOS codes

32 bits NCOand complex (IQ) mixer


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Development procedure

Program in SimulinkCompilationTesting, validation


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Program in SimulinkCompilationTesting, validation

Compiled programsaved in receiver memoryTesting


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Development procedureRealization


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Application of designed receiver:1. GPS EGNOS Receiver for Railway

Features• Based on Experimental GNSS Receiver G2• L1 & L2 RF channels• External EGNOS data input • Certified software


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On Board Unit


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Control Panel of Locomotive On Board Unit

Locomotive On Board Unit

Dispatcher Screen


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Application of designed receiver:2. GIOVE A signal reception


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Application of designed receiver:3. EGNOS Monitoring Station

Features• Experimental GNSS Receiver G2• Four L1 RF units:

– 1x hemisphere antenna for GPS & EGNOS &Galileo

– 3x directional antenna for EGNOS message reception

Improved SNR & BER for EGNOS message channel

Directional antenna prototype

Gain 17 dB


NavSup 2006


Application of designed receiver:4. Research of Egnos Signal Availability

Investigation of the EGNOS satellite shadowing

EGNOSGNSS


NavSup 2006



Country

Town

Unblocked

Blocked

Distance [km]

1 4 8

Unblocked

Blocked

Distance [km]

1 4 8

PRN 120 IOR, Prague, Czech Republic, elevation 15


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positionmeassurement

maximumacceptable age

of message

FLAG

NO FLAG

position OK

message age


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EGNOS Service AvailabilityExample: Msg. No. 2

0 50 100 1500

0.2

0.4

0.6

0.8

1

0 50 100 1500

0.2

0.4

0.6

0.8

1

Sparsely built-up town Undulating country Flat country

0 50 100 1500

0.2

0.4

0.6

0.8

1

Age [s] Age [s] Age [s]

Pro

babi

lity

Pro

babi

lity

Pro

babi

lity

Probability that message age exceeds given threshold

threshold 18 s (for aircraft enroute navigation!)


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EGNOS Service Availability – Expert Finding• EGNOS signal is not generally available for a

land mobile user• EGNOS service can be ensured by

distribution of the EGNOS messages trough data channel with high availability for a land mobile user

EGNOS monitoring station


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EGNOS Monitoring Station

Reasons

• Reception of the EGNOS messages for further distribution via highly available channel

• Monitoring of all EGNOS and GPS satellites in view– Investigation of the GNSS system behavior

– Investigation of the receiver problem


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Plans for Future

• GNSS receiver of the third generation

• Implementation of the Galileo signal processing including E5 band

• Integration with terrestrial navigation and communication systems with good indoor availability like DTV

• Non GNSS signal ranging


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Conclusions

Experimental SW receiver is excellent tool for:

• experiments with GNSS signals• prototyping of algorithms for non standard applications• non standard GNSS measurements• signal reception of early phase Galileo• education in GNSS techniques

Thank you for your attentionFrantišek Vejražka

Czech Technical University in Prague,Czech Republic

[email protected]

gnss receiver - software radio concept františek vejražka czech technical university in prague...

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