GNSS and Positioning for the Future - Kai Borre

DANISH GPS CENTER

GNSS

and

Positioning for the Future

Kai Borre

Danish GPS Center, Aalborg University, Denmark

DANISH GPS CENTER GNSS Development Schedule

• GPS and

GLONASS

evolved slowly

in the first

decades

• In the last

decade the

development

of space and

ground control

segments is

intense

14/12/2011 Copyright © 2011 by Kai Borre 2

Test & deployment GPS III

GPS II

2020 2012 2010 2015

COMPASS

COMPASS 1 (end date unknown)

Test & deployment of L5

GPS III FOC

L1C FOC

L5 FOC

L2C Full Operational Capability (FOC)

GLONASS Full Operational Capability (FOC)

COMPASS 2 test & depl. COMPASS 2/3, regional service; global service depl. COMPASS 3 FOC

New

signals

FOC

SDCM design/tests

GLONASS-M (launched until

2012)

GLONASS-K2 (KM after 2015)

New: L1OC, L3OC, L1SC, L2SC (CDMA), SAR

GLONASS-K1 New: L3OC (CDMA),

SAR

Galileo launch

Sys. testbed v1/v2 IOV Deployment

Galileo operational

SDCM fully deployed

18 SV OC

Test & deployment of L1C

Test & deploym. of L2C, staged roll-out of CNAV

Courtesy of Darius Plaušinaitis

DANISH GPS CENTER The Menu of Future GNSS Signals

• Originally GPS and

GLONASS offered

one civilian signal on

one carrier

• Future GNSS offer

system diversity and

frequency diversity

System Signal

Carrier

frequency

[MHz]

Component Type Data rate

[sps/bps] Modulation

Chipping

rate

[Mcps]

Code length

[chips]

Full

length

[ms]

GLONASS L1 OF 1605.375-

1609.3125

standard Data -/50 BPSK

0.511 511 1

SF high accur. Military 5.11

COMPASS B1 1575.42

B1-CD Open

100/50 MBOC(6,1,1/11) 1.023

B1-CP -/-

B1 Authorized 100/50

BOC(14,2) 2.046

-/-

Galileo E1 1575.42

A PRS cosBOC(15,2.5) 2.5575

B Data, SOL 250/125 CBOC(6,1,1/11) 1.023

4092 4

C Pilot, SOL -/- 4092 * 25 100

GLONASS L1 OC/SC 1575.42

GPS L1 1575.42

C/A Data -/50 BPSK 1.023 1023 1

P(Y) Military

BPSK 10.23 7 days 7 days

M BOC(10,5) 5.115

Galileo E6 1278.75

A PRS cosBOC(10,5)

B Data 1000/500 BPSK(5) 5.115

5115 1

C Pilot -/- 5115 * 100 100

COMPASS B3 1268.52

B3

Authorized

-/500 QPSK(10) 10.23

B3-AD 100/50 BOC(15,2.5) 2.5575

B3-AP -/-

GLONASS L2 OF 1242.9375-

1248.1875

standard Data -/50 BPSK

0.511 511 1

SF high accur. Military 5.11

GPS L2 1227.6

L2 CM Data 50/25

or -/50 TM and BPSK 0.5115 10230 20

L2 CL Pilot -/- 767250 1500

P(Y) Military

BPSK 10.23 7 days 7 days

M BOC(10,5) 5.115

GLONASS L3 OC 1207.14 QBSK(10)

GLONASS L3 OF/SF 1201.743-

1208.088

COMPASS B2 1191.795

B2aD

Open

50/25

AltBOC(15,10) 10.23

B2aP -/-

B2bD 100/50

B2bP -/-

Galileo E5

(1191.795)

E5a 1176.45 a-I Data 50/25

AltBOC(15,10) 10.23

10230 * 20 20

a-Q Pilot -/- 10230 * 100 100

E5b 1207.14 b-I Data, SOL 250/150 10230 * 4 4

b-Q Pilot, SOL -/- 10230 * 100 100

GPS L5 1176.45 I Data 100/50

QPSK 10.23 10230 1

Q Pilot -/- 1


Courtesy of Darius Plaušinaitis

DANISH GPS CENTER GNSS Signal Changes

• Increasing requirements to positioning, increasing

number of systems ask for redesign of GNSS signals


– New modulations are needed due to

• More heavy shearing of spectrum

• More signals per carrier

• Improved ranging performance

– New PRN code generators (Kazami,

Weil, Neuman-Hoffman) are

considered in addition to the

traditional Gold codes

• Several signals in a system and

several systems are using the same

carrier

• Better performance of week signals

• Better interference performance

• Better ranging performance Figure source – “GPS World”

GNSS L1 (carrier) spectrum

DANISH GPS CENTER Global Navigation Satellite Systems

• GPS (II – 1980)

• GLONASS (1993)

• COMPASS

• Galileo


2006

~1981

• 80’s-90’s – the first professional

GPS + GLONASS receivers

• 2011 – “launch year” for the first

consumer, mobile phone GPS +

GLONASS receiver chips (from

Qualcomm, Broadcom, ST-

Ericsson, u-blox and others)

DANISH GPS CENTER Relative Accuracy of Clocks

• Clock stability influences signal and

observation related parameters


Clock type Applications Relative accuracy

[s/s]

Temperature compensated

crystal oscillator (TCXO)

Watches, clocks, consumer GNSS

receivers, mobile phones 10-6 – 5×10-7

Oven controlled crystal

oscillator (OCXO) Geodetic GNSS receivers 10-7 – 10-8

GPS disciplined oscillator

(GPSDO) – GPS + above clock Time and frequency synchronization 10-9 – 10-12

Chip scale atomic clock (CSAC) Future high performance GNSS

receivers 5×10-12

Rubidium atomic clock Special space and terrestrial

applications that require extra high

stability and accuracy

10-11 – 10-12

Cesium atomic clock 10-12 – 10-13

Hydrogen maser Space (new application) and

terrestrial applications 10-15 – 10-16

DANISH GPS CENTER

Satellite Based Augmentation

System (SBAS)

• The primary driver for SBAS is aviation applications

that require high safety

• SBAS provides services that are not available in GPS

or other existing systems


– DGPS type corrections for

improved standard receiver

precision

– Massive signal integrity

monitoring and user alert in

less than 6 seconds from

the start of an integrity

failure

– Other system safety and

service quality data that are

vital for reliable positioning

DANISH GPS CENTER Space Based Augmentation Systems

• Wide Area Augmentation System (WAAS), USA

• European Geostationary Navigation Overlay Service

(EGNOS)

• System for Differential Correction and Monitoring

(SDCM), Russia

• GPS And Geo-Augmented Navigation (GAGAN)

system, India

• Quasi-Zenith Satellite System (QZSS), Japan

• Multi-functional Satellite Augmentation System

(MSAS), Japan


DANISH GPS CENTER Alternative Systems

• Research and development continuously

adapt to or modify existing systems to provide

positioning services

– Legacy ground based systems (no perspectives)

– WiFi (very limited capabilities)

– Mobile Networks (does not meet today’s GNSS

precision level, new versions under development)

– TV (DVB) signals based

– Proprietary, local (for example LOCATA)

– New methods based on GPS+LEO satellites (for

example Boeing Timing & Location)


DANISH GPS CENTER Boeing Timing & Location (BTL) I

• BTL Geo-location builds on Transit heritage. It

complements GPS with an enhanced version

of the existing Iridium system

• BTL Geo-location provides key technical

advantages in 2 parts – (GPS-based systems

can not do this)

– Iridium signal power (BTL) >> GPS – Iridium

penetrates buildings better

– Spot beams form unique local contours. Extremely

difficult to spoof (today spoofing is of big concern

for civil applications in the GNSS world)


DANISH GPS CENTER Boeing Timing & Location (BTL) II


DANISH GPS CENTER Boeing Timing & Location (BTL) III


Figure source – Wikipedia

DANISH GPS CENTER

Receiver Development


DANISH GPS CENTER Current Receiver Development

Copyright © 2011 by Kai Borre 14

2007 Future Research and

development

2008-2010

•Snapshot techniques

•High sensitivity

•Multi-system & multi-

frequency receiver

•Multipath mitigation

•Antenna arrays

•Further SDR

development

•GNSS integrity

•Integration of other

positioning methods

14/12/2011

DANISH GPS CENTER Matlab SDR Plots


4 4.005 4.01 4.015 4.02 4.025 4.03 4.035

x 104

-2000

0

2000

4000

6000

Samples (time)

Co

rre

latio

n

Real correlation result from GNSS SDR

-1 0 1 2

0

0.5

1

1.5

Code Offset [chips]

Corr

ela

tion

Theoretical

correlation

0 5 10 15 20 25 300

5

10

15Acquisition results

PRN number (no bar - SV is not in the acquisition list)

Acq

uisi

tion

Met

ric

Not acquired signals

Acquired signals

14/12/2011

DANISH GPS CENTER Matlab SDR Conclusions

• An extremely convenient educational tool

• Quick prototyping

– A demo acquisition for Galileo in less than an hour

– Students have converted the GPS SDR to EGNOS

and Galileo SDRs in ~6 months

• Very convenient exploration of particular

signal cases (anomalies) or algorithms

because the GNSS signal record can be

replayed again and again …

• Acceleration of some key signal processing

steps is much recommended

Copyright © 2011 by Kai Borre 16 14/12/2011

DANISH GPS CENTER The Old Setup (Virtex IIP)

• Virtex IIP 50

FPGA

• GPS

front-end

from Simrad

• 1 bit samples

• 16 HW

channels

• Adjustable

correlator

spacing (on

the fly)

• About 50%

FPGA in use

• PPC cores

not used Copyright © 2011 by Kai Borre 17

Old

front-end

New

front-

end

14/12/2011

DANISH GPS CENTER DGC SDR Simulink Model

• Simulink receiver version allows modularity

and out of the box good visual representation

• The modularity gives benefits similar to the

Software Communications Architecture (SCA)


The adaptor block inside

calls nearly unmodified C

code of the FPGA receiver

14/12/2011

DANISH GPS CENTER Simulink Model Plots


DANISH GPS CENTER The ML507 Setup


Battery

adapter

New

front-end

14/12/2011

DANISH GPS CENTER DGC Receiver Results


DANISH GPS CENTER DGC Receiver Results


4 m 8 m

14/12/2011

DANISH GPS CENTER Future DGC Receiver Version

• Universal channels for GPS, Galileo, and other GNSS

signals (BOC, BPSK, and other types)

• Real-time operation with optional GNSS signal

recording or processing of such signal records

• Possible options

– Flexible support for multiple front-ends to process multiple

carriers or antennas

– Plotting on a PC of receiver tracking in real-time (non real-

time version already exists)

– Processing of other, non-GNSS signals (under consideration)

• Modular design (friendly for student project)

• Inspiration: AGGA-4, GNU Radio, Artus (IFEN) and

others…


DANISH GPS CENTER

Thank You For Your Attention

Also visit http://gps.aau.dk


DGC is organizing an international

workshop with the same title as the present

talk on August 27-September 2, 2012 at the

North Sea, Denmark. Interested participants

should contact [email protected]

Technology

GNSS and Positioning for the Future - Kai Borre