-
Digital signal processing for satellite-based positioning
Department of Communications Engineering (DCE), Tampere
University of Technology
Simona Lohan, Dr. Tech, Docent (Adjunct
Professor)E-mail:[email protected]
Markku Renfors, Professor, Head of the
DepartmentE-mail:[email protected]
Current group members: 5 PhD students and 2 MSc students (size
of the group is about 9% of DCE total number of MSc/PhD
students)
-
Backgroundz GNSS related positioning activities have started at
DCE since 2003z Previously: WCDMA/UMTS-based positioning studies
(partly funded
by Nokia)z Main goals: { signal acquisition and tracking in
multipath fading environments{ design of low-cost low-power
receiver architectures{ indoor channel modeling (based on
measurement data){ Pseudolite (pseudo-satellites)based
positioning
z Motivation: { Emergency location rules (FCC 911, E-112) {
Development of Galileo (future European GNSS system){ Increasing
penetration rate of 3G mobile phones -> A-GNSS
z Current funding: Tekes (Finnish funding agency for research
and innovation), Academy of Finland, and TISE graduate school
(another EU-FP6 GSA-funded European project just ended; pending
application for its continuation within EU FP7)
-
Co-operation
z Local co-operation with the Department of Digital and Computer
Systems, TUT and with the Department of Mathematics, TUT
(positioning-related research).
z Finnish co-operation with the companies within Tekes projects
(Atheros Communications, Elektrobit, Fastrax, Kalmar Industries,
Patria Aviation, Space Systems Finland, and VTI Technologies)
z International co-operation with the partners in the EU
GSA-funded project Galileo receivers for mass market applications
GREAT (Acorde Spain, DLR Germany, PA Consulting, Qualcomm Germany,
and u-Blox Switzerland). Additionally: co-operation with NavSas
group,Torino, Italy through exchange students.
z Summer course organized on positioning in 2006, together with
Associate Professor Ridha Hamila from Etisalat University College
(UAE)
z Active participation in international GNSS-related
conferences
-
Applications:-Emergency calls-Map location, in-car
navigation-Tag-based location (lostchildren, pets,)-Safety of Life
applications (maritime/ air)- Logistics, etc
Research challenges & applicationsChallenges (signal
level):-Low CNRs (especially indoors and in dense urban
areas)-Multipath propagation and fading (diffraction, reflections,
refractions, scattering)-Non-existent Line Of Sight-Ambiguities in
Galileo acquisition and tracking (due to modulation waveforms)
-
Galileo signal structure-Binary Offset Carrier (BOC) modulation
better separation with GPS signals (see the spectra in the left
figure). Correlation envelopes and ambiguities are visible in the
right figure:-
-4092 chip lengths of Open Services (4 times higher than in
GPS)
-Pilot codes available for better channel
estimation/tracking
-
Overview of the research topics
z Theoretical studies of modulation waveforms, e.g., Binary
Offset Carrier (BOC) modulation z Delay-Doppler acquisition
techniquesz Accurate delay tracking (fine delay estimation)
with
multipath mitigationz Filter design and optimization for
bandwidth-limited
applicationsz Data measurements and indoor channel modeling
(based on GPS and pseudolite signals)z CNR estimation studiesz
Carrier phase estimators
-
Delay-Dopler acquisition techniques
z Doppler shift (due to satellite velocity) + Doppler spread
(due to terminal velocity)
z Several peaks in time due to multipaths and BOC; several peaks
in frequency, e.g., due to Clarke spectrum in Rayleigh fading
(left, GPS) or Rician profile (right, GPS)
500
0
500
05
1015
200
0.05
0.1
0.15
0.2
0.25
Frequency error (Hz)Delay [chips]500
0
500
510
1520
250
0.2
0.4
0.6
Frequency error (Hz)Delay [chips]
-
Challenges related to acquisition of GNSS signals
{Time versus frequencybased correlator structures: tradeoff
between speed and complexity{Serial/Hybrid/Parallel search
strategies: tradeoff
complexity/speed{ Single versus multiple dwells in the
decision
process{Unambiguous BOC processing to deal with BOC
ambiguities{Theoretical models for time-to-first fix and for
detection/false alarm probabilities
-
Unambiguous acquisitionz Several methods have been studied,
based on single or double sideband
processing or based on filter banksz An illustrative shape of
the absolute value of the correlation function (ACF)
before and after unambiguous processing is shown below:
1 0.5 0 0.5 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Normalized envelope of the ACF, SinBOC(1,1), infinite BW
N
o
r
m
a
l
i
z
e
d
e
n
v
e
l
o
p
e
o
f
t
h
e
A
C
F
Delay error [chips]
BPSK modulationBOC modulationSingle SB processing of BOCDual SB
processing of BOC
-
Accurate delay tracking in multipath environments illustration
of the problemz Examples of correlation shapes in multipath
presence. SinBOC(1,1)
modulation (Galileo)
1.5 1 0.5 0 0.5 1 1.50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Multipath delays [chips]
C
o
r
r
e
l
a
t
i
o
n
o
u
t
p
u
t
SinBOC(1,1)
no multipath
with multipaths
channel paths location
-
Accurate delay tracking in multipath environments
z Feedback versus feed-forward delay trackers (or a combination
of both)?
z Several algorithms have been studied and several solutions
have been proposed so far, including Sidelobe cancellation
techniques, Multiple Gate Delay structures (tested also via
hardware prototyping), deconvolution algorithms and various
non-linear structures
z On-going studies to include carrier-aided delay tracking
-
Channel modeling based on measurement data
z Several campaigns based on GPS signals or pseudolite signals
have been carried on, with the purpose of modeling the indoor
channel for Galileo/GPS reception.
z Measurement campaigns were carried out with the help of
Atheros Communications (former u-Nav Microelectronics Finland) and
Space System Finland
z Estimation of signal quality and the fading characteristics:
these estimates are needed both for acquisition/tracking and for
different navigation algorithms.
z On-going studies
-
Example of measurement set-up, Tietotalobuilding
-
Other research topics
zInterference cancellation methods: one MSc thesis completed
(narrowband interference);zCarrier-To-Noise ratio estimation
studies (one
completed MSc thesis dealing partly with this)zSimulink models
for Galileo signal tracking,
based on Multiple Gate Delay structures (one completed MSc
thesis)zCarrier phase estimators
-
Published results
z 2 completed PhD theses + 1 in writing phasez 6 completed MSc
thesesz 15 journal papers, about 50 conference papersz Complete
list of publications and group webpage can be
found as links from:http://www.cs.tut.fi/~simona
-
Conclusions
z We have been mainly focusing on signal processing aspects of
satellite positioning
z No full navigation solution: we aim at giving informative
models (delay error distributions, CNR variation, achievable
accuracy in various scenarios, etc) for the navigation purposes
(RAIM, navigation sensor integration, etc)
z Also, hardware implementation and prototyping is beyond our
scope, but joint work with HW team has been done and some of the
proposed multipath mitigation algorithms have been tested in FPGA
and SystemC.
z Interesting co-operation areas: { Both GNSS-based positioning
and cellular-based positioning; possibility to move
towards other promising positioning areas (e.g., WLAN, UWB,
...){ Signal processing { Navigation layer (feeding our algorithms
into navigation software){ Hardware (FPGA; prototyping){
Applications (?)
Digital signal processing for satellite-based
positioningBackgroundCo-operationResearch challenges &
applicationsGalileo signal structureOverview of the research
topicsDelay-Dopler acquisition techniquesChallenges related to
acquisition of GNSS signalsUnambiguous acquisitionAccurate delay
tracking in multipath environments illustration of the
problemAccurate delay tracking in multipath environmentsChannel
modeling based on measurement dataExample of measurement set-up,
Tietotalo buildingOther research topicsPublished
resultsConclusions
Digital signal processing for satellite-based positioning
Department of Communications Engineering (DCE), Tampere
University of Technology
Simona Lohan, Dr. Tech, Docent (Adjunct
Professor)E-mail:[email protected]
Markku Renfors, Professor, Head of the
DepartmentE-mail:[email protected]
Current group members: 5 PhD students and 2 MSc students (size
of the group is about 9% of DCE total number of MSc/PhD
students)
Background
GNSS related positioning activities have started at DCE since
2003Previously: WCDMA/UMTS-based positioning studies (partly funded
by Nokia)Main goals: signal acquisition and tracking in multipath
fading environmentsdesign of low-cost low-power receiver
architecturesindoor channel modeling (based on measurement
data)Pseudolite (pseudo-satellites)based positioningMotivation:
Emergency location rules (FCC 911, E-112) Development of Galileo
(future European GNSS system)Increasing penetration rate of 3G
mobile phones -> A-GNSSCurrent funding: Tekes (Finnish funding
agency for research and innovation), Academy of Finland, and TISE
graduate school (another EU-FP6 GSA-funded European project just
ended; pending application for its continuation within EU FP7)
Co-operation
Local co-operation with the Department of Digital and Computer
Systems, TUT and with the Department of Mathematics, TUT
(positioning-related research).
Finnish co-operation with the companies within Tekes projects
(Atheros Communications, Elektrobit, Fastrax, Kalmar Industries,
Patria Aviation, Space Systems Finland, and VTI Technologies)
International co-operation with the partners in the EU
GSA-funded project Galileo receivers for mass market applications
GREAT (Acorde Spain, DLR Germany, PA Consulting, Qualcomm Germany,
and u-Blox Switzerland). Additionally: co-operation with NavSas
group,Torino, Italy through exchange students.
Summer course organized on positioning in 2006, together with
Associate Professor Ridha Hamila from Etisalat University College
(UAE)
Active participation in international GNSS-related
conferences
Research challenges & applications
Applications:Emergency callsMap location, in-car
navigationTag-based location (lostchildren, pets,)-Safety of Life
applications (maritime/ air)- Logistics, etc
Challenges (signal level):Low CNRs (especially indoors and in
dense urban areas)Multipath propagation and fading (diffraction,
reflections, refractions, scattering)Non-existent Line Of
SightAmbiguities in Galileo acquisition and tracking (due to
modulation waveforms)
Galileo signal structure
Binary Offset Carrier (BOC) modulation better separation with
GPS signals (see the spectra in the left figure). Correlation
envelopes and ambiguities are visible in the right figure:
4092 chip lengths of Open Services (4 times higher than in
GPS)Pilot codes available for better channel
estimation/tracking
Overview of the research topics
Theoretical studies of modulation waveforms, e.g., Binary Offset
Carrier (BOC) modulation Delay-Doppler acquisition
techniquesAccurate delay tracking (fine delay estimation) with
multipath mitigationFilter design and optimization for
bandwidth-limited applicationsData measurements and indoor channel
modeling (based on GPS and pseudolite signals)CNR estimation
studiesCarrier phase estimators
Delay-Dopler acquisition techniques
Doppler shift (due to satellite velocity) + Doppler spread (due
to terminal velocity)Several peaks in time due to multipaths and
BOC; several peaks in frequency, e.g., due to Clarke spectrum in
Rayleigh fading (left, GPS) or Rician profile (right, GPS)
Challenges related to acquisition of GNSS signals
Time versus frequencybased correlator structures: tradeoff
between speed and complexitySerial/Hybrid/Parallel search
strategies: tradeoff complexity/speed Single versus multiple dwells
in the decision processUnambiguous BOC processing to deal with BOC
ambiguitiesTheoretical models for time-to-first fix and for
detection/false alarm probabilities
Unambiguous acquisition
Several methods have been studied, based on single or double
sideband processing or based on filter banksAn illustrative shape
of the absolute value of the correlation function (ACF) before and
after unambiguous processing is shown below:
Accurate delay tracking in multipath environments illustration
of the problem
Examples of correlation shapes in multipath presence.
SinBOC(1,1) modulation (Galileo)
Accurate delay tracking in multipath environments
Feedback versus feed-forward delay trackers (or a combination of
both)?
Several algorithms have been studied and several solutions have
been proposed so far, including Sidelobe cancellation techniques,
Multiple Gate Delay structures (tested also via hardware
prototyping), deconvolution algorithms and various non-linear
structures
On-going studies to include carrier-aided delay tracking
Channel modeling based on measurement data
Several campaigns based on GPS signals or pseudolite signals
have been carried on, with the purpose of modeling the indoor
channel for Galileo/GPS reception.Measurement campaigns were
carried out with the help of Atheros Communications (former u-Nav
Microelectronics Finland) and Space System FinlandEstimation of
signal quality and the fading characteristics: these estimates are
needed both for acquisition/tracking and for different navigation
algorithms.On-going studies
Example of measurement set-up, Tietotalo building
Other research topics
Interference cancellation methods: one MSc thesis completed
(narrowband interference);Carrier-To-Noise ratio estimation studies
(one completed MSc thesis dealing partly with this)Simulink models
for Galileo signal tracking, based on Multiple Gate Delay
structures (one completed MSc thesis)Carrier phase estimators
Published results
2 completed PhD theses + 1 in writing phase6 completed MSc
theses15 journal papers, about 50 conference papersComplete list of
publications and group webpage can be found as links
from:http://www.cs.tut.fi/~simona
Conclusions
We have been mainly focusing on signal processing aspects of
satellite positioningNo full navigation solution: we aim at giving
informative models (delay error distributions, CNR variation,
achievable accuracy in various scenarios, etc) for the navigation
purposes (RAIM, navigation sensor integration, etc)Also, hardware
implementation and prototyping is beyond our scope, but joint work
with HW team has been done and some of the proposed multipath
mitigation algorithms have been tested in FPGA and
SystemC.Interesting co-operation areas: Both GNSS-based positioning
and cellular-based positioning; possibility to move towards other
promising positioning areas (e.g., WLAN, UWB, ...)Signal processing
Navigation layer (feeding our algorithms into navigation
software)Hardware (FPGA; prototyping)Applications (?)
