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PRESENT SATELLITE RADIO NAVIGATION SYSTEMS, THEIR PERFORMANCE AND USER RECEIVER CONCEPTS František...
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Transcript of PRESENT SATELLITE RADIO NAVIGATION SYSTEMS, THEIR PERFORMANCE AND USER RECEIVER CONCEPTS František...
PRESENT SATELLITE RADIO NAVIGATION SYSTEMS,THEIR PERFORMANCE
ANDUSER RECEIVER CONCEPTS
František Vejražka, Pavel Kovář, Libor Seidl,
Petr Kačmařík, Josef Špaček, Pavel Puričer
Department of Radio EngineeringCzech Technical University in Prague
Czech Republic
Abstract
This contribution gives an overview of present and future navigation systems and their augmentations such as GPS, GLONASS, GALILEO, WAAS, EGNOS, MSAT, QZSS, BEIDOU, GAGAN. Performance of the systems depends on their technical parameters. We will try to evaluate these and to present our opinion on their advantages for different applications and in various situations (reception of weak signals suffering from great attenuation under vegetation canopy, in urban canyons, influence of reflections and multipath).The last part of the contribution deals with an application of software radio technology for user receiver design and results obtained from experiments with different algorithms of processing the satellite navigation systems signals.
Terminology
Satellite (Radio) Navigation Systems
~
Radio Determination Satellite Systems
~
Systems for radio position determination using satellites
Satellite Navigation Systems
Historical Satellite Navigation Systems(not realized)
• 601
• TIMATION
•...
• GEOSTAR
• REXSTAR
GPS - NAVSTAR
Satellite Navigation Systems
Past Satellite Navigation Systems
• NNSS - Transit
• Tsikad GPS - NAVSTARrealized but cancelled
full operational
Satellite Navigation Systems
GLONASS
GPS - NAVSTAR GALILEO
in the air, not fully operational, lack of reliable satellites
projected, in development,operational from 2008
Satellite Navigation Systems
GPS-NAVSTARGLONASSGALILEO
Global systems:
Local systems:
Augmentation systems:
BEIDOU…
WAASNDGPSEGNOSMSASGAGANQZSS
→ GALILEO
Principles of Satellite Navigation Systems
• Doppler systems
• Ranging systems
Principles of Satellite Navigation Systems – Doppler Systems
satellite
fv
fv
t1+t1 t2+t2 t3+t3 t4+t4
fp
f0
crtdtff ii
tt
tt
pi
ii
ii
/Δ )(N11 Δ
Δ
0
receiver
fp
mixer
oscillator
f0 -fp
Ni
counter
time marks
startti+ti
stopti+1+ti+1
Ni = ΔFΔT+(f0/c){√[(xi+1-x)2+(yi+1-y)2+(zi+1-z)2 ] –
√[(xi-x)2+(yi-y)2+(zi-z)2]} i = 1, 2, 3
satellite
orbit T t2
t3
t1
t4
r1
r2 r3 r4
user
Principles of Satellite Navigation Systems – Ranging Systems(x1, y1, z1) (x2, y2, z2)
(x3, y3, z3)
(x4, y4, z4)
d4 = c4
(xi - x)2 + (yi - y)2 + (zi - z)2 = (c (mi - 0) )2 i = 1, 2, 3, 4
(x, y, z)
x
z
y
0 mi
0 i = di /c
0
signaltransmittedby satellite
tuser
signalreceived by user
d1 = c1
d2 = c2
d3 = c3
(xi - x)2 + (yi - y)2 + (zi - z)2 = (c i)2 i = 1, 2, 3
+1
-1
t
m
received
C(t+) code
+1
-1
t
C(t) range
code inside
receiver
- 0
R()
GPSDELAY DISCRIMINATOR
correlator
C()generátor
delay
clock
delay control
C(t+)
C(t)
0
R()
m
C*(t)
C*(t) unwanted satellite range code
C*(t) C(t)
R*()
GPSEARLY-LATE DISCRIMINATOR
correlator
C() generator
clock
m = R +
correlator
filterC(t - m) +
-
C(t - R + /2)uE()
uE()
C(t - R - /2)uL()
/2-/2
uL()
/2-/2
u() = uL() - uE()
u()
R
Receiver Principle
()2
phase lock
m
pseudorange
delay discriminator
C(t)D(t)cos(2ft)
[C(t)D(t)(1+cos(4ft))]1
2
cos(2ft)
C2(t) = 1D2(t) = 1
C(t)D(t)1
2
C(t)
C2(t)D(t) = D(t)1
2
Systems Parameters (Properties)
We will deal with systems:
• GPS – NAVSTAR
• GLONASS
• GALILEO
GPS - NAVSTAR
GPS Constellation
0°
40°
80°120°
160°
320°
280°
240°
200°17°
77°137°
197°257°
317°
satelliteoperationalspare
Equator
Right ascension of ascending node
Mea
n an
omal
y
F E D B A
Plane
Inclination 55°Semimajor axis 26561.75 km (altitude above Earth 20183,6 km)Excentricity nominally e = 0, generally e < 0,02
E1D2
C2B3
B2D1
E4C1
A4
F4A3
F3 F1
F2
D4
A1E2
D3
A2
C3B1
C4 E3
B4
C
GPS Present Signal Structure (1/3)Signal in time domain:
L1: s(t)=ACCC/A(t).D(t)cos(2πf1t)+APP(t).D(t)sin(2πf1t)
L2: s(t)=APP(t).D(t)sin(2πf1t)
Code multiplex - each satellite has own range codes CC/A(t) and P(t)
Signal in frequency domain:L2
1227,6 MHz±12 MHz
L11575,42 MHz
±12 MHz
ARNS/RNSS
1260 1559 1610
C/A
P(Y) P(Y)
MHz1215RNSS
GPS ParametersSignal Structure (2/3)Navigation Message (Data) Content:
• transmitting satellite Kepler parameters• almanac – Kepler parameters of others satellites• satellite „health“• corrections of
– satellite clock frequency– troposphere refraction
• …
Organisation of Data Frame:
54321
navigation message = 25 pages ~ 12,5 mins
frame = 1500 bits ~ 30 s ~ 5 subframes
25 pages
0987654321
subframe=10 words ~ 6 s
word = 30 bits ~ 0,6 sbit ~ 20 ms
GPS ParametersSignal Structure (3/3)Navigation Message FEC Hamming Coding
message receivedin error
errors without message ifsyndrom
bits (control)parity ,...,
bitsn informatio,...,
1000...
........................
0010...
0001...
,...,,,...,
data received
1
1
21
22221
11211
11
0S
0SHBS
HB
TT
m
k
mkmm
k
k
mk
rr
aa
hhh
hhh
hhh
rraa
GPS Services• SPS – Standard Positioning Service
only C/A code accessible
• PPS – Precision Positioning Servicefor authorized usersP(Y) code accessible
GLONASS
GLONASS Constellation
• 24 satellites (8 satellites in each of 3 planes)
• e ~ 0 (circular orbit) • inclination 64.8°• altitude 19 100
km, • orbit period 11h 15m
• angular spacing between orbits 120°
GLONASSSignal Structure• Frequencies:
– L1: fj = 1602 + 9j/16
– L2: fi = 1246 + 7i/16 [MHz]
• Modulation:– Navigation message– Pseudorandom ranging code
• Sequence of maximum length• Period 1 msec• Bit rate 511 kb/s
– 100 Hz auxiliary meander sequence – Manchester code
GLONASS Signal Structure• Data
– Hamming code (84,8)– 50 b/s in strings– 15 strings ~frame– 5 frames ~navigation message ~2.5 min
No Data Parity Time mark
2 sec
0
85 bits111110…110
1.7 sec 0.3 sec
GLONASS Constellation history
9 1012
1412 12 12
16
26
22
16
13 12 11
8 7 810
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
GALILEO
GALILEO Constellation
3 GEO satellites:• Inmarsat III
AOR-E 15.5°W F5 25.0°E
• ESA Artemis 21.5°E30 MEO satellites:
• 9 satellites in each of 3 planes (Walker constellation 27/3/1)• 3 spare satellites (1 in each plane) • e = 0 (circular orbits)• inclination 56°• altitude 23 616 km• orbit period 14h 21.6m ~ 1+2/3 rev. a day ~ ground track
repeats every 3 days
GALILEOArchitecture
USER SEGMENT
IMS
GALILEO CORE SYSTEM
TTC uplink
GCC
L-bandNAV
UHFSAR
….
REGIONALCOMPONENTS
LOCALCOMPONENTS
COSPAS-SARSATGROUND SEGMENT
MEO CONSTELLATION
External ComplementarySystems
C-band uplink
regional uplink
S-b
and
uplin
k GSS
Network
ICC
IMSNetwork
ICC
IMSNetwork IULS
Communication link
LocalInfra-
struct.
Communication link
LocalInfra-
struct.
.
.
.
.
.
.
NAV SIS NAV SIS
NAV SIS NAV SIS
INTEGRITY DETERMINATION& DISSEMINATION
NAVIGATION CONTROL &CONSTELLATION MANAGEMENT
Mission uplink
USER SEGMENT
IMS
GALILEO CORE SYSTEM
TTC uplink
GCC
L-bandNAV
UHFSAR
….
REGIONALCOMPONENTS
LOCALCOMPONENTS
COSPAS-SARSATGROUND SEGMENT
MEO CONSTELLATION
External ComplementarySystems
C-band uplink
regional uplink
S-b
and
uplin
k GSS
Network
ICC
IMSNetwork
ICC
IMSNetwork IULS
Communication link
LocalInfra-
struct.
Communication link
LocalInfra-
struct.
.
.
.
.
.
.
NAV SIS NAV SIS
NAV SIS NAV SIS
INTEGRITY DETERMINATION& DISSEMINATION
NAVIGATION CONTROL &CONSTELLATION MANAGEMENT
Mission uplink
GALILEOServices• OS – Open Service
free of charge, positioning, navigation, timing services
• CS – Commercial Serviceadded value to OS, garanteed services
• SoL – Safety of Lifeintegrity message
• PRS – Public Regulated Servicepolice, customs, ...dedicated signal, under governmental control
• SAR – Search and Rescuecoordinated with COSPAS – SARSAT
GALILEOSignals and Spectra
1164
.00
1215
.00
E5
1260
.00
1300
.00
E6
1563
.00
1587
.00
L1
1559
.00
E2
1591
.00
E1
1544
.10
SA
R d
ownl
ink
L6
≈ ≈ ≈f [MHz]
ARNS960 MHz 1214 MHz
1151 MHz 1300 MHzRNSS
1559 MHz 5250 MHz
1559 MHz 5030 MHzRNSS
ARNS
ARNS – Aeronautical Radio Navigation ServiceRNSS – Radion Navigation Satellite Service
GALILEO Signals and Spectra – BOC(m,n)
s(t) = carrier x subcarier x (ranging)code
subcarrier –
code – PRN
TS
TC
C6
S6
T1,023.10
1n
T1,023.10
1m
BOC modulation BOC(m,n)
GALILEOBOC Spectrum
-5 -4 -3 -2 -1 0 1 2 3 4 5
x 106
-40
-35
-30
-25
-20
-15
-10
-5
0
BOC(1,1) BPSK(1)
m = 1 – subcarrier frequency is 1.023 MHzn = 1 – range code chip frequency is 1.023 MHz
GALILEOBOC Correlation Function
-8 -6 -4 -2 0 2 4 6 8
x 10-6
-0.5
0
0.5
1
BOC(1,1)
m = 1 – subcarrier frequency is 1.023 MHzn = 1 – range code chip frequency is 1.023 MHz
GALILEOBOC modulation
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
x 107
-40
-35
-30
-25
-20
-15
-10
-5
0
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
x 107
-40
-35
-30
-25
-20
-15
-10
-5
0
-5 -4 -3 -2 -1 0 1 2 3 4 5
x 106
-40
-35
-30
-25
-20
-15
-10
-5
0
-8 -6 -4 -2 0 2 4 6 8
x 10-6
-0.5
0
0.5
1
-1.5 -1 -0.5 0 0.5 1 1.5
x 10-6
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-1.5 -1 -0.5 0 0.5 1 1.5
x 10-6
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
BOC(1,1) BOC(5,1) BOC(5,2)
corr
ela
tion
fun
ctio
nsp
ect
rum
GALILEOSignals, Services and Spectra
I
Q
IN P
HA
SE
sin(
)
IN Q
UA
DR
ATU
RE
cos(
)
1575
.420
1561
.098
1589
.742
1559
.00
1591
.00
L1
1563
.00
1587
.00
E2 E1service modulation
codeencryption
data rate[symbol/s]
dataencryption
PRS BOC(15,2.5) yes 100 yes
OS/SoL/CS
BOC(1,1) none 250some(CS)
OS/SoL/CS
BOC(1,1) noneno data(„pilot“)
-
modulationsubcarrierfrequency
MHz
code rateMchips/s
BOC(15,2.5) 15.345 2.5575
BOC(1,1) 1.023 1.023
SoL uses the same signals as OS with integrity message
GALILEOSignals, Services and Spectra
1176
.450
1207
.140
1191
.795
E5a E5b
1164
.00
1215
.00
E5
I
Q
IN P
HA
SE
sin(
)
IN Q
UA
DR
ATU
RE
cos(
)
service modulationcode
encryptiondata rate
[symbol/s]data
encryption
OS/SoL AltBOC(15,10) none 50 none
OS/SoL AltBOC(15,10) none no data („pilot“) -
OS/SoL/CS AltBOC(15,10) none 250 some (CS)
OS/SoL/CS AltBOC(15,10) none no data („pilot“) -
Differerent signals are broadcast• on I and Q channels• in upper (E5b) and lower (E5a) part of the band
E5a and E5b may be used asa single ultra wide channel
GALILEOSpectrum, Services and Spectra
1278
.750
1268
.520
1288
.980
1260
.00
1300
.00
E6
I
Q
IN P
HA
SE
sin(
)
IN Q
UA
DR
ATU
RE
cos(
)
service modulationcode
encryptiondata rate
[symbol/s]data
encryption
PRSBOC(10,5)
TDMAgovernment 100 yes
CS PSK(5) commercial 1000 yes
CS PSK(5) commercial no data („pilot“) -
GALILEOSignal, Services and Spectra
I
Q
1176
.450
1207
.140
1278
.750
1575
.420
1544
.10
1191
.795
1268
.520
1288
.980
IN P
HA
SE
sin(
)
IN Q
UA
DR
ATU
RE
cos(
)
1561
.098
1589
.742
1164
.00
1215
.00
1260
.00
1300
.00
1559
.00
1591
.00
E5 E6 L1
1563
.00
1587
.00
E2 E1
E5a E5b
SA
R d
ownl
ink
L6
≈ ≈ ≈
GALILEOService Parameters
Open Service
(OS)
Commercial Service(CS)
Public Regulated Service(PRS)
Safety of Life Service
(SoL)
Coverage global global local global local global
Accuracyh-horizontal
v-vertical[m]
h=4, v=8dual
frequency
h=15, v=35single
frequency
<1
three frequency
access
<10 cm
localaugmented
signals
h=6.5
v=12
1local
augmentedsignals
4-6dual
frequency
Availability 99.9% 99.9% 99 – 99.9% 99.9%
Integrity No Value added service Yes Yes
BEIDOU
BEIDOU
„China‘s „Beidou“ navigation system is a regional positioning system mainly covering the country and its neighbouring areas, thus making vertical positioning impossible and limiting the number of users.“
• 3 geostationary satellites
• circular orbits
BEIDOUConstellation (Beidou 1B orbit)
Augmentations
transmiter reference
station
correctionsknown coordinates
receiver
receiver
AugmentationDifferential GPS (DGPS)
reference station
user
transmitter reference
station
correctionsknown coordinates
receiver reference
station
user receiver
AugmentationDifferential GPS (DGPS)
Augmentations• Many systems
– NDGPS– maritime systems
• Systems with satellite channel for corrections transmission– WADGPS– SBAS (ICAO) – Satellite Based Augmentation
Systems• WAAS• MSAS• EGNOS → future part of GALILEO• …
AugmentationsSBAS - Constellation
ARTEMIS
GPS
MTSATINMARSAT
INMARSAT
EGNOSMSAS
WAASGAGAN
AugmentationsSBAS - signals
Similar to SATNAV systems signals
AugmentationQZSS
AugmentationQZSS - Constellation
(1) Inclined orbital plane at approximately 45 deg from GSO
Ground track draws a figure “8” centered on the equator
45deg
Side view
Equator
120 deg
Top view
(2) 3 satellites on the 3 orbit planes operate so that the right ascension of the nodes are each 120 degrees apart
Every 8 hours each of the 3 satellites passes over the same point on the figure “8” ground track
AugmentationQZSSSatellite visibility ensured with high elevation angle of more than 70 degrees.
The urban canyon picture
(Shinjuku area)
0 4 8 12 16 20 240
10
20
30
40
50
60
70
80
90(準天頂衛星の仰角 東京)
Time (Hr)
Ele
vation
Ang
le (
deg)
SAT1 SAT2 SAT3 GEO110GEO130GEO150
0 4 8 12 16 20 240
10
20
30
40
50
60
70
80
90(準天頂衛星の仰角 東京)
Time (Hr)
Ele
vation
Ang
le (
deg)
SAT1 SAT2 SAT3 GEO110GEO130GEO150
Elevation angle at Tokyo (24hour)
Minimum elevation angle for QZSS (approx. 70 deg)
Elevation angle for GSO sat (E130deg) Approx. 48 deg
Planed for 2010
MODERNISATION
GPS
Spectrum of Future GPSPresent state
Second civil signal L2
C/A
L21227,6 MHz
±12 MHz
L11575,42 MHz
±12 MHz
ARNS RNSS ARNS/RNSS
960 1215 1260 1559 1610
C/A
P(Y) P(Y)
L51176,45 MHz
±12 MHz
Third civil signal L5 and new military signal L1 a L2
M M
MHz
C/A P(Y) M C/A P(Y) M F1 F2
II, IIA1-28
28 sats7,4 y.
IIR1-8
8 sats7,9 y.
IIR9-20
12 satsc7,9 y.
IIF1-6
6 sats15 y.
IIF7-30
24 sats15 y.
5m
L1 = 1575,42 MHzL2 = 1227, 6 MHzL5 = 1176,45 MHz
GPS1990 2000 2010 2020 2030
L1 L2 L5Frequency and codes
10 m 0.5 m100 mPrecision 95%
24 satellites
89
97
05
97
8 satellites
12 satellites
02
4 d.6 satellites
04
06
6 satellites24 satellites
18 satellites 12 IIR+ 6 IIF
18 satellites
IIF
Comparison of Systems
Comparison of Systems
What is an advantage of modernized or new systems ???
• Systems use two or three frequencies → suppression of ionosphere refraction
• New modulation methods have– very sharp correlation function
→ better precision– broad spectrum
→ thermal noise resistance
Comparison of Systems
• New modulation methods have– very sharp correlation
function→ better precision
– broad spectrum → thermal noise resistance
– higher code rate→ easier multipath mitigation
Comparison of SystemsMultipath Mitigation
BPSK(5)BPSK(10)BOC(10,5)BOC(15,10)
Comparison of Systems• New modulation methods have
– very sharp correlation function→ better precision
– broad spectrum → thermal noise resistance
– higher code rate→ easier multipath mitigation
• Constellations ensure better satellite visibility→ lower PDOP → better precision,
integrity, …
RECEIVER ARCHITECTURERequirements
• Processing of all known and planned SATNAV signals:– GPS L1, L2, L5– GLONASS– GALILEO– Augmentations
• EGNOS• WAAS
• Flexible design and development of powerful algorithms of signal processing
• Easy implementation of them• Rapid and simple prototyping and testing
Software Defined Radio
RECEIVER ARCHITECTURERequirements
Software Defined Radio
What processor to use ???
• DSP• FPGA
RECEIVER ARCHITECTUREDSP Concept
Loops in algorithms – lower computational power
RECEIVER ARCHITECTUREFPGA Concept
No loops in algorithmsparallel processing → higher computational power
RESULTSat
CZECH TECHNICAL UNIVERSITY
Experimental receiver
Experimental Receiver CTU(first version)
• Two-channel RF unit• DSP unit – Virtex II FPGA PCI card• PC Workstation – Windows 2000
LNA
Channel 1
Channel 2
LNA
A/D FPGAVirtex II
PCI Bridge
DSP Xilinx
DSP UnitRadio Frequency UnitGNSS antenna
Synthesizer
High PowerComputer
High Frequency Part of the Receiver
ReceiverProgramming in Simulink
Processor Programming in EDK
Conclusions
• Software Radio is prospective technology for multi-systems GNSS receivers, as well as FPGA technology
• This technology make possible design of receivers for hard receptions conditions (leaves canopy, urban environment, etc.)
Thank you for your attention.Pavel Kovář
&František Vejražka
&Libor Seidl
Czech Technical UniversityPrague, the Czech Republichttp://radio.feld.cvut.cz/per
sonal/vejrazka