galileo signal in space design
TRANSCRIPT
1
GALILEO SIGNAL-IN-SPACE DESIGN
Ester Armengou Miret9th May 2005
2/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Presentation Plan
• Chapter 1 Galileo Signals Overview: – Galileo Frequency Plan– Galileo Signals Baseline Overview
• Galileo Navigation Signals in L1• Galileo Navigation Signals in E6• Galileo Navigation Signals in E5
• Chapter 2 The choice of baseline modulations: modulations, chip rates, multiplexing schemes.
• Chapter 3 Spreading codes design: lengths, types, generation, performance criteria.
• Chapter 4 Navigation message: frame structure, data rates, page format, navigation message types, message contents, navigation data.
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GALILEO SIGNAL-IN-SPACE DESIGN
-Chapter 1: Galileo Signals Overview- Galileo frequency plan
Galileo signals baseline overview
General concepts: signal generator, satellite transmission chain
Galileo Navigation Signals in L1
Galileo Navigation Signals in E6
Galileo Navigation Signals in E5
-Chapter 1: Galileo Signals Overview- Galileo frequency plan
Galileo signals baseline overview
General concepts: signal generator, satellite transmission chain
Galileo Navigation Signals in L1
Galileo Navigation Signals in E6
Galileo Navigation Signals in E5
4/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Galileo Frequency Plan
GALILEO Bands (Navigation) GPS Bands (Current & modernized)
L5
E5 E6 L1E2 E1
1164
MHz
1214
MHz
1260
MHz
1300
MHz
1559
MHz
1587
MH
z
1591
MHz
1563
MHz
1215
MHz
1237
MH
z
L2
RNSS Bands RNSS Bands
ARNS Bands ARNS Bands
GLONASS Bands (Current & modernized)
1610
MHz
1575
.42 M
Hz
1278
.75 M
Hz
1191
.795
MH
z
E2-L1-E1 and E5a/L5 are common to GPS Frequency bands for interoperabilityE2-L1-E1 and E5a/L5 are common to GPS Frequency bands for interoperability
Three Frequency Bands part of the RNSS allocated bands
Three Frequency Bands part of the RNSS allocated bands
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GALILEO SIGNAL-IN-SPACE DESIGN
Galileo Signals Baseline Overview
Navigation signal and signal channel are not the sameNavigation signal and signal channel are not the same12
78.75
MH
z
40x1.023 MHz
E6P Signal:BOCcos(10,5) mod.Rc=5.115 McpsPRS Service
E6C Signal:Data + PilotBPSK mod.Rc =5.115 McpsRs=1000 spsCS Service
1575
.42 M
Hz
40x1.023 MHz
L1P Signal:BOCcos (15,2.5) mod.PRS Service
L1F Signal: Data + PilotBOC(1,1) mod.Rc=1.023 McpsRs=250 spsOS/CS/SOLServices
1191
.795 M
Hz
E5A Signal:Data+PilotBPSK mod.Rc=10.23 McpsRs=50 spsOS/CSServices
E5B Signal: Data+PilotBPSK mod.Rc=10.23 McpsRs=250 spsOS/CS/SOLServices
Frequency(MHz)
90x1.023 MHz
E5 Signal: AltBOC(15,10) mod.
E6 Signal: CASM mod.
L1 Signal: CASM mod.
6/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Definitions : what do we mean by signal???• Composite signal or RF transmitted signal:
– The signal generated on board the satellites in a certain band and carrier frequency. Each signal is the result of applying a given multiplexing scheme to combine a set of components.
• Signal channel or component: – Each of the components transmitted in an specific carrier frequency. It consists of
the modulation of the modulo-two addition of an optional navigation data stream (data channel or pilot channel) and a spreading code.
3 Composite Signals in Galileo: E5, E6 and L1 signals
• Navigation Signal:– Set of components of the composite signals which are characterised by the type of
navigation service they can provide due to the contents of their navigation data stream. Results from the transmission of a data channel, or a combination of a data channel with a pilot channel.
10 signal channels in Galileo: 4 in E5, 3 in E6 and 3 in L1
6 navigation signals in Galileo: L1F, L1P, E6C, E6P, E5a and E5b signals
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GALILEO SIGNAL-IN-SPACE DESIGN
General concepts: Signal Generator
• Base band functional diagram:
Code
Data
ModulationData channel
Pilot channel Modulation
Modulation
Modulation
MultiplexingData
Code
Code
Code
Data channel
Pilot channel(present or not)
X-band signal
• All elements in the signal generator have an impact on the payload architecture and performances and more widely in the ultimate system performance.
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GALILEO SIGNAL-IN-SPACE DESIGN
General concepts: Satellite transmission chain• Functional diagram:
Signal generator
E5
E6
L1
Up-conversion
HPAHPA
HPAHPA
HPAHPA
FilterFilter
FilterFilter
FilterFilter
Amplification
• The definition of signal parameters is tightly related to the overall payload architecture:– The choice of the modulation depends on filter properties (bandwidth, etc)– The choice of multiplexing technique depends on amplifier properties
(non linearity) and on the presence of a filter before amplification (up-conversion stage)
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GALILEO SIGNAL-IN-SPACE DESIGN
Galileo Navigation Signals in L1
• Two Navigation Signals transmitted in the 3 channels of L1-band signal:– L1F: open access signal containing navigation and integrity data– L1P: restricted access signal
• Characteristics:
PRSG/Nav2.5BOCcosDataL1P
--1BOCPilot
CASMOS,CS, SoL
I/Nav2501BOCDataL1F
Multiplex. scheme
ServicesMess. Type
Rd (sps)
Rc(Mcps)
ModulationChannelsSignal
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GALILEO SIGNAL-IN-SPACE DESIGN
Galileo Navigation Signals in E6
• Two Navigation Signals transmitted in the 3 channels of E6-band signal:– E6C: commercial access signal – E6P: restricted access signal
• Characteristics:
PRSG/Nav5BOCcosDataE6P
--5BPSKPilot
CASMCSC/Nav10005BPSKDataE6C
Multiplex. scheme
ServicesMess. Type
Rd (sps)
Rc(Mcps)
ModulationChannelsSignal
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GALILEO SIGNAL-IN-SPACE DESIGN
Galileo Navigation Signals in E5
• Two Navigation Signals transmitted in the 4 channels of E5-band signal:– E5a: open access signal containing basic data for navigation and timing– E5b: open access signal containing navigation and integrity data
• Characteristics:
Multiplex. scheme
ServicesMess. Type
Rd (sps)
Rc(Mcps)
ModulationChannelsSignal
---10BPSKPilot
OS,CS, SoL
I/Nav25010BPSKDataE5b
---10BPSKPilot
AltBOCOS,CSF/Nav5010BPSKDataE5a
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GALILEO SIGNAL-IN-SPACE DESIGN
Chapter 2: The choice of baseline modulations - L1 modulations: design drivers and constraints, the final choice, multiplexing technique
- E6 modulations: design drivers and constraints, the final choice, multiplexing technique
- E5 modulations: design drivers and constraints, the final choice, multiplexing technique, AltBOC modulation
Chapter 2: The choice of baseline modulations - L1 modulations: design drivers and constraints, the final choice, multiplexing technique
- E6 modulations: design drivers and constraints, the final choice, multiplexing technique
- E5 modulations: design drivers and constraints, the final choice, multiplexing technique, AltBOC modulation
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GALILEO SIGNAL-IN-SPACE DESIGN
L1 modulations: design drivers and constraints (1/2)
• L1F open signal: relative small bandwidth desired.• L1P restricted signal: higher performances, larger bandwidth
and spectrally separated from any open signal.• L1 band already crowded!!!
Interoperability and compatibility with GPS desired.Interoperability and compatibility with GPS desired.
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GALILEO SIGNAL-IN-SPACE DESIGN
L1 modulations: design drivers and constraints (2/2)• The solution has to:
– Make a good use of the spectrum– Keep the same carrier frequency than GPS C/A to assure
interoperability– Limit the overlap with other signals
Galileo L1 baseline: L1F BOC(1,1)+L1P BOCcos(15,2.5)
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GALILEO SIGNAL-IN-SPACE DESIGN
Definitions: BOC modulation
• BOC modulation (Binary Offset Carrier modulation) based on applying a squared subcarrier to a BPSK signal
• BOC(n,m): – n: subcarrier frequency in multiples of 1.023 MHz– m: chip rate in multiples of 1.023 Mcps
• Energy allocated around subcarrier frequency and not at the central frequency
1 1 0 11 1 0 1
McpsFsc 15=
McpsRBPSK
c 5.2)5.2(
=BOC(15,2.5)
C/A code is a BPSK(1)C/A code is a BPSK(1)
BOC(1,1)1 1 0 1
McpsFsc 1=
McpsRBPSK
c 1)1(
= 1 1 0 1
McpsFsc 1=
McpsRBPSK
c 1)1(
=
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GALILEO SIGNAL-IN-SPACE DESIGN
Impacts on receiver of the BOC modulation
• Autocorrelation function has multiple peaks, a problem speciallyfor BOC(15, 2.5) where direct acquisition is very difficult
• Side- lobe acquisition possible (filter side-band)• S-curve slope increases: better tracking accuracy but smaller
linear zone
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GALILEO SIGNAL-IN-SPACE DESIGN
Definitions: BOC vs BOCcos
))2(sin()(sin tFsigntsc scπ=
))2(cos()(cos tFsigntsc scπ=
• By default a BOC signal is generated by a sinus subcarrier, a BOCcos signal uses a cosinus subcarrier
• It results in a reduction of the secondary lobes and improvesisolation with signals in the same band
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GALILEO SIGNAL-IN-SPACE DESIGN
L1 modulations: the final choice
• For L1P BOCcos(15,2.5) chosen because:– Enough isolation from the GPS M-code and with the open signals (better
spectral isolation thanks to the 2ary lobes reduction of the BOC cosine subcarrier).
– Wide bandwidth and efficient use of the spectrum: E1 and E2
• For L1F BOC(1,1) chosen because:– Even if BOC(2,2) have better multipath and tracking performances, it is
not compliant with NSCC
• The final choice depends on National Security Compatibility Criteria (NSCC): Spectral Separation Coefficients used to quantify interference with other signals, specially with GPS M-code.– SSC theoretical method to quantify the influence of the overlap between
signals based on signal power spectral density. Agreed method EU-US.
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GALILEO SIGNAL-IN-SPACE DESIGN
L1 multiplexing technique (1/2)
• Three channels to be multiplexed:
– L1F data channel:
– L1F pilot channel:
– L1P data channel: ( ) ( ) ( ) )()5.2,15cos(111 tsctctdts BOCPLPLPL ⋅⋅=
( ) ( ) ( ) )()1,1(111 tsctctdts BOCdFLFLdFL ⋅⋅= −−
( ) ( ) )()1,1(11 tsctcts BOCpFLpFL ⋅= −−
• Constraints:– Amplifier to be used in saturation: constant envelope– Power sharing: 50% for L1P and 50% for L1F– Optimise satellite implementation– Easy to separate the two signals at reception
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GALILEO SIGNAL-IN-SPACE DESIGN
L1 multiplexing technique (2/2)
• CASM : Coherent Adaptative Subcarrier Modulation
11%--IM
44%50%L1P
22%25%L1F pilot
22%25%L1F data
After multiplexing
Before multiplexing
Channels
( ) ( ) ( )[ ] ( ) ( )[ ]tstsjtststS LPLpFLdFLL int,11111 231
32 +⋅+−= −−
INTERMODULATION PRODUCT TO ASSURE CONSTANT ENVELOPE
• Constellation:
I
Q
• Relative power levels:
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GALILEO SIGNAL-IN-SPACE DESIGN
E6 modulations• No constraints in terms of operability or compatibility to chose
E6 modulations because the band is not used by GPS or Glonass
Reduced spectral overlap with BOCcosReduced spectral overlap with BOCcos
• Galileo E6 baseline: – BPSK(5) for E6C commercial signal– BOCcos(10,5) for E6P restricted signal
• BOCcos chosen to have into account NSCC: good isolation ofthe restricted signal from the commercial one
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GALILEO SIGNAL-IN-SPACE DESIGN
E6 multiplexing technique
• Three channels to be multiplexed :
– E6C data channel:
– E6C pilot channel:
– E6P data channel:
• CASM modulation
( ) ( ) ( ) )()5,10cos(666 tsctctdts BOCPEPEPE ⋅⋅=
( ) ( ) ( )tctdts dCECEdCE −− ⋅⋅= 666
( ) ( )tcts pCEpCE −− = 66
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GALILEO SIGNAL-IN-SPACE DESIGN
E5 modulations: design drivers and constraints
• E5 bandwidth is very large and it is interesting to take profit of it using large band signals
• E5 band comprises two adjacent bands: E5a and E5b. E5a band corresponds to GPS L5 band
• GPS L5 signal is a BPSK with 10Mcps: for interoperability at receivers, we choose 10Mcps
BPSK(10) modulations
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GALILEO SIGNAL-IN-SPACE DESIGN
E5 multiplexing technique (1/3)
• Four channels to be multiplexed:
– E5a data channel:
– E5a pilot channel:
– E5b data channel:
– E5b pilot channel:
( ) ( ) ( )tctdts daEaEdaE −− ⋅⋅= 555
( ) ( )tcts paEpaE −− = 55
( ) ( ) ( )tctdts dbEbEdbE −− ⋅⋅= 555
( ) ( )tcts pbEpbE −− = 55
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GALILEO SIGNAL-IN-SPACE DESIGN
E5 multiplexing technique (2/3)• Two possible way to multiplex the two adjacent signals E5a and
E5b (each composed of data+pilot):
HPAUp-Conversion
OutputFilter
SE5(t)AltBOCModulation& SpreadingNavE5b(t)
NavE5a(t)
E5a
E5b
QPSK: 2 BPSK(10) signals in quadratureQPSK: 2 BPSK(10) signals in quadrature
HPA
HPA
OMUXSE5(t)
Up-Conversion
Up-Conversion
NavE5a(t)
NavE5b(t)
QPSKModulation& Spreading
QPSKModulation& Spreading
Filter
Filter
– OPTION 1: Two different QPSK signals:
– OPTION 2: One AltBOC signal:
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GALILEO SIGNAL-IN-SPACE DESIGN
E5 multiplexing technique (3/3)
• OPTION 1: two QPSK signals– Straightforward and simple implementation– Small transition bandwidth for the filters– Less than 24 MHz useful bandwidth for each signal
• OPTION 2: AltBOC– One single chain to transmit the four channels– Constellation constant envelope
– Wide reception signal, like BOC(15,10)– Side-band processing possible– Intermodulation product appears– Complexity in implementation
E5a E5b
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GALILEO SIGNAL-IN-SPACE DESIGN
Definitions: AltBOC Modulation• Theoretical expression
( ) ( ) ( )( ) ( ) ( )[ ]
( ) ( )( ) ( ) ( )[ ]
( ) ( )( ) ( ) ( )[ ]
( ) ( )( ) ( ) ( )[ ]422
1
422
1
422
1
422
1
5
5
5
55
5555
5555
5555
5555
E
xx
E
xx
E
xx
E
xxx
E
scpEpEt
pbEt
dbE
scpEpEt
paEt
daE
scdEdEt
pbEt
dbE
scdEdEt
paEt
daEt
Ttscjtsctsjts
Ttscjtsctsjts
Ttscjtsctsjts
Ttscjtsctsjtsts
−⋅+⋅⋅+⋅⋅
+−⋅−⋅⋅+⋅⋅
+−⋅+⋅⋅+⋅⋅
+−⋅−⋅⋅+⋅⋅
=
−−−−
−−−−
−−−−
−−−−
IM LOSSES 15% POWER
25%E5b pilot
25%E5b data
25%E5a pilot
25%E5a data
Before multiplexingChannels
• Power levels: • Constellation
I
Q
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GALILEO SIGNAL-IN-SPACE DESIGN
Chapter 3: Spreading codes design- Galileo spreading code lengths
- Tiered codes construction
- Type of codes
- Gold codes generation
- Codes performance criteria
- Galileo spreading codes choice
Chapter 3: Spreading codes design- Galileo spreading code lengths
- Tiered codes construction
- Type of codes
- Gold codes generation
- Codes performance criteria
- Galileo spreading codes choice
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GALILEO SIGNAL-IN-SPACE DESIGN
GALILEO spreading code lengths• Spreading codes are used to acquire and track a specific satellite. Each
channel and satellite has a different code (CDMA)
1023000100Pilot1.023L1F pilot
409242501.023L1F data
1023000100Pilot5.115E6C pilot
5115110005.115E6C data
1023000100Pilot10.230E5b pilot
40920425010.230E5b data
1023000100Pilot10.230E5a pilot
204600205010.230E5a data
Code length (chips)
Code period(ms)
Data Rate (symbol/s)
Code rate (Mcps)Channel
• Code lengths:– Data channels: code period duration is equal to one symbol duration. – Pilot channels: long pilot code periods to improve cross-correlation and channel
isolation (determines usable signal dynamic), and noise and interference suppression. Duration chosen 100ms.
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GALILEO SIGNAL-IN-SPACE DESIGN
Tiered codes construction• Most of the codes are very long and code families with good performances
are difficult to find.• Codes longer than 16383 chips are constructed by Tiered codes (all of them
except L1F data and E6C data).• A tiered code consist of successive repetitions of a primary code modulated
by the chips of a secondary code.
PRIMARY CODE
GENERATOR
Period i Period i+1 Period i+NS-1 Period i+N S
NP Chips
Period j
NS Chips
Period j+1 SECONDARY
CODE GENERATOR
NP: Primary code length (chips) NS: Secondary code length (chips)
NP*NS Chips
Chip rate: RS=RP/NP
Chip rate: RP
• Primary codes can be used for fast acquisitions while the entire code can be used for tracking. Aiming at typical integration times for acquisition of 1ms or a few ms, primary code periods is of the order of 10 kchips.
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GALILEO SIGNAL-IN-SPACE DESIGN
d0
0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9
0 1 2 3 0 1 2 3 0 1
d0 d1 d2 d3 d4 d5 d6 d7 d8 d9
18 19 0 1
98 99 0 1
Symbol
Sec. Code
Pri. CodeE5a-d
Sec. Code
Pri. CodeE5a-p
Symbol
Sec. Code
Pri. CodeE5b-d
Pri. CodeE5b-p
98 99 0 1
0 4 ms 10 ms 20 ms1 ms
0 1 2 3 4 5 6 7 8 9
Symbol
Pri. CodeE6C- d
Sec. Code
d1
d0 d1 d2
100 ms
0 1 2 3 4 49 0
Pri. CodeE6C- p
Sec. Code
d0
Pri. Code
SymbolL1F-d
d1 d2
0
Pri. Code
Sec. CodeL1F-p
1 24 0
Message stream k-th symbol One entire primary code period ( Np chips length)dkdk Secondary code n -th chipn
All signals coherently derived from the same
on-board frequency standard. They are
perfectly synchronised.
All signals coherently derived from the same
on-board frequency standard. They are
perfectly synchronised.
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GALILEO SIGNAL-IN-SPACE DESIGN
Type of codes• Primary codes are:
– Truncated Gold codes: can be systematically generated by LSFR (Linear Feedback Shift Registers)
– Memory codes: randomly generated and optimised. Need to be stored in memory, no systematic generation possible
SecondaryPrimary
254092Memory codeL1F pilot
4092Memory codeL1F data
1005115Memory codeE6C pilot
5115Memory codeE6C data
10010230Truncated GoldE5b pilot
410230Truncated GoldE5b data
10010230Truncated GoldE5a pilot
2010230Truncated GoldE5a data
LengthLengthTypeChannel The same secondary code for all
satellites (exhaustive
seach and the best chosen)
• Most secondary codes (enough length) are randomly generated and optimised.
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GALILEO SIGNAL-IN-SPACE DESIGN
Gold codes generation
• The generation of a Gold code require two shift registers (LFSR), the output sequence being the exclusive OR of register 1 and 2 outputs
Register 2 output sequence
Register 1 output sequence C1
R1
2a (Feedback taps register 2)
XOR
XOR
C3R1
CRR1
C2R1
C1R2
C2R2
CRR2 C3
R2 Gold output sequence
SHIFT REGISTER 1
SHIFT REGISTER 2
- R: number of registers
- Feedback tap polynomial: 'switches' that indicate whether a feedback connection exists or not
- Initial states: indicates the stored contents of all the stages in a specific moment. The initial status vector determines which sequence will be generated. Register 1 always initialised to the “all ones” state. Register 2 initial state depends on each channel and satellite.
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GALILEO SIGNAL-IN-SPACE DESIGN
Codes performance criteria
• The autocorrelation function of a code should have in an ideal case a high peak value while all other values should be as small as possible. This behaviour should not be lost if the Doppler effect is taken into account.
• The crosscorrelation values between two given codes should also be as small as possible to get good acquisition performance.
• Criteria in GALILEO code selection process:– Acquisition performances: Mean Excess Welch Square Distance. To quantify the
values of the cross-correlation function that exceed the Welch bound and degenerate the acquisition performance.
– Tracking performances: quantified through the Merit Factor.– Average Excess Line Weight: describes similarity to ideal random codes.
The Welch bound is the theoretical minimum of the maximum value of crosscorrelation that can be obtained for a given code length within a set of codes.
The Welch bound is the theoretical minimum of the maximum value of crosscorrelation that can be obtained for a given code length within a set of codes.
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GALILEO SIGNAL-IN-SPACE DESIGN
Galileo spreading codes choice
• Different families of codes selected for study and optimisation:– TruncatedGold codes– Concadenated Gold codes– Kasami codes– Gold-like codes– Randomly generated codes
• For each channel, the best set of codes of each family identified and compared through the previous performance criteria.
• The best option retained, not only in terms of performances but also having into account implementation issues and future evolutions.
Gold codes in E5 because of their systematic generationMemory codes for E6 and L1 to allow higher flexibility
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GALILEO SIGNAL-IN-SPACE DESIGN
Chapter 4: Navigation message- Frame structure
- Page format
- Message contents
- Navigation data
Chapter 4: Navigation message- Frame structure
- Page format
- Message contents
- Navigation data
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GALILEO SIGNAL-IN-SPACE DESIGN
Frame structure (1/2)• The navigation message is transmitted in the data stream as a sequence of
frames.• Each frame is composed of a certain number (depending on the signal band)
of subframes which are composed of several pages.
Subframe #1 Subframe #2 ……. Subframe #M-1 Subframe #M
Frame #1 Frame #2 ……. Frame #N-1Frame #N Frame #1 Frame #2
Page #1 Page #2 ……. Page #P-1 Page #P
• This arrangement allows to accomplish the three different main categories of data to be transmitted:– repeated at fast rate (for urgent data, such as integrity): page. – medium rate (like data required for warm start TTF) : sub-frame.– and slow rates (like data required for cold start TTF): frame.
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GALILEO SIGNAL-IN-SPACE DESIGN
E6P L1PG/Nav
8151 s.1000 spsL1CC/Nav
18301 s.250 spsE5b L1PI/Nav
12510 s.50 spsE5aF/Nav
#Sub-frames in a frame
#Pages in a sub-frame
Page duration
Data rateSignal
Frame structure (2/2)
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GALILEO SIGNAL-IN-SPACE DESIGN
Page Format• A page contains:
• A three levels error coding is applied to the GALILEO Message Data Stream:- A Cyclic Redundancy Check (CRC) with error detection capabilities after
recovery of the received data- A one-half rate Forward Error Correction (FEC). Tail Bits (sequence of
zeros) to allow Viterbi decoding.- Block Interleaving on the resulting frames: provides robustness to the
FEC decoding algorithm by avoiding packets of errors• FEC and CRC are defined according to BER and FER targets.
Synchro Data CRC Tail
FEC encoded and interleaved (convolutional code with rate 1/2)
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GALILEO SIGNAL-IN-SPACE DESIGN
Message Contents
• F/NAV is the acronym for Freely Accessible Navigation message type.
• I/NAV is the acronym for Integrity Navigation message type.• C/NAV is the acronym for Commercial message type.• G/NAV is the acronym for Governmental Access Navigation message type.
YesNoNoYesYesG/Nav
YesYesNoNoNoC/Nav
YesNoYesYesYesI/Nav
NoNoNoNoYesF/Nav
Service ManagementSupplementarySearch&RescueIntegrityNavigation
Message Data ContentMessage Type
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GALILEO SIGNAL-IN-SPACE DESIGN
Message Contents
• The navigation data includes both satellite and constellation message data.
• The Search and Rescue return link provides the capability to send 8 acknowledgement SAR messages of 64 bits every 50 seconds to a Beacon equipped with a suitable Galileo receiver.
• Supplementary data is provided as part of the CS only navigation message on E6. The supplementary data is expected to provide weather alerts , traffic information and accident warnings, etc.
• Service management data is used to provide key management and other information to enable controlled access to the Galileo signals and message data. For the CS key management data is required to provide access to the encrypted revenue earning data and to the ranging code on E6.
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GALILEO SIGNAL-IN-SPACE DESIGN
Navigation data
• The navigation data contain all the parameters that enable the user to perform positioning service. They are stored on board all the satellite with a validity duration and broadcast world-wide by all the satellite of the constellation.
• 4 types of data needed to perform positioning are specified:– Ephemeris: needed to indicate the position of the satellite to the user with
a sufficient accuracy– Time parameters and Clock correction parameters: needed to compute
pseudo-range measurements– Service parameters: needed to identify the set of navigation data, the
satellites, some indicator of the health of the signal, etc.– Almanacs: to indicate the position of all the satellite in the constellation
with a reduced accuracy needed for the acquisition of the signal by the receiver
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43/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
SummarySummary
44/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Functional implementation of L1 channelReference10.23 MHz
L1F-dCode Generator
L1FData
MessageAdd CRC
Add Tailbits
FECEncoding
Interleaving&
UW Insertion
250 sps
4092040920250 Hz Symbol Clock
4092040920 25-chipsSecondary
Code
L1F-pCode Generator
L1PCode Generator
L1PData
MessageAdd CRC Add Tail
bitsFEC
Encoding
Interleaving&
UW Insertion
XX
1010
1010
1010 LimiterSINBOC(1,1) Subcarrier Waveform
(10/15)(10/15) LimiterCOSBOCcos(15,2.5) Subcarrier Waveform
RESET
X
X XX
XX
++
++
+
-
++
COS
SIN
x 154
fL1=1575.42 MHzCarrier Frequency
L1 Signal
+
-
44
L1P
L1FData Channel
L1FPilot Channel
L1P Symbol Clock
)(1 tsc PL
( )td PL1
( )tc PL1
( )tc pFL −1
( )tc dFL −1
( )td FL1
)(1 tsc dFL −
)(1 tsc pFL −
XOR/Modulo-2 addition
32
32
32
32
31
31
McpsR dFLc −1,
McpsR pFLc −1,
McpsR pFLc −1,
McpsR PLc 1,
32
32
250 Hz Clock
CASMDATA generation
DATA generation
CODE generation
CODE generation
Subcarrier generation
Subcarrier generation
23
45/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Main conclusions
• Main design drivers for signal design: trade-off between technical and programmatic aspects– Target performances: intended use, user type, scenario.– Compatibility and interoperability with other navigation systems.
• All elements in the signal generator have an impact on the payload architecture and performances and more widely in the ultimate system performance.
Good news for your future:A lot of work to do at receiver side and applications
46/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Questions?
Thank you
Questions?
Thank you
24
47/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Auxiliary slides
48/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Functional implementation of E6 channel
CODE generation
CODE generation
CASMDATA generation
DATA generation
Subcarrier generation
Reference10.23 MHz
E6CData
MessageAdd CRC Add Tail
bitsFEC
Encoding
Interleaving&
UW Insertion
1000 sps
10230102301000 Hz Symbol Clock
500 Hz Clock
E6PCode Generator
E6PData
MessageAdd CRC Add Tail
bitsFEC
Encoding
Interleaving&
UW Insertion
XX
22
22
LimiterCOSBOCcos(10,5) Subcarrier Waveform
RESET
X
X XX
XX
++
++
+
-
++
COS
SIN
x 125
fE6 =1278.75 MHzCarrier Frequency
E6 Signal
+
-
22
E6CData Channel
E6CPilot Channel
Symbol Clock
( )td PE6
E6P
)(6 tsc PE
( )tc PE6
E6C-dCode Generator
204062040650-chips
SecondaryCode
E6C-pCode Generator
( )tc pCE −6
( )tc dCE −6
( )td CE 6
XOR/Modulo-2 addition
32
32
32
32
313
1
32
32
McpsR PEc 6,
McpsR dCEc −6,
McpsR pCEc −6,
McpsR pCEc −6,
25
49/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Functional implementation of E5 channelReference10.23 MHz
E5a -dCode Generator
E5aData
MessageAdd CRC Add Tail
bitsFEC
Encoding
Interleaving&
UW Insertion
50 sps
204600204600
20-bitsSecondary
Code
10230102301 kHz Clock
100 -bitsSecondary
CodeE5a -p
Code Generator
E5b -dCode Generator
E5bData
MessageAdd CRC
Add Tailbits
FECEncoding
Interleaving&
UW Insertion
250 sps
4092040920250 Hz Symbol Clock
4-bitsSecondary
Code
10230102301 kHz Clock
100 -bitsSecondary
CodeE5b -p
Code Generator
RESET
Look-upTable
k∈{1,…8}
cos(k. π/4)
sin(k. π/4)
X
X
COS
SIN
x 116.5
1191.795 MHzCarrier Frequency
+
E5 Signal
Counter1..8
AltBOC(15,10) Subcarrier Frequency
+
-
( )tcpaE −5
( )tc daE −5
( )td aE5
( )tc pbE −5
( )tc dbE −5
( )td bE5
E5aData Channel
E5aPilot Channel
E5bData Channel
E5bPilot Channel
50 Hz Symbol Clock
(2/3)(2/3)
McpsRdaEc −5,
McpsR paEc −5,
McpsR dbEc −5,
McpsRpbEc −5,
AltBOC too complicated using
time domain formula. It is
easier with a LUT
AltBOC too complicated using
time domain formula. It is
easier with a LUT
50/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Impacts on receiver of the BOC modulation
• Autocorrelation function has multiple peaks, a problem speciallyfor BOC(15, 2.5) where direct acquisition is very difficult
• Side- lobe acquisition possible (filter side-band)• S-curve slope increases with Fsc/Rc relation
26
51/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Impacts on receiver of the BOC modulation
• Autocorrelation function has multiple peaks, a problem speciallyfor BOC(15, 2.5) where direct acquisition is very difficult
• Side- lobe acquisition possible (filter side-band)• S-curve slope increases with Fsc/Rc relation
52/46Ester Armengou Miret 9th May 2005
GALILEO SIGNAL-IN-SPACE DESIGN
Impacts on receiver of the BOC modulation
• Autocorrelation function has multiple peaks, a problem speciallyfor BOC(15, 2.5) where direct acquisition is very difficult
• Side- lobe acquisition possible (filter side-band)• S-curve slope increases with Fsc/Rc relation