Galileo Signal in Space Design

1

GALILEO SIGNAL-IN-SPACE DESIGN

Ester Armengou Miret9th May 2005

2/46Ester Armengou Miret 9th May 2005


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.

2



-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


-Chapter 1: Galileo Signals Overview- Galileo frequency plan

Galileo signals baseline overview

General concepts: signal generator, satellite transmission chain






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

3



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.



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

4



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.



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)

5




• 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




• Two Navigation Signals transmitted in the 3 channels of E6-band signal:– E6C: commercial access signal – E6P: restricted access signal


PRSG/Nav5BOCcosDataE6P

--5BPSKPilot

CASMCSC/Nav10005BPSKDataE6C

Multiplex. scheme

ServicesMess. Type

Rd (sps)

Rc(Mcps)


6




• 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


Multiplex. scheme

ServicesMess. Type

Rd (sps)

Rc(Mcps)


---10BPSKPilot

OS,CS, SoL

I/Nav25010BPSKDataE5b

---10BPSKPilot

AltBOCOS,CSF/Nav5010BPSKDataE5a



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

7



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.



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)

8



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(

=



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

9



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



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.

10



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



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:

11



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



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

12



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



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

13



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:



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

14



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



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

15



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.



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.

16



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.



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.

17



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.



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.

18



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



Chapter 4: Navigation message- Frame structure

- Page format

- Message contents

- Navigation data

Chapter 4: Navigation message- Frame structure

- Page format

- Message contents

- Navigation data

19



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.



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)

20



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)



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

21



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.



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

22



SummarySummary



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


23



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



Questions?

Thank you

Questions?

Thank you

24



Auxiliary slides



Functional implementation of E6 channel

CODE generation

CODE generation

CASMDATA generation

DATA generation


Reference10.23 MHz

E6CData


bitsFEC

Encoding

Interleaving&

UW Insertion

1000 sps


500 Hz Clock

E6PCode Generator

E6PData


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



Functional implementation of E5 channelReference10.23 MHz

E5a -dCode Generator

E5aData


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


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





• Side- lobe acquisition possible (filter side-band)• S-curve slope increases with Fsc/Rc relation

26











Date post:	13-Nov-2014
Category:	Documents
Upload:	n467rx
View:	817 times
Download:	2 times

Galileo Signal in Space Design

Documents