1 1

6/24/09

ElectronicsandSignalProcessingLaboratoryEPFL‐STI‐IMT‐ESPLABRueA.‐L.Breguet2CH‐2000Neuchâtel

Head:Prof.P.‐A.FarineTeamLeader:Dr.C.BoHeronAuthors:AleksandarJovanovic,YoussefTawk

1

2

Outline CBOC/TMBOCconcept(A.Jovanovic)

  Trackingmetrics&TrackingalgorithmsforMBOC  ComparisonofMBOCalgorithms  ResultsandrecommendationsforMBOCtracking

 AltBOCconcept(Y.Tawk)  Trackingmetrics&TrackingalgorithmsforAltBOC  ComparisonofAltBOCalgorithms  ResultsandrecommendationsforAltBOCtracking

6/24/09 2

3

CorrelaJonandTrackingofMBOC OverviewofMBOCreceivertrackingschemes Performcomparisonw.r.t.trackingmetrics

  ACFpeakamplitude Multipatherrorenvelope  Codetrackingerror Provideadvantages/disadvantagesofeachalgorithm

 Recommendationstoreducereceivercomplexity

6/24/09 3

4

CBOC/TMBOCdefiniJon CBOCvs.TMBOC  Samepowerspectraldensity(PSD)

 Pilotanddatachannelshavedifferentstructures

  DifferenttrackingperformanceforCBOC/TMBOC

CBOC structure TMBOC structure

6/24/09

BOC(1,1)+BOC(6,1)

BOC(6,1) 4chips/33 BOC(1,1)

Pilot TMBOC

Data chanel BOC(1,1)

Data + Pilot channels

Phase Antiphase

4

5

CBOC/TMBOCsignals

6/24/09

•  GPSL1COSTMBOC(6,1,4/33)  BOC(1,1)ondatachannel(25%),TMBOConpilot(75%)

  Multiplexwide‐bandBOC(6,1)withnarrow‐bandBOC(1,1)•  GalileoE1OSCBOC(6,1,1/11,’+/‐’)

  Equallysplitpower(50%),signalsinantiphase  WeightedsumofBOC(1,1)andBOC(6,1)ondata+pilot

5

6

Trackingingeneral  Firststeptoconsider:Autocorrelationfunction(ACF) Maintrackingparameters:

 Trackingsensitivity  MinimumSNRtomaintaintracking

 Trackingrobustness  Stabilitytrackingregion

 Trackingaccuracy  Errors:multipath,noise,interference

•  Multipathmainsourceoferror

 Phasetracking(PLL) Codedelaytracking(DLL)

6/24/09

E P L

E P L

E P L

Search

Track

Lock

6

7

TradiJonalCBOCreceiverarchitecture

  SamereplicaforE,P,Lcorrelator

I&D

NCO

cos()

sin()

I&D

Gene L1B

BOC(6,1)

BOC(1,1)

-Q NCO P

Discri Filter

I&D

I&D

E,P,L

E,P,L

E,P,L P

E,

L

6/24/09 7

8

TradiJonaltrackingperformance TraditionalCBOCtrackingrequiresreplicationoffour‐levelreplica  Complicatesthereceiverarchitecture

  ImprovementintrackingcomparingtoBOC(1,1)isdifferentfordataanddata+pilotchannels=>C/Nocriterionforcomparison

 CBOC(6,1,1/11,’‐’)betterthanTMBOCmodulation

6/24/09

TrackingErrorImprovementvsBOC(1,1)inTermsofEquivalentC/N0(dB)withBW2=24MHzandE‐L=1/12Chips

CBOC(6,1,1/11,’+’) TMBOC(6,1,4/33) CBOC(6,1,1/11,’‐’)

1.9 2.4 3.1

8

9

TM61trackingarchitecture

 Useone‐bitreplica,usingBOC(1,1)andBOC(6,1)only

I&D

NCO

cos()

sin()

I&D

Gene L1B

BOC(6,1)

BOC(1,1)

NCO

Discri Filter

I&D

I&D

E,L

P

E,P,L

P

E,

L

6/24/09 9

10

TM61forTMBOCtracking  TMBOCtrackingusingTM61ismorecomplicated

  CorrelationlosseshighwhenonlyBOC(6,1)isused

  Thiscanbeavoidedusingtime‐multiplexsubcarriers  Usingzero‐padding  WhenBOC(6,1)istracked,BOC(1,1)replicacontainszeros

  andvice‐versa  UsingthismethodTMBOCtrackingissimilartoCBOCtracking

  Still0.2dBworstintrackingthanCBOC

6/24/09

Signalvs.Receiver BOC(1,1) BOC(6,1)

TMBOC(6,1,4/33) 0.85 0.15

CBOC(6,1,1/11,’‐’) 0.95 0.3

10

11

DualCorrelatortracking  DualCorrelatortechniquecomparestwoparallelcorrelations:

  IncomingMBOCwithBOC(1,1)replica  IncomingMBOCwithBOC(6,1)replica

  Correlationsareweighted,withparameters:  βforBOC(1,1)andρforBOC(6,1)

 Optimalβ/ρisintherange[1.6,3.2]w.r.t.MEE(Multipatherror)  Thismethodusestwiceasmanycorrelators

  Andbinaryreplicas  Goodmultipathperformance  Easilyconfigurableinthesoftware

6/24/09

NCO

Gene L1B

BOC(6,1) E,L

P

E,P,L

BOC(1,1)

11

12

S‐Curveshapingmethod Methodproposedistofindtheidealdiscriminator

  UsingidealS‐curve  Fittingthecurve,parametersofthecorrelatorarefound

  Correlatorspacing  Weightofthecorrelator

 Greatnumberofcorrelatorsneeded  Multipathreducedstrongly

 Usesmulticorrelatorstructure  Narrowcorrelator Doubledelatcorrelator

6/24/09 12

13

ASPeCTBOC(1,1)algorithm ASPeCThasbeenproposedforBOC(n,n)signals

  Unambiguoustechnique‐eliminationofthesidepeaksofACF

  Limiteddegradation[0.6‐1dB]comparingtotraditional ASPeCTcanbeappliedtoCBOC(6,1,1/11,’‐’) Pricetopay:

ReducingtheBOC(6,1)inthelocalCBOCreplicabyhalf

 Thisimplies:  anegligiblereductionofresistancetonoise  aslightdegradationofthemultipatherrorenvelope

6/24/09 13

14

Compositetrackingalgorithm  Compositetracking

  Dataandpilottogether  Convexcombinationofdiscriminatoroutputs

  Non‐coherent+coherentchannelcombining

  Trackingjitterreduced  SER(SignErrorRate)

  Newtrackingmetrics

6/24/09 14

15

TrackingCBOC/TMBOCwithBOC(1,1)  Narrowbandreceivers(BW<<12MHz)donothaveaccesstofullrangeofMBOCcharacteristics

  Optimaltrackingperformanceisreachedwiththematchingchannel  Reference:[Dr.MassimoCrisci,ESTEC,GIOVEworkshop,Oct2008]6/24/09

Transmission Receiver reference

Delta Losses [dB]

Relative Noise Jitter

RAME error

Baseline BOC(1,1) 0.0 1.00 1.00

CBOC BOC(1,1) +0.3 0.94 0.97

TMBOC BOC(1,1) +1.7 1.31 1.03

CBOC CBOC 0.0 0.76 0.84

TMBOC CBOC +0.3 0.71 0.84

15

16

Trackingalgorithmscomparison

6/24/09

Tracking scheme

Tracking complexity

Tracking robustness

Tracking accuracy

Applicability to mass-market

receiver TM61 + + - +

Dual Correlator +/- - +/- +/-

S-Curve shaping

+ - + +

ASPeCT + +/- - +/-

Composite tracking

- +/- + +/-

16

17

MulJpathperformance Multipatherrorenvelopes: TM61providesbetterresultsthanpureCBOCtracking

  IfDPdiscriminatorused

 HRCnotgoodsolution  forCBOCtracking

  S‐curveshaping  Providesthebestresults

 Useofadvancedcorrelators:  Strobe Narrow,DoubleDelta [M.Fantino,L.Presti]

6/24/09 17

18

ConclusionsandoutlookMBOC BOC(1,1)receiversreceivingCBOC/TMBOC

  Lossestoohigh Newspecifictrackingalgorithmsproposed:

  TM61andDualCorrelatoroutperformBOC(1,1)  Futurework:

  Compositetracking  Tobefurtherinvestigated

  CommontrackingCBOC/TMBOCarchitecture  Realchallenge

  SeparatealgorithmforCBOCandTMBOC?  Needforadvancedmultipathmitigationalgorithms  Useofnewcorrelatortypes

6/24/09 18

19

Outline CBOC/TMBOCconcept(A.Jovanovic)

  Trackingmetrics&TrackingalgorithmsforMBOC  ComparisonofMBOCalgorithms  ResultsandrecommendationsforMBOCtracking

 AltBOCconcept(Y.Tawk)  Trackingmetrics&TrackingalgorithmsforAltBOC  ComparisonofAltBOCalgorithms  ResultsandrecommendationsforAltBOCtracking

6/24/09 19

20

GalileoE5Signal AltBOC(15,10)isthenewmodulationontheGalileoE5Band.

6/24/09 20

21

ConstantEnvelope

6/24/09 21

22

ConstantEnvelope(cont’)

6/24/09 22

23

ConstantEnvelope(cont’)

6/24/09 23

24

AltBOCCharacterisJcs

6/24/09

E5 Signal Spectrum

E5 Spreading Code Lengths

E5 Signal Parameter

24

25

PowerDistribuJonPower 1st Harmonic (Power Distribution) 2nd Harmonic (Power Distribution)

SSC 85.36% +fs/-fs (94.36%) +7fs/-7fs (1.36%)

PSC 14.64% +3fs/-3fs (61.5%) +5fs/-5fs (22.2%)

90 MHz Bandwidth Theoretical

Power Power

Transmitted

90 MHz 85.34% 100%

75 MHz 80.54% 94.37%

51 MHz 77.88% 91.25%

75 MHz 51 MHz

N.B: Power is shared equally between the four components of the E5 signal

6/24/09 25

26

AutocorrelaJonFuncJon

Autocorrelation vs. Bandwidth

6/24/09 26

27

TrackingPossibiliJes Thepresenceof4componentsontheE5signalallowthereceiverdesignerstohavedifferentpossibilitiesintrackingthissignal:

  FreesubcarriersLocalgeneratedsignal  FullBandCorrelation  8‐PSKlikeprocessing

 Severalcombinationofsignalcomponentsarepossible:

  E5a‐I,E5a‐Q,E5b‐IorE5a‐Q  Dataorpilot  E5

6/24/09 27

28

FreeSubcarriers  Thelocalsignalisgeneratedfreeofsubcarriers  TheE5signalcomponentsaretranslatedtobasebandfromtheircenterfrequencies

  E5a‐I,E5a‐Q,E5b‐I,E5b‐Q,E5aandE5bcanbetrackedindividuallyresultinginaBPSK(10)correlation

6/24/09 28

29

FreeSubcarriers(cont’)

Autocorrelation Function for a single E5 component with a 20 MHz Bandwidth

Comparison between an infinite bandwidth and a 20 MHz AltBOC

receiver

6/24/09 29

30

FullbandCorrelaJon  Thelocalsignalisgeneratedwithsubcarrierfortherequiredsignalcomponent

  Additionalpowerisgainedcomparingtothefreesubcarriermethod

  E5ab,E5‐pilotandE5‐datacanbetrackedinadditiontotheothersignalcomponents

6/24/09 30

31

FullBandCorrelaJon

Comparison between autocorrelation function for a single E5 component with a 75 MHz Full Band correlation

and a 20 MHz Free Subcarrier correlation

Full Band Correlation for different signal components with

a 75 MHz bandwidth receiver

6/24/09 31

32

8‐PSKLikeProcessing OnlythecompleteE5signalistracked  Correlationisdoneusingalookuptable(LUT)of8values

Look up table for AltBOC phase states

6/24/09 32

33

AltBOCSummary

PowerSharing

CodePhaseJitter

ReceiverComplexity

MultipathMitigation

FreeSubcarrier ‐ ‐ + ‐

FullBand ‐/+ ‐/+ ‐/+ +

8‐PSK + + ‐ +

Performance of the different tracking architectures

6/24/09 33

34

Conclusions GoodtrackingperformanceofnewBOCsignals

  Bettermultipathmitigation  Improvedcodetrackingperformance  Newtrackingstrategiesrequirements

 Morecomplexreceiverarchitecture Moreprocessingpower,higherfs,morecorrelators Highcost–needsimplifications

6/24/09 34

35

 ThankYoufortheattention Q&A?

 Contacts:

6/24/09

Aleksandar Jovanovic PhD student

EPFL-IMT-ESPLAB Rue A.-L. Breguet 2 CH-2000 Neuchâtel

Phone: +41 32 718 34 39 Fax. +41 32 718 34 02

E-mail : aleksandar.jovanovic@epfl.ch

Youssef Tawk PhD student

EPFL-IMT-ESPLAB Rue A.-L. Breguet 2 CH-2000 Neuchâtel

Phone: +41 32 718 34 42 Fax: +41 32 718 34 02

Email: youssef.tawk@epfl.ch

35

36

Back–upslides

6/24/09 36

37

Algorithmcomparison•  Falsecorrelationpeaksat0.6chips

  CorrelationlossesTM61 ACFpeakvariationα=[0.1,1]

6/24/09 37