Interplex modulation for navigation systems at the L1 band

Transcription

1 Ierplex modulaio or avigaio yem a he L bad Emilie Rebeyrol, Chriophe Maabiau, Lioel Rie, Jea-Lu Iler, Mihel Bouque, Marie-Laure Bouhere To ie hi verio: Emilie Rebeyrol, Chriophe Maabiau, Lioel Rie, Jea-Lu Iler, Mihel Bouque, e al.. Ierplex modulaio or avigaio yem a he L bad. ION NTM 006, Naioal Tehial Meeig o The Iiue o Navigaio, Ja 006, Moerey, Uied ae. pp 00-, 006, <hp:// <hal-00777> HAL Id: hal hp://hal-ea.arhive-ouvere.r/hal ubmied o 7 O 0 HAL i a muli-diipliary ope ae arhive or he depoi ad diemiaio o ieii reearh doume, wheher hey are publihed or o. The doume may ome rom eahig ad reearh iiuio i Frae or abroad, or rom publi or privae reearh eer. L arhive ouvere pluridiipliaire HAL, e deiée au dépô e à la diuio de doume ieiique de iveau reherhe, publié ou o, émaa de éablieme d eeigeme e de reherhe raçai ou érager, de laboraoire publi ou privé.

2 Ierplex Modulaio or Navigaio yem a he L bad Emilie Rebeyrol, ENAC/TeA Chriophe Maabiau, ENAC Lioel Rie, Jea-Lu Iler, CNE Mihel Bouque, UAERO Marie-Laure Bouhere, ENEEIHT BIOGRAHY Emilie Rebeyrol graduaed a a eleommuiaio egieer rom he INT Iiu Naioal de Téléommuiaio i 00. he i ow a h.d ude a he aellie avigaio lab o he ENAC. Currely he arrie ou reearh o Galileo igal ad heir geeraio i he aellie payload i ollaboraio wih he CNE Cere Naioal d Eude paiale, i Touloue, Frae. Chriophe Maabiau graduaed a a eleroi egieer i 99 rom he ENAC Eole Naioale de l Aviaio Civile i Touloue, Frae. ie 99, he ha bee workig o he appliaio o aellie avigaio ehique o ivil aviaio. He reeived hi h.d. i 997 ad ha bee i harge o he igal proeig lab o he ENAC ie 000. Lioel Rie i a avigaio egieer i he "Tramiio Tehique ad igal roeig Deparme", a CNE ie Jue 000. He i repoible o reearh aiviie o GN igal, iludig BOC modulaio ad moderied G igal LC & L5. He graduaed rom he Eole olyehique de Bruxelle, a Bruel Free Uiveriy Belgium ad he peialized i pae eleommuiaio yem a upaero ENAE, i Touloue Frae. Jea-Lu Iler i head o he Tramiio Tehique ad igal proeig deparme o CNE, whoe mai ak are igal proeig, air ierae ad equipme i Radioavigaio, Teleommuiaio, TT&C, High Daa Rae TeleMery, propagaio ad perum urvey. He i ivolved i he developme o everal paebore reeiver i Europe, a well a i udie o he Europea RadioNavigaio proje, like GALILEO ad he eudolie Nework. Wih DRAT ad DGA, he repree Frae i he GALILEO igal Tak Fore o he Europea Commiio. Wih Lioel Rie ad Laure Learqui, he reeived he aroaui prize 00 o he Freh Aeroauial ad Aroauial Aoiaio AAAF or hi work o Galileo igal deiiio. Mihel Bouque i a roeor a UAERO Freh Aeropae Egieerig Iiue o Higher Eduaio, i harge o graduae ad po-graduae program i aeropae eleroi ad ommuiaio. He ha over wey ive year o eahig ad reearh experiee, relaed o may ape o aellie yem modulaio ad odig, ae ehique, oboard proeig, yem udie... He ha auhored or o-auhored may paper i he area o digial ommuiaio ad aellie ommuiaio ad avigaio yem, ad exbook, uh a aellie Commuiaio yem publihed by Wiley. Marie-Laure Bouhere graduaed rom he ENT Breage i 985 Egieerig degree i Elerial Egieerig ad rom Teleom ari i 997 hd degree. he worked a a egieer i Alael pae rom 986 o 99 he moved o ENT a a Aoiaed roeor he a roeor. Her ield o iere are digial ommuiaio modulaio/odig, digial reeiver, muliarrier ommuiaio, aellie oboard proeig iler bak, DBFN ad avigaio yem. ABTRACT Beaue o he limied availabiliy o he perum alloaed or avigaio yem, he umerou avigaio igal broada by Moderized G ad Galileo yem will have o be ombied ad employ badwidh-eiie modulaio. Ideed, he G moderizaio heme eail he addiio o he ew miliary igal M-ode o he eablihed C/A ad Y ode a he ame arrier requey. Oe o he mo impora queio i how o ombie hi ew igal wih he legay oe a he 00

3 payload level, while maiaiig good perormae a reepio. Thi problem alo exi or Galileo ie: - i he L bad, he Ope ervie O igal wo hael ad he ubli Regulaed ervie R igal mu be ramied o he ame arrier. - i he E6 bad, he Commerial ervie C igal mu be ramied wih he R igal. The Ierplex modulaio, a pariular phae-hiedkeyed/phae modulaio K/M, wa hoe o rami all hee igal beaue i i a oa-evelope modulaio, hereby allowig he ue o auraed power ampliier wih limied igal diorio [TF, 00; Raja ad Irvie, 005]. The mai objeive o hi paper i o udy he Ierplex modulaio, a i i ued or he G ad Galileo igal. I a ir par we will pree he Ierplex modulaio, i geeral ormulaio ad i appliaio or he muliplexig o hree igal. The, we will be iereed i he appliaio o hi modulaio o he G L igal ad he Galileo L igal. We will give he geeral expreio o he G L Ierplex igal ad how he modiiaio whih mu be made o he geeral expreio o he Ierplex modulaio o apply i o he ae o he ombiaio o he C/A ad Y ode wih he ew M-ode. Wih regard o he Galileo igal we will udy wo diere ae. I he ir ae we will oider ha he O igal i a laial BOC,. I he eod ae we will make he udy, aumig ha he O igal i he ew igal alled Compoie Biary Coded ymbol CBC, reely publihed [Hei e al., 005]. To olude, he heoreial ormula o he power perum deiie o he G L Ierplex igal ad o he Galileo L Ierplex igal are give. I. INTRODUCTION The moderizaio o G ad he developme o he GALILEO yem have led o he udy o diere modulaio ehique i he L bad i order o obai he be perormae a he reepio level. everal ehique were propoed o olve hi problem: he Cohere Adapive ubarrier Modulaio CAM, whih i mahemaially equivale o he Ierplex modulaio, preeed i [Buma ad Timor, 97], wa propoed by Daeh e al 999; he Quadraure rodu ubarrier Modulaio QM mehod whih wa developed or geeral quadraure-muliplexed ommuiaio yem [Daeh, 999]; ad he oalled majoriy voe logi ehique explored by pilker ad Orr 998. be overall aellie power eiieie by ombiig muliple igal io a phae modulaed ompoie igal ha keep a oa evelope. Thak o hi modulaio, he aellie high-power ampliier may be operaed io auraio wih limied udeirable Ampliude- Modulaio o Ampliude-Modulaio AM/AM ad Ampliude-Modulaio o hae-modulaio AM/M diorio. However i mai diadvaage i ha i implie iermodulaio erm i order o obai a oa evelope, ad hu wae par o he ramied power hrough hi ompoe. For GN, hi wae o ueul power hould be areully aalyzed beaue i i a eleme or he yem opimizaio. The Ierplex modulaio, propoed or eah ew igal, hould be udied beaue he produ ould oume more or le power ad hereore idue wore or beer perormae. Thi paper propoe a review o he Ierplex modulaio. Fir a geeral ormulaio o hi modulaig ehique will be preeed. The, we will how whih modulaio idex may be hoe i he ae o he G yem ad he Galileo yem a he L bad. For he Galileo yem we will udy wo diere ae, wheher he O igal i a laial BOC, or he O igal i a CBC Compoie Biary Coded ymbol. For boh avigaio yem, he phae diagram o he Ierplex modulaio will be preeed. Fially we will give he expreio o he power perum deiie or he G L Ierplex igal, ad or he Galileo L Ierplex igal. II. FORMULATION A already meioed, he Ierplex modulaio i a pariular phae-hied-keyed/phae modulaio K/M, ombiig muliple igal io a phae modulaed ompoie igal. The geeral orm o he Ierplex phae-modulaed igal, a preeed i [Buma ad Timor, 97], i: where: θ o i he oal average power i he arrier requey i he phae modulaio i a radom phae I he ae o GN appliaio he phae modulaio a be deied a: The Ierplex modulaio wa eveually preerred [Wag e al., 00; TF, 00] beaue i provide he 0

4 N θ wih: ± q d where q i a quare-wave ub-arrier, d i he maerializaio o he daa meage i he maerializaio o he preadig ode N i he umber o ompoe, ad i he modulaio agle or modulaio idex whih hoie deermie he power alloaio or eah igal ompoe. The mo ommo ae or uure GN igal oiguraio i he ramiio o hree igal o he ame arrier: oe igal i he quadraure hael: wo igal i he i-phae hael: ad The Ierplex igal a he be expreed a: o Noe ha i ake equal o - / beaue he igal i i quadraure wih he wo oher igal. uh a igal a be geeraed hak o he ollowig heme, preeed i Figure [U ae, 00]. Figure : Ierplex geeraor heme By developig Equaio, i a be how ha: i i o o 5 i o o i o i i o o i ad ially, 6 i i i o o o i o o i Thak o Equaio 6, i a be oied ha he ir hree erm orrepod o he deired ueul igal erm,, ; he ourh erm i he udeired iermodulaio erm. Thi erm i equal o he produ o he hree deired igal balaed by he modulaio idexe ad. I oume ome o he oal ramied power ha ould be available or he hree deired igal. Ideed, wih he Ierplex modulaio, he power o eah ompoe i equal o: i i i o o i o o 7 Equaio 7 how ha he power o eah igal ompoe oly deped o wo variable ad. Thu he expreio o he equivale baebad Ierplex igal a be re-wrie a: ˆ j 8 where { } j exp ˆ Re Figure repree he power o he diere igal a a uio o he value o he modulaio idexe. The ir graph repree he power o eah igal ompoe i uio o wih / ad he eod graph repree he power o eah igal ompoe i uio o wih /. 0

5 igal igal igal igal I-phae igal Quadraure igal oi o modulaio oellaio Figure :Ierplex modulaio oellaio Noe ha i /, we have he ame igure bu wih he omplemeary agle. Figure : Variaio o igal power a a uio o Ierplex modulaio idexe The Figure how ha he hoie o ad deped o he power ha we wa o give o eah igal. A rade-o mu be made o have uiie power o he deired igal ad o-diadvaageou power o he igal. A aurae udy mu be made o id he mo uiable value or ad. The diere ae o he Ierplex igal a be repreeed o a phae diagram whoe x-axi i he iphae ompoe ad whoe y-axi i he quadraure ompoe. For he pree ae, he diagram o he modulaio oellaio i how i Figure : Thi diagram how ha eve i he iroduio o he produ oume ome o he available power, he Ierplex modulaio keep he magiude o he ompoie igal evelope oa, whih ailiae he ue o auraed ampliier i he payload. III. ALICATION TO THE NAVIGATION YTEM AT THE L BAND G Cae I he L bad, moderized G aellie will rami hree igal: he C/A ode igal ompoe,. he ode igal ompoe,. he ew miliary igal M-ode,. The igal i a C/A-ode a.0 Mhip per eod ode hippig rae i No-Reur o Zero NRZ orma. The igal i a -ode a 0. Mhip/ ode hippig rae i NRZ orma. The M-ode igal i he produ o a ode ormed wih NRZ ymbol ruig a 5*.0 Mhip/ ad a quare-wave ub-arrier ruig a 0*.0 MHz. I i a Biary Oe Carrier, a BOC0,5. I [Daeh e al., 999; Daeh e al., 000], he Cohere Adapive ubarrier Modulaio CAM i propoed a a peii oluio or ramiig he hree G igal pree i he L bad. Thi modulaio ould be oidered a a hree ompoe Ierplex modulaio wih a pariular ad opimal hoie o he modulaio idexe. The CAM propoe o pu he - ode igal ad he M-ode i he i-phae ompoe ad he C/A ode i he quadraure ompoe wih he produ. We will ake hi igal layou a reeree bu oher ae have bee udied, pariularly i [Wag e al., 00], where he -ode ad he C/A ode igal are i he i-phae ompoe ad he M-ode i he quadraure ompoe. 0

6 I he pree ae, i deied hak o he wo ollowig equaio, propoed i [Daeh e al., 000]: o where Q I i 9 I i he power o he iiial igal i phae Q i he power o he iiial igal i quadraure i he oal average power. ad. I hi ae, he produ o he hree G igal i a BOC0,0 ub-arrier, o he produ i a BOC0,0. The modulaio oellaio o he G Ierplex modulaio i preeed i Figure : The oly modulaio idex, whih i o e, i. I i reamed m. Coequely, he power o eah igal deped oly o m ad i equal o: o o i Q I Q I m m m m i 0 Noe ha he oal average power i maiaied oa: I Q The G igal ramied wih he CAM modulaio a be wrie a: o m o i i o I Q Q I o m i m o m o m i m o m i i m i o m o i m o o i m i A already ee i he previou eio, he iermodulaio produ i he produ o he igal, 5 Figure :G Ierplex modulaio oellaio A previouly he evelope o he igal i oa eve i ome o he available power i waed i he produ. GALILEO yem The modulaio heme ued o rami he L Galileo igal ad propoed i [GJU, 005] i imilar o he modulaio heme propoed, previouly, or he G ae. Le aume ha i he ae o he Galileo yem he igal ha will be broada i he L bad are: he R igal. I i a oie-phaed BOC5,.5 igal,. he daa O igal. I i a BOC, igal. he pilo O igal. I i a BOC, igal. The oly dieree bewee he igal ad i heir ode, whih do have he ame value eve i hey have he ame ode rae. I he pree ae, a reerred i [GJU, 005], he oal power hould be equally divided io he i-phae ompoe ad he quadraure ompoe. Moreover he power o he daa O ompoe hould be equal o he power o he pilo O ompoe. Coequely, he parameer ad are e by he ollowig relaiohip: 0

7 o i o i o o 6 Thi yem lead o - m0.655 rad. Coequely, he expreio o he igal ramied i: o m m i m o m o o i m m o m i i m I hi ae, he power o eah ompoe i equal o: o i m o m m i m 9 7 The diagram o he modulaio oellaio i how i Figure 5: 8 rami a liear ombiaio o a BOC, ub-arrier ad a Biary Coded igal BC ub-arrier iead o a laial BOC, ub-arrier. Followig hee aumpio, he igal ramied o Galileo L would be: A daa O igal ha a be repreeed a: o θ BOC, o θ BC, A pilo O igal ha a be repreeed a: o θ BOC, o θ BC, he R igal already deribed earlier. To rami hee igal wih he Ierplex modulaio we mu, i a, oider eparaely he BOC, ad he BC. o he igal ramied wih he Ierplex modulaio are:, he BOC5,.5 iludig he R RN ode., he BOC, ub-arrier oly., he BC ub-arrier oly. The expreio o he Ierplex igal ramied i he: o θ θ A A B B 0 6 where C A i he O daa hael ode preadig ode ad daa ad C B i he O pilo hael ode preadig ode oly. Equaio 0 how ha he value o he modulaio idexe are expreed a a uio o he agle ad, whih deped o he pereage o power ha i pu o he BC ompoe. I a be oied ha he model ued or he opimized Galileo L igal i i a a Ierplex modulaio model wih 5 igal ompoe ad o oly hree a he previou oe. 5 Developig he equaio 0 give: Figure 5: Galileo Ierplex modulaio oellaio The Figure 5 how ha he modulaio oellaio i oly ompoed o 6 plo. Thi i due o he a ha he igal ad are boh BOC, ub-arrier ad by he way he oellaio goe hrough he poi ad 5 wie. Currely, oher udie are made o rami a Galileo L igal whih perormae i beer ha he oe obaied wih a BOC,. [Hei e al., 005] propoe o A B o A B o i A B θ θ i θ θ o i θ i θ i 05

8 Thi expreio i he expreio o he opimized igal whih i propoed o rami he O igal ad he R igal i he L bad ad preeed i [Hei e al., 005]. I hi ae he produ igal hape deped oly o he R igal, C A ad C B. I doe o deped o he BOC, ub-arrier or o he BC ub-arrier. A oirmed i [Hei e al., 005], he power o eah ompoe i equal o: θ o θ o O i θ i θ R i θ i θ We a alo oie ha: o θ BOC ad o θ, BC Coequely he value o ad allow o e he pereage o deired BC or BOC, power. The phae diagram o he modulaio oellaio i imilar, a he oher example, o he phae diagram o a 8-K modulaio: θ i θ i _ CBC _ BOC, we oie ha or he ae o he BOC, igal he power deped o oly oe modulaio idex, wherea or he ae o he CBC igal he power deped o wo modulaio idexe. o he eig o he power eem o be eaier wih he opimized igal. The ompario o boh produ will be more preiely aalyzed i he ex par wih he udy o heir power perum deiie. IV. OWER ECTRUM DENITIE, i m I order o udy he impa o he igal o he perum o he L G ad Galileo igal, we will give, i hi par, he heoreial expreio o he power perum deiie o he Ierplex igal preeed previouly. G Cae where ˆ The G igal i he L bad ould be wrie a: { ˆ exp j } Re j ˆ j j 5 o he auoorrelaio uio o uh a igal i: τ R ˆ τ o R 6 wih [ ˆ ˆ ] R τ E τ ˆ Figure 6: Opimized Galileo Ierplex modulaio oellaio j ˆ j R τ E τ τ j τ j τ τ τ 7 I we ompare he power o he produ o he BOC, igal ad o he CBC igal: The diere ode whih ompoe he igal, ad have a very low ro-orrelaio, o he roorrelaio bewee he diere ode i herei aumed o be equal o zero. Coequely, 06

9 τ R τ τ R τ R ˆ τ R 8 R The power perum deiy o he G Ierplex igal i he Fourier Traorm o he auoorrelaio uio: wih ˆ ˆ TF ˆ ˆ [ R τ ] ˆ R TF R 9 τ R τ τ R τ 0 I p/q i eve ad i he ub-arrier i ie-phaed, he power perum deiy o a BOCp,q igal, i equal o [Bez, 00]: The power perum deiy o a NRZ modulaio i: i T T T wih T he ode period. 5 Coequely, he power perum deiy o he C/A ode igal ompoe i: i T T T 6 ad he power perum deiy o he -ode igal ompoe i : Fially, T i T 0 0 T 0 7 BOC T i i T T T o wih T he ode period. ˆ T T 5 i T 5 a 0 T 0 i 0 T i T 0 i 0 8 o he power perum deiy o he BOC0,5 M-ode igal i : T T i i T T o 0 wih T /.0e6. wih T /.0e6. The ex graph repree he urve obaied wih imulaio ad he urve obaied hak o he heoreial expreio o he power perum deiy. We oider ha 0.5 db, 0 db ad - db [Fa e al., 005] ad he urve whih orrepod o he imulaio ae i ormalized by i ample umber. Ad i he ae o he BOC0,0 igal: T T i i T T o 0 07

10 T i.5.5 T o T 0 T o 0 The erm i he produ o he igal, ad, o i i a BOC5,.5 a he R igal. I power perum deiy i hereore imilar o he equaio. o, he power perum deiy o he Galileo L igal i: Figure 7: ower perum Deiy o he L G igal GALILEO yem I he ae o a BOC, igal i oidered, he Galileo L igal ould be wrie : where { ˆ exp j } Re ˆ j j 9 The alulaio o he power perum deiie o hi igal i imilar o he alulaio o he power perum deiie o he G igal, o: ˆ ˆ wih ˆ 0 The power perum deiy o he igal ad he igal are equal. Their expreio i: T i i T T T o The igal i a oie-phaed BOC5,.5, o he power perum deiy o hi igal i: m m o ˆ o m i m i Now he ae o he Galileo L opimized igal i oidered, he expreio o he igal ramied i he Galileo L bad i: wih ˆ { ˆ exp j } Re A B i j o θ o θ o θ o θ θ i θ i θ i θ The igal ould alo be wrie: ˆ OA i j OB θ i θ i θ i θ 5 6 where OA ad OB repree he daa Ope ervie igal ad he pilo Ope ervie igal, iludig repeively he ode A ad he ode B ad he weighed aor depedig o ad. A previouly, we have: wih R τ R ˆ τ o [ ˆ ˆ ] R τ E τ ˆ 08

11 The roorrelaio bewee he diere ode i agai aumed o be equal o zero. Coequely, R ˆ τ R OA τ R τ OB i θ i θ R τ i θ i θ R τ 7 The power perum deiie o he opimized Galileo igal i he Fourier Traorm o he auoorrelaio uio: wih TF ˆ ˆ ˆ ˆ [ Rˆ τ ] i θ OA OB i θ i θ i θ 8 The alulaio o he power perum deiie o he OA ad OB igal are preeed i [Hei e al., 005]. o we have: T i.5.5 o 0 BOC 5,.5 o T T 0 BOC, ad BC T i i T T T o i i j i o T 5 5 j i i j 5 where reer o he umber o ymbol i oe hip. The power perum deiy o a BC[ ], wa preeed i [Hei e al., 005]. The Galileo opimized igal he BC, iveigaed by [Hei e al., 005], i he BC[ ],. I i propoed ha he pereage o BC power repree 0% o he oal O power. Thi odiio ivolve 0.5 rad ad. rad, oiderig ha he O power hould be equal o he R power. OA T C OB T C o o θ o θ BOC, θ o θ Re FT p BOC, o o BC * { FT p } θ o θ BOC, θ o θ Re FT pboc, BC BC * { FT p } BC 9 50 wih BOC, ad BC he power perum deiie o he BOC, ad he BC modulaio. The igal ad he produ are boh oiephaed BOC5,.5 modulaio. o, he power perum deiy o he igal i: o ˆ wih BOC, o θ θ i θ θ BC 5 i BOC5,.5 Figure 8: ower perum Deiy o he opimized L Galileo igal Now ha he power perum deiie o he produ or he wo Galileo igal ae were alulaed, we a oie ha i boh ae he produ i a BOC5,.5 ub-arrier, oly he power o he wo produ i diere. A already meioed, we have: _ CBC i θ i θ, i m _ BOC, 09

12 Coiderig he opimal value or he modulaio idexe i eah ae ad ha he oal power i equal o, we have: - or he BOC, ae, [TF, 00] propoe m0.655 o -9.5 db. - For he CBC ae, [Hei e al., 005] propoe 0% o BC, o -.7 db. Thereore he power waed i he produ i more impora i he ae o he laial BOC, igal. To olude, i he ex graph he G igal ad he opimized Galileo igal power perum deiie evelope have bee ploed: ACKNOWLEDGMENT The auhor are hakul o Olivier JULIEN or hi valuable remark ad uggeio. REFERENCE [Bez, 00]: Biary Oe Carrier Modulaio or Radioavigaio Joh W. Bez Joural o he Iiue o Navigaio, Wier [Bez, 00]: Brie Overview o Biary ad Quadraphae Coded ymbol or GN Joh W. Bez Deember 00. [Buma ad Timor, 97]: Ierplex A eiie Mulihael K/M Telemery yem. Buma ad U. Timor IEEE Traaio o Commuiaio, Volume 0, No. Jue 97. [Daeh e al., 999]: Cohere Adapaive ubarrier Modulaio CAM or G moderizaio. A. Daeh,. Lazar, T. M. Nguye roeedig o 999 ION Naioal Tehial Meeig a Diego, Jauary 999. [Daeh, 999]: Quadraure rodu ubarrier Modulaio QM.A. Daeh IEEE Aeropae Coeree, 999. Figure 9:ower perum Deiie o he L bad igal V. CONCLUION Thi paper ha provided wo mai poi. Fir i ha bee how ha he expreio o he ombied L G igal ad he expreio o he ombied L Galileo igal ould be liked o a uique ormula oidered a he deiiio o he Ierplex modulaio. I wa alo how ha he opimized Galileo L igal ould be liked o hi ormula. For he diere ae he phae diagram o he modulaio wa preeed. eodly he expreio o he power perum deiie o all he avigaio L igal have bee heoreially alulaed ad a pariular aeio i made o he iermodulaio erm. Ideed he Ierplex modulaio guaraee a oa evelope or he avigaio igal by reaig a iermodulaio erm whih i uele or he avigaio bu mu be ake io aou or a igal power opimizaio. Beide i ha bee how ha he produ power o he opimized Galileo igal i weaker ha he produ power o he laial Galileo igal. [Daeh e al., 000]: Compaibiliy o he Ierplex Modulaio Mehod wih C/A ad Y ode igal.a. Daeh, L. Cooper, M. arridge ION G 000 al Lake Ciy, epember 000. [Fa e al., 005]: The RF ompaibiliy o Flexible Navigaio igal Combiig Mehod T. Fa, V.. Li, G.H. Wag, K.. Maie,.A. Daeh ION NTM 005 a Diego, -6 Jauary 005. [Hei e al., 005]: A adidae or he Galileo L O opimized igal G.W. Hei, J-A Avila-Rodriguez, L. Rie, L. Learqui, J-L Iler, J. Gode, T. ra ION GN 005 Log Beah, epember 005. [GJU, 005]: L Bad par o Galileo igal i pae ICD GJU G TG GERAN meeig Caada, May [Raja ad Irvie, 005]: G IIR-M ad IIF: ayload Moderizaio J.A. Raja ad J. Irvie ION NTM 005 a Diego, -6 Jauary 005. [pilker ad Orr, 998]: Code Muliplexig Via Majoriy Logi or G Moderizaio J.J. pilker Jr. ad R.. Orr ION G 998 Nahville, 5-8 epember

13 [TF, 00]: au o Galileo Frequey ad igal Deig G. W. Hei, J. Gode, J-L. Iler, J-C. Mari,. Erhard, R. Lua-Rodriguez, T. ra roeedig o he ION G 00 epember 00. [U ae, 00]: rogrammable Waveorm Geeraio or a Global oiioig yem Gee L. Cagiai U ae 6595 Jauary 00. [Wag e al., 00]: udy o igal Combiig Mehodologie or G III Flexible Navigaio ayload G.H. Wag, V.. Li, T. Fa, K.. Maie,.A. Daeh ION GN 00 Log Beah, epember 00.