IS-GPS-800D (797938), страница 4
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The tables provide code segments for 63 PRN numbers that are designated for GPS use.3.2.2.1.1 Ranging Code StructureBoth L1CPi(t) and L1CDi(t) are constructed using the same method. Each ranging code is derivedfrom a unique length-10223 sequence with a common 7-bit expansion sequence inserted at aPRN signal number-dependent point.The unique length-10223 sequence for each ranging code is derived from a single fixed length10223 sequence called a Legendre sequence L(t), for t = 0, …, 10222.
L(t) is defined as,L(0) = 0 ;L(t) = 1,if there exists an integer x such that t is congruent to x2 modulo 10223;L(t) = 0,if there exists no integer x such that t is congruent to x2 modulo 10223.Table 6.2-1 in Section 6.2.3 provides the generated sequence of the above defined L(t).The above Legendre sequence is used to construct the unique length-10223 sequence used foreach ranging code.
This sequence, called a Weil-code, is the exclusive-or of L(t) and a shift ofL(t). A Weil-code Wi(t ; w) is specified by Weil Index w, ranging from 1 to 5111, whichrepresents the shift of L(t) and is defined as,Wi(t ; w) = L(t) ⊕ L( (t + w) modulo 10223 )for t = 0 to 10222.Assignment of Weil Index, w, by PRN signal number, i, is given in Table 3.2-2.Finally, the ranging code is constructed by inserting a fixed expansion sequence into the Weilcode. The expansion sequence is composed of seven bit values 0 1 1 0 1 0 0. The insert point isspecified by Insertion Index p, where p = 1 to 10223. The expansion sequence is inserted beforethe pth value of the Weil-code.Thus the ranging code L1CPi(t)/L1CDi(t) is defined as,7IS-GPS-800D24 Sep 2013L1CPi(t)/L1CDi(t) = Wi(t ; w),for t = 0, 1, . .
. , p - 2;L1CPi(t)/L1CDi(t) = 0,for t = p - 1;L1CPi(t)/L1CDi(t) = 1,for t = p;L1CPi(t)/L1CDi(t) = 1,for t = p + 1;L1CPi(t)/L1CDi(t) = 0,for t = p + 2;L1CPi(t)/L1CDi(t) = 1,for t = p + 3;L1CPi(t)/L1CDi(t) = 0,for t = p + 4;L1CPi(t)/L1CDi(t) = 0,for t = p + 5;L1CPi(t)/L1CDi(t) = Wi(t - 7 ; w),for t = p + 6, p + 7, .
. ., 10229.Assignment of Insertion Index, p, by PRN signal number, i, is given in Table 3.2-2. Thegeneration of L1CP-code and L1CD-code is conceptually described in Figure 3.2-1.3.2.2.1.2 Overlay Code StructureThe overlay codes L1COi(t) are constructed using Linear Feedback Shift Register (LFSR)methods. These codes are 2047 bits long truncated to 1800-bit long sequences and areconstructed using 11-stage LFSR generators as described below. This section provides the codegeneration method for the first 63 PRN numbers and Section 6.3.1.2 provides the generationmethod for the additional PRN signal numbers 64 through 210.The overlay codes are derived from the addition (exclusive-or) of two sequences.8IS-GPS-800D24 Sep 2013The two sequences, denoted as S1 and S2, are each derived from a PRN signal numberdependent code generator polynomial represented by Pi(x).
The generator polynomial for S1 isdefined as,11Pi (x ) = ∑ mi , j x jj =0,where the coefficient mi, j is defined for each PRN signal number, i. For PRN signal numbers 1 63, only the sequence S1 is used and, as such, S2 is not needed. The sequence S2 is added to S1sequence to generate the additional PRN signal numbers 64 through 210 as further described inSection 6.3.1.2.The generator polynomial coefficient mi, j for PRN signal numbers 1 - 63 are specified in Table3.2-3. Table 3.2-3 also specifies the initial 11 bits of the sequence, which is also the initialcondition of the code generator for each PRN signal number.
The final 11 bits of the sequenceare also shown in Table 3.2-3; these are the last 11 values after the code generator is clocked for1800 bits. The L1CO-code generator is conceptually described in Figure 3.2-2.9IS-GPS-800D24 Sep 2013Table 3.2-2. L1C Ranging Codes Parameter Assignments (sheet 1 of 3)GPSPRNSignalNo.123456789101112131415161718192021L1CDL1CPWeilIndex(w)511151095108510651035101510050985095509450935091509050815080506950685054504450275026InsertionIndex(p)412161130320749714496545574852534676166448528219352117294848982Initial 24Chips(Octal)Final 24Chips(Octal)057520677014640132066222721251214232327301650642213034463550426366434311526316230473307650352603320266120747604222210746307063767576461073202225472274261606412666415734201737423543715400161056714354371503566132606570034756441131657523047575073552461521011372643606634573334662362435467322701165676273164314040613077505253717121101302134WeilIndex(w)509751105079440341215043504251044940503543725064508450484950501950763736499350605061InsertionIndex(p)1813597211101480503446221454782662844195368147965231517139850573434Initial 24Chips(Octal)Final 24Chips(Octal)770014252334275430523404037776351050564042134174004717113223704516004766662347270375531420604227254772333202544335503400705044072616342152176727725573146204320607151343522316464670335100145161112612737136460355012662303737010770652371741157423475231274612234634113475550630122111637125437322036646216263435012616004372323213036551515733NOTES:10IS-GPS-800D24 Sep 2013Table 3.2-2 L1C Ranging Codes Parameter Assignments (sheet 2 of 3)GPSPRNSignalNo.22232425262728293031323334353637339404142L1CDL1CPWeilIndex(w)501450044980491549094893488548324824459137065092498649654920491748584847479047704318InsertionIndex(p)595598056704642942939461694574429477136597059489419399478248643476776544Initial 24Chips(Octal)Final 24Chips(Octal)276002706610162717717055475002325205761576153566224446706233004413674337606351467352765363772350335642155223605564506521735611331264712116640265111613372205526011546064376722353220123037437553233105440715241502571041522706646131710443137330203364674074565650272475756043015255026615334214534457037113602401607455734674215437245411526534WeilIndex(w)509649834783499148154443476948794894498550564921503648124838485549044753448349424813InsertionIndex(p)61421906444675384801594445094374307590637894489432584955479546913240337663Initial 24Chips(Octal)Final 24Chips(Octal)160271752626734036272365677076770776037473633310304012577260625137370402742556611017114712242515174261007564775671265340743550734525301412452274070112133514375026442600736623135541671222550142315060624460334405252052706036165164321630417163200745702620417607105451310622273651601607641474350655200315501034041736201625610160375540541055NOTES:11IS-GPS-800D24 Sep 2013Table 3.2-2 L1C Ranging Codes Parameter Assignments (sheet 3 of 3)GPSPRNSignalNo.434445464748495051525354555657585960616263L1CDL1CPWeilIndex(w)412639613790491148814827479547894725467545394535445841974096348434813393317523601852InsertionIndex(p)6312980427894614444839414498751971156467410035450459937430535590916226284Initial 24Chips(Octal)Final 24Chips(Octal)247650041404250453512265153170061615122467454561475427436505723077415771753646517566433044600202232114255150474047712554673252336151701543217554525200627707371656350460165221737405370352211303726551470121215210410122224730736314522065734110251674351752413647064764140161561172302576760325047246157250474351215201006304737121760550200707WeilIndex(w)495746184669496950315038474040734843497948674964502545794390476346124784371647034851InsertionIndex(p)684971133361241021642519893988446274449979898542721261002443410295612896384353Initial 24Chips(Octal)Final 24Chips(Octal)672141236227436223371051251210572036262233050463653340516552345653741004663603413442165104530741126210316233045267510404007266050020015437533004737715104407170734665654647506267255001636130364252361754373220402316015002123703516365533771603411612557625726133512503162374662412033611103121364675266644401070455364267261056366333342142704NOTES:12IS-GPS-800D24 Sep 2013Table 3.2-3.
L1CO Overlay Code Parameter Assignments (sheet 1 of 3)GPS PRNSignal No.S1 PolynomialCoefficient (Octal) *(mij)Initial 11 Bits (Octal †) **Final 11 Bits (Octal †)151113266041025421204031533550115271767454033307213456417375635106614130262260763510562243386501042035209620534152652106235033720501177510265007012662312301605136733220412471476271440077315566724122377165051351615251776652761153118632537503540194365270105242047451206103521763315443337NOTES:* The polynomial coefficient is given as 1, m10, … , m1, 1.
Thus octal 5111 corresponds tothe generator polynomial P1(x) = 1 + x3 + x6 + x9 + x11.** The initial 11 bits also represent the initial condition, n11, ……, n1, for each PRN signalnumber. (See Figure 3.2-2)†The initial and the final bit values are obtained after dropping the initial bit value 0. Forexample octal 3266 corresponds to binary 1 1 0 1 0 1 1 0 1 1 0.13IS-GPS-800D24 Sep 2013Table 3.2-3 L1CO Overlay Code Parameter Assignments (sheet 2 of 3)GPS PRNSignal No.S1 PolynomialCoefficient (Octal) *(mij)Initial 11 Bits (Octal †) **Final 11 Bits (Octal †)2267471774017623447505460244244225221310272570633707175326442320513502276651365000642841611777227529723732030044304473176227773154772100036732616305710535337223371037763463233535267735712531100102367035142625203743410255244438***43530321377039***41073124151740***57350572113341***67411736375442***707133060033NOTES:* The polynomial coefficient is given as 1, m10, … , m1, 1.
Thus octal 5111 corresponds tothe generator polynomial P1(x) = 1 + x3 + x6 + x9 + x11.** The initial 11 bits also represent the initial condition, n11, ……, n1, for each PRN signalnumber. (See Figure 3.2-2)*** Note: PRNs 38-63 are required per this Table if a manufacturer chooses to include thesePRNs in their receiver design.†The initial and the final bit values are obtained after dropping the initial bit value 0.14IS-GPS-800D24 Sep 2013Table 3.2-3 L1CO Overlay Code Parameter Assignments (sheet 3 of 3)GPS PRNSignal No.S1 PolynomialCoefficient (Octal) *(mij)Initial 11 Bits (Octal †) **Final 11 Bits (Octal †)434563130711704457553763156745612716043534464671102125154745112624010448453304063343495357011415105056070077217051667334770710526153100033755375653460265054710726073307556211205722625643213467216157720107062076584451203212005954111464064360514105202000617041176633776266373270160563457703411552NOTES:* The polynomial coefficient is given as 1, m10, … , m1, 1.
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