IS-GPS-800A - US Coast Guard Navigation Center

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The above Legendre sequence is used to construct the unique length-10223 sequence used for each ranging code.This sequence, called a Weil-code, is the exclusive-or of L(t) and a shift of L(t). A Weil-code W i (t ; w) is specifiedby Weil Index w, ranging from 1 to 5111, which represents the shift of L(t) and is defined as,W i (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 Weil-code. The expansionsequence is composed of seven bit values 0 1 1 0 1 0 0. The insert point is specified by Insertion Index p, where p =1 to 10223. The expansion sequence is inserted before the p th value of the Weil-code.Thus the ranging code L1C Pi (t)/L1C Di (t) is defined as,L1C Pi (t)/L1C Di (t) = W i (t ; w), for t = 0, 1, . . . , p – 2;L1C Pi (t)/L1C Di (t) = 0, for t = p – 1;L1C Pi (t)/L1C Di (t) = 1, for t = p;L1C Pi (t)/L1C Di (t) = 1, for t = p + 1;L1C Pi (t)/L1C Di (t) = 0, for t = p + 2;L1C Pi (t)/L1C Di (t) = 1, for t = p + 3;L1C Pi (t)/L1C Di (t) = 0, for t = p + 4;L1C Pi (t)/L1C Di (t) = 0, for t = p + 5;L1C Pi (t)/L1C Di (t) = W i (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. The generation of L1C P -codeand L1C D -code is conceptually described in Figure 3.2-1.3.2.2.1.2 Overlay Code StructureThe overlay codes L1C Oi (t) are constructed using Linear Feedback Shift Register (LFSR) methods. These codes are2047 bits long truncated to 1800-bit long sequences and are constructed using 11-stage LFSR generators asdescribed below. This section provides the code generation method for the first 63 PRN numbers and Section6.3.1.2 provides the generation method for the additional PRN signal numbers 64 through 210.8 IS-GPS-800A8 June 2010
The overlay codes are derived from the addition (exclusive-or) of two sequences. The two sequences, denoted as S1and S2, are each derived from a PRN signal number-dependent code generator polynomial represented by P i (x).The generator polynomial for S1 is defined as,11P i (x) = j0m i, j x j ,where the coefficient m i, j is defined for each PRN signal number, i. For PRN signal numbers 1 - 63, only thesequence S1 is used and, as such, S2 is not needed. The sequence S2 is added to S1 sequence to generate theadditional PRN signal numbers 64 through 210 as further described in Section 6.3.1.2. The generator polynomialcoefficient m i, j for PRN signal numbers 1 - 63 are specified in Table 3.2-3. Table 3.2-3 also specifies the initial 11bits of the sequence, which is also the initial condition of the code generator for each PRN signal number. The final11 bits of the sequence are also shown in Table 3.2-3; these are the last 11 values after the code generator is clockedfor 1800 bits. The L1C O -code generator is conceptually described in Figure 3.2-2.GPSPRNSignalNo.WeilIndex(w)Table 3.2-2. L1C Ranging Codes Parameter Assignments (sheet 1 of 3)InsertionIndex(p)L1C PInitial 24Chips(Octal)Final 24Chips(Octal)WeilIndex(w)InsertionIndex(p)L1C DInitial 24Chips(Octal)Final 24Chips(Octal)1 5111 412 05752067 20173742 5097 181 77001425 522316462 5109 161 70146401 35437154 5110 359 23342754 467033513 5108 1 32066222 00161056 5079 72 30523404 001451614 5106 303 72125121 71435437 4403 1110 03777635 112612735 5103 207 42323273 15035661 4121 1480 10505640 713646036 5101 4971 01650642 32606570 5043 5034 42134174 550126627 5100 4496 21303446 03475644 5042 4622 00471711 303737018 5098 5 35504263 11316575 5104 1 32237045 077065239 5095 4557 66434311 23047575 4940 4547 16004766 7174115710 5094 485 52631623 07355246 5035 826 66234727 4234752311 5093 253 04733076 15210113 4372 6284 03755314 1274612212 5091 4676 50352603 72643606 5064 4195 20604227 3463411313 5090 1 32026612 63457333 5084 368 25477233 4755506314 5081 66 07476042 46623624 5048 1 32025443 0122111615 5080 4485 22210746 35467322 4950 4796 35503400 3712543716 5069 282 30706376 70116567 5019 523 70504407 3220366417 5068 193 75764610 62731643 5076 151 26163421 6216263418 5054 5211 73202225 14040613 3736 713 52176727 3501261619 5044 729 47227426 07750525 4993 9850 72557314 0043723220 5027 4848 16064126 37171211 5060 5734 62043206 3213036521 5026 982 66415734 01302134 5061 34 07151343 51515733NOTES:* PRN sequences 33-37 are reserved for other uses (e.g., ground transmitters)9 IS-GPS-800A8 June 2010
Page 1 and 2: IS-GPS-800A8 June 2010GLOBAL POSITI
Page 3 and 4: REVISION RECORDLTR DESCRIPTION DATE
Page 5 and 6: 3.2.3.3 Cyclic Redundancy Check ...
Page 7 and 8: LIST OF FIGURESFigure 3.2-1. Genera
Page 9 and 10: 1. INTRODUCTION1.1 ScopeThis Interf
Page 11 and 12: 3. SIGNAL REQUIREMENTSThe requireme
Page 13 and 14: Carriers of the two L1C components
Page 15: 3.2.2 PRN Code CharacteristicsThe c
Page 19 and 20: 3.2-2 L1C Ranging Codes Parameter A
Page 21 and 22: GPS PRNSignal No.3.2-3 L1C O Overla
Page 23 and 24: FIXED LENGTH-10223 LEGENDRE SEQUENC
Page 25 and 26: 3.2.2.2 Non-Standard CodesThe non-s
Page 27 and 28: corresponding to MSB = 0. (A SV tra
Page 29 and 30: This code has the following charact
Page 31 and 32: 3.2.3.5 InterleavingThe 1748 encode
Page 33 and 34: 3.3 Signal ModulationThe signals mo
Page 35 and 36: Bit valueL1C DbitstreamSubcarrier s
Page 37 and 38: 3.5 Message DefinitionAs shown in F
Page 40 and 41: DIRECTION OF DATA FLOW FROM SV100 B
Page 46 and 47: 3.5.3 Subframe 2Subframe 2 provides
Page 48 and 49: Table 3.5-1. Subframe 2 Parameters
Page 50 and 51: 3.5.3.1 Transmission Week NumberBit
Page 52 and 53: 3.5.3.6 Ephemeris Parameter Charact
Page 54 and 55: Table 3.5-2. Elements of Coordinate
Page 56 and 57: The user shall use the broadcast UR
Page 58 and 59: where, ISC L1CD is provided to the
Page 60 and 61: 3.5.3.10.1 Integrity Status Flag (I
Page 62 and 63: The ionospheric data shall be updat
Page 64 and 65: 3.5.4.2.3 User Algorithm for Applic
Page 66 and 67:
transmitted by the SVs will degrade
Page 68 and 69:
Table 3.5-7.Midi Almanac Parameters
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MSBCDC = Clock Differential Correct
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3.5.4.5 Subframe 3, Page 6 - TextSu
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5. RESERVED66 IS-GPS-800A8 June 201
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LSF - Leap Seconds FutureL1C - Comm
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Table 6.2-1.Legendre Sequence (Octa
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Table 6.2-2 LDPC Submatrix A for Su
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Table 6.2-3. LDPC Submatrix B for S
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Table 6.2-7. LDPC Submatrix T for s
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Table 6.2-7. LDPC Submatrix T for s
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Table 6.2-8. LDPC Submatrix A for s
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Table 6.2-8. LDPC Submatrix A for s
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Table 6.2-9. LDPC Submatrix B for S
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Table 6.2-13. LDPC Submatrix T for
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Table 6.2-16. Number of 1’s in LD
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6.3 Supporting Material6.3.1 Additi
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Table 6.3-1 Additional L1C Ranging
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PRNSignalNo.Table 6.3-2. Additional
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PRNSignalNo.Table 6.3-2 Additional
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