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

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WRITECombined LDPC Encoded Subframes 2 and 3Row 1 Row 2 Row 31 2 ………. 45 46 47 48 ………. 91 92 93 94 ………. Direction of Data FlowRow 1Row 2Row 3Row 381 2 3 ……......... 44 45 4647 48 49 ................. 90 91 9293 94 95 ……......... 136 137 138................…….............…….........1703 1704 1705 ……......... 1746 1747 1748................46 columnsREADInterleaved Subframes 2 and 31 47 93 ………. 2 48 94 ………. 3 49 95 ………. 4 50 96 Direction of Symbol Flow from SVRow 11 2 3……......... 44 45 46Row 2Row 347 48 49 ................. 90 91 9293 94 95 ……......... 136 137 138…….............................................…….........Row 381703 1704 1705 ……......... 1746 1747 174846 columnsFigure 3.2-6. Conceptual Block Interleaver24 IS-GPS-800A8 June 2010
3.3 Signal ModulationThe signals modulated on the L1 RF carrier include C/A, P(Y), M, and L1C, which consists of two components:L1C P and L1C D . The modulation used is binary offset carrier (BOC) as described in reference document [2]. Themodulation is essentially shaped BPSK where a subcarrier is used to shape the spectrum.The bitstream of the L1C P signal is constructed by modulo-2 addition of L1C P -code and L1C O -code. The overlaycode, L1C O , is described in section 3.2.2.1.2. The PRN ranging codes, L1C P and L1C D , are described in section3.2.2.1.1. The bitstream of L1C D is constructed by modulo-2 addition of L1C D -code and the L1C message symboltrain, D L1C (t). The timing relationship of L1C signal components is described in Figure 3.3-1.The bitstream of the L1C D signal is modulated on L1 carrier frequency using BOC (1, 1) modulation, with asubcarrier frequency of 1.023 MHz and a chipping rate of 1.023 Mbps. Each bit of the bitstream is applied to aBOC (1,1) spreading symbol consisting of one cycle of a 1.023 MHz squarewave, defined as binary 10 (1= positivebinary bit value, see Figure 3.3-2a) with total duration 1/1.023 microseconds. The BOC (1,1) spreading symbols aredefined using sine-phasing, so they are aligned with the bits of the L1C D -code. Contrary to convention, a “0” is inphasewith the carrier and a “1” is 180 degrees out of phase with the carrier.The bitstream of the L1C P signal is modulated on L1 carrier frequency using TMBOC modulation technique. TheL1C P TMBOC technique uses a mixture of BOC (1, 1) spreading symbols and BOC (6,1) spreading symbols, whereeach BOC (6,1) spreading symbol consists of 6 cycles of a 6 x 1.023 MHz squarewave, defined as binary101010101010 (1= binary bit value), with total duration 1/1.023 microseconds (see Figure 3.3-2b).The pattern of BOC (1,1) and BOC (6,1) spreading symbols repeats every 10230 spreading symbols correspondingto a new bit of L1C O -code. Let the index of the spreading symbols for L1C P be t = 0, 1, . . ., 10229, where t = 0 isthe first spreading symbol in the next bit of L1C O -code. Write t as t = u t + 33 v t , where u t = 0, . . ., 32 and v t = 0, . . .,309. Then all spreading symbols in L1C P are BOC (1,1), except for those that are BOC (6,1) that occur for those twith u t = 0, 4, 6, and 29 (i.e, t = 0, 4, 6, 29, 33, 37, 39, 62, …, 10197, 10201, 10203, 10226). This pattern is shownin Figure 3.3-2c.The BOC (1,1) and BOC (6,1) spreading symbols are defined using sine-phasing, so they are aligned with the bits ofL1C P -code. The phase relationship between L1C D and L1C P is defined in section 3.2.1.6.25 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 and 16: 3.2.2 PRN Code CharacteristicsThe c
Page 17 and 18: The overlay codes are derived from
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: 3.2.3.5 InterleavingThe 1748 encode
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
Page 70 and 71: MSBCDC = Clock Differential Correct
Page 72 and 73: 3.5.4.5 Subframe 3, Page 6 - TextSu
Page 74 and 75: 5. RESERVED66 IS-GPS-800A8 June 201
Page 76 and 77: LSF - Leap Seconds FutureL1C - Comm
Page 78 and 79: Table 6.2-1.Legendre Sequence (Octa
Page 80 and 81: Table 6.2-2 LDPC Submatrix A for Su
Page 82 and 83:
Table 6.2-2 LDPC Submatrix A for Su
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Table 6.2-3. LDPC Submatrix B for S
Page 92 and 93:
Table 6.2-7. LDPC Submatrix T for s
Page 94 and 95:
Table 6.2-7. LDPC Submatrix T for s
Page 96 and 97:
Table 6.2-8. LDPC Submatrix A for s
Page 98 and 99:
Table 6.2-8. LDPC Submatrix A for s
Page 100 and 101:
Table 6.2-9. LDPC Submatrix B for S
Page 102 and 103:
Table 6.2-13. LDPC Submatrix T for
Page 104 and 105:
Table 6.2-16. Number of 1’s in LD
Page 106 and 107:
6.3 Supporting Material6.3.1 Additi
Page 108 and 109:
Table 6.3-1 Additional L1C Ranging
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
PRNSignalNo.Table 6.3-2. Additional
Page 116 and 117:
PRNSignalNo.Table 6.3-2 Additional
Page 118 and 119:
Page 120 and 121:
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IS-GPS-800A - US Coast Guard Navigation Center

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