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

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2. APPLICABLE DOCUMENTS2.1 Applicable DocumentsThe following documents of the issue specified contribute to the definition of the interfaces between the GPS SpaceSegment (SS) and the User Segment (US), and form a part of this IS to the extent specified herein.SpecificationsNoneStandardsNoneOther PublicationsIS-GPS-200 (current issue)GP-03-001A (20 April 2006)Navstar GPS Space Segment/Navigation User InterfacesGPS Interface Control Working Group Charter2.2 Reference DocumentsThe following documents are for reference only and are not controlled by the GPSW:[1] T. Richardson, R. Urbanke, “Efficient Encoding of Low-Density Parity-Check Codes,” IEEE Transactions onInformation Theory, Vol. 47, N0. 2, February 2001.[2] J. Betz, “Binary Offset Carrier Modulations for Radionavigation,” Journal of the Institute of Navigation,vol. 48, pp. 227–246, 20012 IS-GPS-800A8 June 2010
3. SIGNAL REQUIREMENTSThe requirements specified in this section define the requisite characteristics of the SS/US interface for the GPS L1Csignal.3.1 Signal StructureThe GPS SV typically transmits multiple distinct signals modulated on the L1 RF carrier. The signals include C/A,P(Y), M, and L1C which are modulated on the carrier frequency. The L1C signal defined in this IS consists of twomain components; one denoted L1C P to represent a pilot signal, without any data message, that is spread by aranging code, and L1C D that is spread by a ranging code and modulated by a data message. The L1C P is alsomodulated by an SV unique overlay code, L1C O .The L1C P and L1C D components are transmitted using ranging codes defined in Section 3.2.2. The SVs shalltransmit intentionally "incorrect" versions of the respective ranging codes as needed to protect users from receivingand utilizing anomalous signals. These "incorrect" codes are termed non-standard L1C P (NSCP) and non-standardL1C D (NSCD). Non-standard codes are not for utilization by the users and, therefore, are not defined in thisdocument.The data message on L1C D , denoted D L1C (t), includes SV ephemerides, system time, system time offsets, SV clockbehavior, status messages, and other data messages. The message structure and data encoding techniques aredefined in Section 3.2.3.The L1C D signal is modulated on the L1 RF carrier using a Binary Offset Carrier (BOC) (1, 1) modulationtechnique. The L1C P signal is modulated on the L1 RF carrier using a Time-Multiplexed BOC (TMBOC)modulation technique. The TMBOC technique utilized by L1C P signal uses a combination of BOC (1, 1) and BOC(6, 1) modulation as described in Section 3.3.3.2 Signal Definition3.2.1 Signal CharacteristicsThe following specifies the characteristics and quality of the L1C signal.3.2.1.1 Frequency PlanThe carrier frequency for the L1C signal shall be coherently derived from a frequency source common with othersignals within the SV. The nominal frequency of this source as it appears to an observer on the ground is 10.23MHz. The SV carrier frequency and clock rates, as they would appear to an observer located in the SV, are offset tocompensate for relativistic effects. The clock rates are offset by f/f = -4.4647E-10, which is equivalent to achange in the L1C-code chipping rate of 1.023 MHz by a f = -4.5674E-4 Hz. This results in an offset L1C-code3 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: 1. INTRODUCTION1.1 ScopeThis Interf
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 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
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3.5.3.10.1 Integrity Status Flag (I
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The ionospheric data shall be updat
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3.5.4.2.3 User Algorithm for Applic
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transmitted by the SVs will degrade
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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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IS-GPS-800A - US Coast Guard Navigation Center

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