GLOBAL NAVIGATION SATELLITE SYSTEM GLONASS INTERFACE CONTROL DOCUMENT

Transcription

1 GLOBAL NAVIGATION SATELLITE SYSTEM GLONASS INTERFACE CONTROL DOCUMENT Code Division Multiple Access Open Service Navigation Signal in L3 frequency and Edition.0 MOSCOW 06

2 Tale of contents List of figures... 3 List of tales... 4 Definitions and acronyms... 5 Scope... 7 L3OC signal structure General scheme of L3OC signal generation Structure of L3OC PRN generator....3 Convolution encoder structure BC and NH overlay codes General overview of L3OCd navigation message structure Service field structure of L3OCd data General structure of L3OCd string Service fields of L3OCd string Anomalous strings of L3OCd signal CRC (300,76) CRC (00,76) of string Type CRC (400,76) of string Type Data field structure of L3OCd Data fields of L3OCd strings and types of L3OCd strings L3OCd strings Type 0, and L3OCd string Type L3OCd string Type L3OCd string Type L3OCd strings Type 3 and L3OCd string Type L3OCd string Type Anomalous strings Type and... 5

3 List of figures Figure. L3OC signal structure... 9 Figure. L3OC signal generation scheme... 0 Figure.3 Convolution encoder structure... 4 Figure 4. General structure of L3OCd data string... 7 Figure 4. Anomalous L3OCd data string Type... Figure 4.3 Anomalous L3OCd data string Type... Figure 4.4 CRC (300,76) encoding scheme... 3 Figure 4.5 CRC (300,76) syndrome calculation scheme... 4 Figure 5. String Type 0 of L3OCd data... 7 Figure 5. String Type of L3OCd data... 8 Figure 5.3 String Type of L3OCd data... 9 Figure 5.4 String Type 0 of L3OCd data Figure 5.5 String Type 5 of L3OCd data Figure 5.6 String Type 6 of L3OCd data Figure 5.7 String Type 3 of L3OCd data Figure 5.8 String Type 3 of L3OCd data Figure 5.9 String Type 60 of L3OCd data Figure 5.0 String Type 0 of L3OCd data

4 List of tales Tale. First and last 3 chips of L3OCd PRNs... Tale. First and last 3 chips of L3OCp PRNs... 3 Tale 4. Parameters of L3OCd service fields... 8 Tale 4. CRC (300,76) in a 3-second string structure of L3OCd signal... 3 Tale 5. Types of string and their content for L3OCd... 6 Tale 5. Parameters of data fields of strings Type 0, and Tale 5.3 Ephemeris and time accuracy factors... 3 Tale 5.4 Parameters of data fields for string Type Tale 5.5 Parameters of data fields for string Type Tale 5.6 Parameters of data fields for string Type Tale 5.7 Parameters of data fields for strings Type 3 and Tale 5.8 Parameters of data fields for string Type Tale 5.9 Parameters of data fields for string Type

5 Definitions and acronyms BC Baker code BPSK Binary Phase-Shift Keying CE Convolution Encoder CDMA Code Division Multiple Access CRC Cyclic Redundancy Check d symol in signal name, indicating attriution to a data component DC Digital Circuit (shift register) EI Ephemeris Information f Base frequency (.03 MHz) FDMA Frequency Division Multiple Access GLONASS Gloal Navigation Satellite System ICD Interface Control Document IS Initial State L3OC CDMA Open Service Navigation Signal in L3 frequency and L3OCd time time scale determined y phase of L3OCd signal at the phase center of an SV antenna L3OCp time time scale determined y phase of L3OCp signal at the phase center of an SV antenna LDMP Long-term Dynamic Model Parameters MS Meander Sequence MSD Mean Solar Day MT Moscow Time NF Newman-Huffman code OC Overlay Code p symol in signal name, indicating attriution to a pilot component PRN Pseudorandom Noise sequence (ranging code) RMS error (σ) Root mean square error S Sequence SC Synchronous Counter SV Space Vehicle TAI International Atomic Time TS Time Stamp 5

6 UE User Equipment UT Universal Time is mean solar time at 0 longitude accounted for the effect of polar motion on position of meridians UTC Coordinated Universal Time UTC(SU) Coordinated Universal Time of Russia 6

7 Scope. This Interface Control Document (ICD) defines the parameters etween the space segment, represented y Glonass-K space vehicles (SV), and the navigation user equipment (UE) of GLONASS for L3 Code Division Multiple Access (CDMA) navigation. Information common to all GLONASS CDMA signals is given in the document GLONASS. Interface Control Document. General Description of Code Division Multiple Access Signal System (hereinafter General Description ICD) which consists of the following sections: - purpose, composition and concept of GLONASS-ased positioning; - time scales used in GLONASS; - GLONASS geodetic reference; - general characteristics of GLONASS signals; - monitoring GLONASS signal-in-space; - recommendations and algorithms for processing of data transmitted in GLONASS signals.. Russian Rocket and Space Engineering and Information Systems Corporation, Joint Stock Company () the designer of the GLONASS mission payload is assigned as the developer of ICD and is responsile for its drafting, coordination, revision and maintenance. The current Document comes into force provided that it is signed y the following persons/entities: - GLONASS Chief Designer; - Russian Rocket and Space Engineering and Information Systems Corporation, Joint Stock Company () of ROSCOSMOS State Space Corporation which is the leading organization on the GLONASS payload, service radiofrequency and telemetry systems, ground control and command facilities, and a set of user equipment for different user groups; - Academician M.F. Reshetnev Information Satellite Systems (ISS, JSC) of ROSCOSMOS State Space Corporation prime for development and integration of GLONASS satellites, including system integration of space, launch, and ground control complexes, on-oard mission software used to generate navigation message and SV control data; 7

8 - Research and Development Center (Korolev) of the Central Research Institute of the Russian Federation Space Forces leading research and development organization of the Russian Ministry of Defense on the GLONASS system; - Russian Institute of Radionavigation and Time (RIRT, OJSC) of Ministry of Industry and Trade of Russian Federation responsile for developing timing facilities of special and dual use, facilities for generating space segment time scale; synchronization of GLONASS timing facilities and developing user equipment for different user groups; - Central Research Institute of Machine Building, Federal State Unitary Enterprise (TSNIIMASH, FSUE) the head research institute of the ROSCOSMOS State Space Corporation. ICD is approved y authorized representatives of ROSCOMOS State Space Corporation and Space Forces. ICD comes into force on approval y the Commanding General of the Space Forces and the Director General of the ROSCOSMOS State Space Corporation. In the course of GLONASS system evolution, its individual parameters may change. The developer of ICD ears responsiility for coordination of the suggested modifications with all responsile parties and, if necessary, for drafting new edition of the Document containing such modifications. Modifications and new editions of ICD come into force on approval y the Commanding General of the Space Forces and the Director General of the ROSCOSMOS State Space Corporation. The is responsile for official distriution of GLONASS ICD. 8

9 L3OC signal structure. General scheme of L3OC signal generation L3OC signal is transmitted on carrier frequency (nominal value) f L3 75 f MHz 0.05 MHz and consists of two BPSK(0) components of the same power: L3OCd (data component) and L3OCp (pilot component). These components are in phase quadrature with each other and L3OCd is delayed y 90 (Figure.). Q L3OCp BPSK(0) I L3OCd BPSK(0) Figure. L3OC signal structure Figure. shows L3OC signal generation scheme. 9

10 ms s BC 00 sps CE 00 ps Data L3OCd DC PRN L3OCd S L3OCd IS = * 0 63 I Quadrature modulator L3OCd DC +90º Σ L3 IS = Q L3OCp f T ms IS3 = f T = 0.3 MHz 0.3 MHz SC ms s DC3 * 0 63 PRN L3OCp NH S L3OCp ms s * = SV ID numer IS = IS3 = + 64 cos(π f L3 t) Figure. L3OC signal generation scheme Zero SV ID numer is the reserved one, which can only e enaled upon termination of GLONASS CDMA and FDMA signals comined use. Modulation sequence of symols of L3OCd signal (S L3OCd ) is the modulo- sum of PRN L3OCd chip stream clocked at f Т = 0.3 MHz (see.), Barker code (BC) symol stream clocked at 000 sps (see.4), and convolution encoder (CE) symol stream clocked at 00 sps (see.3). Sequence S L3OCd is used to phase-shift key I-component of carrier frequency in L3 y 80. Modulation sequence of symols of L3OCp signal (S L3OCp ) is the modulo- sum of PRN L3OCp chip stream clocked at f Т = 0.3 MHz (see.) and Newman-Huffman code (NH) symol stream clocked at 000 sps (see.4). Sequence S L3OCp is used to phase-shift key Q-component of carrier frequency in L3 y 80. 0

11 . Structure of L3OC PRN generator PRN L3OCd and PRN L3OCp generation scheme is shown in Figure.. PRN L3OCd and PRN L3OCp are truncated Kasami sequences of length N = 030 and period T = ms. These sequences generated y the modulo- addition of inary digits ( and 0) incoming at clock rate f T 0.3 MHz from digital circuits DC, DC, DC3 shown in Figure.: - DC and DC for PRN L3OCd generation; - DC and DC3 for PRN L3OCp generation. The shift register of DC has 4 triggers and feedack from triggers numer 4, 8, 3, 4. The shift register of DC and DC3 has 7 triggers and feedack from triggers numer 6 and 7. The shift direction in all registers is from lower to higher trigger numer. The following initial state (IS) codes are set into DC registers at ms intervals: - IS = into DC; - IS = = , into DC, where is SV ID numer; - IS3 = + 64 = , into DC3, where is the SV ID numer. IS, IS and IS3 (inary numers) are recorded in DC, DC and DC3 in such a way that the least significant it enters the last trigger of register. Short pulses at ms intervals marking moments of IS codes registering to DCs are formed in synchronous counter (SC) shown in Figure. ased on 0.3 MHz signal and s pulses. Tales. and. shows first and last 3 chips of L3OCd and L3OCp PRNs in HEX. For example, CB350 denotes The record of sequences means that the left-most chip is generated first.

12 Tale. First and last 3 chips of L3OCd PRNs IS (Figure.) PRN L3OCd IS (Figure.) PRN L3OCd First 3 chips Last 3 chips First 3 chips Last 3 chips CB350 9DB5069 5D360B55 DC30FC 3C79A3 BD778E4B 7DF48477 FCF900E 0CD58 8DD446F8 4D574CC4 CC558BD C0DDA3 AD6C9DA 6D95C3E6 EC93D79F 483B6D8 9585AA 5506A89D D400BCE FA B547D83 75C47BF F4C33C6 04EF49 85E4E EF0C C46FB75 407E6B A566A 65A560E E4A B0657 BC74A793 7D3777 EF9CD6B5 88CF3EC4 5809F00 DB74FE 4668EE6 F5CAE 688EBBDA A696B38 3B66CAFC 5C358D C7A8349 0FDD53AB 99F6F CB A9B7 98AE ED89 6B30E0 FFFD94 35A4C6 AC5E00 FBC43A 8F3B5FE 4C5465C DBC4D8 B648CA9 B078D6D E5A05D8F 78EFFC4B AB44F4 99AD508D 59E5AB D884EC8 3869CBD6 B96FDFAF 79ECD593 F8EACEA 08CA CC7C 494FD0 C C47 A90E983E 698D90 E88B867B 09BE73C 99DF345 5EF979 D08ED E B5F7C67 7DC765B F0DA6 00FAA0AD 8FCB4D4 47FBEE8 C079AA9 038F8F A3E3BF6 6BD3CA E0BB5B C94A08 07EDF063 9AA5A7 FDFB9D6 60BE8 AE9C8F FF9D0C DB03CC8 D37ECA 4E584DEE 90BA59F B444045B 7AE3D4B9 E7AC757D BE788F6 337EA5 ED90FE47 70DF5F83 78CB7F 8AC C6D4 D9B670 6A8938 F7CD3EC 396AE0E A4543CA C376ABBB 5E390A7F 909EDA9D 0DD7B59

13 3 Tale. First and last 3 chips of L3OCp PRNs IS3 (Figure.) PRN L3OCp IS3 (Figure.) PRN L3OCp First 3 chips Last 3 chips First 3 chips Last 3 chips EBF3DE 9FB999B 5F3A3A7 DE3C37DE 3E7DBC0 BF7BA6B9 7FF8AC85 FEFEB8FC 0EDE7A73 8FD86E0A 4F5B6436 CE5D704F ECF55 AFAE8 6F99EB4 EE9FFF6D 68F9EA 97898A53 570A806F D60C D08 B74B057 77C80F4D F6CEB34 06EED9BB 87E8CDC 476BC7FE C66DD387 6C5699 A7A4E0 67A948DC E6AF5CA5 BA445DE 86EBE4A 484C34F8 D503953C B507D4D FFDC89 EB80C6B 7CF7ADAF CF5E5997 5F853 9CB68B 0F AA604 FBE5C0C A80DBE6 FD94BFA 6C96EA3E A33ADC 3F7E9B8 58D7369 C56DAD 0BC504F 968AA38B 5357B3 B86CF677 76CB695 EB CD76F0 98CEE4 DF3FE06 470BFC AA76C06 9BA787F 5B743 DA4663A 3A65E34 BB63F75D 7BE0FD6 FAE6E98 0AC6B97 8BC03FEE 4B4335D CA45AB A04A4B5 AB0B0CC 6B8BAF0 EA87AE89 97CFCE 939DBB7 53D8B D4C5F 35540EC B D05EA9 FD64AD0 0F6885F 83F09C A C D A B938 EB70D4 6E9ACCC F3D D7B3EA A03DE C76EFA5F 5A5B9B 94868B79 09C9ABD BA60DE85 7F7F4 E988AFA3 74C70E67 394E66 8EDB47D 407C9730 DD3336F4 84E7CCE8 9A86DC D70FBDCE 4A40C0A D3F47B B05C55BF 7EFB855D E3B DD0A CD F5A87 9EBA0043 F9E9E83 64A649F6 AA E38D0

14 .3 Convolution encoder structure The 00 ps data stream of L3OCd signal is encoded y a rate / convolution encoder (33,7) shown in Figure.3. The switch of the encoder is set to position (lower position) for the first half of a 0-millisecond data it period. Data f T f T = 00 Hz f T Figure.3 Convolution encoder structure.4 BC and NH overlay codes BC (Baker code) is a periodic 5-symol code 0000 synchronized with CE symols (Т CE = 5 ms) and transmitted with the most significant its first (the fourth symol of BC for a CE symol duration is ). NH (Newman-Huffman code) is a periodic 0-symol code synchronized with data its (T data = 0 ms) and transmitted with the most significant its first (the first symol of NH for a data it duration is 0). 4

15 3 General overview of L3OCd navigation message structure The following definitions are used to descrie data structure of navigation messages: it inary symol of data; string sequence of inary symols its of specific length; string field aggregate of string its containing a specific parameter or zeros; service fields of a string fields that contain service data. The semantic scope of these fields is the same for all strings of this signal; data fields of a string fields that contain data which semantic scope is different for different strings of this signal; reserved fields of a string fields which semantic scope and value are not descried in ICD. UE shall ignore these fields. Navigation message of L3OCd signal is transmitted as a continuous sequence of strings of non-fixed and non-predetermined structure. Navigation message of L3OCd signal is transmitted at 00 ps. Navigation message consists of 300-it strings of 3-second duration, as well as of 00- and 400-it anomalous strings of - and 4-second duration, respectively. 5

16 4 Service field structure of L3OCd data 4. General structure of L3OCd string 4.. Bit sequence in a string Figure 4. shows general structure of a string of L3OCd signal. The string is 300 its long and of 3 seconds duration. The string consists of fields separate its or groups of its containing specific parameters. 6

17 Preamle Type TS H l P 4 9 P KP CRC 4 Figure 4. General structure of L3OCd data string Figure 4. shows string it numeration, field designation and the numer of its in each field. According to this it numeration, transmission of a string starts with it (the first it of Preamle field) and ends with it 300 (the last it of a cyclic redundancy check (CRC) field). 4.. Types of fields Each string has two types of fields: service and data. These fields are defined in accordance with Section 3. 7

18 Figure 4. shows service fields, locations of data fields are shaded. Shaded fields in figures depicting strings of specific type (for example, Figure 5.) are reserved fields, which shall e ignored y UE Rule for recording digits in fields In the words which numerical values may e positive or negative, the most significant it is the sign it. Symol 0 corresponds to + and symol corresponds to -. The most significant it is registered in the field it which is transmitted first. For example, if = = (SV ID numer, see 4...4), then it numer 47 of a string (Figure 4.) is registered as and its numer 4 to 46 are registered as Service fields of L3OCd string 4.. List of L3OCd service fields Each L3OCd string contains service fields of permanent set and position, namely repeated in each string. Tale 4. shows the list and parameters of service fields (also see Figure 4.). Tale 4. Parameters of L3OCd service fields Field Numer of its Least significant it Value range Preamle Type TS s H 0, - l 0, - P 4 see P see KP 00, 0, 0, - A 0, - CRC 4 see Unit 8

19 4.. Semantic scope of service fields 4... Field Preamle contains the constant value: Preamle = Field Type is a type of a current string. It determines the data (set and position of string data fields) transmitted in the string that contains this field. For example, if the current string is of Type, then Type = Field TS is time stamp, i.e. L3OCd time at the start of a current string. TS is expressed in 3-second intervals within a current day (in L3OCd time). TS = 0 for the first 3-second interval within a day Field is the ID numer of the SV that transmits this navigation message. Semantic scope of field is constant for strings of any type except for those containing almanac. In strings containing almanac, field is denoted and means the ID numer of the SV, to which almanac data elongs. Zero SV ID numer is the reserved one, which can only e enaled upon termination of GLONASS CDMA and FDMA signals comined use Field of the SV ID numer Field current string of the SV ID numer. H is the attriute of healthy ( 0 ) or non-healthy ( ) navigation signal l is the attriute of validity ( 0 ) or non-validity ( ) of data in the Field P denotes SV call to ground control. This field is not used y a user Field P denotes regime of SV orientation: P = 0 for the duration of current string in L3OCd time, SV is Sun-pointing; P = for the duration of current string in L3COd time, SV either performs noon/midnight turn maneuver or transits from Sun-pointing to noon/midnight turn maneuver or vice versa Field KP is the indication of the expected UTC (SU) correction y plus or minus s at the end of current quarter in GMT (at 3:00 in MT). UTC(SU) corrections shall result in the corresponding corrections of L3OCd time: KP = 00 no correction planned; KP = 0 day length is increased y s in L3OCd time; KP = 0 correction decision is pending; KP = day length is decreased y s in L3OCd time. 9

20 4...0 Field A is the indication of correction L3OCd time y plus or minus s at the end of the next string: A = 0 no correction is planned A = correction is planned Comination of A = and KP = in the current string denotes that the next string will e the anomalous string Type which is s shorter and of s duration. If the current string shows the comination of A = and KP = 0, then the next string will e the string Type which is s longer and of 4 s duration (also see Appendix E in General Description ICD) Field CRC is cyclic redundancy check its. CRC field is formed as descried in Anomalous strings of L3OCd signal 4.3. L3OC anomalous strings are those which are longer or shorter than 3 s. Strings of Types and are anomalous Figure 4. shows L3OC string of Type. This string is used for leap second corrections of L3OC time when a day length is reduced y s. The string has non-standard duration of s and contains 00 its. 0

21 Preamle Type TS H l P 4 9 P KP CRC 4 Figure 4. Anomalous L3OCd data string Type The string transmits service fields (see 4.), the only difference is that CRC field is generated using cycle encoding scheme descried in 4.5 (also see Appendix E in General Description ICD) Figure 4.3 shows L3OC string of Type. This string is used for leap second corrections of L3OC time when a day length is increased y s. The string has a non-standard duration of 4 s and contains 400 its. The string transmits service fields (see 4.), the only difference is that CRC field is generated using cycle encoding scheme descried in 4.6 (also see Appendix E in General Description ICD). Bits numer 30 to 30 are filled y Preamle (see 4...).

22 Preamle Type TS H l P 4 43 P KP Preamle CRC 4 Figure 4.3 Anomalous L3OCd data string Type

23 4.4 CRC (300,76) CRC (300,76) is used in L3OCd signal for filling CRC field in 3 second strings of navigation message. The location of the CRC field in a string is given in Tale 4.. The string contains 300 its, where 4 its are allocated for check its of CRC code, 0 its for Preamle, and 56 its for data. String transmission starts from Preamle field. Tale 4. CRC (300,76) in a 3-second string structure of L3OCd signal Preamle Data CRC Data its Check its CRC (300,76) generator polynomial is as follows: g(x) X X 3 X 4 X 5 X 6 X 7 X 0 X X 4 X 7 X 8 X 3 X 4 CRC field is filled y using CRC encoding scheme shown in Figure it data lock is delivered to the input of encoder (starting from st it of Preamle and ending with 56 th it of data). 300-it code lock is generated at the output of encoder y adding 4 check its. logical zero input data lock (76 it) 4 Figure 4.4 CRC (300,76) encoding scheme output code lock (300 it) The following steps descrie the encoding procedure using the device shown in Figure 4.4: ) Initial state of the 4-it shift register is zeros. 3

24 ) During first 76 shifts oth keys are set to position, data lock is eing directly transmitted to the output of the encoder, the register feedack is closed, and the register state is eing updated. 3) After transmitting the last 76 th data it, oth keys are set to position, the register feedack is opened, and during next 4 shifts the register state is eing replaced y zeros, check its are eing transmitted to the output of encoder. Error detection in a string is performed y analyzing the syndrome, which is calculated for each string of data y using the scheme shown in Figure 4.5. logical zero received lock (300 it) Figure 4.5 CRC (300,76) syndrome calculation scheme 4 syndrome (4 it) The following steps descrie the procedure of error detection in a received lock (a string, starting from the st it of Preamle and ending with the 4 th it of CRC field) using the device shown in Figure 4.5: ) Initial state of the 4-it shift register is some its (ones and zeros). ) During first 4 shifts oth keys are set to position, the received lock (first 4 its) is eing downloaded to the register. 3) After downloading the 4 th it of the received lock, keys are set to position, the received lock (the remaining 76 its) keeps eing downloaded to the register. Syndrome is the name of the state of the register at the instant when the last 300 th it of the received lock is downloaded to trigger. 4) After downloading the 300 th it of the received lock to the register, oth keys are set to position for the next 4 shifts in order to enale extraction of the syndrome from the register (and simultaneous downloading of first 4 its of the next string to the register). Zeros in all 4 its of the syndrome indicate asence of errors. Otherwise it shall e decided that the received lock (string) contains errors. 4

25 4.5 CRC (00,76) of string Type CRC (00,76) is used in L3OCd signal to fill in CRC field in strings Type. It is generated similarly to code (300,76) through the scheme shown in Figure 4.4 except for the numer of its delivered to the input (76 instead of 76). Error detection is realized through the scheme shown in Figure 4.5 except for the numer of its transmitted to the input (00 instead of 300). 4.6 CRC (400,76) of string Type CRC (400,76) is used in L3OCd signal to fill in CRC field in strings Type. It is generated similarly to code (300,76) through the scheme shown in Figure 4.4 except for the numer of its delivered to the input (376 instead of 76). Error detection is realized through the scheme shown in Figure 4.5 except for the numer of its transmitted to the input (400 instead of 300). 5

26 5 Data field structure of L3OCd 5. Data fields of L3OCd strings and types of L3OCd strings Content of data fields depends on a string type indicated in a service field Type (see 4...). Data fields in a string are occupied y its numered: in all strings except Type and (see Figure 4.); in strings of Type (see Figure 4.); and in strings Type (see Figure 4.3). Tale 5. enlists string Types used in L3OCd signal. Susequently in case of navigation message update necessity, new types of strings with updated data or new types of data will e introduced. Tale 5. Types of string and their content for L3OCd String type Content 0,, Immediate data 0 Almanac data 5 Parameters of Earth s rotation, ionosphere model parameters, parameters of models for relating time scales UTC(SU) and TAI 6 SV attitude parameters during noon/midnight turn maneuver 3, 3 Long-term dynamic model parameters (LDMP) 60 Text messages 0 For technological tasks. Ignored y a user Anomalous string which is used for leap second correction purpose in case a day length is reduced y s Anomalous string which is used for leap second correction purpose in case a day is increased y s Note: Strings Type 0, and compose a data package, so string Type always follows Type 0, and string Type follows string Type. 6

27 5. L3OCd strings Type 0, and 5.. Structure of strings Type 0, and Figures show the structure of strings Type 0, and. String Type always follows Type 0, and string Type always follows string Type. These strings transmit of immediate data Preamle Type TS P N 4 N T M РS t 0 H E Е 8 l P KP E T 8 R E R T F E 5 F T 5 ( t ) ( t ) ( t ) 9 5 τ c (t ) c ( t ) CRC 4 Figure 5. String Type 0 of L3OCd data 7

28 Preamle Type TS P x (t 40 ) H l P KP y (t 40 ) z (t 40 ) x (t 35 ) y (t 35 ) CRC 4 Figure 5. String Type of L3OCd data 8

29 Preamle Type TS P z (t 35 ) H x (t 5 ) l P KP y (t 5 ) z (t 5 ) x pc у pc z pc 3 3 L GPS ( t ) CRC 4 Figure 5.3 String Type of L3OCd data Parameters of data fields of strings Type 0, and are given in Tale 5.. Horizontal doule lines divide the fields that refer to different strings. 9

30 Tale 5. Parameters of data fields of strings Type 0, and Field Numer of its Least significant it Value range N year interval N T 46 day M 3 see PS t s E E, R E, F E, Unit E T hours R T see F Т 5 see t ) 38 3 ( t ) 48 9 ( t ) 57 5 ( s N 4 s c ( t ) s t ) 49 3 c ( Reserved 35 x (t ) t, z (t ), km x (t ), y (t ) km/s Reserved 9 z (t ) km/s x (t ), y (t ), z (t ) 39 5 x pc, у pc, z 0 pc 3 ±4 m 38 L3 8 t ) GPS ( s s Reserved 5 km/s Note: Field c ( t ) has 56 range in case of future cancellation of GLONASS time correction y s. 30

31 5.. Semantic scope of fields of strings Type 0, and 5... Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field N 4 is the numer of the four-year interval in Moscow time (MT) that includes MT day containing the instant t (hereinafter ephemeris N 4 ). At the oundary of a four-year interval the value of ephemeris N 4 can differ from the numer cur N 4 of a current fouryear interval in MT (see Appendix F of General Description ICD). The first year of the first current four-year interval corresponds to 996, namely cur N 4 = for (in MT) Field N T is the numer of the day in MT within ephemeris N 4 that contains the instant t (hereinafter ephemeris N T ). At the day s oundaries the value of ephemeris N T may differ from cur N T of a current day in MT (see Appendix G of General Description ICD). January in MT of each leap year corresponds to cur N T =. January, 00 which y the Gregorian calendar is not a leap year also corresponds to cur N 4 and cur N T =. Appendix K of General Description ICD descries the algorithm for transformation of cur N T values to Gregorian calendar date and Greenwich Mean Sidereal Time (GMST) Field current navigation message): M denotes a modification of an SV ID numer (which transmits the M = 000 GLONASS-M with L3 navigation payload transmits L3 CDMA signals; M = 00 GLONASS-K transmits L3 CDMA signals; M = 0 GLONASS-K transmits L and L3 CDMA signals; M = 00 GLONASS-K transmits L, L, and L3 CDMA signals. In the course of GLONASS modernization SV with new modifications from 00 to may e introduced in the orital constellation. Introduction of such SVs in the constellation shall not result in disruption of UE manufactured earlier Field PS is a pseudoframe size. This field is defined as a numer of strings to e transmitted starting from the current string Type 0 to the next string Type 0. For example, PS=5 means that the current string Type 0 will e first followed y four strings of different types and then y a string Type 0. PS=0 means that no data on pseudoframe size is transmitted. 3

32 5...6 Field t is the instant in MT to which immediate data (ephemeris and clock data) relates. t is expressed y 90-second intervals during current day that instant is referred to as the instant t (timescale MT is implied). N T in MT. In this document Any change of immediate data is accompanied y a compulsory change of t field. In case data is updated every 30 minutes, the first and the last instant t are 5 minutes apart from the oundary of a day. The data can e updated every 90 seconds upon necessity. In this case t ecomes multiple of 90 s Fields E E, E T denote an age of ephemeris and clock data, respectively, of an SV ID numer (which transmits this navigation message) expressed in the numer of six-hour intervals elapsed either etween ephemeris and clock data receipt and the instant t for the relay regime or etween initial data receipt and the instant (propagation) regime. respectively: Fields R E, R E,Т = 0 relay; R E,Т = 0 prediction (propagation); t for the ephemeris prediction R T denote regime for generation of ephemeris and clock data, R E,Т = use of intersatellite measurements Fields F E, F Т denote accuracy factors dependent on ephemeris and clock errors, respectively. These fields contain equivalent pseudorange errors (σ) to SV ID numer at the instant t. Tale 5.3 shows values of F E and F Т (in decimals) and their corresponding errors σ. Tale 5.3 Ephemeris and time accuracy factors F E, F Т σ, m F E, F Т σ, m F E, F Т σ, m not defined 3

33 Recommendations on use of General Description ICD. F E and F Т accuracy factors are provided in Appendix P of Field t ) denotes a correction to L3OCd time of the SV ID numer ( (transmitting current navigation message) for transformation to GLONASS time at the instant t. The relations of field t ) to L3OCd time ( T L3OCd the instant t are as follows: ( ) and GLONASS time ( T GL ) at T GL (t ) T (t ) (t ). L3OCd 5... Field t ) denotes relative deviation of carrier frequency t ( numer from the nominal carrier frequency f c at the instant t : f of SV ID f C (t ). fc t f 5... Field t ) is a half rate of relative deviation ( t )) of carrier frequency ( f t from nominal carrier frequency c t ) shall e defined as follows: ( f of SV ID numer at the instant t. The value in field ( d (t) dt (t ). ins tan t t Appendix D of General Description ICD descries the transformation from time of incoming signal to GLONASS time Field t ) denotes a correction for transformation from GLONASS time to c ( MT at the instant t. Field c ( t ) relates to GLONASS time ( T GL follows: ) and MT at the instant t as T MT (t ) T (t ) (t ). GL c 33

34 5...4 Field c ( t ) denotes rate of correction c ( t ) at the instant t. The value in field t ) is defined as follows: c ( d (t) c c (t ). dt instan t t to MT. Appendix D of General Description ICD descries transformation from GLONASS time Fields x (t ), y (t ), z (t ) denote the coordinates of the center of mass of the SV ID numer at the instant t in the orthogonal geocentric Greenwich coordinate system employed in GLONASS. Fields x (t ), y (t ), z (t ) (coordinates) calculated ased on precise dynamic model. contain precise ephemerides Fields x (t ), y (t ), z (t ) denote velocity vectors of the SV ID numer center of mass at the instant t in the orthogonal geocentric Greenwich coordinate system employed in GLONASS. Fields x (t ), y (t ), z (t ) contain the coordinated ephemerides (velocities) which are calculated ased on precise ephemerides in the manner which allows minimizing methodological errors of ephemeris prediction using the simplified dynamic model inherent to many receivers Fields x (t ), y (t ), z (t ) denote vector components of perturing odies induced accelerations of the SV ID numer center of mass at the instant t in the orthogonal geocentric Greenwich coordinate system accepted for GLONASS. Fields x (t ), y (t ), z (t ) contain the coordinated ephemerides (accelerations) which were calculated ased on precise ephemerides in the manner which allows minimizing methodological errors of ephemeris prediction using the simplified dynamic model inherent to many receivers. Algorithms for calculation of coordinates and velocity vector components for the SV s center of mass ased on ephemeris data is descried in Appendix J of General Description ICD Fields x pc, у pc, z pc denote coordinates of the antenna phase center transmitting L3OC signal in the coordinate system which axes are parallel to an SV-fixed reference system and its origin is referenced to the SV s center of mass. Description of the SVfixed reference system is provided in Appendix R of General Description ICD. This Appendix 34

35 also contains algorithm for transformation SV s center of mass coordinates to coordinates (in PZ-90) of its antenna phase center. ( T L3OCd ): Field L3 denotes offset of L3OCp time ( T L3OCp ) relative to L3OCd time T T. L3 L3OCp L3OCd Parameter L3 is necessary for transformation from L3OCp time to L3OCd time and then to GLONASS time Field t ) is a fractional part of a second in the offset of the GPS time GPS ( ( T GPS ) relative to GLONASS time ( T GL ) at the instant t : t ) T T 0800 T, GPS ( GPS GL where T is a integer offset expressed in integer seconds and calculated y a user ased on the received GPS navigation messages. Transformation from GLONASS time to GPS time is descried in Appendix C of General Description ICD. 35

36 5.3 L3OCd string Type Structure of string Type 0 Figure 5.4 shows a structure of string Type 0. Strings of this type are used for transmission of almanac data for one SV transmitting one or several CDMA signals Preamle Type TS H l P 4 N S 6 E 6 N SR 5 3 М τ 4 P KP ТО λ t A ε Δi ω ΔТ T A CRC 4 Figure 5.4 String Type 0 of L3OCd data 36

37 Parameters of data fields for string Type 0 are given in Tale 5.4. Tale 5.4 Parameters of data fields for string Type 0 Field Numer of its Least significant it Value range ТО see N S Unit E A day N 46 day SR 5 see M 3 see A s half a cycle t 5 A s i 0 A half a cycle 0 A A 6 half a cycle T 9 A 9 5 s T 4 A s/orit Reserved Semantic scope of fields of string Type 0 transmitted Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field is a numer of the SV for which almanac data in the current string is Field TO orit type. Content and structure of data fields for string Type 0 depend on the value in the Field TO. TO = 00 corresponds to the circular orit of 9,00 km (current GLONASS orit). This document summarizes data fields for string Type 0 only for TO =

38 Field N S denotes the numer of SVs in the orital constellation transmitting one or several CDMA signals for which almanac is roadcast Field E A denotes age of SV s almanac from the time almanac parameters (ephemeris and clock data) were uploaded to an SV till the date numered N (see ) Field N is a calendar numer of days in MT within a four-year interval to which almanac relates. January of a leap year corresponds to not a leap year in the Gregorian calendar also corresponds to N =. January, 00 which is N = Field SR denotes status register of L, L and L3 signals. This field contains 5 its. The first (most significant) it represents L status, the second one represents that of L, the third one that of L3. Bit denotes transmission of the corresponding signal; 0 means asence of the signal. Health of the given navigation signal and its data validity is determined y attriutes H and l (see и 4...6). 4 th and 5 th its of Field M denotes a modification of the SV : SR field are reserved ones. M = 000 Glonass-M carrying L3 navigation payload transmitting L3 CDMA; M = 00 Glonass-К transmitting L3 CDMA signals; M = 0 Glonass-К transmitting L and L3 CDMA signals; M = 00 Glonass-К transmitting L, L, and L3 CDMA signals. In the course of GLONASS modernization SV with new modifications (from 00 to ) may e introduced in the orital constellation. Introduction of such SVs in the constellation shall not result in disruption of UE manufactured earlier Field A denotes rough correction for transformation from L3OCd time of SV to GLONASS time at the eginning of day N ) in MT. ( A T GL,N TGL,N T L3OCd,N TL3OCd,N 86400, where TGL,N is time in GLONASS time corresponding to the eginning of day ( N ) in MT; T is L3OCd time of SV L3OCd, N corresponding to the eginning of day ( N ) in MT. 38

39 Operator denotes the nearest integer. Note: value A in almanac data of each SV is the same and its accuracy is aout ms for all signals of this SV. within day within day Field denotes geodetic longitude of the first ascending node of SV orit N in geocentric coordinate system employed in GLONASS Field N. t denotes the instant in MT when SV passes the first ascending node A Field i A denotes correction to the nominal value of orit inclination (64.8º) of SV at the instant A t (MT) Filed A is eccentricity of SV orit at the instant A t (MT) Field A denotes argument of perigee for SV orit at the instant A t (MT) Filed TA denotes correction to a nominal value (40,544 s) of mean draconic orital period of SV at the instant A (MT). t (MT) Field T A denotes draconic orital period rate for SV at the instant A Appendix M of General Description ICD provides the algorithm for calculating coordinates and velocity vector components for the SV s center of mass ased on almanac. t 5.4 L3OCd string Type Structure of string Type 5 Figure 5.5 shows the structure of a string Type 5. This type of a string is used for transmission of the Earth rotation parameters (see Appendix L of General Description ICD), ionosphere model parameters (see Appendix Q of General Description ICD), UTC(SU) and TAI offset model parameters (see Appendix H of General Description ICD) and other parameters. 39

40 Preamle Type TS P N B x p y p 6 6 H l P KP x p 9 y p x p y p B B 0 B 8 c_a c_f c_a p 9 UTC TAI CRC 4 Figure 5.5 String Type 5 of L3OCd data Parameters of data fields for string Type 5 are provided in Tale

41 Tale 5.5 Parameters of data fields for string Type 5 Field Numer of its Least significant it Value range N B 46 day x p, y 4 p 6 x p, y 4 p 9 x p, y 4 p Unit arc second 8 0 arc second/day 0 arc second/day B s B 6 0 B s/msd.9 0 c _ A s / msd c _ F SFU c _ A 0 p nt UTC TAI 9 55 s Reserved 6 Notes: For Field B 0 56 range is selected to allow for possile future cancelation of UTC(SU) correction. SFU solar flux unit, SFU = 0 W /(m Hz) Semantic scope of fields for string Type Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field N B denotes calendar numer of a day (MT) within a four-year interval to which parameters transmitted in the current string relate. January of a leap year corresponds to N B =. January, 00 which is not a leap year according to Gregorian calendar also corresponds to N B = Fields x p, y p, x p, y p, x p, y p are parameters of quadratic polynomial used to determine the position of the instantaneous Earth s pole. These parameters are specified as for the eginning of day N B in MT (T MT ). 4

42 Fields B 0, B, B are parameters of quadratic polynomial which are used to determine difference T T, UT UT UTC where T UT is mean solar time at 0 longitude accounted for the effect of polar motion on position of meridians; T UTC is Coordinated Universal Time of Russia UTC(SU) which determined y atomic clock whose readings are periodically corrected for minus or plus s to keep difference UT within 0,9 s. Parameters B 0, B, B are set at the eginning of day B 0 is UT T difference; N B in MT: B denotes daily change of difference during a mean solar day; B denotes rate of difference change. The algorithm for calculating time in UT scale is provided in Appendix B of General Description ICD. model: Fields c _ A, c _ F 0. 7, c _ Ap are the current parameters of the Earth ionosphere c _ A is a numerical factor of peak TEC (total electron content) of ionospheric F-layer; c _ F 0.7 is solar activity index value; c _ A p is of geomagnetic activity index value Field UTC TAI denotes UTC(SU) to TAI offset at the eginning of a day N B in MT. UTC TAI = TUTC TTAI. Appendix H of General Description ICD descries transformation from UTC(SU) to TAI. 4

43 5.5 L3OCd string Type Structure of string Type 6 Figure 5.6 shows the structure of string Type 6. This string type is used for transmission of parameters enaling recalculation of coordinates of the SV s center of mass into those of its antenna phase center during the noon/midnight turn maneuver Preamle Type TS P T in in max 5 7 H l P KP A in sn CRC 4 Figure 5.6 String Type 6 of L3OCd data 43

44 Parameters of data fields of string Type 6 are provided in Tale 5.6. Tale 5.6 Parameters of data fields for string Type 6 Field Numer of its Least significant it Value range T 5 in s Unit 4 in 5 0 half cycle sn 0, 6 max in half cycle /s 4 0 half cycle /s 5 0 half cycle /s s s Reserved 0 Overview of data fields of string Type 6 is provided elow. Appendix R of General Description ICD contains the detailed description of an SV s attitude parameters and the algorithm for their use Semantic scope of fields for string Type Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field T in denotes the instant in signal time of noon/midnight turn maneuver start Field in is the yaw angle at the instant T in Field sn is a sign of the maneuver (see Appendix R of General Description ICD) Field max is the maximum angular rate of the SV performing the maneuver Filed in is the angular rate of the SV at the instant T in Field is the constant angular acceleration (deceleration) of the SV Field denotes either the interval etween 44 T in and the termination moment of angular rate increment with the constant angular acceleration, or the duration of angular rate decrement with the constant deceleration up to the value the noon/midnight turn maneuver. at the instant the SV exits out in

45 Field denotes the time it takes to perform the turn maneuver with a given maximum angular rate max. 45

46 5.6 L3OCd strings Type 3 and Structure of strings Type 3 and 3 Figures 5.7 and 5.8 show the structure of strings Type 3 and 3. These strings are used for transmission of long-term dynamic model parameters (LDMP). LDMP enale the usage of an SV s movement prediction parameters for a 30-minute or less interval of the SV s orit to predict its movement for a 4-hour interval Preamle Type TS P t a x (t 8 ) H l P KP A a y (t ) a (t ) a (t ) a (t ) x0 y0 a z (t 8 8 ) z0 a x (t 8 ) a (t ) y a z(t ) CRC 4 Figure 5.7 String Type 3 of L3OCd data

47 Preamle Type TS P t 0 a x3 (t 8 ) a y3 (t 8 ) H l P KP A a z3(t ) a x 4 (t ) a y4(t ) a z4 (t 8 ) CRC 4 Figure 5.8 String Type 3 of L3OCd data Parameters of fields for strings Type 3 and 3 are provided in Tale 5.7. The doule horizontal line separates fields elonging to different strings. 47

48 Tale 5.7 Parameters of data fields for strings Type 3 and 3 Field Numer of its Least significant it Value range t s a (t ), a (t ), a (t ) 4 5 x0 y0 a x (t ), a y (t ), a (t ) a x (t ), a y (t ), a (t ) z0 Unit km/s km/s 3 54 z 8 67 z 8 50 km/s 4 Reserved 86 t s a x 3(t ), a y 3(t ), a 3(t ) a x 4(t ), a y 4(t ), a 4(t ) 80 z z 8 78 km/s 5 km/s 6 Reserved Semantic scope of fields for strings Type 3 and Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field t is descried in Field t is the same for strings Type 3 and 3. It denotes the instant of MT to which parameters a (t ), a (t ) (see ) are referenced. These parameters are intended for comined use with parameters of ephemeris data in strings Type 0,, referenced to the same instant t Fields a (t ), a (t ) contain coefficients of four-degree polynomials which allow calculating additional accelerations a x (t, t ), a y (t, t ), a z (t, t ) of an SV. When summing these accelerations together with accelerations x (t ), y (t ), z (t ) (see 5...7) one can predict the SV movement with a very high accuracy for 0 to 4 hours interval relative to the instant t. 48

49 5.7 L3OCd string Type Structure of string Type 60 Figure 5.9 shows the structure of string Type 60 used to roadcast text messages. For this purpose the string Type 60 contains 9 its Preamle Type TS H l P Text Message 4 9 P KP A CRC 4 Figure 5.9 String Type 60 of L3OCd data Parameters of data fields for string Type 60 are provided in Tale

50 Tale 5.8 Parameters of data fields for string Type 60 Field Numer of its Least significant it Value range text message 9 Unit 5.7. Semantic scope of fields of string Type 60 document Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field of text message contains text data. Its structure is descried in a separate 50

51 5.8 L3OCd string Type Structure of string Type 0 Figure 5.0 depicts the structure of string Type 0. This string type is used for engineering purposes associated with SV commissioning. UE equipment shall ignore strings Type Preamle Type TS H l P Technological Data 4 9 P KP A CRC 4 Figure 5.0 String Type 0 of L3OCd data 5

52 Parameters of data fields for string Type 0 are provided in Tale 5.9. Tale 5.9 Parameters of data fields for string Type 0 Field Technological data Numer of its Least significant it Value range 9 Unit 5.8. Semantic scope of fields for string Type Preamle, Type, TS,, H, l, P, P, KP, A, CRC are service fields (see 4.) Field of technological data contains technological data. 5.9 Anomalous strings Type and String Type is descried in String Type is descried in Numer of its allocated for data fields are given in 5.. These its constitute reserved fields. 5