Galileo OS SIS ICD (797928), страница 7
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11, with the binary signal componentseE1-B(t) and eE1-C(t).395HBBBBs E1 (t ) =12[eE1− B (t ) − eE1−C (t )]Eq. 11Note that as for E6, both pilot and data channel are modulated onto the same carriercomponent.7.2 LOGIC LEVELSThe correspondence between the logic level code bits used to modulate the signal and thesignal level is according to the values stated in Table 13.396HLogic Level10Signal Level-1.0+1.0Table 13: Logic to Signal Level Assignment©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p. 2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page327.3 TRANSMITTED SIGNAL PHASE NOISEThe phase noise spectral density of the un-modulated carrier must allow a second-orderphased locked loop with 10 Hz one-sided noise bandwidth to track the carrier to an accuracyof 0.04 radians RMS.7.4 TRANSMITTED SIGNAL CODE/DATA COHERENCYThe edge of each data symbol coincides with the edge of a code chip.
Periodic spreadingcodes start coincides with the start of a data symbol.7.5 PAYLOAD AND COMPONENT RECEPTION LOSSESThe correlation loss due to payload distortions will be below 0.6 dB. For the ideal receiverbandwidth definition as for in Table 2, additional losses due to receiver filtering are to beconsidered, as shown in Table 14.397H398HSignalLoss (dB)E50.4E60.0E10.1Table 14: Additional losses due to Rx filtering©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p.
2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page338. GALILEO SPREADING CODES CHARACTERISTICS8.1 CODE LENGTHSThe ranging codes are built from so-called primary and secondary codes, by using a tieredcodes construction.The code length to be used for each signal component is the value stated in Table 14.39HChannelCode Length(ms)E5a-IE5a-QE5b-IE5b-QE1-BE1-C2010041004100Code length (chips)PrimarySecondary102302010230100102304102301004092409225Table 15: Code lengths8.2 SPREADING CODES GENERATIONThe primary spreading codes can be either: linear feedback shift register-based pseudo-noise sequences, or optimized pseudo-noise sequences.Optimized codes need to be stored in memory and therefore are often called ‘memory codes’.Register based codes used in Galileo are generated as combinations of two M-sequences,being truncated to the appropriate length.
These codes can be generated either with pairs ofLinear Feedback Shift Registers (LFSR) or might be also stored in memory.8.2.1 Spreading codes generation for long codesLong spreading codes are generated by a tiered code construction, whereby a secondary codesequence is used to modify successive repetitions of a primary code, as shown in Figure 9.The first chip of the secondary code in binary ('logical level') representation is used to controlthe polarity of the first epoch of the primary code sequence by Exclusive OR combination.40H©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p.
2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page34Figure 9: Tiered codes generation8.2.2 Generation of truncated and combined M-sequences for primary codesFigure 10 shows an example standard implementation of the LFSR method for generation oftruncated and combined M sequences.For truncation to primary code-length N, the content of the two shift registers is reinitialised(reset) after N cycles (Primary code Epoch) of the registers with so-called start-values s j(=[sj1,…,sjR]).401HBPBPBPBP©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p. 2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page35Figure 10: Linear shift register based code generator for truncated andcombined M-sequencesThe transformation between the polynomial feedback description and the vector description ājfor the feedback tap positions is defined as follows: after transferring the octal vector notationinto binary notation, the bits are counted right to left starting with i=0 from the leastsignificant bit (LSB, see Figure 11) and ending with i=R at the most significant bit, where Ris the code register length.
Then the ith bit applies for the feedback tap aj,i for i=1, …, R, asshown in Figure 10.Note, aj,R is always one and aj,0 is not considered in the register feedback tap.This is illustrated with an example (for E5a-I) in Figure 11.B402HPB403HBBBB40H©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p. 2-4.BBMSBGAL OS SIS ICD/D.0Draft023/05/2006Page364 0 5 0 3Polynomial notation (octal):Binary notation:Reference:Issue:Revision:Date:100 000 101 000 011 LSBRegister feedback taps: 1 0 0 0 0 1 0 1 0 0 0 0 0 1 = [1,6,8,14]aj,1 aj,2aj,13 aj,14......Figure 11: Code register feedback taps representation (example for E5a-I)The transformation between the octal format start-value representation and the logic levelstart-values sji of the individual register cells is defined as follows.After transferring the octal notation in binary notation, the bits are counted right to leftstarting with i=1 (note the different start value compared to the feedback definition) from theleast significant bit (LSB, see Figure 11) and ending with i=R at the most significant bit,where R is the code register length.
Then the ith bit applies for sji. This mapping definitionapplies for ‘i’ in the range [1, …, R].This is illustrated for an example-code (of E5a-I) in Figure 12 below.BPBP405HBPBP406H3 0 3 0 5Polynomial notation (octal):Binary notation:MSB011 000 011 000 101LSBStart Value (logic level): 1 0 1 0 0 0 1 1 0 0 0 0 1 1s12 s22......14s 132 s2Figure 12: Start value representation for Base-register 2(example for first code of E5a-I)Note: In this example the MSB is zero in order to complete the 14-bits binary value sequenceto fit into a sequence of octal symbols.©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p. 2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page378.3 PRIMARY CODES8.3.1 E5 Primary CodesE5 primary codes either can be considered as memory stored binary sequences or can begenerated with LFSR.In case of memory codes, the E5a-I, E5a-Q, E5b-I and E5b-Q primary codes are according tothe representation provided in Annex 1.In case of generation via LFSR, the E5a-I, E5a-Q, E5b-I and E5b-Q primary codes use theprinciple defined in Par.8.2.2, using the parameters defined in Table 15.407H408HSignalLength of shift registercomponent(polynomial order)E5a-I14E5a-Q14E5b-I14E5b-Q14Base register polynomial (octal)124050350661405035066164021514456402143143Table 16: Primary Codes SpecificationTwo parallel registers (as defined in Figure 10) are used: base register 1 and base register 2.The primary output sequence is the exclusive OR of register 1 and 2 outputs; the shiftbetween the two sequences is zero.The start values for all base register 1 cells, in logic level notation, are '1' for all codes E5a-I,E5a-Q, E5b-I and E5b-Q.409H©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p.
2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page388.3.1.1 Base register 2 start value for E5a-IThe octal format base register 2 start value with the convention defined in Par. 8.2.2 is asdefined in the following Table 16 for each primary code.The hexadecimal format of the first 24 code-chips is also given in the table with the followingconvention. The n-th group (n = 1, …, 6) of four consecutive code-chips in time c4n-3,..c4n (inlogic level notation) translates into the n-th hexadecimal symbol from the left, representingthe decimal number 8c4n-3 + 4c4n-2 + 2c4n-1 + c4n.410H41HCodeNoStartValueInitialSequence12345678910111213141516171819202122232425303051423427213205772331233463156141253701527302362734407272363771704606434154052425211631247760063011560172722744531702130123CEA9D9D8CF145D1C87A013364D42323300D91CEF2AA82DCF2A17D3D84AE446D38C514F20C01848767E0CB8EFF93EBCD5D55CEB19B7C5805FCF99EA1B23CE58515E843682230F77BA7D629CodeNoStartValueInitialSequence26272829303132333435363738394041424344454647484950144013472722627306232725601520142113146522164335160273721316354253563324655140542702706604314553446525273207633172117312132779BFAC718A25B69A39F39B27D454598F2BC629DDBC63328276E2FCA22C6D5E881D974C4DB13AB031193235948869F4D8947A3C0C9ED533349941B2A305513F37831C130B93A84D5B4A5029CTable 17: Base register 2 start values and first code chip for E5a-I©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p.
2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page398.3.1.2 Base register 2 start value for E5a-QThe octal format base register 2 start value with the convention defined in Par. 8.3.1.1 is asdefined in the following Table 17 for each primary code number (1-50).The hexadecimal format of the first 24 code-chips with the convention defined in Par. 8.3.1.1is also given in Table 17.412H413H41H415HCodeNoStartValue1234567891011121314151617181920212223242525652051422472331751273662466033655274500762601705127173212216075166443755602477022650643025046127350426211230000370613704312InitialSequence515537D6753958B2E5305914442710593CF8214AD7435EA6C1A7D5F0E94AA8C2392EB63B8F0A46896DD40245F1EB0160ED28B3CB9F5B576592A88811DD3649B59F42FF81F6CE8128DCD55CCodeNoStartValue2627282930313233343536373839404142434445464748495020606111622225230533246140776732705050522755303711020413477505274373561620536270066002677317375352673625512044264422162125411InitialSequence79E450B634606D562B3A901059CD72C0211A28EB96D7554B425126E0DAFBEF79F218085DD50CD80447B98DE8770D1FA0C9FCF748116D840BCC1520040D4897AF6D254B759371BB1B53DA0ETable 18: Base register 2 start values and first code chip for E5a-Q©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p.
2-4.Reference:Issue:Revision:Date:GAL OS SIS ICD/D.0Draft023/05/2006Page408.3.1.3 Base register 2 start value for E5b-IThe octal format base register 2 start value with the conventions defined in 8.3.1.1 is asdefined in the following Table 18 for each primary code number (1-50).The hexadecimal format of the first 24 code-chips with the conventions defined in 8.3.1.1 isalso given in Table 18.416H417H418H419HCodeNoStartValueInitialSequence1234567891011121314151617181920212223242507220260470025217166141610254001537260230172520637023642773130640341740646407676322311035300755260771164411537351152045234645C5BEA14F6248FD548886277B9E39D5EA7EDEF283214FB0C9F0AB6479833BEC2D91409B11397E161E0FCDCB2F5AC1079A2D9BC6BC5146F848B04F01E8B16C9BB2827D16C8097B570F1969C0CodeNoStartValueInitialSequence2627282930313233343536373839404142434445464748495025664214033225302337307772712222377361753307533151131340743310216354660253305351301211401032576303263743326022357700667012017512FA973F36B2D5317EC839038037446B4DE6C01D90E0BB62708C7265B55A68E1CC3916EBDC5951327D0EA921FD458693EB98A9FDE162A04CA3CA56F03928A4FB5B9101EC7C91D4FAFC22BTable 19: Base register 2 start values and first code chip for E5b-I©, 2006, European Space Agency / Galileo Joint UndertakingDocument subject to terms of use and disclaimers p.
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