European GNSS (Galileo) open service (797926), страница 5
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Galileo Signals Receiver Reference BandwidthsThe transmitted signals are Right-Hand Circularly Polarized (RHCP).AFCoTn2.3. ModulationltaIn the following sections, modulation expressions are given for the power normalizedcomplex envelope (i.e. base-band version) sX(t) of a modulated (band-pass) signal SX(t).Both are described in terms of their in-phase sX-I(t) and quadrature sX-Q(t) components bythe following generic expressions in Eq. 1.[]suS X (t ) = 2 PX s X − I (t )cos(2π f X t ) − s X −Q (t )sin (2π f X t )s X (t ) = s X − I (t ) + j s X −Q (t )Eq. 1DRTable 3 defines the signal parameters used in this chapter, with the indices:●● ‘X’ accounting for the respective carrier (E5, E5a, E5b, E6 or E1) and●● ‘Y’ accounting for the respective signal component (B, C, I or Q) within the signal ‘X’.ParameterExplanationUnitCarrier frequencyHzPXRF-Signal powerWLX-YRanging code repetition periodRanging code chip lengthubTC,X-YTS,XlicfXchipsssTS,X-YSub-carrier periodsTD,X-YNavigation message symbol durationsRC,X-Y= 1/TC,X-Y code chip rateHz= 1/TS,X sub-carrier frequencyHzRS,X-Y= 1/TS,X-Y sub-carrier frequencyHzRD,X-Y= 1/TD,X-Y navigation message symbol rateHzSX(t)Signal band-pass representationN/ABinary (NRZ modulated) ranging codeN/ABinary (NRZ modulated) navigation message signalN/ABinary (NRZ modulated) sub-carrierN/ABinary NRZ modulated navigation signal component including code,sub-carrier (if available) and navigation message data (if available);(= cX-Y(t) scX-Y(t) DX-Y(t))N/ArPSub-carrier periodFoRS,XCX-Y(t)DX-Y(t)scX-Y(t)eX-Y(t)© European Union 2014Document subject to terms of use and disclaimers p.
i-iiOS SIS ICD, Issue 1.2, dd.mm 20143ParameterExplanationUnitNormalised (unit mean power) baseband signal= sX‑I(t)+j sX-Q(t)N/AcX-Y,kkth chip of the ranging codeN/AdX-Y,kkth symbol of the navigation messageN/ADCX-Y= TD,X-Y/TC,X-Y number of code chips per symbolN/Ai modulo LN/AInteger part of i/DCN/A|i|L[i]DCrectT(t)tionsX(t)Function “rectangle” which is equal to 1 for 0≤t<T and equal to 0elsewhereN/ATable 3.
Signal Description ParametersltaAFCoTn2.3.1. E5 Signal2.3.1.1. Modulation SchemeCE5a-IDRCE5a-QeE5a-IDE5a-IeE5a-QCE5b-IAltBOCMUXsE5eE5b-IDE5b-IeE5b-QlicCE5b-QsuThe diagram in Figure 3 provides a generic view of the E5 signal AltBOC modulationgeneration.Figure 3.Modulation Scheme for the E5 SignalubThe E5 signal components are generated according to the following:●● eE5a-I from the F/NAV navigation data stream DE5a-I modulated with the unencryptedranging code CE5a-IrP●● eE5a-Q (pilot component) from the unencrypted ranging code CE5a-Q●● eE5b-I from the I/NAV navigation data stream DE5b-I modulated with the unencryptedranging code CE5b-IFo●● eE5b-Q (pilot component) from the unencrypted ranging code CE5b-QThe respective definitions are following (Eq.
2):4()∑ [()∑ [()∑ [()∑ [||(||||||([])]([]()])]© European Union 2014Document subject to terms of use and disclaimers p. i-iiOS SIS ICD, Issue 1.2, dd.mm 2014Eq. 2)]The Galileo satellites transmit the E5 signal components with the ranging codes chip ratesand symbol rates stated in Table 4.E5aE5bRanging Code Chip-RateRC,X-Y (Mchip/s)Symbol-RateRD,X-Y (symbols/s)I10.23050Q10.230No data (‘pilot component’)I10.230250Q10.230No data (‘pilot component’)Table 4.
E5 Chip Rates and Symbol Rates2.3.1.2. Modulation TypetionSignalComponent(Parameter X) (Parameter Y)√√((DR√( )(√(( )) [( )(su( )ltaAFCoTnThe wideband E5 signal is generated with the AltBOC modulation of side-band sub-carrierrate RS,E5 = 1/TS,E5=15.345 MHz (15 x 1.023 MHz) according to the expression in Eq. 3 withthe binary signal components eE5a-I, eE5a-Q, eE5b-I and eE5b-Q as defined in Eq. 2. Note thatE5a and E5b signals can be processed independently by the user receiver as though theywere two separate QPSK signals with a carrier frequency of 1176.45 MHz and 1207.14MHz respectively.⁄ )]( )( )) [( )(⁄ )]( )( )) [( )(⁄ )]( )( )) [( )(⁄ )]Eq. 3licThe respective dashed signal components ēE5a-I, ēE5a-Q, ēE5b-I and ēE5b-Q represent productsignals according to Eq. 4:e E 5 a − I = e E 5 a −Q e E 5b − I e E 5b −Qe E 5 a −Q = e E 5 a − I e E 5b − I e E 5b −Qe E 5b − I = e E 5b −Q e E 5 a − I e E 5 a −Qe E 5b −Q = e E 5b − I e E 5 a − I e E 5 a −QEq.
4rPubThe parameters scE5-S and scE5-P represent the four-valued sub-carrier functions for thesingle signals and the product signals respectively:( )∑( )∑||||⁄(⁄ )⁄(⁄ )FoThe coefficients ASi and APi are according to Table 5.i2.ASi2.APiEq. 501234562 +11-1− 2 −1− 2 −1-111-1-11− 2 +12 −12 −172 +1− 2 +1Table 5. AltBOC Sub-carrier Coefficients© European Union 2014Document subject to terms of use and disclaimers p. i-iiOS SIS ICD, Issue 1.2, ?????????? 20145AFCoTntionOne period of the sub-carrier functions scE5-S and scE5-P is shown in Figure 4.One Period of the Two Sub-carrier Functions Involved in AltBOC ModulationltaFigure 4.2.3.1.3.
Equivalent Modulation TypesuEquivalently, the AltBOC complex baseband signal sE5(t) can be described as an 8‑PSKsignal according to Eq. 6. The corresponding phase states are illustrated in Figure 5.k (t ) ∈ {1,2,3,4,5,6,7,8 },Eq. 6ublicDR πs E 5 (t ) = exp j k (t ) with4Figure 5.8-PSK Phase-State Diagram of E5 AltBOC SignalForPThe relation of the 8 phase states to the 16 different possible states of the quadrupleeE5a‑I(t), eE5a‑Q(t), eE5b‑I(t), and eE5b‑Q(t) depends also on time. Therefore, time is partitionedfirst in sub-carrier intervals Ts,E5 and further sub-divided in 8 equal sub-periods.
The indexiTs of the actual sub-period is given by Eq. 7 and determines which relation between inputquadruple and phase states has to be used.[()]{}The dependency of phase-states from input-quadruples and time is given in Table 6.6© European Union 2014Document subject to terms of use and disclaimers p. i-iiOS SIS ICD, Issue 1.2, ?????????? 2014Eq. 7Input QuadrupleseE5a-I-1 -1 -1 -1 -1 -1 -1 -1111111eE5b-I-1 -1 -1 -11111-1 -1 -1 -11111eE5a-Q-1 -111-1 -111-1 -111-1 -111eE5b-Q-1-11-1-11-1-11-11-111t’ = t modulo Ts,E51111[0,Ts,E5/8[54436312657278811[Ts,E5/8, 2 Ts,E5/8[54832312657674812[2 Ts,E5/8, 3 Ts,E5/8[14872312657634853[3 Ts,E5/8, 4 Ts,E5/8[18872316257634454[4 Ts,E5/8, 5 Ts,E5/8[18872756213634455[5 Ts,E5/8, 6 Ts,E5/8[18476756213238456[6 Ts,E5/8, 7 Ts,E5/8[58436756213278417[7 Ts,E5/8, Ts,E5[544367588126tion0AFCoTnt’ltak according to sE5(t)=exp(jkπ/4)iTs13272.3.2.
E6 SignalsuTable 6. Look-up Table for AltBOC Phase StatesFigure 6 provides a generic view of the E6 signal generation.DE6-BeE6-BDRCE6-BCE6-CFigure 6.1–√2sE6eE6-CModulation Scheme for the E6 SignallicThe E6 signal B and C components are generated according to the followingub●● eE6-B from the C/NAV navigation data stream DE6-B modulated with the encryptedranging code CE6-B●● eE6-C (pilot component) from the ranging code CE6-CForPEquation 8 provides their mathematical description.( )∑ [||( )∑ [||)]([](Eq.
8)]The Galileo satellites transmit the E6 signal components with the ranging codes chip ratesand symbol rates stated in Table 7.Component(Parameter Y)Ranging Code Chip-RateRC,E6-Y (MChip/s)Symbol-RateRD,E6-Y (symbols/s)B5.1151000C5.115No data (‘pilot component’)Table 7.
E6 Chip Rates and Symbol Rates© European Union 2014Document subject to terms of use and disclaimers p. i-iiOS SIS ICD, Issue 1.2, ?????????? 20147The E6 signal is generated according to Eq. 9, with the binary signal components eE6‑B(t)and eE6-C(t).s E 6 (t )1=2[eE 6− B (t ) − eE 6−C (t )]Eq.
9Note: both pilot and data components are combined on the same carrier component,with a power sharing of 50 percent.tion2.3.3. E1 SignalsultaAFCoTnFigure 7 provides a generic view of the E1 CBOC signal generation.Modulation Scheme for the E1 CBOC SignalDRFigure 7.The E1 CBOC signal components are generated as follows:●● eE1-B from the I/NAV navigation data stream DE1-B and the ranging code CE1-B, thenmodulated with the sub-carriers scE1-B,a and scE1-B,blic●● eE1-C (pilot component) from the ranging code CE1-C including its secondary code, thenmodulated with the sub-carriers scE1-C,a and scE1-C,bubEquation 10 provides the mathematical description of these components.∑ [rP( )( )∑ [||||(||()]Eq.10)]FoGalileo satellites transmit ranging signals for the E1 signal with the chip rates and subcarrier rates defined in the following Table 8.Component(Parameter Y)Sub-carrier TypeSub-carrier RateBCBOC, in-phase1.0236.1381.023CCBOC, anti-phase1.0236.1381.023RS,E1-Y,a (MHz) RS,E1-Y,b (MHz)Ranging Code ChipRate RC,E1-Y (Mcps)Table 8.
E1 CBOC Chip Rates and Sub-carrier RatesThe navigation data message stream, after channel encoding, is transmitted with thesymbol rate as stated in Table 9.8© European Union 2014Document subject to terms of use and disclaimers p. i-iiOS SIS ICD, Issue 1.2, ?????????? 2014Component(Parameter Y)Symbol RateRD,E1-Y (symbols/s)B250CNo data (‘pilot component’)Table 9. E1-B/C Symbol Rates( )(√( )(( )( ))( )(( )())(tionThe E1-B/C composite signal is then generated according to equation Eq.
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