On Generalized Signal Waveforms for Satellite Navigation (797942), страница 17
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QZSS L1 signal technical characteristicsGNSS SystemQZSSQZSSQZSSService NameC/AL1CSAIFCentre Frequency1575.42 MHz1575.42 MHz1575.42 MHzFrequency BandL1L1L1Access TechniqueCDMACDMACDMASpreadingmodulationBPSK(1)BOC(1,1)BPSK(1)Sub-carrierfrequency-1.023 MHz-Code frequency1.023 MHz1.023 MHz1.023 MHzSignal ComponentDataPrimary PRN CodeDataPilotData1023102301023Code FamilyGold CodesWeil CodesGold CodesSecondary PRNCode length--1800-Data rate50 bps50 bps-250 bpsSymbol rate50 sps100 sps-500 spsMinimum ReceivedPower [dBW]-158.5-157-161Elevation5°5°5°lengthEqually, for L2, L5 and E6, the technical characteristics of the QZSS signals are summarizedin the following table.
As we can clearly recognize, except for the LEX signal in E6, QZSSand GPS are practically identical. It is interesting to note that this signal makes use of a veryinteresting multiplexing scheme for its experimental LEX signal, based on Code Shift Keying(CSK) [QZSS SIS ICD].52Global Navigation Satellite SystemsTable 2.18. QZSS L2, L5 and E6 signal technical characteristicsGNSSSystemQZSSQZSSQZSSQZSSQZSSQZSSService NameL2CML2CLL5 IL5 QLEXLEXCentreFrequency1227.60MHz1227.60MHz1176.45MHz1176.45MHz1278.75MHz1278.75MHzFrequencyBandL2L2L5L5E6AccessTechniqueCDMACDMACDMACDMACDMABPSK(10)BPSK(10)BPSK(5)SpreadingmodulationSub-carrierBPSK(1) result ofmultiplexing 2 streamsat 511.5 kHz-----Codefrequency511.5 kHz511.5 kHz10.23 MHz10.23 MHz5.115 MHzSignalComponentDataPilotDataPilotDataPilotPrimaryPRN Codelength10230(20 ms)767250(1.5 s)1023010230102301048575frequencyCode FamilyM-sequence from amaximal polynomial ofdegree 27SecondaryPRN Codelength--Data rateIIF50 bpsIIR-MAlso 25bps-MinimumReceivedPower [dBW]-160.0 dBWElevation5°Combination and shortcycling of M-sequences1050 bps100 sps20--2 kbps--250 sps--157.9 dBW5°Small Kasami Set.Chip by chipmultiplex-155.7 dBW5°5°53Global Navigation Satellite Systems2.8.2Indian Regional(IRNSS)2.8.2.1IRNSS System OverviewNavigationSatelliteSystemThe IRNSS is an independent seven-satellite constellation that will be built and operated byIndia.
IRNSS will seek to maintain compatibility with other GNSS and augmentation systemsof the region and is planned to provide services for critical national applications.Of the seven satellites that comprise the constellation, three are geostationary and are knownas GAGAN. GAGAN will be further explained in the following chapter.
The other four,geosynchronous. The geostationary satellites have designated positions at 34º E, 83º E and132º E, while the geosynchronous (GSO) have equatorial crossings at 55° E (two satellites)and 111° E (two satellites), with an inclination of 29° and a relative phasing of 56°.The first IRNSS payload is expected to reach FOC in 2012. The constellation parameters ofIRNSS as well as the ground tracks were shown in the previous chapter together with QZSS.2.8.2.2IRNSS Signal PlanThe final definition of all the IRNSS signals has not been concluded yet and investigations arestill on course. We summarize in the next table the first proposal for the Signal and FrequencyPlan presented in November 2006 during the First ICG Meeting in Vienna.Table 2.19. IRNSS L5 Band technical characteristicsGNSS SystemIRNSSIRNSSIRNSSIRNSSService NameL-bandL-bandL-bandS-bandCentre Frequency [MHz]1191.7951191.7951191.7952491.75Frequency BandL5 AL5 BL5 CSAccess TechniqueCDMACDMACDMACDMASpreading modulationBOC(10,2)BPSK(10)BPSK(10)N/ASub-carrier frequency10.23 MHz--N/ACode frequency2.046 MHz10.23 MHz10.23 MHzN/ASignal ComponentDataDataPilotN/APrimary PRN Code lengthN/AN/AN/AN/ACode FamilyN/AN/AN/AN/ASecondary PRN CodelengthN/AN/AN/AN/AData rateN/A50 bps /100 spsN/A50 bps /100 spsMinimum Received PowerN/AN/AN/AN/AElevationN/AN/AN/AN/A54Global Navigation Satellite SystemsGiven the similarity with the Galileo signals in terms of services that IRNSS might beproviding, the same convention as for Galileo was employed.
That is A for the PRS and B andC for the Open Service data and pilot signals respectively. Furthermore, the spectralproperties of the IRNSS signal would be as follows:Figure 2.38. Spectra of IRNSS Signals in the E5b bandTo conclude, it is interesting to mention that the Indian Satellite Navigation Programme hasbeen doing much work in the past years on ionospheric and tropospheric modelling in theRegion of India what could mean that IRNSS does not plan to use dual frequency at least inthe first generation.Moreover, India also plans to transmit similar signals for the S-band to those we have justdescribed for the L5 band.
The carrier frequency of S-band is at 2491.75 MHz. Themodulation schemes and data rates would be the same as for L5 but no final decision on theother parameters has been made yet. In addition, it seems that India also plans to transmitsignals in L1 as announced during the second Meeting of the ICG in India, in 2007.As a summary of the studied regional satellite systems so far, the signal plan of QZSS andIRNSS is shown in the next figureFigure 2.39. QZSS and IRNSS planned signals.
It must be noted that IRNSS is alsoexpected to send augmentation signals on L155Global Navigation Satellite Systems2.8.3BeidouBeidou (in Chinese 北斗卫星导航定位系统 where 北斗 means North Dipper) is the firststone to build up Compass, an independent Global Navigation System under control of thePeople’s Republic of China. Beidou is the name of a Chinese constellation, which isequivalent in the Chinese astronomony to the Big Dipper of Western culture.In September 2003, China joined the Galileo project after signing an Agreement with theGalileo Joint Undertaking (GJU).
It was agreed that China would invest 230 € million inGalileo over the following years. On November 2nd, 2006 however, China announced itsintention of building its own navigation system, Beidou, offering equivalent open services tothose of Galileo. The Chinese Council Information Office on October 12th, 2006 publiclyannounced that China will independently develop application technologies and products inapplying satellite navigation, positioning and timing services.China is planning to build Beidou and its modernized version Compass on the basis of pureChinese technology. Both the satellite and carrier rocket are being developed by the ChineseResearch Institute of Space Technology and China Academy of Launch Vehicle Technology,which are under the China Space Science and Technology Group.2.8.3.1Beidou System OverviewBeidou is the experimental version of the Global Navigation System Compass that we saw inthe previous chapter. Beidou will be composed of 5 geostationary satellites, covering an areaon earth from 70°E to 140°E and from 5°N to 55°N.The first Beidou Navigation Test Satellite, Beidou 1A, was launched by a Chinese LongMarch 3M booster on October 31st, 2000, into a geostationary orbit slot at 140° E, to the eastof China.
It was followed by Beidou 1B on December 21st, 2000, which was placed in ageostationary slot at 80 degrees East longitude. Beidou 1C was launched into an orbit at110.5°E on May 25th, 2003 from the Xichang Satellite Launch Centre on a CZ-3A booster andthe last Beidou satellite of the 1X generation, namely Beidou 1D, has been successfully put inorbit on February 2nd, 2007, on another CZ-3A booster. Some weeks later, on April 13th, 2007China made the first clear step to the Global Navigation System Compass after launching itsfirst MEO, known as Beidou 2A.
The spacecraft began transmitting signals on three of fourfrequencies within a few days.2.8.3.2Beidou Signal PlanThe Beidou signal plan was already described in chapter 2.6.2. Indeed, Beidou is the firststone to Compass and the five GEO satellites we talked about in this chapter constitute whatwe call here the Beidou system.
For more details on the technical characteristics of thesignals, refer thus to this chapter.56Global Navigation Satellite Systems2.8.3.3Beidou Modernization (Compass)The four GEO satellites (1A, 1B, 1C, 1D) mentioned above were designed as experimentalsatellites. Nevertheless, the plans for the modernized system, also known as Compass (seechapter 2.6 for more details) are to have 35 satellites in orbit, offering then a completecoverage of the globe. Of the 35 satellites, 30 will be MEO satellites (Beidou 2) and the restfive will be the geostationary satellites of Beidou 1.The first MEO Beidou 2 satellite is already in the space and as we show in the next figures,the emitted signals correspond to those we have described in chapter 2.6.1. The measurementswere made by the French Space Agency CNES on April 24th, 2007.
In addition, it must benoted that the following figures include partial RF equalization.Figure 2.40. Compass Spectra centered on E1 carrier, observed on April 24th, 2007(Courtesy of CNES)Compass Spectra centered on L1 carrier, observed onAs we can clearly recognize from the figure above, of the two planned QPSK(2) signals at -14and +14 MHz with respect to the L1 carrier, only the left side was being transmitted as ofMay 10th, 2007.In the case of E6, we can clearly recognize the BPSK(10) signal. If we recall the parametersand description given in chapter 2.6.1, we can clearly see that this signal will be sittingdirectly on top of the Galileo PRS of E6.57Global Navigation Satellite SystemsFigure 2.41.
Compass Spectra observed on E6 carrier, observed on April 24th, 2007(Courtesy of CNES)Finally, the results for E5 show the superposition of a BPSK(2) and a BPSK(10) at 1207.14MHz in consonance with the description of Compass given in chapter 2.6.2 of this chapter.Figure 2.42. Compass Spectra observed on E5 carrier, observed on April 24th, 2007(Courtesy of CNES)58Global Navigation Satellite Systems2.9GNSS Augmentation Systems2.9.1Satellite Based Augmentation SystemsA Satellite Based Augmentation System (SBAS) is a system that supports wide-area orregional augmentation of any GNSS in general through the use of at least one dedicatedsatellite. If we recall the thoughts on regional augmentation systems of previous chapters, wecan see that the same reflexions on the future need of such systems are also valid here.Figure 2.43. Existing and planned GNSS Augmentation SystemsFrom the figure above it is important to note that the GRAS system is Australia was includedfor completeness although it is not a satellite based augmentation system (SBAS) but aGround Based Augmentation System (GBAS).We describe next all the different Augmentation Systems that already exist or are planned.2.9.1.1Wide Area Augmentation System (WAAS)The Wide Area Augmentation System (WAAS) augments GPS over the North Americanterritory to provide the additional accuracy, integrity, and availability needed to enable usersto rely on GPS for safety-critical applications, particularly in the field of aviation.
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