A geostationary satellite named. ETS-V is scheduled to be launched in the summer of. 1987. ... Automobile earth stations with voice or data ter- minal employ.
LAND MOBILE COMMUNICATION EXPERIMENTS WITH F I S V SATELLITE T. Ikegami, R. Suzuki, Y. Hase, S. Ohmoriand
K. Kosaka
RadioResearchLaboratory, Ministry of PostsandTelecommunications Koganei, Tokyo, 184 JAPAN
Abstract geostationary A satellite named ETS-V is scheduledtobelaunched in thesummerof 1987. Withthissatellite,experiments on mobilesatellite services will beperformed t o studybasictechnologyforfutureintegratedmobilesatellitesystems through the Experimental Mobile Satellite System (EMSS) L-band by frequencies (1.6/1.5GHz). Several kinds of land mobile earth stations are provided for the experiments. G/T and ElRP of theseearthstationsrangefrom -20dBK to -18dBK afnr do6 m d 2Bt0W od Br W espectively. Automobileearthstationswithvoiceordataterminal employ ACSSB and 2.4kbps BPSK-SSMA as the modulation technique. A hand-held earthstationispreparedasbi-directional low speed messagecommunicationterminal which employ lOObps Digital FM (CPFSK). Field tests will be carried Experimental from out autumn the of 1987. results of the EMSS will contribute future to operationalmobilesatellitesystems.
1.Introduction With the growing demand for nation-wide land mobile communication services, much attention has been given realization to of satellite based land mobile communication systems. In ord etrore a l i zlea nm d o b i lsea t e l l i tsey s t e m s (LMSS), important isit decide to the link parameters such fading as margins and outage rates,andtostudykeytechnologyfordeveloping landmobile earthstationssuchasmodulationand coding techniques. Many studies have been on LMSS using 800MHz band, L-band carriedout or other frequency bands[l][2][3]. However, the link parameters strongly depend on e l e v a t i o n angle, terrain, effect of buildings, etc. in the areawheretheservice is considered. TheRadioResearchLaboratory(RRL), Ministry of PostsandTelecommunications,hasa plan on mobile satellite comt o conduct experiments munications with the Engineering Test Satellitefive (ETS-V). This project is named the Experimental Mobile Satellite System (EMS), and will be the first integrated mobile satellite systems in the world,sinceitincludesaeronautical, maritime and land mobile satellite services[4].
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@ 1987 IEEE
The ETS-V scheduled is to be launched by the National Space Development Agency(NASDA) of Japan at 150"E in the summer of 1987, and is thefirstJapanese550kg-classgeostationarysatellite. A major purpose of theexperiments is to studybasictechnologyforfuturemobilesatellite communicationsystemswhichprovide high quality communication services for small ships, aircraft and land mobile vehicles. This paper describes outline of the system and land mobile experiments.
2. Outline of E M S As depicted in Figure l . , the EMSS consists of the ETS-V satellite,theKashimaearthstation, secondary a station for two hop ranging, and mobile earth stations such as small ship earth station, aircraft earth station and land mobile earth station. The kashima earth station is a feeder link station and located in Kashima Space Research Center of RRL. C-band frequencies (6/5GHz) are used for feeder links between the satellite and the Kashima earth station. L-band frequencies (1.6/1.5GHz) are used between the satellite and mobile earth stations. In both frequency bands, left-handed circular polarization is used. Onboard communication equipments of the ETS-V consist of L-band andC-bandantennas and W i t h double transponders as shown in Table 1. conversion type transponders, one of four link configurations can selected, be i.e. C/L, L/C, L/L, and C/C links. The L-band antenna has two beams as shown in Figure 2. The service area of the ETS-V includesJapan,theNorthand the West PacificOceans. 3. Earth stations 3.1 Kashima earth station The Kashima earth station has role a of the system management center which provides such functions as establishment of communication links and satellite control through the C-band TT&C channel. has both It C-band and L-band facilities. The diameters of C-band and L-band antennasare 10 metersand3 metersrespectively.
L-band facilities are used for AFC of C/L and L/C links, for simulating mobile stations and for monitoring L-band signals. Specifications of the Kashimaearthstationare shown in Table 2
.
Figure 1.
3.2 Land mobile earth stations of land mobile earth Therearetwotypes a hand-held stations;automobileearthstationsand 3. describes outline of the earth station. Table land mobile earthstations. Amplitude Companded SSB (ACSSB) is adoptedfor an analogvoiceterminal,because SSB has minimum bandwidth the same that as of original voice. Digital voice and data terminal areequippedwithspreadspectrummodulationand coherent matched filter techniques(51. Considering access capability, low traffic operation, random and multipath fading condition, SSMA is one of possible candidates for access technique in land mobile satellite links. Terminals with 2.4kbps BPSK-SCPC and NBFM-SCPC are also under development. The hand-held message communication terminal (HMCT)[G] looks likeanattachecaseandit weighs about 10 kilo grams. The HMCT communicates with the Kashima earth station in a half duplex mode. Message data is keyed in and on a ready-made pocket computer, displayed is and 20 t o 30 charactersaretransmittedthrough a lOObps packet channel. As the Kashima earth stationestimatesthereceivingfrequencyfromthe HMCT transmittingfrequency,the HMCT doesnot need a frequencysearchnor a AFCfunction.
Concept of the EMSS
4. Land mobileexperiment
Figure 2
RadiationPattern
of Onboard L-band Antenna
Onboard Transponders and Antennas
Table 1.
4.1 Propagationexperiments Main purpose of the land mobile experiments is to obtain propagation data on mobileof Lsatellite links in L-band. Field strengths band signal, vehicle speeds and bearings are measured while a mobile van moves in urban, suburban, rural and mountainous areas. In addition, surroundings of the vehicle and clearance frommobileantenna tothesatellitearerecorded withtheaid of TV cameratoanalyzeshadowing effects. Field strengths of both right-handed and left-handed polarization components can be measuredsimultaneously using a dualportantenna to analyze degradation of cross polarization dis-
Table 2
-3 dM
-8 dB
Uax. Tx P m r
25 watts
7 watts
WW. EIRP
35.5 dB#
24.5 dBw
Bandwidth
3 Wz (except 4L. link)
Weight
65 kg (including antennas)
Pcuer Consmtioo
300 watts
~~~~~~~
~
167
programs
Kashima Earth Station
criminationduetomultipath or shadowingeffects. Theabovepropagationdata will beobtainedwith as micro strip different types of antennas such patch,helix,cross dipole, etc. Multipath delay profile is m e a s u r etdo analyze delay spread or coherent bandwidth of mobile-satellite link withanapparatus which utilizesspreadspectrumandcoherentmatchedfilter techniques[S]. The coherent matched filter receiver can track the line-of-sight signal, and multipath delay profile obtained is continuously fromeachtap of thefilter.
4.2 Communication experiments Land mobile communication experiments in t hEe M aSr e intended t o develop small sized mobileearthstationsfor high qualitycommunicationservices,andthefollowingsareevaluated; (1) narrowbandmodulationtechnique (2) recovering technique from synchronization loss caused by shadowing
Table 3.
Table 4.
(3) error correcting technique suitable for mobile-satellite links (4) compensationtechnique of multipath fading Field tests will be performed typical at places along with propagation measurements. Bit or S/N characteristicsareoberrorperformances tainedundermultipathfadingandshadowingconditions. Error patterns of bit streams are recordedtostudypropererrorcorrectingtechniques for land mobile satellite links. In the experiments using the HMCT, initial acquisition and throughputperformancesarealsoobtained. In addition to the above fundamental experiments, advanced communication experiments a r e also to be carried out, e.g. facsimile communication, transmission of medical information, data transmission between hand-held computers andahostcomputer,etc. Table 4. shows typical link budgets with
Land Mobile Earth Stations
Link Budgets for Typical Automobile Eartb Station
KASEIMA-TO AUTOUOBILE LINK
AUTOMOBILE TO KASIMA LINK AutomobilestationTXPower
;
Automobile station EIRP
KashimaearthstationEIBP
i
j 16.0 dB1
Up-link loss path
; 199.6 dB
Up-link loss path
: 188.3 dB
Satellite G/T
i
Sate 1 1G/T i te
j -5.1 dBK
Up- 1 ink C/No
: 51.2 dBKz
Transponder gain
10.0 dBw
66.6 dB1
-8.0 dBK
: 87.6 deaz
C/No Up-link Transponder gain
i
164.9 dB
Satellite EIBP
;
Satellite EIBP
: -7.4 dB1
Down-link path loss
i
Down-link path loss
i
Automobile station antenna gain
i 6.0 i -19.5
Kashimaearthstation Down-link C/No Satellite link
C/No
G/T
198.4 dB
G/T
165.4 dB 32.4 dBW 187.7 dB dB
: 30.1 dBK
Automobile station
dBK
j 52.9 dBUz
Down-link C/No
: 53.8 dBUz
: 49.0 mz
Satellite C/No link
i
53.8 dBUz
the ACSSB terminal.Therequired C/NO foreach modem would as be follows; ACSSB:48.5dBHz, BPSK(2.4kbps):43.ldBHz, CPFSK(lOObps):31.5dBHz, and NBFM:49.0dBHz0 5. Conclusion
Thispaperdescribesfacilities of t h eE M S and land mobile communication experiments. Some of thesefacilitiesandmeasuringequipments are under development, and those be are to reported later. Field tests will be carried out from the autumn of 1987. Much attention has beengiventopropagationdata to beobtained in of the experiments. the Experimental results E M S will contributetothefutureoperational integratedmobilesatellitesystems.
References [ l ] A.E.Winter e t al.;"Land Mobile SatelliteCommunication via MSAT", 35th IAF84-279, Oct. 1984. [2]F.Naderi e t al.;"NASA's Mobile SatelliteCommunications Program, Ground and Space SegmentTechnologies",35th IAF84-84, Oct. 1984. [3] A.Jongejans e t al.;"PROSAT Phase I Report", ESA STR-216, May 1986. [4] Y.Hase e t al.;"Experimental Mobile Satellite System Using ETS-V", 15th ISTS, May 1986. 151 R.Suzuki e t al.;"Spread Spectrum Satellite CommunicationTerminalwithCoherentMatched Filter", GLOBECOM'86, 21.3, Dec. 1986. [6] Y.Hase e t al.;"Very Low Speed Message Communication System Using Hand-Held Earth Station", ICC87, June 1987.
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