Satellite Communication Systems. mgr inż. Krzysztof Włostowski Instytut Telekomunikacji PW

Transcription

1 Satellite Communication Systems mgr inż. Krzysztof Włostowski Instytut Telekomunikacji PW

2 Satellite Communication Satellite Communication combines the missile and microwave technologies The space era started in 1957 with the launching of the first artificial satellite (sputnik)

3 Advantages of Satellite Communication LARGE CAPACITY One satellite = 10 transponders = 10x120 Mbit/s Total transmission capacity = 1 Gbit/s DISTANCE INSENSITIVE COST WIDEBAND SERVICE allows for transmission of: - TV - high bit date rate BROADCAST TRANSMISSION CAPABILITY: allows for point to multipoint distribution of information

4 History of satellite communication first satellite SPUTNIK: 85 kg in Earth orbit first geostationary satellite SYNCOM first commercial geostationary satellite Satellit Early Bird (INTELSAT I): 240 duplex telephone channels l three MARISAT satellites for maritime communication first mobile satellite telephone system INMARSAT-A (starts fully operational GEO global systems, for mobile maritime service) First Land Mobile Satellite System OMNITRACS starts to provide in North America land mobile satellite messaging and localization services ITALSAT (Italy) The first satellite with on board processing and multibeam coverage first digital satellite telephone system global satellite systems for small mobile phones

5 Satellite Communication Major Organisations: INTELSAT(1964), global (about 140 countries), FSS and BSS systems EUTELSAT (1977) 47 countries (Europe and former USSR countries), FSS and BSS systems INMARSAT (1979) global, mobile systems SES Astra (1988) private, DTH-TV

6 Satellite Orbits LEO GEO MEO LEO: km MEO: 5,000-15,000 km GEO: 35,786 km LEO: Low Earth Obit MEO: Medium Earth Orbit GEO: Geostationary Earth Orbit

7 Satellite Orbits GEO advantages: - the satellite appears to be fixed (immovable) when viewed from the Earth, no tracking required for earth station antennas - about. 40% of the earth`s surface is in view from the satellite disadvantages: - high attenuation level (power loss) (200dB) on the path - large signal delay ( ms) - polar regions (latitudes > 81 deg.) are not covered LEO advantages: - much smaller attenuation compare GEO satellites - low signal delay disadvantages: - short period satellite visibility (through earth station), many times during the day - Doppler effect - many satellites are required for establishing continuous transmission

8 Frequency Bands Band Uplink (GHz) Downlink (GHz) C 5,925-6,425 3,700-4,200 6/4 X 7,900-8,400 7,250-7,750 8/7 K u 14,000-14,500 10,950-11,200 14/11 11,450-11,700 K a 27,500-30,000 17,700-20,200 30/20 L 1,6265-1,6605 1,530-1,559 mobile FSS transponders: Typical values Bandwidth: 36 to 72 MHz EIRP 30 to 52 dbw

9 Space segment PAYLOAD FUNCTIONS: collect microwave signals from given zone of earth amplify radiofrequency carrier convert carrier frequency fro uplink to downlink frequency transmit microwave signals to given zone of earth

10 Satellite characteristics Transponder frequency and bandwidth G/T (db/k) in each point of satellite reception coverage EIRP (dbw) Effective Isotropic Radiated Power. It is satellite P T G T product. Transponder operation point. It works in saturation in order to use all available power

11 Satellite Transponder C - band transponder 14 GHz 12 GHz Amp Mixer Amp Receiving Antenna Local Oscillator Transmitting Antenna Uplink Downlink

12 Satellite Services 10 FSS Fixed Satellite Services (VSAT networks,..) 10 MSS Mobile Satellite Services (Inmarsat systems,...) 10 BSS Broadcasting Satellite Services ( TV, DVB..) 10 RDSS Radiodetermination Satellite Services (GPS)

13 Applications Traditionally radio and TV broadcast satellites military satellites navigation and localization (GPS) weather satellites Telecommunication global telephone connections backbone for global networks connections for communication in remote places or underdeveloped areas global mobile communication