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1、The Physical Layer,Chapter 2,Radio Transmission,(a)In the VLF,LF,and MF bands,radio waves follow the curvature of the earth.(b)In the HF band,they bounce off the ionosphere.,Politics of the Electromagnetic Spectrum,The ISM bands in the United States.,Communication Satellites,Geostationary Satellites
2、Medium-Earth Orbit SatellitesLow-Earth Orbit SatellitesSatellites versus Fiber,Communication Satellites,Communication satellites and some of their properties,including altitude above the earth,round-trip delay time and number of satellites needed for global coverage.,Communication Satellites(2),The
3、principal satellite bands.,Communication Satellites(3),VSATs using a hub.,Low-Earth Orbit SatellitesIridium,(a)The Iridium satellites from six necklaces around the earth.(b)1628 moving cells cover the earth.,Globalstar,(a)Relaying in space.(b)Relaying on the ground.,GSMGlobal System for Mobile Commu
4、nications,GSM uses 124 frequency channels,each of which uses an eight-slot TDM system,GSM(2),A portion of the GSM framing structure.,CDMA Code Division Multiple Access,(a)Binary chip sequences for four stations(b)Bipolar chip sequences(c)Six examples of transmissions(d)Recovery of station Cs signal,
5、Third-Generation Mobile Phones:Digital Voice and Data,Basic services an IMT-2000 network should provideHigh-quality voice transmissionMessaging(replace e-mail,fax,SMS,chat,etc.)Multimedia(music,videos,films,TV,etc.)Internet access(web surfing,w/multimedia.),Cable Television,Community Antenna Televis
6、ionInternet over CableSpectrum AllocationCable ModemsADSL versus Cable,Community Antenna Television,An early cable television system.,Internet over Cable,Cable television,Internet over Cable(2),The fixed telephone system.,Spectrum Allocation,Frequency allocation in a typical cable TV system used for Internet access,Cable Modems,Typical details of the upstream and downstream channels in North America.,
