1、The Physical LayerChapter 2Radio 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 SpectrumThe ISM bands in the United States.Communication Satellitesa) Geostationary Satellit
2、esb) Medium-Earth Orbit Satellitesc) Low-Earth Orbit Satellitesd) Satellites versus FiberCommunication SatellitesCommunication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage.Communication Satellit
3、es (2)The 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 Mobi
4、le CommunicationsGSM uses 124 frequency channels, each of which uses an eight-slot TDM systemGSM (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
5、Cs signalThird-Generation Mobile Phones:Digital Voice and DataBasic services an IMT-2000 network should providea) High-quality voice transmissionb) Messaging (replace e-mail, fax, SMS, chat, etc.)c) Multimedia (music, videos, films, TV, etc.)d) Internet access (web surfing, w/multimedia.)Cable Telev
6、isiona) Community Antenna Televisionb) Internet over Cablec) Spectrum Allocationd) Cable Modemse) ADSL versus CableCommunity Antenna TelevisionAn early cable television system.Internet over CableCable televisionInternet over Cable (2)The fixed telephone system.Spectrum AllocationFrequency allocation in a typical cable TV system used for Internet accessCable ModemsTypical details of the upstream and downstream channels in North America.
