[计算机网络英文教材ppt.ppt

The Mobile Telephone System First-Generation Mobile Phones: Analog Voice Second-Generation Mobile Phones: Digital Voice Third-Generation Mobile Phones:Digital Voice and Data Advanced Mobile Phone System (a) Frequencies are not reused in adjacent cells. (b) To add more users, smaller cells can be used. Channel Categories The 832 channels are divided into four categories: Control (base to mobile) to manage the system Paging (base to mobile) to alert users to calls for them Access (bidirectional) for call setup and channel assignment Data (bidirectional) for voice, fax, or data D-AMPS Digital Advanced Mobile Phone System (a) A D-AMPS channel with three users. (b) A D-AMPS channel with six users. GSMGlobal System for Mobile Communications 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 C’s signal Third-Generation Mobile Phones:Digital Voice and Data Basic services an IMT-2000 network should provide High-quality voice transmission Messaging (replace e-mail, fax, SMS, chat, etc.) Multimedia (music, videos, films, TV, etc.) Internet access (web surfing, w/multimedia.) Cable Television Community Antenna Television Internet over Cable Spectrum Allocation Cable Modems ADSL 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. * Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 20