CS 313 Introduction to Computer Networking Telecommunication DSL

CS 313 Introduction to Computer Networking & Telecommunication DSL and Cable Chi-Cheng Lin, Winona State University

Topics l Digital Subscriber Line l Cable l ADSL versus Cable 2

Digital Subscriber Lines l Bandwidth versus distanced over category 3 UTP for DSL. 3

Digital Subscriber Lines l Operation of ADSL using discrete multitone modulation (OFDM, actually) - Channels – 0: voice, 1 -5: not used, 6 -30 upstream, 31 -255 downstream - Each channel: QAM at the rate of 4000 baud, 0 -15 bits/symbol depending on SNR - Multiplexing: FDM? TDM? Both? None? 4

Digital Subscriber Lines l A typical ADSL equipment configuration. 5

Cable Television Community Antenna Television l Internet over Cable l Spectrum Allocation l Cable Modems l 6

Community Antenna Television l An early cable television system. 7

Internet over Cable l Cable television 8

Compared to Telephone System l The fixed telephone system. 9

Spectrum Allocation l Frequency allocation in a typical cable TV system used for Internet access 10

Cable Modems l Typical details of the upstream and downstream channels in North America. - Three lights on the cable modem when it’s on … - 6 -8 MHz channels 36 Mbps w/ QAM-64 27 Mbps w/ overhead subtracted - Multiplexing: FDM? TDM? Both? None? Anything else? 11

ADSL versus Cable l Discussions … q. Bandwidth capacity q. Availability q. Security q. Reliability 12