9.1Using Wireline Networksfor Data TransmissionNetworking Fundamentals
9.2TELEPHONE NETWORKTELEPHONE NETWORKTelephone networks use circuit switching. TheTelephone networks use circuit switching. Thetelephone network had its beginnings in the latetelephone network had its beginnings in the late1800s. The entire network, which is referred to as the1800s. The entire network, which is referred to as theplain old telephone systemplain old telephone system ((POTSPOTS), was originally an), was originally ananalog system using analog signals to transmit voice.analog system using analog signals to transmit voice.
9.3DIAL-UP MODEMSDIAL-UP MODEMSTraditional telephone lines can carry frequenciesTraditional telephone lines can carry frequenciesbetween 300 and 3300 Hz, giving them a bandwidth ofbetween 300 and 3300 Hz, giving them a bandwidth of3000 Hz. All this range is used for transmitting voice,3000 Hz. All this range is used for transmitting voice,where a great deal of interference and distortion canwhere a great deal of interference and distortion canbe accepted without loss of intelligibility.be accepted without loss of intelligibility.
• Bit rate is the number of bits or data elements sent persecond. Baud rate is the number of signal elements persecond. Each signal element sends one piece ofinformation ie. Symbol, thus Symbol rate and Baud rateis the same.• In the analog transmission of digital data, the bit rate isequal to the baud rate times the number of bits or dataelements /symbol .9.4
9.5Telephone line bandwidthHence, Baud rate of most modems is 2400
9.6Modulation/demodulationModemstands for modulator/demodulator.
9.8The V.32 and V.32bis constellation and bandwidth
9.10DIGITAL SUBSCRIBER LINEDIGITAL SUBSCRIBER LINEAfter traditional modems reached their peakAfter traditional modems reached their peakdata rate, telephone companies developed anotherdata rate, telephone companies developed anothertechnology, DSL, to provide higher-speed access to thetechnology, DSL, to provide higher-speed access to theInternet.Internet. Digital subscriber lineDigital subscriber line ((DSLDSL) technology is) technology isone of the most promising for supporting high-speedone of the most promising for supporting high-speeddigital communication over the existing local loops.digital communication over the existing local loops.The set of technologies is often referred asThe set of technologies is often referred asxDSL.xDSL.
Internet over CableThe fixed telephone system.
9.12ADSL• ADSL is an asymmetric communicationtechnology designed for residential users; it isnot suitable for businesses.• It uses the existing local loops that canhandle bandwidths up to 1.1 MHz.• It uses an adaptive technology. Thesystem uses a data rate based on thecondition of the local loop line.
9.14Discrete multitone techniqueContrary to its name, while a DSL circuit provides digital service, it is actually not a digitalsignal. The underlying technology of transport across DSL facilities uses high-frequencysinusoidal carrier wave modulation, which is an analog signal transmission.
9.16ADSL modemADSL Modem – DSP set up to work as 250 QAM modems in parallel withappropriate center frequencies
9.17DSLAMDSLAM– Functions similar to the ADSL Modem; in addition, packetizes the datato be sent to the ISP.
DSL SystemA typical ADSL equipment configuration.
Digital Subscriber LinesBandwidth versus distanced over category 3UTP for DSL.
9.20CABLE TV NETWORKSCABLE TV NETWORKSTheThe cable TV networkcable TV network started as a video servicestarted as a video serviceprovider, but it has moved to the business of Internetprovider, but it has moved to the business of Internetaccess. We discuss how this network can be used toaccess. We discuss how this network can be used toprovide high-speed access to the Internet.provide high-speed access to the Internet.
9.21Traditional cable TV networkDue to a large No. of Amps, communication in thetraditional cable TV network is unidirectional.What is CATV?
9.24CABLE TV FOR DATA TRANSFERCABLE TV FOR DATA TRANSFERCable companies are now competing with telephoneCable companies are now competing with telephonecompanies for the residential customer who wantscompanies for the residential customer who wantshigh-speed data transfer.high-speed data transfer.
9.25Bandwidth• Downstream Video _ 54 – 550 MHz ie more than 80TV channels at 6 MHz/ch.• Downstream Data Band _ 550 – 750 MHz also at 6MHz/ch. Uses the 64-QAM modulation technique. Thetheoretical downstream data rate is 30 Mbps.• Upstream Data Band _ 5 – 42 MHz also at 6 MHz/ch.Uses the QPSK modulation technique, as lowerfrequencies more susceptible to noise. The theoreticalupstream data rate is 12 Mbps.Division of coaxial cable band by CATV