MSIS 4523 Ch9.Using Telephone and Cable NWs

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Data Communications SystemsCh 9: Using Telephone and Cable

Networks for Data Transmission

JinKyu Lee, [email protected]

Include the course code (MSIS4523) in every email subject!!


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Topics

Telephone NetworksConcepts

Local loop, Trunks, Switching office, LEC, IXC, LATA, PoP

SignalingBandwidth Utilization

Dial-up ModemDigital Subscriber Line (DSL)

Cable TV NetworksHybrid Fiber-Coaxial (HFC) Network


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TELEPHONE NETWORK

Telephone networks use circuit switching. The telephone network had its beginnings in the late1800s. The entire network, which is referred to as

the Plain Old Telephone System (POTS), was originally an analog system using analog signals to transmit voice.


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Major Components

Local loop: Twisted pair that connects thesubscriber to the end officeFirst three digits of the phone numberidentify that office; next four digitsidentify the local loop number

Trunks: Transmission media betweenoffices (fiber, satellite)

Switching office: Houses the switches likethose introduced in Chapter 8


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A telephone system


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Switching offices in a LATA


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Major Concepts (US Market)

Local Access Transport Area (LATA)One or more Local Exchange Carriers (LECs) provideservices in each LATAIncumbent LEC: the original LEC that started toprovide service in a LATA (used to hold a monopolyuntil 1996)Competitive LEC: new carriers.

Inter-eXchange Carriers (IXCs) (long distancecompanies) provide connection between LATAs

Any IXC that want to provide services inside a LATAmust have a Point of Presence (POP) in the LATAThe local exchange carrier must provide everysubscriber with all POPs inside the LATA


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Signaling

Modern phone systems have in-bandsignalingOne network transfers data, another sets up the calland provide control information to the endpointsTwo networks may use separate channels, but theyare part of the same physical link

The protocol for signaling is SignalingSystem Seven (SS7)


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DIAL-UP MODEMS

Traditional telephone lines can carry frequencies between 300 and 3300 Hz, giving them a bandwidth of 3000 Hz. All this range is used for transmitting voice,where a great deal of interference and distortion can

be accepted without loss of intelligibility.

Covered in Chapter 6 Bandwidth Utilization


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Modulation/demodulation


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Uploading and downloading in 56K modems


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DIGITAL SUBSCRIBER LINE

After traditional modems reached their peak data rate, telephone companies developed another technology, DSL, to provide higher-speed access to

the Internet. Digital subscriber line (DSL) technology is one of the most promising for supporting high-speed digital communication over the existing local loops.

Covered in Chapter 6 Bandwidth Utilization


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DSL

Local loop twisted pair can handle up to 1.1MHz, but voice only requires 4kHzPhone companies were filtering the higherfrequencies, by removing the filters they hadaccess to more frequenciesAsymmetric DSL was one of the firsttechnologies in this set

Use Discrete Multi-tone (DMT) Technique for modulationCombination of QAM (within channel) and FDM (for the 256channels)

Bandwidth of 1.104 MHz divided into 256 channelsAdaptive; tests the conditions and bandwidth availability of thelocal loop before settling on a data rate


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Bandwidth division in ADSL


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Discrete multitone technique


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ADSL modem


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DSLAM

Telephone company uses a DSL access multiplexerto multiplex the data, packetize it, and send it to the ISPs


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Other Forms of DSL

ADSL Lite: Splitting between low pass and high pass isdone at the telephone companyplugs into your standard phone jackHigh-bit-rate DSL (HDSL) uses two twisted pair toachieve full duplex transmissionSymmetric DSL: Achieves a higher bit rate like HDSL,but only uses one pairVery-high-bit-rate (VDSL): Can use fiber, coax, or TP toachieve high bit rates


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Summary of DSL technologies


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CABLE TV NETWORKS

The cable TV network started as a video service provider, but it has moved to the business of Internet access. Cable companies are now competing with telephone companies for the residential customer

who wants high-speed data transfer. we discuss how this network can be used to provide high-speed access to the Internet.


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Traditional cable TV network

Unidirectional


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Hybrid fiber-coaxial (HFC) network

Bi-Directional


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Division of coaxial cable band by CATV

Downstream data are modulated using the 64-QAMmodulation technique. The theoretical downstream

data capacity is 30 Mbps. Upstream data aremodulated using the QPSK modulation technique.

The theoretical upstream data rate is 12 Mbps.


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How they do it

Users need a cable modemmore of afilter than a modem to split the signalsbetween video and voiceThe cable companies install a cablemodem transmission system (CMTS) inthe distribution hubs

Receives data from the Internet and passes itto the combiner

Combines it with video signals for transmission

Pushed to subscriberReceives data from subscriber and passes itto the Internet


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Cable modem (CM)


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Cable modem transmission system (CMTS)

MSIS 4523 Ch9.Using Telephone and Cable NWs

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