using telephone and cable networks for data transmissions 01204325: data communication and computer...

Using Telephone and Cable Networks for Data

Transmissions

01204325: Data Communication and Computer Networks

Asst. Prof. Chaiporn Jaikaeo, Ph.D.chaiporn.j@ku.ac.th

http://www.cpe.ku.ac.th/~cpjComputer Engineering Department

Kasetsart University, Bangkok, ThailandAdapted from lecture slides by Behrouz A. Forouzan© The McGraw-Hill Companies, Inc. All rights reserved

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Outline Telephone lines Dial-up modems Digital Subscriber Line (DSL) Cable TV networks

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Telephone Lines 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 A great deal of interference and

distortion can be accepted without loss of intelligibility

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Telephone Line Bandwidth

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Dial-Up Modems

Modemstands for modulator/demodulator.

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V.32 and V.32bis

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56K Modems

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Digital Subscriber Line (DSL) Provides higher-speed access to the

Internet Supports high-speed digital

communication over the existing local loops

The existing local loops can handle bandwidths up to 1.1 MHz.

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ADSL ADSL – Asymmetric Digital

Subscriber Line Downstream bit rate > upstream bit rate Designed for residential users Unsuitable for businesses

ADSL operates on existing local loops Local loops can handle up to 1.1 MHz of

bandwidth The distance limit is ~18,000 feet The system uses a data rate based on

the condition of the local loop line

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Bandwidth Division in ADSL

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Discrete Multi-Tone Modulation Or DMT, based on OFDM (Orthogonal

Frequency-Division Multiplexing) technique

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Allocation and modulation of each channel are determined adaptively

4 kHz

Bandwidth Division

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Voice – Channel 0 Idle – Channels 1-5 Upstream – Channels 6-30

24 data channels, 1 control channel 1.44 Mbps (max) upstream bit rate Actual bit rate: 64 Kbps to 1 Mbps

Downstream – Channels 31-255 224 data channels, 1 control channel 13.4 Mbps (max) downstream bit rate Actual bit rate: 500 Kbps to 8 Mbps

Bandwidth Division

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ADSL Customer Residence

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DSL Access Multiplexer Or DSLAM

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Other DSL Technologies HDSL – High-bit-rate DSL VDSL – Very-high-bit-rate DSL SDSL – Symmetric DSL ADSL2 ADSL2+

See also http://en.wikipedia.org/wiki/

Digital_subscriber_line

Source: AWARE. ADSL2 and ADSL2+ The new ADSL standard.

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OFDM Orthogonal Frequency-Division

Multiplexing Widely used in wideband digital

communications Digital TV ADSL Powerline communications Wireless networks: Wi-Fi, WiMAX 4G mobile communications

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OFDM Concept Sub-carriers are orthogonal to each

other No cross-talk; guard bands not

necessary

Source: http://connectedplanetonline.com

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200 300 400 500 600 700 800

Orthogonality in OFDM

Frequency (Hz)

t

20 ms

Modulated @500 Hz

tModulated @550 Hz

tModulated @600 Hz

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OFDM ImplementationTransmitter

Receiver

Source: Wikipedia

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Cable TV Networks Started as a video service provider,

then moved to the business of Internet access

Communication is simplex

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Hybrid Fiber-Coaxial Network Or HFC Bidirectional communication is

achieved

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Data Transfer over CATV Standard: DOCSIS (Data Over Cable

Service Interface Specification) Division of coaxial cable band by Cable

TV

Theoretical downstream data rate is 30 Mbps

Theoretical upstream data rate is 12 Mbps

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Cable Modem

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Cable Modem Transmission System Or CMTS

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Fiber To The X Optical broadband network architectures

Fiber-to-the-node

Source: Wikipedia

Fiber-to-the-curb

Fiber-to-the-building

Fiber-to-the-home