using telephone and cable networks for data transmissions 01204325: data communication and computer...
TRANSCRIPT
Using Telephone and Cable Networks for Data
Transmissions
01204325: Data Communication and Computer Networks
Asst. Prof. Chaiporn Jaikaeo, [email protected]
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