الفهرس 
ADSL Standard ModelOnly 14 pages are availabe for public view
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Abstract
The public switched telephone network is a well developed
telecommunication network with a huge number of local loop lines.
These twisted wire pairs are used only to transmit analog speech
signal with bandwidth limited to 4 KHz only so, such resources are
not efficiently used. On the other side there is an enormous demand
on new services such as data, digital video and digital audio
transmission.
There is a lot of research work to make full use of huge cupper
network by extending the twisted wire pair bandwidth to few
megahertz according to the customer distance from the central office.
One of the promising systems to transmit wide band signals on plain
old telephone without disturbing the existing phone services is the
Asymmetrical Digital Subscriber Line (ADSL) modems.
Asymmetric Digital Subscriber Line (ADSL) is an access technology
intended to provide up to 8 Mbps downstream digital transmission
from the central office to customers and up to 640 kbps upstream
transmission over the existing non loaded copper loop plant. The
transfer characteristics of twisted pairs make high-speed data
transmission very difficult. Sharply increasing attenuation with the
increase of frequency makes the higher frequency band unavailable
for transmission and also gives very severe inter-symbol-interference
(lSI). In ADSL, instead of using conventional single carrier transmission the preferred approach is to employ discrete multitone
(DMT) transmission. The main idea of DMT is to change a high-rate
transmit data sequence into some frequency-division multiplexed low- rate data sequences. With narrow-band subchannels, DMT systems
can make much better use of the bandwidth where the available
bandwidth is divided into subbands of 4 KHz bandwidth each. Each
subband has its own carrier which is modulated with a variable data
stream according to its SIN ratio.
In this thesis, design, simulation and implementation of Asymmetric
Digital Subscriber Line (ADSL) modem is presented which can be
applied to different telephone networks. The ADSL modem is
modeled and simulated under the MATLAB version 7.3 (R2006b)
environments by which the simulation is achieved for both the
downstream and upstream directions of the modem. The ADSL
modem with a transmission throughput between 640 kbps and 6
Mbps operating over most of existing telephone subscriber loops has
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been implemented on TI TMS320C6713 DSP for consumer
multimedia applications. Except the Analog Front End, all the basic
building blocks of the ADSL modem functionalities are implemented
with DSP platform. We use Real-Time Data ’Exchange (RTDX) as a
way to debug and test our DSP designs.