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 nonloaded 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 (ISI). 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 S/N 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 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.