DSL TECHNOLOGY

DSL TECHNOLOGY

INTRODUCTION:

1. Internet

Today is the era of the computer. Every one is having a PC at his/her home or office and he/she can interact with anybody in the world with the excellent facility provided to the pc called as Internet. Due to Internet, world has come closer. Everybody thinks of the Internet as some magnificent, powerful tool for communication among many corners of the world. Just see the miracle!! A man sitting at home can watch anything on his PC within just a few seconds of time. Internet is a very good facility which uses telephone lines laid down between a telephone set of a subscriber and telephone office nearby and using the telephone network, makes him able to communicate with the entire world.
But every coin has two faces. Can anybody of you think of the disadvantages of the Internet facility provided by ISP or NSP? Obviously one is that nobody can use his telephone set when the Internet is on. Also the main practical problem occurs while downloading any document is the huge time. Time factor is also important today. To overcome these problems new technologies are being developed, one of which is DSL technology, which is a topic of discussion

2. DSL (Digital Subscriber Line)

Digital Subscriber Line technology provides transport of high-bit-rate digital information over telephone subscriber lines. Telephone lines, whose heritage dates back to Alexander Graham Bell’s invention of the telephone in 1875, can now transport data at millions of bits per second. This is accomplished via sophisticated digital transmission techniques, which compensate for the many transmission impairments common to telephone lines. The digital transmission techniques involve complex algorithms that
have recently become practical due to the enormous processing power of digital signal processors based on very –large-scale (VLSI) circuits. Marketing alchemists claim that DSLs turn copper into gold.
DSL technology has added a new twist to the utility of telephone lines. Telephone lines, which were constructed to carry a single voice signal with a 3.4 kHz bandwidth channel, can now convey nearly 100 digitally compressed voice signals, or a video signal with quality similar to broadcast television. High-speed digital transmission via telephone lines requires advanced signal processing to overcome transmission impairments due to signal attenuation, cross talk noise from the signals present on other wires in the same cable, signal reflections, radio frequency noise and impulse noise.
The twisted-wire-pair infrastructure connects to virtually every home and workplace in the world, but DSLs have their limitations. Approximately 15% of the telephone lines in the world will require upgrade activity to permit high-speed DSL operation. A corrective measure for long loops includes installation of mid-span repeaters, installation of fiber-remoted multiplexers, and removal of load coils.


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