This situation has occurred
due to asymmetric channel characteristics as well as significant reach limitations, especially
noticeable in the case of DSL technology, where deployment price grows almost
exponentially as distance increases from the central office of the ISP.
The most widely deployed ???broadband??? solutions today are digital subscriber line
(DSL) and cable modem (CM) networks. While they certainly represent a significant
step forward from what used to be 56 kbps dial-up connections, they are still unable to
provide sufficient bandwidth for such emerging digital services as VoD, online gaming,
or multichannel video conferencing.
DSL technology uses the same copper twisted-pair cable as telephone lines and
requires a special DSL modem located at the customer premises, as well as a digital
subscriber line access multiplexer (DSLAM) terminating the given subscriber line in the
CO of the ISP. DSL technology is mainly all about efficient spectrum division, providing
a means of subdividing the available line spectrum into a number of transmission windows
(one of which, located in the lower frequency region, is reserved for the standard
telephone channel being used by the plain-old telephone service (POTS) equipment).
Pages:
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443