Will - >>Do you have more?<< Yea! Try these >>
Initially, the DMT standard was developed to make 6 Mb/s bandwidth available up to 12,000 feet, also known as the CSA distance. The ADSL Forum estimates that up to 60% of U.S. phone lines are within the CSA distance. DMT rate adaptation enables data transmission at greater than the CSA requirement and has been measured at lengths in excess of 18,000 feet. By considering lines beyond 12,000 feet, 80% or more of all customers can be served.
In operation, the 256 tones are transmitted from the ADSL terminal unit at the CO (ATU-C) to an ADSL remote terminal unit (ATU-R) at the
customer premises. The ATU-R measures and continually updates the
quality of each of the tones received and then decides whether a tone
has sufficient quality to be used for further transmission. Depending on the quality, the ATU-R instructs the ATU-C as to how much data this tone should carry relative to the other tones that are used. This procedure maximizes performance and minimizes error probability at any data specific rate.
I was wrong to pass over the advantages of DMT, by saying most of us know already know the Advantages.
Maybe they don't, here are a few you may or may not know about.
* Higher performance. The DMT modem permits the maximum data rate
available on any given line depending on distance extremes or noisy
environments.
* Tariffed service. DMT-based modems enable service that can be tariffed with a minimum committed information rate (CIR). The CIR can be decided by the service provider on the basis of market needs and loop demographics.
* Automatic performance reports. A DMT-based modem provides not only
information rates to a simple network management protocol system but
also complete readings of line information and status. This information is essential in network maintenance for a higher quality of service.
* Automatic evaluation of line capacity. Being able to evaluate and
determine line capacity automatically--without any service provider
input or intervention--is crucial because it decreases maintenance
requirements and network operating expenses. For example, the DMT modem might alert the LEC that a line is water-logged, thus allowing LECs to take a more proactive approach to troubleshooting. Such automatic evaluations also can aid in averting problems, thereby eliminating potential service lapses.
* Security. DMT-based ADSL modems engage in a substantial amount of
handshaking during operation. As a result, it is extremely difficult for the signal to be received by any connection other than the targeted remote unit. The transmitted signal looks like unintelligible noise
without the bit-loading key, which is only applicable to the two end
modems.
*DMT also offers a maximum spectral mask that the telephone company can program (or it can use the default specified by Bellcore in the T1.413 standard) to avoid interference with other users. DMT can then adapt within this constraint, again assuring the maximum performance for a given line's characteristics.
Source: John M. Cioffi
Hope the above helped all to better understand why some of us are Amatiphiles.
JW@KSC |
