TWO CONTROVERSIAL STANDARDS
CAP - Carierless Amplitude & Phase Modulation
In this technology the transmit and receive signals are modulated into two wide-frequency bands.
Advantages
- relatively less expensive than its competitor
- some companies are pursuing CAP in conjunction with DMT and therefore the benefits of CAP can be examined
Disadvantages
- could complicate ADSL by potentially fragmenting the market
- may delay the implementation of ADSL on a large scale as many companied will have to change over to CAP
DMT - Discrete Multitone Modulation
This technology uses digital signal processors to divide the signal into 255 subchannels.
Advantages
- sends a seperate signal down each channel preventing noise from disrupting the entire signal
- has been widely adopted by many companies in the industry
- ANSI (American National Standards Institute) has showed their support for DMT and tend to use a 'majority rule' approach to standardization
Disadvantages
- relatively more expensive to implement (i. e. a CAP based system may cost around $2000 whereas a DMT based system may run up tp $6000)
- there are many firm believers in the CAP standard and will refuse to accept the DMT standard
These two standardization issues have been an on-going debate between different companies. There are large investments at stake in this heated debate. Until a standard is set, companies will continue to pursue one or the other. In fact, there are many companies who are trying to win the battle by testing out both technologies.
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