Carrierless Amplitude/Phase Modulation definition communications
(CAP) A design of Asymmetric Digital Subscriber Line transceiver
developed by Bell Labs
. CAP was the first ADSL design to be commercially deployed and, as of August 1996, was installed on more lines than any other.
CAP is a variation of Quadrature Amplitude Modulation
, the modulation used by most existing modems
in 1997. With CAP, the three channels (POTS
, downstream data and upstream data) are supported by splitting the frequency spectrum. Voice occupies the standard 0-4 Khz frequency band, followed by the upstream channel and the high-speed downstream channel.