Discrete multitone (DMT) is a method of separating a Digital Subscriber Line (DSL) signal so that the usable frequency range is separated into 256 frequency bands (or channels) of 4.3125 KHz each. DMT uses the fast Fourier transform (FFT) algorithm for modulation and demodulation. Dividing the frequency spectrum into multiple channels allows DMT to work better when AM radio transmitters are present. Within each channel, modulation uses quadratude amplitude modulation (QAM). By varying the number of bits per symbol within a channel, the modem can be rate-adaptive. Both G.DMT and G.Lite use DMT.
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Other modulation technologies for DSL are carrierless amplitude modulation (CAP) and multiple virtual line (MVL). However, DMT is the most widely used and appears to be becoming the industry standard.