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[2] [4] [5] For ADSL deployments CAP was the de facto standard up until 1996, deployed in 90 percent [citation needed] of ADSL installs. The standardized variants of ADSL, ANSI T1.413 Issue 2 and G.dmt , as well as the successors ADSL2 , ADSL2+ , VDSL2 , and G.fast , do not specify CAP, but rather discrete multi-tone (DMT) modulation.
In telecommunications, ITU-T G.992.1 (better known as G.dmt) is an ITU standard for ADSL using discrete multitone modulation (DMT). G.dmt full-rate ADSL expands the usable bandwidth of existing copper telephone lines, delivering high-speed data communications at rates up to 8 Mbit/s downstream and 1.3 Mbit/s upstream.
Tones are spaced apart by 4.3125kHz. In the Annex A, L and M frequency standards, POTS (analog PSTN voice) occupies (what would be) tones 0-3, tones 4-7 are reserved for a ‘guard band’, and the upstream DSL transmission band uses tones 8-31 in Annex A and L, or 8-56 in Annex M. In Annex B, ISDN occupies tones 0-31, DSL upstream uses tones ...
It defines the minimum requirements for satisfactory performance of ADSL systems using the Discrete Multi-Tone (DMT) line code. DMT divides the useful bandwidth of the standard two wire copper medium used in the public switched telephone network (PSTN), which is 0 to 1104 kHz, into 256 separate 4.3125 kHz wide frequency bands called sub-carriers.
ITU G.992.3 is an ITU (International Telecommunication Union) standard, also referred to as ADSL2 or G.dmt.bis.It optionally extends the capability of basic ADSL in data rates to 12 Mbit/s downstream and, depending on Annex version, up to 3.5 Mbit/s upstream (with a mandatory capability of ADSL2 transceivers of 8 Mbit/s downstream and 800 kbit/s upstream). [1]
[1] [5] RADSL is not interoperable with discrete multi-tone (DMT) modulation variants of ADSL, standardized in ANSI T1.413 Issue 2 and G.dmt (G.992.1). [5] Upstream and downstream are frequency-division duplexed , the upstream and downstream transmit PSD masks are identical to those in ANSI T1.413.
CAP was the de facto standard for ADSL deployments up until 1996, deployed in 90 percent of ADSL installations at the time. However, DMT was chosen for the first ITU-T ADSL standards, G.992.1 and G.992.2 (also called G.dmt and G.lite respectively).
G.992.5 (also referred to as ADSL2+, G.dmt.bis+, and G.adslplus) [1] is an ITU-T standard for asymmetric digital subscriber line (ADSL) broadband Internet access. The standard has a maximum theoretical downstream sync speed of 24 megabits per second (Mbit/s). Utilizing G.992.5 Annex M upstream sync speeds of 3.3 Mbit/s can be achieved.