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DSL technologies
	Standard
ADSL	ANSI T1.413 Issue 2 ITU G.992.1 (G.DMT) ITU G.992.2 (G.Lite)
ADSL2	ITU G.992.3/4 ITU G.992.3 Annex J ITU G.992.3 Annex L
ADSL2+	ITU G.992.5 ITU G.992.5 Annex M
HDSL	ITU G.991.1
HDSL2
IDSL
MSDSL
PDSL
RADSL
SDSL
SHDSL	ITU G.991.2
UDSL
VDSL	ITU G.993.1
VDSL2	ITU G.993.2

Rate-adaptive DSL (RADSL) is a variation of ADSL technology. With RADSL the modem adjusts the upstream speed of the connection (in an upstream/downstream speed tradeoff) depending upon the length and quality of the line between the DCE (Telephone Exchange) or DSLAM and the DTE (Modem), in an attempt to maintain a certain downstream speed.

When the modem connects using RADSL the upstream bandwidth is adjusted to create a greater frequency band for the downstream traffic. Using this technique the line is more tolerant of errors caused by noise and signal loss.

As the frequency is adjusted, the upstream bandwidth may be markedly decreased if there is a large amount of line noise or signal degradation - this may reduce the upstream bit rate to as little as 64 kbit/s - the same speed as a single ISDN B channel.

[edit] See also

• Digital subscriber line (DSL)
• Asymmetric Digital Subscriber Line (ADSL)
• Single-Pair High-speed Digital Subscriber Line (SHDSL)