Multi-rate symmetric DSL (MSDSL or MDSL) is a
proprietary, non-standardized
symmetric digital subscriber line technology with a maximum distance of .
It is capable of multiple transfer rates, as set by the
Internet service provider, typically based on the service and/or price. Eight data rates are available, ranging from 160 kbit/s to 2.32 Mbit/s.
Technology
MSDSL uses either
2B1Q Two-binary, one-quaternary (2B1Q) is a line code used in the U interface of the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) and the high-bit-rate digital subscriber line (HDSL). 2B1Q is a four-level pulse-amplitude modulat ...
or
carrierless amplitude phase modulation Carrierless amplitude phase modulation (CAP) is a variant of quadrature amplitude modulation (QAM). Instead of modulating the amplitude of two carrier waves, CAP generates a QAM signal by combining two PAM signals filtered through two filters desig ...
(CAP) transmission with a capacity of up to 2.32 Mbit/s.
The bandwidth is generally split between a full
E-carrier E1 payload (2.048 Mbit/s), with the remaining bandwidth accommodating up to three voice channels or two
ISDN channels.
Additional bandwidth is used for management purposes. Transmission over the single pair requires
echo cancellation and adaptive equalizers in order to achieve the maximum range at a specific rate. For each user rate, the modem changes the 2B1Q or CAP transmission rate, employing different filters and equalizer settings. The modem's adaptive setting is determined during its initial use, and continues constantly during operation.
References
Digital subscriber line
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