6.2 Standards for Multirate SHDSL

ITU-T Recommendation G.991.2 (also referred to as G.shdsl) defines the interface specification for SHDSL transceivers. G.shdsl defines a multirate single-pair symmetric DSL transport using 16-level trellis coded PAM. The main body of Recommendation G.991.2 defines the interworking specification that is independent of any regional requirements. Annex A of G.991.2 defines requirements and objectives that are specific to North America; similarly, Annex B of G.991.2 defines requirements and objectives that are specific to the European community.

Japan does not use TC-PAM for SHDSL. Because the Japan network has an abundance of time compression multiplexed ISDN (TCM-ISDN), the line code chosen for SHDSL applications in the Japan access network is DMT as defined in Annex H of G.992.1.

G.shdsl defines symmetric data rates from 192 kb/s up to 2,312 kb/s in increments of 8 kb/s for transmission on a single wire pair. The same Recommendation also defines an option for operation on two wire pairs. This option may be used to either increase the reach by operating on two wire pairs at half the payload rate on each pair, or to simply double the capacity on a given link.

ETSI TM6 has developed ETSI TS 101 524 [2] that defines SDSL. This regional standard is the primary source of content to Annex B of G.991.2.

Committee T1 has defined T1.422 [4], which is a regional standard that points to the ITU-T Recommendation G.991.2, with specific reference to Annex A, which contains regional specific requirements for North America.

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