ZyXEL Communications VMG3925-B10A User Manual page 77

Table 13 Network Setting > Broadband > Advanced (continued)
LABEL DESCRIPTION
Bitswap Select Enable to allow the VMG to adapt to line changes when you are using G.dmt.
Bit-swapping is a way of keeping the line more stable by constantly monitoring and
redistributing bits between channels.
SRA Enable or disable Seamless Rate Adaption (SRA). Select Enable to have the VMG
automatically adjust the connection's data rate according to line conditions without
interrupting service.
ADSL
Modulation
PTM over ADSL Select Enable to use PTM over ADSL. Since PTM has less overhead than ATM, some ISPs
use this for better performance.
G.Dmt ITU G.992.1 (better known as G.dmt) is an ITU standard for ADSL using discrete multitone
modulation. 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.
G.lite ITU G.992.2 (better known as G.lite) is an ITU standard for ADSL using discrete multitone
modulation. G.lite does not strictly require the use of DSL filters, but like all variants of
ADSL generally functions better with splitters.
T1.413 ANSI T1.413 is a technical standard that defines the requirements for the single asymmetric
digital subscriber line (ADSL) for the interface between the telecommunications network and
the customer installation in terms of their interaction and electrical characteristics.
ADSL2 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).
AnnexL Annex L is an optional specification in the ITU-T ADSL2 recommendation G.992.3 titled
Specific requirements for a Reach Extended ADSL2 (READSL2) system operating in the
frequency band above POTS, therefore it is often referred to as Reach Extended ADSL2 or
READSL2.The main difference between this specification and commonly deployed Annex A is
the maximum distance that can be used. The power of the lower frequencies used for
transmitting data is boosted up to increase the reach of this signal up to 7 kilometers
(23,000 ft).
ADSL2+ ADSL2+ extends the capability of basic ADSL by doubling the number of downstream
channels. The data rates can be as high as 24 Mbit/s downstream and up to 1.4 Mbit/s
upstream depending on the distance from the DSLAM to the customer's premises.
AnnexM Annex M is an optional specification in ITU-T recommendations G.992.3 (ADSL2) and
G.992.5 (ADSL2+), also referred to as ADSL2 M and ADSL2+ M. This specification extends
the capability of commonly deployed Annex A by more than doubling the number of
upstream bits. The data rates can be as high as 12 or 24 Mbit/s downstream and 3 Mbit/s
upstream depending on the distance from the DSLAM to the customer's premises.
VDSL Profile VDSL2 profiles differ in the width of the frequency band used to transmit the broadband
signal. Profiles that use a wider frequency band can deliver higher maximum speeds.
8a, 8b, 8c, 8d, The G.993.2 VDSL standard defines a wide range of profiles that can be used in different
12a, 12b, 17a, VDSL deployment settings, such as in a central office, a street cabinet or a building.
US0
The VMG must comply with at least one profile specified in G.993.2. but compliance with
more than one profile is allowed.
Apply Click Apply to save your changes back to the VMG.
Cancel Click Cancel to return to the previous configuration.
Chapter 6 Broadband
VMG3925-B10A User's Guide
77