ANSI T1.413
ADSL (T1.413) allows the provision of voice band services including plain old telephone service
(POTS) and data services up to 56 kbit/s, and a variety of digital channels.
ADSL 2
ITU G.992.3 is 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. ADSL2 uses the same bandwidth as ADSL but achieves higher throughput via improved
modulation techniques.
Annex L
Increases the range of the DSL service enabling the link to work at a distance of 7 kilometres (23,000
ft)
ADSL 2+
ITU G.992.5 is an ITU standard, also referred to as ADSL2+ (or ADSL2Plus), is notable for its
maximum theoretical download speed of 24 Mbit/s. ADSL2+ allows port bonding, also known as
G.998.x or G.Bond
Annex M
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.
Bit Swapping
Bit Swapping is a way of keeping the line more stable by constantly monitoring the frequency bins
(carriers) in use and reusing them if possible.
The bit swap process enables the connection to either change the number of bits assigned to each
individual sub channel or if necessary increase/decrease the power level (gain) whilst still maintaining
the data flow.
With bit swapping the Case 6401 Rugged router can swap the bits around and redistribute the bits to
other channels by using any spare SNR at other frequencies or increasing the gain.
Without bit-swapping, your connection would lose sync every time there was a noise burst that meant
any sub-channel wasn't able to transmit its allocated number of bits.
SRA - Seamless Rate Adaption
Seamless Rate Adaption is a method which dynamically adapts your line rate /sync speed on the fly
depending upon the current condition of your line without having to perform a full retrain or resync.
With SRA, line conditions are constantly monitored and any increases/decreases in SNR result in an
increase/decrease in the line connection speed without having to go through the initialisation process.
Line speed will always be at the highest possible rate depending upon your set target SNR, which is
particularly useful if you have had a low synch and line conditions later improve, as SRA will ensure
that your line speed will increase in line with the better conditions.
While the Case Communications 6401 Rugged Router supports SRA its necessary for the ISP’s
DSLAM to support SRA for it to be used. By default this will not be enabled.
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