Charting DMT bits per Bin data from xDSL routers

Charting the DMT bits per Bin/Tone returned from an xDSL routers DSL link status pages or a cisco show DSL int ATM# command.
Example data can be found at the bottom of the page.

Paste your DMT bits per tone data from the router below, and hit the button.

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DMT modulated ADSL sections up the available frequecies transmittable over the BT copper telephone network to enable more data to be transmitted asynchronously, each section (bin or tone) being 4.3125kHz wide and each centered on a multitple of 4.3125. The G.GMT ADSL1 standard (upto 8Mb) has 256 bins in total, of which only 255 are usable, these are split into 31 lower bins for the ADSL upstream data and 224 upper bins for the ADSL downstream data.

Bin numbering starts at 1 whilst Tone numbering starts at 0, the first bin, bin 1 (tone 0), is not used hence there being 255 usable bins, because many ADSL lines also carry a PSTN voice service which uses the second bin, with the following 4 bins being left unused to prevent interferrance between the two services, there are only 25 bins left for the Upstream ADSL data. Between the 25 upstream and 224 downstream bins, around bins 31 to 32, many DSLAM manufactures may also leave a few bins unused to help prevent interferrance between the upstream and downstream frequencies. There are also usually a few other bins not used for data, there is a pilot tone at downstream bin 65 and DSLAM manuafactures may leave some other bins unused.

For ADSL1 each bin can have between 2 and 15 bits encoded into it, there must be at least two bits encoded for the bin to be usable, the better the phone line, higher quality, fewer faults and of shorter length, the more bits that will be able to be encoded per bin and hence the more data, faster download speeds, the circuit can handle. For a bit to be encoded reliably within a bin there needs to be 3dB of SNR and because there needs to be at least two bits encoded per bin a circuit needs at least 6dB of SNR in a bins frequency range to reliable transfer data. Less than this and packet erroring will occur, data will need to be resent and eventually when error connection cannot cope any longer at some SNR less than 6dB the circuit will loose sync.

ADSL2+ (upto 24Mb) has 512 bins in total, double ADSL1, the only change with regard to the bins is that the downstream bin range doubles, still starting at bin 33. Also the downstream pilot tone does not have to be at bin 65 on ADSL2+ and can be placed where ever the signal is strongest during synchronisation.
ADSL2+ AnnexM shifts a portion of the lower downstream bins across and designates them as upstream bins, thereby enabling greater upload sync rate however with a small reduction in download sync rate.