DMT Bits Per Bin detailed description for WIC-1ADSL 1

[JeffyB]

Could some please explain what the "DMT Bits Per Bin" values represent towards the end of this show command? I have a partial understanding, something to do with the bandwidth upload/download speeds and QoS of line/ADSL splitter, but could do with a better understanding.

This is the second time of posting as I received no replys the first post. Any help would be greatly appreciated.

The router is a Cisco 1760 with a WIC-1ADSL.

Many thanks

#sh dsl int atm0/0
Alcatel 20150 chipset information
ATU-R (DS) ATU-C (US)
Modem Status: Showtime (DMTDSL_SHOWTIME)
DSL Mode: ITU G.992.1 (G.DMT)
ITU STD NUM: 0x01 0x1
Vendor ID: 'ALCB' 'TSTC'
Vendor Specific: 0x0000 0x0000
Vendor Country: 0x00 0xB5
Capacity Used: 16% 37%
Noise Margin: 35.5 dB 26.0 dB
Output Power: 20.0 dBm 10.5 dBm
Attenuation: 27.0 dB 14.0 dB
Defect Status: None None
Last Fail Code: None
Selftest Result: 0x00
Subfunction: 0x15
Interrupts: 1347 (0 spurious)
PHY Access Err: 0
Activations: 3
Init FW: embedded
Operation FW: embedded
SW Version: 3.8131
FW Version: 0x1A04

Interleave Fast Interleave Fast
Speed (kbps): 0 1152 0 288
Reed-Solomon EC: 0 0 0 0
CRC Errors: 0 0 0 0
Header Errors: 0 0 0 0
Bit Errors: 0 0
BER Valid sec: 0 0
BER Invalid sec: 0 0

DMT Bits Per Bin
00: 0 0 0 0 0 0 0 0 0 2 3 4 5 6 6 5
10: 5 6 6 6 6 6 5 5 4 4 3 3 3 2 0 0
20: 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2
30: 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3
40: 0 2 2 2 2 2 3 3 3 3 3 2 3 3 3 3
50: 3 3 3 3 3 3 3 3 3 3 3 2 3 3 3 3
60: 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
70: 3 3 3 2 2 3 2 2 2 2 2 2 2 2 2 2
80: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
90: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
A0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
B0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
C0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
D0: 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
F0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0


DSL: Training log buffer capability is not enabled

 

[Warcorp]

My Apologies if this seems over explanatory but there are some basics to ADSL that need to be draw out before explaining the Bits per Bin specifics.

ADSL operates in the frequency spectrum that is above
the POTS frequency band of 0 to 4KHz. The ADSL spectrum is
above the POTS frequencies, the ADSL spectrum is divided into two
major bands- the upstream band and the downstream band.
Upstream frequencies are used to carry data from the ADSL modem
at the customer premise to the DSLAM. Downstream bands carry
data from the DSLAM to the ADSL modem. The downstream
spectrum is much wider than the upstream, giving more capacity
downstream compared to upstream- thus the “Asymmetric” in
Asymmetric Digital Subscriber Line. ADSL subdivides its spectrum into frequency sub-channels called
bins. Each orthogonal sub-channel is spaced at 4.3125KHz. The bins
are numbered starting at 1 which is the frequency range reserved for
POTS. Bins 2 through 5 are a guard band that separates POTS and
ADSL. Bins 6 through 32 are used for upstream transmission. For
ADSL, downstream data uses bins 33 through 255, while for ADSL2+
the downstream spectrum extends to bin 512.Each of these bins can be thought of as separate and independent
communication channels. In other words, one can view an ADSL
downstream link as 223 (255-32) individual modems. User data is
transmitted by modulating each of the bin frequencies with a
technique known as quadrature amplitude modulation (QAM). The
process is referred to as “bin loading” reflecting the fact that each of
bins is carrying a certain number of payload data bits. In theory, each
bin is capable of carrying up to 15 bits of information.
Since each bin operates independently from all other bins, the
number of bits that are loaded in each bin can vary. ADSL link data
rates are computed by aggregating the capacity in each bin over the
frame rate of the ADSL link.

So to look at your BpB table:

DMT Bits Per Bin
00: [0](pots) [0 0 0 0](guard) [0 0 0 0 2 3 4 5 6 6 5
10: 5 6 6 6 6 6 5 5 4 4 3 3 3 2 0 0](Upstream)
20: [0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2
30: 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3
40: 0 2 2 2 2 2 3 3 3 3 3 2 3 3 3 3
50: 3 3 3 3 3 3 3 3 3 3 3 2 3 3 3 3
60: 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
70: 3 3 3 2 2 3 2 2 2 2 2 2 2 2 2 2
80: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
90: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
A0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
B0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
C0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
D0: 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
F0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0](downstream)

So if we aggregate the upstream (adding up all the bits)
=90 * 4000(hz) = 360,000 or 360kbits.
and if we aggregate the downstream
=324 * 4000(hz) = 1,296,200 or 1.296mbits.

Keep in mind that this number will change as the noise levels change on the line and
that the BpB map may not be exactly the same each time you look at it.