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How low can the Margin go???

Posts: 382
Thanks: 1
Registered: 01-08-2007

How low can the Margin go???

Hi All
Having been away over Xmas with the router left as such a short break.  I looked at Routerstats ealier late this afternoon and noticed the margin had dropped to had hovered around 3 for a good while but I did see it dip to 1.9  !!!!
However, here are the stats for you can see the total uptimes IMO are very nice for such figures.
Noise Margin:     2.0   dB
Connection Rate:  3913  Kbps
Line Attenuation: 55.0  dB
Power:            0.0   dBm
Max Rate:         4620  Kbps

SuperFrames:      98081078
SF (CRC) Errors:  12017
Reed Solomon:     2178383858
RS Corrected:     460798675
RS Un-Corrected:  175906
HEC:              10301
Errored Seconds:  6876
Severe ES:        28
Interleave Depth: 32
Bitswaps:         494591

Noise Margin:     6.6   dB
Connection Rate:  820   Kbps
Line Attenuation: 28.4  dB
Power:            12.9  dBm
Max Rate:         840   Kbps

SuperFrames:      93425601
SF (CRC) Errors:  0
Reed Solomon:     1963158
RS Corrected:     3
RS Un-Corrected:  0
HEC:              0
Errored Seconds:  0
Severe ES:        0
Interleave Depth: 4
Bitswaps:         23203
Total uptimes
Total Uptimes (From SF counts):
WAN:   19 days, 07:13:18
LAN:   19 days, 07:13:18

CRC:  12021
LOS:  1
LOF:  0
ES :  6879

Was just about to post and the Margin now says 1.9db
Just checked BT speedtest:-
Speed 3.31Mbps
IP 3.45Mbps
UL speed 0.7Mbps
UL IP 0.83Mbps
PlusNet IP 3.5Mbps
All as as has been since the IP mismatch was sorted out early'ish into my current sync of 3913
Rising Star
Posts: 811
Thanks: 10
Registered: 07-02-2012

Re: How low can the Margin go???

It often depends on the router, and also of course on the normal night-time dip amount.  Some routers will even hold connection at -1dB.
What has probably happened over time is that bit-swapping has occurred to the level that certain frequencies/bins have been ruled out by the router for effective use.
As the other bins' spare space, (their margin) is swallowed up by the bit allocation swapped in to maintain the sync speed, the average noise margin across them all, which is we see at this level, has to fall. Once it does that they don't come back into service until a router re-sync.
And if there isn't sufficient spare capacity in any bins to do any more bit-swapping, that's when you get a disconnection.