OK well i'll see how the line goes stability wise.
It dropped from circa 6dB to just above 4dB noise margin overnight @ 10000kbps sync so a 10735kbps sync and it might see 3dB tonight.

As my post above i had ~5000 FEC's within 90 minutes during the evening so over 24 hours thats 90000 FEC's although i'd expect less due to the lower daytime noise.

Well i'm hovering at mid 3dB's down from 6.5dB at the resync at 11.15am this morning.

adsl: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 8000
Max: Upstream rate = 960 Kbps, Downstream rate = 11312 Kbps
Path: 0, Upstream rate = 960 Kbps, Downstream rate = 10763 Kbps

Link Power State: L0
Mode: ADSL2+
TPS-TC: ATM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 3.6 12.3
Attn(dB): 37.5 20.2
Pwr(dBm): 0.0 13.1
ADSL2 framing
MSGc: 53 10
B: 122 44
M: 2 4
T: 3 3
R: 8 6
S: 0.7293 5.9520
L: 2786 250
D: 64 4
Counters
SF: 1896406 774206
SFErr: 191 181
RS: 167831936 3384029
RSCorr: 306567 673
RSUnCorr: 4578 0

HEC: 179 196
OCD: 0 0
LCD: 0 0
Total Cells: 776858336 69140802
Data Cells: 5211682 716249
Drop Cells: 0
Bit Errors: 0 25703

ES: 119 82
SES: 0 0
UAS: 30 30
AS: 30601

INP: 0.73 0.38
PER: 16.13 17.85
delay: 11.66 5.95
OR: 29.24 7.16

Bitswap: 3993 15

Since Link time = 8 hours 30 min 1 sec
FEC: 306567 673
CRC: 191 181
ES: 119 82
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0

OK the FEC's are up compared to what i thought i might see. ES averaging 1 every 4-5mins.

Sorry, I can't accept that.

Which bit?

I'm assuming that you're taking issue with the statement that FEC is present regardless of whether you're using fast or interleaved path.

I must admit that the standard is impenetrable as far as I'm concerned but look at this summary, especially figure 8 which shows the superframe structure together with FEC overhead in the fast path.

Also there's a better explanation of interleaving, with diagrams over on kitz

FEC itself would not introduce latency on the transmit side - you can do reed-solomon effectively on the fly accepting the first byte byte and starting transmission/computing the error correction block simultaneously, on the receive side it's no worse than adding a CRC interms of latency. Interleaving does, because you have to accept a bunch of data before transmitting it all.

As to practical implementations, I couldn't say, so how the BE setup works exactly I don't know - I do note that the kitz page says "interleaving and error correction are turned on together" so it's possible that I interpreted the FEC bit of the superframe as mandatory but, in fact, it's optional.

I probably should have mentioned that the interleaved path as more error correction, though (again as far as I understood).

Anyone know for sure?

Edited by mr_bean (Wed 18-Jan-12 20:48:04)

In reply to a post by mr_bean:

Also there's a better explanation of interleaving, with diagrams over on kitz

See the bottom of this page, which hasn't been altered since the site was created in 2009.

Well it did sit between 3dB and 4dB overnight (dipped to just under 3dB for a short period) but router held on so that was a 3.5dB drop....is this kinda normal on ADSL2+? My ADSL1 swing was 1dB.

One oddity is that the noise margin didnt rise to ~6dB once it was daytime which is what it was at the day before when it had been resynced, instead it kept around 5dB or a touch over.....odd?

Also couldnt resist so got XILO to reduce my target noise margin to 9dB and fastpath from their default of 12dB and interleaved (i had it tweaked down to 6dB previous using the routers SNR tweaking capability). Currently down to 6.5dB from 9dB......will see how it goes overnight!

Those changes are normal.

A possible reason it didn't rise as high next day is that some frequencies had been eliminated from the "usable" spectrum, so when the noise fell they didn't come back into use. Which is fine if the noise the next night affects the same frequencies, so the margin might fall to the previous low level but not much lower.

That won't apply to tonight of course as you've had it all reset.