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[Steven_belfast]

Greetings folks.

After getting my second line installed and FTTC up and running at my new home the sync speed is not as good as I thought it might be.
At this point in sync at 58Mbps / 19.9Mbps

With my Dsl line I am in sync at 17.9Mbps so thought i would have got more on the FTTC line.

My line length to the cab is at most 400 meters.

I have tested a number of firmware on the Openreach modem with no real change.
Also there is a large number of CRC errors on the line for a short up time and low data usage.
There is over 30K errors for 20 hours uptime.

Code: [Select]

xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 20587 Kbps, Downstream rate = 62572 Kbps
Path:   0, Upstream rate = 19999 Kbps, Downstream rate = 58511 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3971)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3971)
       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      20587 kbps         62572 kbps
Actual Aggregate Tx Power:        7.4 dBm          12.8 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  5.5     28.0    41.9     N/A    13.7    33.8    52.7

Signal Attenuation(dB):  5.5     27.1    40.8     N/A    13.7    33.8    52.7

        SNR Margin(dB):  6.4     6.4     6.4      N/A    4.2     3.9     3.9

         TX Power(dBm):  0.6    -15.2    6.4      N/A    9.0     7.9     6.8


Code: [Select]

Link Power State:       L0
Mode:                   VDSL2 Annex B
VDSL2 Profile:          Profile 17a
TPS-TC:                 PTM Mode
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):        4.1             6.4
Attn(dB):        0.0             0.0
Pwr(dBm):        12.8            7.4


Code: [Select]

INP:            3.00            0.00
PER:            1.67            3.97
delay:          8.00            0.00
OR:             114.95          64.47


[kitz]

We can take road length as an approximate guide, but it can fall short as the cable may not always take the direct route and may even double back on itself. 

Out of curiousity I just did a 'google walk' for my own line and even following the actual route that I know for sure the cable takes, and I know how long the cable run is (thanks to a friendly BToR engineer ) its still out by a bit. 

However looking at your maps you seem to have allowed some leaway for this.   Your Max attainable doesnt show that there is that much more in that line (I notied the 6.4 SNRm).


>>> There is over 30K errors

Is your internal wiring good? 
Do you know if that is a brand new FTTC cab or has it been up for a while (wondering about crosstalk from other lines)

[Steven_belfast]

Hi kitz

Internal wiring is not an issue, new SSPF / Vdsl socket installed on the 10th June.
No other slave sockets wired to it.

Tested the EE bright box 2 and 2 openreach modems also a number of filters and DSL cables, standard and short ones. ( I work for another well known ISP )

After taking some time graphing and testing I agree I think the line is as good as it's going to get,
Cab is from 2011 from what I know so guessing it will be cross talk, did not bother to check the capacity before leaving work at the weekend.

I can confirm there is no more crc errors on the line they stopped at 32k and have not changed from 1pm today.
Looks like the line is starting to settle down.

Still no ip profile from btw speed test site just "test error" but will give it another week or so. . . .

[kitz]

What did BT estimate your line rate as.  They are normally pretty conservative.

>> Cab is from 2011 from what I know so guessing it will be cross talk,

hmmm  possibly.   I know that Ive lost 20Mb from my max headline due to crosstalk over the past 9mths.  Most of us on here have seen their speeds deteriorate anything up to 20Mb as more ports on the cab get used. 

Mines still dropping and as observed you can sometimes literally see your SNRm take a dive each time a new line goes live, so goodness knows how low it will go before the cab is full.   

Although we are all aware of the impact of crosstalk on vdsl2, I wouldnt be too amazed if even BT has been surprised at just how much its affecting fttc in the field and outside of laboratory testing


--
eta

 Ive no idea how close to capacity my cab is, but if my line length is similar to yours -which I suspect it may be... then the speeds you are getting are about bob-on to what BT estimate my line would be if 'impacted'.

[Steven_belfast]

Greetings Kitz

BT Say 65 - 47Mbps / EE Said 37.5 So more then happy with that 

[kitz]

Your BT estimates are a bit lower than mine, based on that you are possibly a wee bit more than 400m... or your cab is more impacted.
Im not sure what info you can get from your place of work, but you may be able to find out how many lines are on the cab, your port no may be a good indication of this, if that info is available to you.

Since you come in the top part of the estimate on what isnt a new cab, then the bad & hard news is that BT wont do anything about it.  All you can do is check your internal (done) and monitor for any abnormalities.   We can have a look at your hlog and QLN graphs from dslstats if you want to post them, to see if we can see anything obvious there.  The errors may be worth keeping an eye on too.

 

With my Dsl line I am in sync at 17.9Mbps so thought i would have got more on the FTTC line.

Its the D-side (copper side) that makes the difference.   There will now be some lines that previously may have only got say 8Mb, but now can get near full 80 because they live near a cab and not exchange.   I used to get a full 24Mb/2.6Mb on annex-m, but fttc hasnt really shortened my copper run by that much.  Im still above the BT estimate though (62.6 - 41.3), so I guess BT expect mine to drop further still.

Roll on vectoring.