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Standard User nemeth782
(member) Tue 01-Sep-15 14:51:51
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Alu FTTC line


[link to this post]
 
I have two FTTC lines, both are delivered from a street pole, over a couple of neighbours gardens.

I get ~45-48 down, and 5.5-6.8 up, on both lines. Neither has any extension wiring etc, just a master socket with faceplate.

BT wholesale checker estimates the following:

FTTC Range A (Clean) 60 40 16.2 9.9 -- Available
FTTC Range B (Impacted) 50.2 30 15.8 7.2 -- Available

As you can see, I'm within the (rather wide) range for the Clean estimate on the downstream, but below even the low end of the impacted estimate on the up, on both lines.

I talked PlusNet/BT into sending an engineer to look at one of the lines, and I've been told that the run from pole back to cab is Aluminium, and there is nothing they can do.

Bit annoying that it's still below estimates - to me the line is faulty - but is this the sort of impact you'd expect from Aluminium?

Bitloading Graph from DSLstats:
http://i.imgur.com/cdRKx6I.png

Stats:

xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 3
Last initialization procedure status: 0
Max: Upstream rate = 7037 Kbps, Downstream rate = 47992 Kbps
Bearer: 0, Upstream rate = 6866 Kbps, Downstream rate = 47993 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 6.2 6.0
Attn(dB): 21.9 0.0
Pwr(dBm): 12.9 3.1
Standard User MHC
(sensei) Tue 01-Sep-15 16:02:45
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
The fact that is aluminium is NOT a fault although It may not be optimum.

Looking at the graph there is something wrong - some notches at tones 1050, 2050, 2130, 2160 (approx) and then a drop to zero at 2330 whereas U2 normally goes up to 2775. I would not expect to see a sudden drastic cut off - and that is not due to aluminium. Do you know what is causing those notches? They could explain some of the lack of upstream speed.

Can you capture the Bitloading Graph with the SNR superimposed.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User nemeth782
(member) Tue 01-Sep-15 18:40:48
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Re: Alu FTTC line


[re: MHC] [link to this post]
 
In reply to a post by MHC:
The fact that is aluminium is NOT a fault although It may not be optimum.

Looking at the graph there is something wrong - some notches at tones 1050, 2050, 2130, 2160 (approx) and then a drop to zero at 2330 whereas U2 normally goes up to 2775. I would not expect to see a sudden drastic cut off - and that is not due to aluminium. Do you know what is causing those notches? They could explain some of the lack of upstream speed.

Can you capture the Bitloading Graph with the SNR superimposed.


Don't know how to superimpose them, but here is a snapshot of all the graphs...

http://imgur.com/a/BhmPG

I assumed the drop off at 2330 or so was just because alu didn't carry higher frequencies well?

No idea what is causing the notches, although the engineer apparently did a pair swap so I don't suppose I'm going to talk BT into much else!


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Standard User MHC
(sensei) Tue 01-Sep-15 18:50:54
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
In DSL Stats select <Configuration>, then <Items to monitor> Under Others, ensure SNR per Tone, Show as sepatate graph, & Include with bitloading are checked..


From what I can see, with ZERO loading from 2100, to just under 2300 and nothing from 2300 up that could be where you are losing quite a bit of upstream.

Yes, aluminium does not work as well at higher frequencies, however it is not a sharp cut off. I would expect to see the SNR drop from 10 down to 0 over a large block of tones - possibly up to 400.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit

Edited by MHC (Tue 01-Sep-15 19:06:04)

Standard User nemeth782
(member) Tue 01-Sep-15 20:14:19
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Re: Alu FTTC line


[re: MHC] [link to this post]
 
http://i.imgur.com/W1eAdf1.png

That's actually a much more helpful graph!

Still not sure what else I can do though frown
Standard User MHC
(sensei) Tue 01-Sep-15 20:21:20
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
Now you see ... That block with zero bitloading - even if it was at 1 bit per tone you could be looking at maybe up to 10% improvement.

there are also a couple of nasties in the downstream too - 1700 to 1750 ...

I would suggest a "managed" reboot tomorrow morning. Power off the hub, without disconnecting the line. Wait 5 minutes and then disconnect the line. Wait say 15 minutes, make sure you have minimal devices on in the house - no lights, no TV &c. Power up tyeh modem and wait 5 minutes for it to fully boot. Then reconnect the line - give it a minute or so and then recheck the stats/graph.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Administrator MrSaffron
(staff) Tue 01-Sep-15 20:27:31
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Re: Alu FTTC line


[re: MHC] [link to this post]
 
Long shot, but don't happen to have a radio ham living near by?

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User MHC
(sensei) Tue 01-Sep-15 22:08:04
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Re: Alu FTTC line


[re: MrSaffron] [link to this post]
 
Interesting thought ...

The Amateur HF bands are here: http://rsgb.org/main/operating/band-plans/hf/

Tone 2342 is at 10.1 MHz Might explain the missing top end but not the missing block.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User simon194
(experienced) Wed 02-Sep-15 00:14:54
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
At least you have a single run of Al and not a 120m section between two copper sections with deteriorating joints. The recent very heavy rain doesn't appear to have helped as I've lost another 8 Mbps off my sync speed unless it's just a coincidence.
Standard User WWWombat
(knowledge is power) Wed 02-Sep-15 04:56:43
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
In reply to a post by nemeth782:
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 3
Last initialization procedure status: 0
Max: Upstream rate = 7037 Kbps, Downstream rate = 47992 Kbps
Bearer: 0, Upstream rate = 6866 Kbps, Downstream rate = 47993 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 6.2 6.0
Attn(dB): 21.9 0.0
Pwr(dBm): 12.9 3.1


Looking at other lines on MyDSLWebStats, with an attenuation of 22dB or so, you can see speeds of 43/7 - 50/8. It seems to be fairly common to see upstream speeds of 7-8Mbps alongside downstream speeds anywhere from 35Mbps to 50mbps.

In reply to a post by nemeth782:
Don't know how to superimpose them, but here is a snapshot of all the graphs...

http://imgur.com/a/BhmPG


What I notice most especially is that there is no obvious "power mask" in the downstream D1 band.

Ordinarily, I'd expect to see a *big* trough in SNR and bit-loading values somewhere between tones 200 and 500.

For example, mine looks like this, with a trough at tone 325:
http://postimg.org/image/vlcbhlakn/

What distance is the cabinet from the exchange?

Of course, if power is reduced, speeds will end up even lower...
Standard User nemeth782
(member) Wed 02-Sep-15 09:50:30
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Re: Alu FTTC line


[re: WWWombat] [link to this post]
 
Me to cab is ~331meters, in a straight line down the road.

Cab to exchange is 332meters, assuming the line follows the road it is a gentle S shape so more like 345meters.

[censored] MSpaint drawing:

http://i.imgur.com/fVrB14b.png

Blue arrow points to the Cabinet. Yellow box is a manhole cover I know my line is in, large red blob is the pole my line is on.

Smaller red blob is where my house is, black line is the line itself, for the known parts of it's route.

Green dots are houses forecast 74mbit down 20mbit up on the address checker, that don't seem to come via the pole (can see cable entry points on the front of their houses).

I almost think if I order a 3rd line they will bring it in via the front of the house (as my overhead line is draped over 3 peoples gardens, getting permission to get ladders in to replace it could be awkward).
Standard User MHC
(sensei) Wed 02-Sep-15 09:54:24
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
Have you done a reboot this morning?


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User nemeth782
(member) Wed 02-Sep-15 09:57:27
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Re: Alu FTTC line


[re: MHC] [link to this post]
 
In reply to a post by MHC:
Have you done a reboot this morning?


No, was almost late for work so didn't get chance, will do it tonight/tomorrow morning.

It is a bit variable, when the BT engineer was there yesterday, he resynced the line a number of times. I was monitoring sync speeds and saw as high as 51m down, and as high as 7mbit up, although not at the same time.
Standard User MHC
(sensei) Wed 02-Sep-15 10:07:20
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
I know I commented on te upstream being "missing" above tone 2350, what is also difficult to understand is that there is no data for anything including D3 which starts at 2793. Even if the bins were empty, I would still expect to see something on the SNR, QLN and HLog graphs.

Can you copy the pbParams page from DSLStats?


One reason I suggested a morning reboot was that it tends to be a low noise time - less electronics running and if there is a Radio Ham close by, he is more likely to be off at that time. Still try it when you get home though - a managed drop of connection should not have any adverse effects.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Administrator MrSaffron
(staff) Wed 02-Sep-15 11:22:46
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
If a third line is difficult to provide BT may charge you full cost of delivering it, fixed price installs under USO only apply to the first line at a property.

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User nemeth782
(member) Wed 02-Sep-15 13:25:24
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Re: Alu FTTC line


[re: MHC] [link to this post]
 
xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 3
Last initialization procedure status: 0
Max: Upstream rate = 7312 Kbps, Downstream rate = 47992 Kbps
Bearer: 0, Upstream rate = 6866 Kbps, Downstream rate = 47993 Kbps

Discovery Phase (Initial) Band Plan
US: (6,31) (882,1193) (1984,2770)
DS: (33,857) (1218,1959) (2795,4083)
Medley Phase (Final) Band Plan
US: (6,31) (882,1193) (1984,2330)
DS: (41,857) (1218,1959)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 7312 kbps 47992 kbps
Actual Aggregate Tx Power: 3.2 dBm 12.9 dBm
====================================================================================
VDSL Band Status U0 U1 U2 U3 U4 D1 D2 D3
Line Attenuation(dB): 4.1 31.9 49.9 N/A N/A 16.5 46.8 76.7
Signal Attenuation(dB): 4.1 31.8 49.7 N/A N/A 15.7 46.4 N/A
SNR Margin(dB): 6.3 6.1 6.3 N/A N/A 6.2 6.2 N/A
TX Power(dBm): -3.5 -9.6 1.8 N/A N/A 11.5 7.3 N/A
#


Wow, that attenuation really climbs on the higher bands!
Standard User MHC
(sensei) Wed 02-Sep-15 14:26:49
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
Could be the Al tail off ...

I notice that the Final Band Plan stops at 2330 so nothing would happen after that.

Do the reboot later and see if it changes much at the high end and also see if the QLN, Hlog and SNR lists have any data above 2330 - do not paste them here though


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User WWWombat
(knowledge is power) Fri 04-Sep-15 19:03:32
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
In reply to a post by nemeth782:
Cab to exchange is 332meters, assuming the line follows the road it is a gentle S shape so more like 345meters.


Right - that is quite a short distance, so the cabinet doesn't have to reduce power much for FTTC connections. You can see a small dip in SNR and bit-loading on the tones just below 512; above 512, bit-loading jumps back to normal.

In reply to a post by nemeth782:
Me to cab is ~331meters, in a straight line down the road.


Eek. My previous line was around 370 metres, and I believe it was 0.5mm copper all the way. It achieved 80/20 speeds for a long time (crosstalk from neighbours eventually reduced it to 78/20, but that was 4 years after the cab was installed). That line had an attenuation of around 16dB.

It just goes to show the impact of a stretch of aluminium.

I agree with the others that the drop-off you see is because aluminium is just not as good for the higher frequencies - as you note later:

In reply to a post by nemeth782:
Text
1
23
45
67
====================================================================================
  VDSL Band Status      U0      U1      U2      U3      U4      D1      D2      D3  Line Attenuation(dB): 4.1     31.9    49.9    N/A     N/A     16.5    46.8    76.7
Signal Attenuation(dB): 4.1     31.8    49.7    N/A     N/A     15.7    46.4    N/A        SNR Margin(dB): 6.3     6.1     6.3     N/A     N/A     6.2     6.2     N/A
         TX Power(dBm): -3.5    -9.6    1.8     N/A     N/A     11.5    7.3     N/A#


Wow, that attenuation really climbs on the higher bands!


To give you a comparison of my previous, 370m copper, line:
Text
1
23
45
6
====================================================================================
  VDSL Band Status       U0      U1      U2      U3      U4      D1      D2      D3  Line Attenuation(dB):  4.4     22.2    33.4     N/A     N/A    11.6    28.0    42.6   
Signal Attenuation(dB):  4.4     21.2    32.3     N/A     N/A    16.2    27.7    42.6           SNR Margin(dB):  7.1     7.2     7.1      N/A     N/A    6.3     6.2     6.2    
         TX Power(dBm): -2.5    -21.0    6.5      N/A     N/A    9.7     7.8     6.9


In reply to a post by nemeth782:
I almost think if I order a 3rd line they will bring it in via the front of the house (as my overhead line is draped over 3 peoples gardens, getting permission to get ladders in to replace it could be awkward).


Good luck with that. If you could avoid that aluminium, it would be reasonably worthwhile.
Standard User Nightglow
(regular) Fri 04-Sep-15 21:01:11
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
In reply to a post by nemeth782:
I almost think if I order a 3rd line they will bring it in via the front of the house (as my overhead line is draped over 3 peoples gardens, getting permission to get ladders in to replace it could be awkward).


If there is a spare pair on your exsisting cable, they will use them, rather than putting a new cable at the front.
Standard User nemeth782
(member) Fri 04-Sep-15 23:10:47
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Re: Alu FTTC line


[re: Nightglow] [link to this post]
 
In reply to a post by Nightglow:
In reply to a post by nemeth782:
I almost think if I order a 3rd line they will bring it in via the front of the house (as my overhead line is draped over 3 peoples gardens, getting permission to get ladders in to replace it could be awkward).


If there is a spare pair on your exsisting cable, they will use them, rather than putting a new cable at the front.


The drop wire from my roof to the two master sockets is 4 pair, it was fitted when I ordered the 2nd line (previously figure-8 cable). The overhead cable ( http://i.imgur.com/jPUiWkf.jpg ) is two pair according to the engineer that fitted the 2nd line.

It would be necessary to replace this cable for a 3rd line, it's copper, but from the estimates given to neighbouring houses that don't go via that pole, I think the Alu section is the bit that goes to said pole.

I feel like they would probably just refuse to install a 3rd line without massive excess construction costs though.
Standard User nemeth782
(member) Fri 04-Sep-15 23:13:44
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Re: Alu FTTC line


[re: MrSaffron] [link to this post]
 
In reply to a post by MrSaffron:
Long shot, but don't happen to have a radio ham living near by?


Perhaps if I install a load of powerline adaptors and dump traffic over them on my LAN I will flush one out or make him give up wink
Standard User Nightglow
(regular) Sat 05-Sep-15 08:48:27
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
" I've been told that the run from pole back to cab is Aluminium, and there is nothing they can do".

Don't you believe it, make yourself unpopular with BTOR as I did & you'll get results.

I had terrible problems with alumimum cable here, neighbour could get 75Mb, me 8-14Mb.
There were no spare pairs on front pole & was told to accept what speed I had.
Made myself very,very unpopular with BTOR continually complaining,took months & months of complaining before they moved me from the front pole to the rear pole.
Still had some problems with low speed & rotten aluminum cable running along High St, so complained higher up to Joe Garner, & got moved to a copper cable, now getting 76Mb.

Edited by Nightglow (Sat 05-Sep-15 09:33:04)

Standard User nemeth782
(member) Sat 05-Sep-15 08:59:17
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Re: Alu FTTC line


[re: Nightglow] [link to this post]
 
Oooh, you give me hope!

Although, I am getting 43mbit, which is much more than 8-14, and makes me think my odds are slimmer than yours...

I haven't actually given up entirely yet and have a couple of other tricks up my sleeve.
Standard User Nightglow
(regular) Sat 05-Sep-15 09:38:10
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Re: Alu FTTC line


[re: nemeth782] [link to this post]
 
I even went to my neighbours & got speed tests from them, showing their speed, & results from DSL Checker to back up my case.
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