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Standard User Ribble
(committed) Sat 17-Nov-12 19:33:03
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Re: What happens those too far from cab?


[re: CurlyWhirly] [link to this post]
 
http://www.thinkbroadband.com/news/4050-openreach-an...
Standard User TimJ
(committed) Sun 18-Nov-12 09:08:24
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Re: What happens those too far from cab?


[re: MrSaffron] [link to this post]
 
A friend is in a similar but worse situation.

He is too far for ADSL MAX to get any sync, Openreach engineer said that the line length to the exchange is 9.7km.

Prior to the cabinet being enabled the BT Checker siad that he would he get a service at 900kbps, but now the cabinet has been enabled there is no mention of FTTC.

He is 1.2miles from the cabinet, nearly all of which is on overhead poles.

If he could really get a reliable 900kbs service it would be well worth it compared to his current dial up, but how would he persuade an ISP to try it?
Administrator MrSaffron
(staff) Sun 18-Nov-12 10:27:45
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Re: What happens those too far from cab?


[re: TimJ] [link to this post]
 
Problem being that if memory is working, Openreach generally don't install below 5 Mbps, so needs an ISP that will push hard and as most go via BT wholesale this makes things more difficult

Andrew Ferguson, [email protected]
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.


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Standard User MHC
(sensei) Sun 18-Nov-12 11:04:00
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Re: What happens those too far from cab?


[re: MrSaffron] [link to this post]
 
Even a pushy ISP is unlikely to get an installation of that type. I have heard of ones where the forecast was around 4Mbps being "forced" through but at 900k with overhead lines which are more susceptible to noise there is a good chance that it would fail.


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

M H C


taurus excreta cerebrum vincit
Standard User Bald_Eagle1
(committed) Sun 18-Nov-12 12:21:04
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Re: What happens those too far from cab?


[re: TimJ] [link to this post]
 
PLusnet seem to cater for low speed FTTC customers.

1.2 miles or around 2000m does not seem an excessive distance from the cabinet.

I would imagine that download speeds could be substantially higher than 900kbps, possibly around 6Mb to 8Mb or so.
However, I would expect upload speeds to be as low as 0.5Mb over that distance.

I have seen a 1 mile FTTC connection achieve 12Mb dowload & 0.9Mb upload.


EDIT:

Sorry, my memory played tricks on me.

It was more like 12.7Mb & 0.67Mb actual sync speeds:-

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# xdslcmd info --pbParams 
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max:    Upstream rate = 721 Kbps, Downstream rate = 13232 Kbps
Path:   0, Upstream rate = 670 Kbps, Downstream rate = 12726 Kbps 
Discovery Phase (Initial) Band PlanUS: (0,95) (880,1195) (1984,2771) 
DS: (32,859) (1216,1959) (2792,4083) Medley Phase (Final) Band Plan
US: (0,95) DS: (32,859) 
       VDSL Port Details       Upstream        DownstreamAttainable Net Data Rate:        721 kbps         13232 kbps
Actual Aggregate Tx Power:        1.2 dBm           8.2 dBm============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.2     65.4    62.3     N/A    26.4    0.1     0.1    
Signal Attenuation(dB):  8.2      N/A     N/A     N/A    26.4     N/A     N/A           SNR Margin(dB):  7.6      N/A     N/A     N/A    4.4      N/A     N/A   
         TX Power(dBm):  1.2      N/A     N/A     N/A    8.2      N/A     N/A

Edited by Bald_Eagle1 (Sun 18-Nov-12 12:31:39)

Standard User WWWombat
(experienced) Tue 20-Nov-12 23:56:03
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Re: What happens those too far from cab?


[re: Bald_Eagle1] [link to this post]
 
I'm of the opinion that 2km is very much a problem.

Unfortunately, it is one of those areas that is hard to be even semi-accurate about. Some searches online suggest that BT's practical limit is around 1500 metres - but everyone is focussing on what is happening to the downstream speed at this distance (particularly when BT was limiting downstream to 15Mbps), and the race to 80/20 speeds may have impacted on lengthier lines; some VDSL2 products specify 2km as the maximum distance (such as this one), while this card has dropped to 16 down, 0.3 up at 5,000 feet (1600 metres). This primer asserts that VDSL2's long reach is up to 2.4km.

Some of the semi-technical write-ups specify that VDSL2 starts to behave like ADSL2+ at the 2km point. Wikipedia mentions this (but it also mentions a LR-VDSL2 protocol for long range). ZDNet had this to say a while back.

Practical experience (but only from seeing what other people post; it isn't first-hand experience) makes me think that it is really upstream that is the limiting factor on extreme distance cases - and that the UK variant of VDSL2 is not behaving like ADSL2+ at distances beyond that. I'm not sure if that is a consequence of the way we use the US0 band for the final, longest range, upstream capability. Or the way we use the power levels of our 17a profile or, more particularly, the power masks applied over the low frequencies so the cabinet does not interfere with exchange-based ADSL (and ADSL2+) - although they're more for downstream than upstream.

Or perhaps BT's upstream power-backoff mechanism is tuned for short lines, rather than long lines. Even though it only applies to the power in the higher-frequency bands, the tuning does make a difference to the upstream speed available out at 1500 metres. Take a look at this document on The art of spectral management, UPBO, especially page 3. I guess BT have used a reference length close to the first 2 graphs.

(BTW: There's also a matching document on The art of Spectral Management, Frequency Allocations.

As bald-eagle notes - that 1600 metre line could still manage 12.7Mbps down, but only 0.7Mbps up. and one device predicted 0.3Mbps up.

Is it worth installing FTTC lines when the upstream speed is getting lower than 0.3Mbps?
Standard User NuttyMucker
(member) Wed 21-Nov-12 01:29:29
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Re: What happens those too far from cab?


[re: Bald_Eagle1] [link to this post]
 
1.3 miles from the cabinet.

Getting 19Mb downstream and 1.2Mb up with Plusnet.

When the FOD becomes available I will look into it but if I am even considered and the survey talks telephone numbers they can jump!

Standard User WWWombat
(experienced) Wed 21-Nov-12 01:45:56
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Re: What happens those too far from cab?


[re: NuttyMucker] [link to this post]
 
I'll have to re-think then. That's 2.1km, so quite impressive.
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