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Standard User MCM
(fountain of knowledge) Fri 14-Dec-12 23:49:08
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Re: Affect of distance on fibre line


[re: Bob_s2] [link to this post]
 
In reply to a post by Bob_s2:
Always plenty nof daft posters that no nothingh about what they are talking about. You are another of those
Your ignorance must make your mummy proud, now may I suggest asking her to put your toys back in the pram and get back to playing with them.
Standard User WWWombat
(experienced) Sat 15-Dec-12 03:14:43
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Re: Affect of distance on fibre line


[re: chubsta] [link to this post]
 
Ignoring the flame war going on in the other part of the thread...

I've had 2 FTTC lines, from which I've experienced the good & the average.

- The first line was 550 to 600 metres, as reported by the engineer's test equipment. On the old frequency plans, and a package of 40/10, it originally estimated at 31/8 and sync'ed at 40/10. The error rate on the line meant DLM intervened to take it down to 36/10 after 2 days.

When the new frequency plan was introduced (ready for 80/20), the modem went back to a full 40/10 sync. At the time, the modem indicated it had a maximum attainable speed of 60/16, but DLM would have probably reduced that to 50/16. However, we left that place before 80/20 packages became available.

The current checker for that line predicts 51/11.

- The new line is 400 metres, measured on Google maps along the likely cable route. This currently predicts at 55/18, but syncs at 80/20, without any DLM intervention.

The modem originally showed a maximum attainable speed of 83/25, but that has gradually dropped to 81/26 over the last year, until 3 weeks ago. Right now it shows 78/26, but we haven't re-synced for a month so still get 80/20. (Is this latest drop caused by neighbours, weather, or christmas lights? Who knows, but perhaps we'll see in January...)

Conclusion:
From my experience, it shows that a line of 400 metres *can* get a full 80/20 connection, but only in the absence of any interference.

Unfortunately, the biggest source of interference is going to come from neighbours getting FTTC too - and so could come at any time, before or after you connect yourself. The impact would be seen by DLM intervention that steals 10-20% of the capacity of the line, which (I think) is what was happening on my original line.

So... Hope for the best, but accept that future take-up might see your speed drop back to the predicted one.

Until vectoring has an impact...
Standard User Bald_Eagle1
(committed) Sat 15-Dec-12 08:48:57
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Re: Affect of distance on fibre line


[re: WWWombat] [link to this post]
 
In reply to a post by WWWombat:
Unfortunately, the biggest source of interference is going to come from neighbours getting FTTC too - and so could come at any time, before or after you connect yourself. The impact would be seen by DLM intervention that steals 10-20% of the capacity of the line, which (I think) is what was happening on my original line.


Just one comment to add:-

For connections unable to max out a 40Mb/2Mb service, increasing the US profile from 2Mb to 10Mb can increase US speed, at the expense of some DS speed.

I conducted extensive tests & experiments in conjunction with my ISP, Plusnet using differing connection profiles & on my own connection when US profile is 2Mb, I can achieve around 32Mb+ DS sync speed.

When using the 10Mb US profile, I can achieve around 5Mb to 6Mb US sync speed (i.e. 3Mb to 4Mb increase) at the expense of DS sync speed reducing to 28Mb to 29Mb (i.e. 3Mb to 4Mb decrease).

e.g. currently in sync at 29262 kbps / 5782 kbps, against attainable rates of 35100 kbps / 5804 kbps.

Last week it was 28543 kbps / 5582 kbps against attainable rates of 33356 kbps / 5687 kbps.

Maybe coincidence, but I ALWAYS seem to achieve slightly higher speeds when the weather is wet & very cold.

This week, temperatures have been around -5 degrees C earlier in the week & it has been very, very wet for the last couple of days.

My D-side connection is anywhere between 850m & 1000m from the PCP (depending on the exact, unconfirmed route), with the fibre cabinet itself being around 30m or so further away.

The connection resynced "on the fly" at its currently higher speed yesterday morning.

Whenever DLM has been reset following many external fault repairs, at a wide open profile, (interleaving completely OFF), DS sync speed has been as high as 36Mb until DLM takes action to improve stability - usually within the first couple of days, but very occasionally around 8 days or so later.

As I monitor my own connection (& some other users' connections) somewhat obsessively, I can state that all my comments are based on empirical & factual data.

P.S. My connection doesn't seem to be affected by Christmas lights - not too many houses on the way from the cabinets (in my direction), but our own aren't on (yet).
I have, however, seen some other connections suffer (slightly) due to Christmas lights being switched on.

Edited by Bald_Eagle1 (Sat 15-Dec-12 08:55:24)


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Standard User R0NSKI
(experienced) Sat 15-Dec-12 08:58:58
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Re: Affect of distance on fibre line


[re: Bald_Eagle1] [link to this post]
 
I'm putting ours up today, only one set flash, I think the others are static. Plenty of lights up along the route our line takes, although it is underground.

Standard User Bald_Eagle1
(committed) Sat 15-Dec-12 09:22:06
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Re: Affect of distance on fibre line


[re: R0NSKI] [link to this post]
 
@ RONSKI,

Have you thought about running with the ECI modem for a week or so, just to see if speeds do increase, as we suspect there may just be a slight incompatibility when using a HG612 on an ECI DSLAM connection (despite Openreach engineers apparently having been told there is NO incompatibility - as reported by an engineer in the Kitz forum a few weeks ago)?

Grabbing the stats immediately after eventually reinstating the HG612 might just reveal some interesting data.

The last time I looked (yesterday), your connection was still exhibiting blocks of high DS FEC/RSCorr error counts that MIGHT just be having a slightly negative effect upon how DLM interprets your connection's stability, despite otherwise low error counts.
Standard User R0NSKI
(experienced) Sat 15-Dec-12 09:56:44
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Re: Affect of distance on fibre line


[re: Bald_Eagle1] [link to this post]
 
I did finally did get an unlocked ECI V1 modem - I bought it off ebay, I also have another V1 type, which I couldn't unlock, and two new types, also I couldn't unlock them either, none of them would seem to take any input from my two UART adapters, I did get plenty of output though. Yes that is a total of 4 ECI modems, need to check they still work and stick two of them on ebay.

Any way, last weekend I decided to try my new unlocked ECI modem, it reported a lower attainable rate of around 45Mbps (51 on the HG612), wish I'd got a screen shot now, but I soon ran into problems. I lost access to my router, and eventually the router it'self seemed to lose all it's setting - had to restore from a backup, not sure if this was just coincidence or not, I'll try again one day.

Standard User Chrysalis
(eat-sleep-adslguide) Sat 15-Dec-12 10:21:08
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Re: Affect of distance on fibre line


[re: WWWombat] [link to this post]
 
the error rate I suspect also has to be consistent, yesterday my line generated over 7000 errors (or rather the last 24 hours). No DLM kicked in.

First 4000 came when I lost 20 meg attainable sync and probably came when the line was readjusting (probably a new install), then I got another burst of 3000 this morning around 1am, in between those times however the crc error rate is pretty much 0 so its not an ongoing thing.

Talktalk stated on their forum to a customer their own DLM requires an error rate of 300 per hour for at least 3 consecutive hours then will kick in, so thats a ballpoint although from another isp.

My attianable rate was 110mbit when I first checked, no idea if it was ever even higher, BT estimated me at 65mbit and my cabinet to socket distance is 200m. Documents I have read on crosstalk consider that with 20 lines active in a bundle on vdsl2 a average loss of sync speed is estimated at 40% so quite significant, 50% of 110mbit is 55mbit, so my 65mbit estimate I guess isnt too far of a 40% loss and I think thats what BT base their estimates on.

Reports from people like Qas who have shorter lines than me but lower attainable speeds the probable reasons are they have more crosstalk, vectoring apparently will get rid of this unpredictability as will get rid of most of interference aka crosstalk.

I also read in a few places Huawei are quite advanced on vectoring tech but ECI not as much, so I wonder if this will lead to a staggered rollout of the tech or will BT wait for both vendors to be ready, alcatel already rolling it out, because vectoring seems quite powerful removing most of this 40% or so of crosstalk. With this I think lines at 400m will get 80mbit sync (as they can do now with no crosstalk). I hope tho if vectoring is used speeds stay at 80 so people can enjoy healthy snr margins with DLM leaving them alone rather thn pushing for a slightly higher speed product of 100mbit and then have lines fighting with DLM again.

Edited by Chrysalis (Sat 15-Dec-12 10:23:09)

Standard User yarwell
(sensei) Sat 15-Dec-12 11:01:36
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Re: Affect of distance on fibre line


[re: RobertoS] [link to this post]
 
In actual fact it is the cold, causing the diameter, and similarly the circumference, of the copper wire to decrease. As current flows along the outside of the copper it therefore has lower conductivity.
I thought the electrons were sluggish in cold weather, thereby increasing the impedance.

--

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Standard User Uilebheist
(legend) Sat 15-Dec-12 11:10:30
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Re: Affect of distance on fibre line


[re: yarwell] [link to this post]
 
In reply to a post by yarwell:
I thought the electrons were sluggish in cold weather, thereby increasing the impedance.

Of course not. And if the weather is cold enough, the copper becomes superconductive and you get infinite bandwidth.
Unfortunately, by that point anybody who can use the bandwidth is dead.
Standard User timl
(member) Sat 15-Dec-12 12:52:21
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Re: Affect of distance on fibre line


[re: R0NSKI] [link to this post]
 
That's interesting I've got an ECI CAB and modem and wondered if swapping it for the HG612 would affect the stability of the line. From your experience is the HG612 better?

Thanks
Tim

Edited: didn't include my name!

Plusnet FTTC 80/20

Edited by timl (Sat 15-Dec-12 12:52:59)

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