Disappointing FTTC predicted speed

Dear all,

We currently have poor rural broadband download speeds of around 0.5-0.75Mbps. I'd heard that the village was due to be upgraded to fibre soon - this was really exciting until I read the following on the BT Wholesale Broadband Availability Checker:

"Your cabinet is planned to have WBC FTTC by 31st December 2012. Our test also indicates that your line currently supports a fibre technology with an estimated WBC FTTC Broadband where consumers have received downstream line speed of 1.8Mbps and upstream line speed of 900Kbps."

We're currently around 500m from the cabinet in our village - can this be right? If it is correct then I'll have to suppress my excitement as, although it will be 2-3 times faster, it'll still be difficult (impossible) to do much on iPlayer, Youtube, LoveFilm, etc.

Any advice or feedback would be very much appreciated.

Mandy (living the rural dream, apart from the Internet connection, for 11 months)

The estimates can sometimes be pessimistic, so it is wait until the service is live and see what close neighbours get or take the gamble yourself.

If the 500m is the actual distance of the cable route then that figure is well under what you would expect. At around 450m I get 40Mbps with a potential for 65Mbps.


The statement is also confusing in that the says FTTC by December then goes on to say that your line currently supports fibre technology ... Something is not quite right on the results.

Can you try a couple of neighbouring properties and their numbers?

In reply to a post by MHC:

The statement is also confusing in that the says FTTC by December then goes on to say that your line currently supports fibre technology ... Something is not quite right on the results.

Sadly that's normal for the website - mine said "currently supports" for over 2 years before my FTTC cab was installed and enabled.

Many thanks to Andrew and MHC for their responses. I will try to be patient. In the meantime I tried MHC's suggestion to try a neighbour's number - unfortunately the only local one I know at the moment seems not to be a BT line. So I tried the poscode checker and got the following:

"Your cabinet is planned to have WBC FTTC by 31st December 2012. Our test also indicates that your line currently supports a fibre technology with an estimated WBC FTTC Broadband where consumers have received downstream line speed between .1 to 76.5 Mbps and upstream line speed between .1 to 20 Mbps."

I think I'm going to have to be patient. Thanks for your advice in the meantime.

Mandy

Postcodes can be pretty large in some rural areas, so not the best guide.

A date at the end of December is also just a quarterly date, those dates are the ones most likely to be missed, if it said in a few weeks time then it would really be time to get excited.

Mandy
Nice to know another rural area is getting FTTC, if you are only 500m from the Cab your speed should be much better than that.

The line estimator doesn't seem to work well until there are some working lines in the area, then it's guesses get more educated!

I have no evidence except empirical but it seems to work by taking the attenuation over the distance house back to the exchange then pro-rata for the house to cab. If the house to cab is better than Cab to exchange you will get a far far better speed.

The state of your internal wiring can also affect the above so check that you can't improve the existing by unplugging all extensions then using the test socket only direct to the modem and wired to the PC. Wait 10 min after unplugging beofre turning it all back on and see if the speed improves.

Just interested but what exchange are you on?

At least that is a little more optimistic ...

Yes, mine and many others posted on these forums said "currently supports" long before the cabinet was installed. I think it was included at the time the cabinet was first scheduled.

It's only recently that I've seen this claim that it doesn't appear until the cabinet is live.

We are 400 metres from the cabinet, by the shortest possible (and most likely) road route. We get a full 80/20 sync.

The kind of numbers that you are being predicted would match a line length of over 1km - perhaps nearer 1500m (assuming copper lines). Is it possible that you are connected to a different cabinet? You aren't always connected to the closest one.

One way to find out which cabinet, and get a better idea of dates, is to question Openreach themselves. Their email is given in the FAQ on this page... something like nga.enquiries@...

In reply to a post by WWWombat:

We are 400 metres from the cabinet, by the shortest possible (and most likely) road route. We get a full 80/20 sync.

The kind of numbers that you are being predicted would match a line length of over 1km - perhaps nearer 1500m (assuming copper lines). Is it possible that you are connected to a different cabinet? You aren't always connected to the closest one.

One way to find out which cabinet, and get a better idea of dates, is to question Openreach themselves. Their email is given in the FAQ on this page... something like nga.enquiries@...

TBH that's more akin to an estimate on a 5.5+ KM line. Various lines I know to be over 5KM in length have estimates of 1.5 ~ 3 Mbit on the BT Wholesale checker.

It may simply be that the lines have poor composition - they may be lead, aluminium, some antiquated alloy, any number of things especially considering it's a rural area.

Doesn't even have to be a rural area. My mother used to live only 1.9KM from the exchange but couldn't get more than 3Mbit due to a high quantity of aluminium and thin guage copper in the line. I'm half a kilometer further from the same exchange and get over double the speed.

As others have said though, may just be the checker being pessimistic. Good luck!

In reply to a post by izools:

TBH that's more akin to an estimate on a 5.5+ KM line. Various lines I know to be over 5KM in length have estimates of 1.5 ~ 3 Mbit on the BT Wholesale checker.

We're talking about the FTTC predictions here, not the ADSL ones.

We're not going to get VDSL2 to work over 6km!

In reply to a post by WWWombat:

In reply to a post by izools:

TBH that's more akin to an estimate on a 5.5+ KM line. Various lines I know to be over 5KM in length have estimates of 1.5 ~ 3 Mbit on the BT Wholesale checker.

We're talking about the FTTC predictions here, not the ADSL ones.

We're not going to get VDSL2 to work over 6km!

Doesn't matter what the DSL protocol is, at 1500M actual line length the sync rate is going to be circa 20 Meg; dependent on line composition.

VDSL2 deteriorates quickly from a theoretical maximum of 250 Mbit/s at source to 100 Mbit/s at 0.5 km (1,600 ft) and 50 Mbit/s at 1 km (3,300 ft), but degrades at a much slower rate from there, and still outperforms VDSL. Starting from 1.6 km (1 mi) its performance is equal to ADSL2+.[3]

Edited by deleted (Sat 20-Oct-12 04:34:32)

I don't know where you got that quote from, but in practice it seems to be not true.

Downstream is definitely well below 20Mb before 2km. However, it seems that the upstream speed is most limiting - and that runs out first, so that VDSL2 is no use whatsoever. I believe someone posted their stats on here, showing upstream to be very slow on a sub-2km line.

Some further corroborating evidence on this TBBnews article (speeds at DR) and in the pdf's on this old thread

In reply to a post by WWWombat:

I don't know where you got that quote from, but in practice it seems to be not true.

Downstream is definitely well below 20Mb before 2km. However, it seems that the upstream speed is most limiting - and that runs out first, so that VDSL2 is no use whatsoever. I believe someone posted their stats on here, showing upstream to be very slow on a sub-2km line.

Some further corroborating evidence on this TBBnews article (speeds at DR) and in the pdf's on this old thread

Fair enough. I will disregard that part of the VDSL2 Wikipedia article then!

I suppose the difference is likely to be the boundary between the last upstream BIN and the first downstream BIN on the frequency spectrum. It's a pity Openreach haven't configured their DSLAMs to support auto-fallback to ADSL 2+, 2, or 1.

In reply to a post by izools:

Doesn't matter what the DSL protocol is, at 1500M actual line length the sync rate is going to be circa 20 Meg; dependent on line composition.

VDSL2 deteriorates quickly from a theoretical maximum of 250 Mbit/s at source to 100 Mbit/s at 0.5 km (1,600 ft) and 50 Mbit/s at 1 km (3,300 ft), but degrades at a much slower rate from there, and still outperforms VDSL. Starting from 1.6 km (1 mi) its performance is equal to ADSL2+.[3]

That's a very accurate prediction (at least for this line..)

The loop length, according to TDR, is 5200ft (just shy of 1600 metres).

http://asbokid.picturepush.com/showformat.php?&alid=...

Openreach just did a great job repairing a noisy intermittent short and the ADSL2+ sync rate is now ~20Mbps.

http://asbokid.picturepush.com/showformat.php?&alid=...

cheers, a


edit: one day i might post a URL that actually works! *sigh*

Edited by deleted (Sun 21-Oct-12 13:42:43)

There is no boundary like in the sense of G.DMT

There are blocks of bins such that the upstream is not a single contigous block occuping the lowest frequency bins, but is split into two of three blocks across the 17MHz.

Hence why upstream tails off. Can't find the bin plot screenshot I have somewhere showing this.

See the Discovery and Medley phases. IIRC most show the Medley/Final as a missing a few frequencies compared to the Discovery.

# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 13963 Kbps, Downstream rate = 58032 Kbps
Path:   0, Upstream rate = 14641 Kbps, Downstream rate = 57485 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      13963 kbps         58032 kbps
Actual Aggregate Tx Power:        6.6 dBm          13.4 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  5.3     29.6    44.5     N/A    14.4    36.3    55.7
Signal Attenuation(dB):  8.9     28.5    43.3     N/A    14.4    36.3    55.7
        SNR Margin(dB):  5.9     5.7     5.7      N/A    6.1     6.1     6.2
         TX Power(dBm): -3.9    -12.8    6.3      N/A    11.1    7.9     4.2

Edit - Hmmmm. The first band starts seem to overlap. That can't be right.

Edited by RobertoS (Sun 21-Oct-12 12:07:05)

In reply to a post by MrSaffron:

There is no boundary like in the sense of G.DMT

There are blocks of bins such that the upstream is not a single contigous block occuping the lowest frequency bins, but is split into two of three blocks across the 17MHz.

Hence why upstream tails off. Can't find the bin plot screenshot I have somewhere showing this.

Like this one from taken from my modem. Bit Loading Plot

In reply to a post by RobertoS:

See the Discovery and Medley phases. IIRC most show the Medley/Final as a missing a few frequencies compared to the Discovery.

# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 13963 Kbps, Downstream rate = 58032 Kbps
Path:   0, Upstream rate = 14641 Kbps, Downstream rate = 57485 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      13963 kbps         58032 kbps
Actual Aggregate Tx Power:        6.6 dBm          13.4 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  5.3     29.6    44.5     N/A    14.4    36.3    55.7
Signal Attenuation(dB):  8.9     28.5    43.3     N/A    14.4    36.3    55.7
        SNR Margin(dB):  5.9     5.7     5.7      N/A    6.1     6.1     6.2
         TX Power(dBm): -3.9    -12.8    6.3      N/A    11.1    7.9     4.2

Edit - Hmmmm. The first band starts seem to overlap. That can't be right.

Part of the lower band can be shared apparently. They show up on the bit loading plot I posted above.

Edited by simon194 (Sun 21-Oct-12 16:06:13)

In reply to a post by simon194:

Like this one from taken from my modem. Bit Loading Plot

You're doing better than mine Bits graph

# xdslcmd info --pbParams 
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:	0
Max:	Upstream rate = 9867 Kbps, Downstream rate = 58564 Kbps
Path:	0, Upstream rate = 10049 Kbps, Downstream rate = 49161 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783) 
DS: (32,859) (1216,1963) (2792,3959) 
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783) 
DS: (32,859) (1216,1963) (2792,3959) 
       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:       9867 kbps         58564 kbps
Actual Aggregate Tx Power:        4.8 dBm          12.2 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):	 6.2	 33.5	 49.7	  N/A	 16.0	 41.1	 62.2	
Signal Attenuation(dB):	 8.9	 32.5	 47.6	  N/A	 16.0	 41.1	 62.2	
        SNR Margin(dB):	 6.2	 6.0	 6.0	  N/A	 6.4	 6.4	 6.6	
         TX Power(dBm):	-4.4	-9.2	 4.1	  N/A	 9.2	 7.8	 3.6

In reply to a post by simon194:

Part of the lower band can be shared apparently. They show up on the bit loading plot I posted above.

I'm afraid that proves nothing, as our two sources are the same scripts. Yours is merely the graphical representation of the (similar) figures that I gave. Which is not to say there cannot be sharing, but to me that is counter-intuitive.

I do not doubt the scripts themselves. I do question the data returned by the HG612. We know for a fact some of the other stuff is incorrect, although most appears valid. In particular it can show FECs on Fast Path.

The scripts show the "shared" or overlapping tones in blue.

From my observations, I have deduced the following:-


As the HG612 NEVER displays any US data for QLN, Hlog & SNR when connected to a Huawei DSLAM, the blue data that is shown MUST be used for DS bitloading.

However, ECI DSLAMS do SOMETIMES report US QLN. Hlog & SNR data to the HG612 modem.

Most times it can still be assumed that the blue tones are used for DS bitloading.

A few connections (very close to the cabinet) do not use US0 band for upstream bitloading at all as maximum speeds can be obtained via the US1 & US 2 bands alone , thus for those connections the "shared" tones are definitely made available for DS bitloading.

In reply to a post by Bald_Eagle1:

The scripts show the "shared" or overlapping tones in blue.

From my observations, I have deduced the following:-


As the HG612 NEVER displays any US data for QLN, Hlog & SNR when connected to a Huawei DSLAM, the blue data that is shown MUST be used for DS bitloading.

However, ECI DSLAMS do SOMETIMES report US QLN. Hlog & SNR data to the HG612 modem.

Most times it can still be assumed that the blue tones are used for DS bitloading.

A few connections (very close to the cabinet) do not use US0 band for upstream bitloading at all as maximum speeds can be obtained via the US1 & US 2 bands alone , thus for those connections the "shared" tones are definitely made available for DS bitloading.

Looking at the SNR plot the first blue area on the bit loading plot is in the downstream area but a majority of the 2nd is in a gap between DS0 and US1.

FWIW, here's some band plan data from unlocked ECI & HG612 modems - from the same user on the same ECI DSLAM connection:-

From the ECI modem:-

(00,(0010,0031),(0010,0031))
(01,(0882,1193),(0882,1193))
(02,(1984,2770),(1984,2770))

(00,(0033,0857),(0033,0857))
(01,(1218,1959),(1218,1959))
(02,(2795,3950),(2795,3935))


From the HG612:-

Discovery Phase (Initial) Band Plan
US: (0,95) (880,1195) (1984,2771)
DS: (32,859) (1216,1959) (2792,4083)

Medley Phase (Final) Band Plan
US: (0,95) (880,1195) (1984,2771)
DS: (32,859) (1216,1959) (2792,4083)

As these are very early days of looking at any stats from an unlocked ECI modem, there is no guarantee about the reliability of any such obtained data.

At some stage & when I have a bit more spare time, I hope to test an unlocked ECI modem on my Huawei DSLAM connection for comparison against the HG612.

Edited by deleted (Mon 22-Oct-12 19:38:06)