General Discussion
  >> Fibre Broadband


Register (or login) on our website and you will not see this ad.


  Print Thread
Standard User Bald_Eagle1
(committed) Sun 03-Jun-12 10:35:35
Print Post

17a Profile v 8c Profile


[link to this post]
 
After many months & many engineer visits, it appears that my connection is finally stable again.

The issues appear to have been :-

a) A number of faulty SSFPs (I am now on the 4th one).
The fault was an immediate connection drop when using the phone.
Quite often, dialling IN would effect a "fix" for a few hours at a time.
Each time they were replaced, there was an improvement, but only for a few days at a time.

b) A "dodgy" underground cable to DP joint.
I first reported this in early February when 2 separate engineers climbing the pole for other purposes (more than 1 DP on this pole) repeatedly disconnected me, despite being adamant that they had not touched my connection at all.

When last week's engineer finally agreed to check that connection, the end of the UG cable fell off in his hand before he could actually check the connection!


Anyway, my question is:-

My sub-40Mb connection appeared to deteriorate speed-wise when switched from 8c to 17a profile.
It has deteriorated even further since the D3 DS band plan was tweaked recently, from DS: (32,859) (1216,1963) (2792,3939) to DS: (32,859) (1216,1963) (2792,3959)
i.e. 20 additional tones available for DS bit-loading.

Coinciding with this latest tweak, my US1 & US2 Line Attenuation has increased to over 55dB & 80dB respectively:-

Line Attenuation(dB): 8.3 53.3 64.7 N/A 21.6 63.5 0.1

Line Attenuation(dB): 8.4 55.1 80.9 N/A 21.9 64.8 0.1

Both my DS & US sync & throughput speeds have taken a hit as a result.

Has anyone else seen a similar effect of these band plan/profile "improvements"?

I wonder if this is similar to speed/stability reductions when switched from ADSL2 to ADSL2+?
i.e. speeds are now shared between higher frequencies that are more highly attenuated than previously, thus lowering overall speed & stability.
Standard User MHC
(legend) Sun 03-Jun-12 12:51:07
Print Post

Re: 17a Profile v 8c Profile


[re: Bald_Eagle1] [link to this post]
 
It should not have affected the upstream at all.

The only figure that should have changed is the D3 band attenuation as the high attenuation on those at the top end will have an effect on the "averaged" attenuation for D3.

It should not have adversely affected the downstream speeds either, as all it does is make more tones available - the previous ones are still there and even if the very top ones are unusable you would still fill the lower tones.

The attenuation figures you give, I presume they are U0, U1, U2, N/A(??), D1, D2, D3.


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

M H C


taurus excreta cerebrum vincit
Standard User Bald_Eagle1
(committed) Sun 03-Jun-12 13:37:44
Print Post

Re: 17a Profile v 8c Profile


[re: MHC] [link to this post]
 
In reply to a post by MHC:
It should not have affected the upstream at all.

The only figure that should have changed is the D3 band attenuation as the high attenuation on those at the top end will have an effect on the "averaged" attenuation for D3.

It should not have adversely affected the downstream speeds either, as all it does is make more tones available - the previous ones are still there and even if the very top ones are unusable you would still fill the lower tones.

The attenuation figures you give, I presume they are U0, U1, U2, N/A(??), D1, D2, D3.


Yes,

This is today's pbParams data:-

Text
1
23
45
67
89
1011
1213
1415
1617
1819
2021
22
# xdslcmd info --pbParams 
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max:    Upstream rate = 4803 Kbps, Downstream rate = 33572 Kbps
Path:   0, Upstream rate = 4785 Kbps, Downstream rate = 28568 Kbps 
Discovery Phase (Initial) Band PlanUS: (0,95) (868,1207) (1972,2783) 
DS: (32,859) (1216,1963) (2792,3959) Medley Phase (Final) Band Plan
US: (0,95) (868,1207) DS: (32,859) (1216,1963) 
       VDSL Port Details       Upstream        DownstreamAttainable Net Data Rate:       4803 kbps         33572 kbps
Actual Aggregate Tx Power:        6.3 dBm          12.5 dBm============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.4     55.1    80.9     N/A    21.9    64.8    0.1    
Signal Attenuation(dB):  9.6     54.4     N/A     N/A    21.9    64.8     N/A           SNR Margin(dB):  6.2     6.1      N/A     N/A    6.2     6.3      N/A   
         TX Power(dBm): -4.2     5.8      N/A     N/A    11.4    6.0      N/A


Here the US attenuation change (24th May for my connection) that coincided with the DS band plan change to 3959 tones can be clearly seen:-

US Line Attenuation

I gather that it changed for quite a few users some time in April, or even March.

So, in theory these changes should not have affected my speeds, but in practice they do appear to have done so.

Due to distance from the cabinet, I can't use the higher tones anyway.
Even on a good day, I can only use up to tone 1750, which is not even all of the middle DS band plan.

I suppose that in theory, switching to ADSL2+ shouldn't have made anything deteriorate, but in practice, for some longer lines, it does appear to have the same effect.


Register (or login) on our website and you will not see this ad.

Standard User MHC
(legend) Sun 03-Jun-12 18:38:05
Print Post

Re: 17a Profile v 8c Profile


[re: Bald_Eagle1] [link to this post]
 
An odd one ... if there was a line fault then I would expect all attenuations to rise.

Withouit knowledge of exactly how the DSLAM front end is designed it is impossible to say. I wonder if there is a soft filter in there which has a notch where U2 is located? And this was included in a firmware update when the bandplan was changed and cuts off the top half of U2 ... plenty of other possibilities too!

I see your connection only uses U1 any way! Which makes it even stranger!


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

M H C


taurus excreta cerebrum vincit
Standard User Bald_Eagle1
(committed) Sun 03-Jun-12 19:43:00
Print Post

Re: 17a Profile v 8c Profile


[re: MHC] [link to this post]
 
In reply to a post by MHC:
I see your connection only uses U1 any way! Which makes it even stranger!


Yes, I wish I could understand it too.

It's a shame I'm not connected to an ECI DSLAM as they report data for US QLN & Hlog.

My DS attenuation has increased slightly (not recently), the cut-off point for bit-loading being -74dB at tone 1742.

Hlog Data

If nobody else has seen this on their connections, it would potentially indicate yet another physical line fault.
As attenuation has not increased across all the bands though, I wonder if it could indicate an actual DSLAM problem?
Standard User MHC
(legend) Sun 03-Jun-12 19:51:28
Print Post

Re: 17a Profile v 8c Profile


[re: Bald_Eagle1] [link to this post]
 
A nice clean curve on the Tone vv Attenuation graph!


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

M H C


taurus excreta cerebrum vincit
Standard User Bald_Eagle1
(committed) Sun 03-Jun-12 19:53:22
Print Post

Re: 17a Profile v 8c Profile


[re: MHC] [link to this post]
 
Yeah.

Pity it's more vertical than horizontal though frown
  Print Thread

Jump to