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Author Topic: Help with line stats......  (Read 6219 times)

corradostorm

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Help with line stats......
« on: June 18, 2013, 10:48:56 PM »

Hello all,

I have a situation here in Ireland, we have just got VDSL in some towns and as such good knowledge is short on the ground.

I look after the IT in two business premises and both have just had VDSL installed.

Its an industrial estate, business 1 is around 700 meters from the VDSL Cabinet.

Business 2 is around 750 - 770.

I know the exact distance as I had it confirmed by our local telecoms engineer. He laid the cable 20 years ago.

Business 1 is connecting at 25.595Mbps down 7.167Mbps up
Business 2 is connecting at 30.720Mbps down 8.191Mbps up

Stats for Business 1
Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a
            Traffic Type:   PTM Mode
             Link Uptime:   0 day: 2 hours: 35 minutes
============================================================================
       VDSL Port Details       Upstream         Downstream
               Line Rate:      7.224 Mbps       25.670 Mbps
    Actual Net Data Rate:      7.167 Mbps       25.595 Mbps
          Trellis Coding:         ON                ON
              SNR Margin:       16.5 dB           19.1 dB
            Actual Delay:          6 ms              8 ms
          Transmit Power:        7.2 dBm          12.1 dBm
           Receive Power:       -6.7 dBm          -8.5 dBm
              Actual INP:        2.0 symbols       3.0 symbols
       Total Attenuation:       13.8 dB           20.6 dB
Attainable Net Data Rate:     15.362 Mbps       54.104 Mbps
============================================================================
      VDSL Band Status    U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  7.2    39.9    59.6     N/A    18.7    49.9    76.5   
Signal Attenuation(dB):  7.2    39.2    56.8     N/A    18.7    49.9     N/A 
        SNR Margin(dB): 16.6    16.5    16.0     N/A    19.1    19.2     N/A   
   Transmit Power(dBm):  0.4     5.8   - 7.2     N/A    10.1     7.6     N/

Stats for Business 2


I dont have enough knowledge at present to decode those numbers or more importantly why Business 1 is not getting any Signal Attenuation on the D3....

I have had the local engineer out to do a test on the line, he said if I was still not happy he would swap the current pair for another pair that the business has spare.

Can anyone point me in the right direction as to what might be wrong.....

On paper Business 1s line looks better to me......

Any help would be greatly appreciated!
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Bald_Eagle1

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Re: Help with line stats......
« Reply #1 on: June 19, 2013, 08:51:07 AM »

Looking at the SNRM values, both lines appear to be capable of more speed.

Are you on some sort of speed-capped business service (possibly in order to provide increased stability at the expense of some sync speed)?

Who is your ISP?



Generally speaking, Line 2 looks 'better' to me.
i.e. generally lower attenuation values for each band plan.


I wouldn't worry about Line 1's lack of D3 Signal Attenuation data.
I think the line length is too long to achieve anything really useful from that highest frequency band.
The values actually captured for D3 on Line 2 look too high to be of much use anyway.


For curiosity, which make & model of modem/modems (or other equipment) are you using to obtain the stats that you posted?
Your stats are formatted a little differently to the data usually obtained via a Huawei HG612.

Do you have any record of error counts for each line?
It's 'possible' that DLM has detected many errors, applied a high level of Interleaving & capped sync speeds accordingly.

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corradostorm

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Re: Help with line stats......
« Reply #2 on: June 19, 2013, 09:22:25 AM »

Thanks a million for your reply.

Line 2 does look better in terms of what it is achieving, I agree. However line 1 looks like it should be doing more/better than line 1. Marginally lower Atten and higher SNRM.

Have I got that completely wrong?

Both lines were ordered without me being involved. As far as I know both are capped at 30mbps.

I called to get the profile changed yesterday on line 2 (isp is eircom, Ireland's BT equivalent) and was told that the line can't take anymore....

I pointed out to them that I had one of their engineers on site that morning and he had hooked up a unit that runs tests on the line. He showed me the live results on screen and he said line 1 should take between 33-37mbps without fault. He also showed me that the current sync speeds were only using 60 something % of what it is capable of.

Eircom are telling me their system can not put the line on a higher profile, it won't let them.

I asked if I could have a line reset, they didn't know what I was talking about.

Two things are bothering me.....

If I had ordered the line I would have put it on the 50mbps plan. Eircom would have done this as they had no data for the line.

Why is line 2, which is further away getting better results?

The local engineer is a top bloke, he knows the business owners and will do what he can to help, including trying different pairs back to the cabinet.

The modem is an eircom own branded unit. Their own firmware. I believe its a zyxel P-2812.
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Bald_Eagle1

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Re: Help with line stats......
« Reply #3 on: June 19, 2013, 05:29:13 PM »

Line 1: Total Attenuation: 13.8 dB 20.6 dB
Line 2: Total Attenuation: 13.8 dB 20.7 dB
 
I'm not 100% convinced those values are correct.
I presume they are calculated via software from the band plan values.



If you compare these stats from Line 1 with those from Line 2, it appears that Line 2 has lower attenuation values, despite being slightly longer:-

     VDSL Band Status    U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  7.2    39.9    59.6     N/A    18.7    49.9    76.5   
Signal Attenuation(dB):  7.2    39.2    56.8     N/A    18.7    49.9     N/A 
        SNR Margin(dB): 16.6    16.5    16.0     N/A    19.1    19.2     N/A   
   Transmit Power(dBm):  0.4     5.8   - 7.2     N/A    10.1     7.6     N/


There could be a number of reasons for differing values such as aluminium cabling a high resistance joint in the cabling etc.



In UK (BT) target SNRM is 6dB.

These values (SNR Margin(dB): 16.6    16.5    16.0     N/A    19.1    19.2     N/A) would suggest the connection is capable of much higher speed unless, it is 'capped' for some reason.

I gather the zyxel P-2812 has a Lantiq chipset, so my monitoring/graphing program won't work with it.

However, if you were to purchase a cheap Huawei HG612 modem via ebay, you could very easily unlock it & see a picture of a VDSL2 connection's connection stats (as per the attached).

A Huawei HG622 (combined modem/router) will also provide the same level of stats, but they are in shorter supply.


Line 1 could actually be experiencing more crosstalk than Line 2. Hence lower connection sync speed as DLM takes 'corrective' action.

My own connection seems to be now suffering from increased crosstalk as more users are connected (the 'evidence' is exhibited in the Hlog graph).

« Last Edit: June 19, 2013, 05:37:21 PM by Bald_Eagle1 »
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corradostorm

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Re: Help with line stats......
« Reply #4 on: June 19, 2013, 05:58:35 PM »

Line 1: Total Attenuation: 13.8 dB 20.6 dB
Line 2: Total Attenuation: 13.8 dB 20.7 dB
 
I'm not 100% convinced those values are correct.
I presume they are calculated via software from the band plan values.


The quoted values are from both the Modem and the kit the engineer hooked up to the line. He disconnected the wall plate, disconnected all wiring and hooked directly into where the line enters the building.

Is it correct that those figures are that way because of profile settings on the ISP end?

There is around 20 pairs of telecom cables entering the building, its a business. The engineer tells me that there is one joint between us and the cabinet. He also says the joints, under a manhole cover, should have been checked before the VDSL roll out.

The telecoms cables are a bit too close to the electricity supply for my liking, bad planning when the building was built put them entering the building very close to eachother. Line 2s telecoms lines are not near the electricity cables.

I have been thinking that this could be causing a problem.......

Is there anyway I can add shielding to the telecoms cables?

I know its a fairly trivial matter and not life and death but I like to get the best for my customers and want to get as much from the line as I can. It opens up so many more options.

Do you think the Huawei HG612 would work on our lines here in Ireland?

Thanks again for taking the time to help.

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Bald_Eagle1

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Re: Help with line stats......
« Reply #5 on: June 19, 2013, 11:33:11 PM »


The quoted values are from both the Modem and the kit the engineer hooked up to the line. He disconnected the wall plate, disconnected all wiring and hooked directly into where the line enters the building.


I only questioned the values as the HG612 doesn't report a total attenuation value at all & some other Lantiq modems e.g. Fritz!Box only report downstream.

The HG612 does however report Line & signal attenuation for each US & DS band or N/A for any bands that are unable to be used.

Quote

Is it correct that those figures are that way because of profile settings on the ISP end?


Line attenuation is the physical attenuation of the cable & Signal attenuation is usually very close or the same value.

Quote
There is around 20 pairs of telecom cables entering the building, its a business. The engineer tells me that there is one joint between us and the cabinet. He also says the joints, under a manhole cover, should have been checked before the VDSL roll out.

Was he suggesting a possible fault at the joint or that there can't be a fault as the joint had been checked?


Quote
The telecoms cables are a bit too close to the electricity supply for my liking, bad planning when the building was built put them entering the building very close to eachother. Line 2s telecoms lines are not near the electricity cables.

I have been thinking that this could be causing a problem.......

Is there anyway I can add shielding to the telecoms cables?


I have read that interference is likely when telecoms & power cables are close & parallel to each other for a fair distance, but I don't know how severe that can be.

I would expect SNRM values to be reduced if that was the case. However, SNRM seems to be high enough to allow higher speeds (if the speed wasn't capped at all).

Quote
I know its a fairly trivial matter and not life and death but I like to get the best for my customers and want to get as much from the line as I can. It opens up so many more options.

Do you think the Huawei HG612 would work on our lines here in Ireland?

Thanks again for taking the time to help.

I can't see why it wouldn't work as it is exactly the same mode & profile as used in England:-

Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a
            Traffic Type:   PTM Mode

Bear in mind though that the HG612 is simply a modem in bridge mode for VDSL2 connections, so a compatible router would also need to be connected.

An unlocked HG612 allows the 2nd LAN port (LAN2) to be used to obtain connection stats, either directly from a PC with a fixed IP address in the same range as the modem's (192.168.1.1 by default) or via the router using a 2nd cable from a spare router LAN port to the HG612's LAN2 port.


EDIT:

Shielded cables can be used but there is a school of thought that unearthed shielding can actually cause more issues than it cures.

Somewhere in the Kitz forum is a thread dedicated to pros & cons of shielded cabling.
I don't have a link at hand, but you'll probably find it via a search.

When FTTC was installed at my home, the engineer reused my 20m unearthed shielded cable crimped to the incoming drop wire to extend the master socket from upstairs to a room downstairs.

Using a spare pair in the shielded cable he back-wired from the new master socket position to the upstairs room making what was originally the master socket an extension.

I had lots of problems with my connection & one engineer provided a new drop cable round the back of the house directly into the downstairs master socket & just used the shielded cable as a telephone extension cable.

Doing that didn't seem to make much (if any) difference.

« Last Edit: June 19, 2013, 11:47:20 PM by Bald_Eagle1 »
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