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    3db SNR and poor download speeds following migration from O2

    This is a discussion on 3db SNR and poor download speeds following migration from O2 within the Sky Broadband help forums, part of the Sky Broadband help and support category; Hi All Ever since migrating from O2, I have seen poor D/L speeds (~ 200K to 800K). Also Ping times ...

    1. #1
      nholland_uk's Avatar
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      Unhappy 3db SNR and poor download speeds following migration from O2

      Hi All
      Ever since migrating from O2, I have seen poor D/L speeds (~ 200K to 800K). Also Ping times are poor. I never seem to have this with O2.

      My Line syncs ~ 6-7M, and it seem to be worse at night (feels like the network is congested..). My Galaxy S4 keeps reporting "you Internet connection is unstable"

      These are my router sats now (16-3-14)

      Broadband Link Downstream Upstream
      Connection Speed 6723 kbps 440 kbps
      Line Attenuation 45.0 dB 25.6 dB
      Noise Margin 1.4 dB 25.25 dB

      I have never seen my Noise Margin go above 3.1db.

      If it is down at 1db-3db, will this have an impact on my speeds?

      Thanks


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    3. #2
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      Re: 3db SNR and poor download speeds following migration from O2

      Quote Originally Posted by nholland_uk View Post
      I have never seen my Noise Margin go above 3.1db.

      If it is down at 1db-3db, will this have an impact on my speeds?
      Short answer - yes. But there's also the issue of how you are connecting. If wireless then it is perfectly possible to have a seemingly good sync but a very poor throughput. Assuming it's not a wireless issue:

      When did you migrate across? Were you an auto migration i.e. just BB transparently moved or did you move across phone and BB to Talk and Sky BB?

      If the latter then after 2 or 3 days your line would have gone into DLM training* which will then run for up to 10 days. During that time it will raise your sync/decrease your noise margin down to as low as 3db if the line is good enough. If it isn't coping with 3db then it will raise it until the line is stable. So, if you're currently in DLM it will sort itself out in a few days. If you're not in DLM then something is wrong and you need to call Sky and get this sorted. This may mean initiating DLM training again.

      If the former then it seems to be hit and miss whether ex O2 customers go into DLM or not. Some report they have, some not. Either way you need to call Sky if this problem persists for more than a couple of days.


      *DLM is usually initiated for all new connections. It is always running but after the initial training it doesn't do anything more unless triggered to by line issues in which event it goes into an active training phase. This should be auto but sometimes needs to be manually triggered.

    4. #3
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      Re: 3db SNR and poor download speeds following migration from O2

      It doesn't looking like your exchange is Sky LLU enabled, so you must be on the dreaded Sky Connect (rebadged BT) product.

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      Re: 3db SNR and poor download speeds following migration from O2

      Well spotted - profile says Sky Connect .

      So presumably he wasn't O2 LLU either - didn't realise O2 did Connect? In which case the connection was Connect and still is Connect so no change and ought to be the same line/equipment. Which if so leads to this problem not being a migration issue but coincident with it.

      @ nholland_uk - probably a bit more info needed in that case but that 3db issue isn't right and you'll need to get on to Sky

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      Re: 3db SNR and poor download speeds following migration from O2

      It looks like he has been transferred to Connect, but is on the 21CN network, ie, BT's ADSL2+ service. Best advice, get out when you can, even if your line was giving 100%, you would be severely throttled especially at peak times, which is probably what is happening now.

      Just to check that your internal setup is OK you should plug into your test socket using only the cable and filter supplied by Sky. Post your stats from there. (If you don't have the SR101 as your Profile says, use the ADSL cable and filter supplied by O2).

      TomD


      Please note the views and recommendations in my posts are my own and in no way reflect the views of SkyUser.


      Useful Utilites

      http://www.nirsoft.net/utils/wifi_information_view.html/ TCPOptimiser /Test Socket

      Note - When downloading always select the Custom install or you will end up with stuff you don't want.





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      Re: 3db SNR and poor download speeds following migration from O2

      Hi all
      I was migrated on 4th Feb. I have only been watching router stats for last 3 weeks odd since I noticed throughout struggling with video watching etc.

      i have swapped cables and micro filters etc to my old O2 parts. No difference .

      Also I have and older version of master socket, so no test socket available to plug straight into.

      So on the noise margin, is higher than 3db better? I have seen that 6db is standard but is this dependant on distance from exchange etc.

      I was on connect staff product with O2 and same applies to new setup with sky. What would have occurred in exchange (if anything) to migrate me?

      thanks

      - - - Updated - - -

      Forgot to say migrated BB and phone (phone went over on 10th).

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      Re: 3db SNR and poor download speeds following migration from O2

      The higher the noise margin the better the router is able to distinguish between noise and signal. However, the higher the noise margin the lower the sync. For most lines around 6db on the downstream gives the best compromise. Poor lines may need higher whereas good, short clean lines may be OK at 3db. Your attenuation suggests your line isn't particularly short and a noise margin of only 1.4db would give problems with even the best of lines. If as you say the noise margin is never above 3db then something's not right.

      So, you need to call Sky and get them to investigate.

      With regard to your throughput, with a sync of 6723kbps that should be much better. One cause could be you are connecting wirelessly and have signal problems. Another is that your connection is erroring so badly that data is being continually retransmitted (a very noisy line and a low noise margin can cause this). Lastly, as you are on Connect, you are likely to see a much reduced throughput at peak times as it is prone to over subscription/congestion and speed "throttling" is common. Only you can resolve wireless problems. Only Sky (through BT) can resolve the low noise margin by setting a new (lower) sync rate. If you have a noisy line, you have to sort out any problems your side of the master socket and only BT can sort out any problems with your line. Sadly, I suspect you have no alternative to Connect as your exchange doesn't appear to be LLU.

      So again, first step is to contact Sky. Once they have done a line test and resolved any issues found and once they have reprofiled your connection, you'll be in a position to determine whether changes to your home wiring would offer further benefit.

     

     

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