I've read a few posts on here and it seems a fair few people are having problems with the 21CN upgrade. I was upgraded on Thursday 11th March and noticed that after rebooting my router my connection speed has dropped from 2.5mb to 1.3mb. The attenuation figure went up from around 56db to 75db which as far as I can tell is contributing to the speed drop.

Does anyone have any ideas on how to get my speed back up to at least what it was on the "up to" 8mb product? I wasn't actually expecting too much of a speed increase but to have the speed drop is just ***. My router is ADSL2 compatible (Belkin N F5D8633) and I'm using a BT iplate (highly recommended by the way).

I know this is likely to be BT's fault and not Zen's so I'm not blaming Zen.

Hi

can you post your router statistics . The attenuation looks very odd you would expect no more than about 2db increase due to the higher frequencies used .  With your original attenuation your synch rate should have been about 3400Kbps with the default target SNR margin of 6db the most you could expect on 21cn  is about 3700Kbps . Obviously something is wrong with the connection. 

to be sure its not your internal wiring  check  your connections 

regards jeff

 

 

Hi Jeff, sure, here are my router stats:           
       
Downstream    Upstream  

Data rate(Kbps)    
1400Kb    738Kb
           
Noise Margin    
6    5
           
Output power(dBm)    
128    164
           
Attenuation(dB)    
74    35

If you need any more, let me know and I'll post some more but these are the main ones to look at afaik.

The noise margin of 6 has stayed the same since the upgrade.

I spent several months last year making sure the internal wiring was all sorted out. I've tried a few tests (all of the ones from the link you posted) since my upgrade too. The internal wiring didn't change when I received my upgrade so if it is indeed the wiring that's causing the problem it's a bit of a puzzle for me. I get the same attenuation when plugged directly into the master socket, with and without an iplate etc.

One thing I've just noticed is that my upstream speed has increased.

Cheers!

Hello,

I myself had major trouble of the same kind after my regrade to 21CN & ADSL2+ service.

No.1 What you have to essentially realize is that your connection is now 100% being controlled by BT's automated line management system & what that means is that your connection speed is completely determined by the automated system. NOTE:- the end user cannot tweak or change any pararmeters like before. Your now dealing with a different animal as it were?

No.2 The best way to regain your speeds to some degree is to keep the router connected 24/7 and not and I repeat this NOT keep rebooting it as rebooting the router will lower your speeds even more.

No.3 Your speeds will slowly recover over time given that you leave the router connected 24/7 and leave it alone, but it could take a good 10 days or more.

No.4 when users are moved to 21CN your connection has to undergo a fresh 10day training phase by the automated line management system it creates a profile & this also sets your BRAS (this includes your MSR & MFR, maximum stable rate & fault rate).

No.5 Also note that what your connection sync speed is going to be higher than your actual downlink & uplink rate in reality. My line for example sync's at 8.5megs but I'm still only getting 6.2 to 7megs on speed tests.

Hope this helps?

Ivan

Very strange that the attenuation has increased like that!

Best bet is to give support a ring - if the worst comes to the worst you can always be put back on 8Mb Standard ADSL, but hopefully there may be some other things they can do for you to resolve it.

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Kindest regards,

James Sweet
http://www.zen.co.uk

Thanks Ivan, I'll leave it alone and switched on. It's been on 24/7 anyway but I've rebooted it once every day or so to see if it connects any higher. Totally get what you're saying about it being in BT's control now. And it scares me lol.

And thanks James, I'll leave it a few days and will give support a call. They've been fantastic in the past so I'm sure they'll sort me out.

If your connection is on a physically long line i.e. distance from the nearest BT exchange perhaps the attenuation figures are not so weird? because its common for longer lines to experience greater line attenuation, this is related to signal strength and signal strength is affected more proportionately over distance. i.e. those people close to the exchange will by default have a stronger signal strength than someone living 4K away. Again sadly there is little or nothing you can do about the attenuation figures its down the ALM system once again as far as my understanding goes.

Ivan

My line is around 3-3.6km from the exchange (line length, not as the crow flies) so I know this accounts for a fairly high attenuation. My attenuation was in the 50's before the "upgrade" to 21CN so the upgrade has increased this significantly.

So, if there's nothing to be done about the attenuation figure I'm wondering if there's a way to go back to ADSL1 to get my higher speed back. If that fails, I'll consider cancelling my BT line and grabbing a 3G connection. A 1 meg connection these days is laughable, especially when it's caused by an upgrade that's going to give those with 6mb+ an even better line at the cost of my own connection speed.

Replying:-

No.1 Its my understanding that 21CN ADSL2+ connections work using a much higher set of frequencies than ADSL1 so that also might go some way in explaining the higher attenuation figures.

No.2 Good luck switching back to your old connection. When I contacted Zen support they said Sorry! thats not possible as everyone was being moved to 21CN.

No.3 I'm wondering if there is an option to regrade back to ADSL1 using the regrade wizard via the Zen customer portal?

**In my case I've decided to leave things as they are for now because I'm back to where I started i.e. no better & no worse off than before. But its still pretty disappointing to only get 6.2 mbps on a theoretical upto 24mbps line.

Ivan

Hi,

On point 2 - you've been mis-informed on switching back to ADSL1, I'm afraid. :(  You can't switch back to 20CN, but you can get an 'up to' 8Mbit/s service on 21CN - which is essentially the same as ADSL Max.

In point 3 - you should have the regrade option available in the portal (basically it's anything with '8000' in the product name).  

From our testing we know that those with sub-4 Mbit/s are least likely to see an improvement in speeds.  As you get closer to 2Mbit/s and less it becomes more likely that you'll see the same or lower speeds.  For this reason we've kept the ADSL1 service regrade option as for some customers ADSL2+ is either going to offer no improvement, or actually a worse service (if downloads is more important than the increased upload speed ADSL2+ can deliver).

kind regards,

Phil. 

 

 

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Phil Long
Performance and Process Improvement Manager - Zen Internet Ltd.

Hi Phil,

Thank you for clarifying those points and its refreshing to receive a bit of honesty about what some 21CN customers might get despite all the BT hype which I find very annoying to be honest with you. 

Ivan

Thanks Phil, I got a repy from tech support saying the same as yourself. I need to try a different router that lets me manualy change my modulation (although I'm loathe to buy one just to test it) and also try a regrade back to ADSL1. It would have been nice to know about the potential speed decrease for lines with 2mb connections before I regraded though.

Any idea whether the attenuation rate would go back down after a regrade to ADSL1? This seems to be the issue that's affecting my speeds (download speed is more important than upload speed for me by the way, as I imagine it is for most people).

I am annoyed by all of this (and this annoyance is directed at BT, not Zen) as this "upgrade" to 21CN seems to only increase the speeds for those getting high speeds anyway and those of us struggling with poor lines/poor speeds are being screwed over in favour of those with nice connections anyway. Is there a way to bring this up with BT at all?

If I had the same connection speed as before it wouldn't be so bad but to reinforce Ivan's point about getting 6.2mbps on an up to 24mb line, I'm getting 1mbps on an up to 20mb line which is 1/20th of its potential and more than half what I had previously and well below the 2mb minimum that the (still proposed?) broadband tax is meant to deliver.

On the plus side, I'll be moving to Bristol in 3-4 months time and they have a good spread of exchanges and speeds in various points of the city are around the 6-8mb level and they're hooked up to cable too so I have the coice of switching to cable (alas, I would have to leave Zen for that :( ).

Thanks for everyone's help with all of this.

I would be inclined to press for a check on that attenuation increase before switching back to ADSL1. I would ring support about that. If the first person you speak to does not consider that a fault ask to speak to a team leader.

A question for Zen about this...

If you saw in your tests that people with less than a 4mb connection would not see an improvement, and that those close to 2mb would possibly see a decrease in speed then why wasn't this information presented up front before I wasted my time with the upgrade? What on earth was the point of running the trials if no information about who would benefit would be forthcoming from it? I have been grossly misinformed about this from the start. Surely the increase in attenuation should have been highlighted at the very least. I'm rather annoyed that all I got was the marketing *** and no real advice up front.

To be fair to Zen they are being sold this product just the same as we are and it is difficult for any ISP to tell exactly how any line will behave specifically because they have to rely on what BT tell them.

 

 

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Attempting to answer the unanswered
Interest: PCs, servers and networks