topic Re: Lower than expected speeds due to high SNR in Archive

Lower than expected speeds due to high SNR

dcwt2010 — Mon, 09 Apr 2012 16:22:25 GMT

No idea there was a business forum but here's what's happened so far

http://community.bt.com/t5/BB-Speed-Connection-Issues/Lower-than-expected-speeds-due-to-high-SNR/td-p/453861/highlight/false

So, how do I contact the mods on here then? They were pretty nifty on the residential forums (replied today when I sent the message on Sat, pretty good considering it's still Bank holiday!) but I got told that my issues have to be handled by the business BT team.

Basically, my connection can't seem to hold sync at above 1760 kbs; during night time when the SNR drops (due to increased electrical usage etc) if I had the connection syncced at 2Mbs or above (highest I've seen is 2.4Mbs) then it will lose connection and resync at ~1760kbs. My estimated linespeed is 2Mbs but I'm not really seeing that and it is frustrating. With a 52 db downstream attenuation I should see up to 4Mbs but obviously that's dependent on perfect conditions.

Anyway, loads of details on that 4 page thread I won't repeat myself on here.

PS I tried to use this page

https://secure.business.bt.com/FaultManagement/Online/M701AuthenticateViaBBNumberWithCaptcha.aspx?faultType=Broadband

I put in our number but it came back as unrecognised, what gives?

Re: Lower than expected speeds due to high SNR

MHC — Mon, 09 Apr 2012 16:45:25 GMT

Can you install and run Router Stats Lite for 24 hours with plots of sync speed and SNR and 1 minute intervals?

http://www.vwlowen.co.uk/internet/files.htm

And provide images here for comment.

Re: Lower than expected speeds due to high SNR

dcwt2010 — Mon, 09 Apr 2012 18:34:23 GMT

Hey, I'm away from the location till the weekend but I'll be sure to do that first thing from Friday evening. In the mean time, is there any chance you can arrange for the SNR to be reset, should be interesting to see again where it finds stability. I'm assuming that 6 db is default and it works its way up by 3 db each increment till it's stable?

Re: Lower than expected speeds due to high SNR

MHC — Mon, 09 Apr 2012 19:17:38 GMT

I'm not one of the mods here and cannot do anything but will try to help.

To get te SNR reset the easiest way is to call teh Tech Support desk and explain - they don't bite, honest!

By getting a detailed RS or RSL plot you will be able to see what the SNR does overnight - does it vary by 2dB from day to night or 7 dB (or more) which can happen. Are there any specific noise pulses that cause a resync ... or long bursts of noise.

Re: Lower than expected speeds due to high SNR

dcwt2010 — Mon, 09 Apr 2012 19:29:51 GMT

Hmm, I guess I can give them a ring later.

From what I can see so far (look at the posts on bt forum) the SNR will fluctuate by as much as 6 db over the course of the day. Haven't pinned it down to the cause yet, there's a lot of electrical appliances nearby (like big fridge motor, microwave, CRT TV) but they've been turned on and off at different times without affect the line. Might need to do a more thorough investigation but I'm stumped. It's currently syncced at 2.2Mbs downstream with ~12 db SNR so hopefully by the time I return home it'll be more than 3 days of stability.

Personally, I think the HH2 is partly to blame and will be replacing it with a TP Link.

But yeah, what you've suggested is a good idea, I really wish I'd know/thought about it earlier!

Re: Lower than expected speeds due to high SNR

MHC — Mon, 09 Apr 2012 21:39:21 GMT

How is that you have a HH2 on a business service?

Given your line length, have a look on a certain "auction site" and see if you can get a 2wire2700HGV with v6 firmware. Good on high attenuation lines and will hiold sync down to quite low levels.

Something is nagging though about the HH2 and RS/RSlite and I am not sure if it will work. The HH2 is not listed, some claim to have got it to work. If not, can you borrow a hub to try and grab some data?

Re: Lower than expected speeds due to high SNR

dcwt2010 — Mon, 09 Apr 2012 22:19:39 GMT

Reusing it as my sister used to have a residential line with BT. I wouldn't have used it but it was free and I only had G Wireless routers.

I've ordered a TP-Link TD-W8960N as recommended in the BTcare forums.

I'll take your recommendation into consideration for future though.

Hmm, like I said it'll have to wait till Friday evening before I can start but thanks for the tips so far.

Re: Lower than expected speeds due to high SNR

kuerten — Wed, 11 Apr 2012 13:19:14 GMT

Keep us updated. Let us know on how it works out for you. 🙂

Re: Lower than expected speeds due to high SNR

dcwt2010 — Wed, 11 Apr 2012 19:27:19 GMT

Well the new router should arrive by Friday. I've got a feeling, just like the last two times, the connection will have been up since I was away but with disconnect and resync shortly after I turn up (my parents are still there so it's not like all electricals got turned on when I arrive). Hopefully I can log those SNR details with the HH2 just to see how bad it is.

Re: Lower than expected speeds due to high SNR

dcwt2010 — Fri, 13 Apr 2012 17:09:09 GMT

Ok, just arrived back at my parents and here are the stats

ADSL line status

Connection information

Line state	Connected
Connection time	3 days, 20:59:22
Downstream	2,144 Kbps
Upstream	448 Kbps

ADSL settings

VPI/VCI	0/38
Type	PPPoA
Modulation	ITU-T G.992.1
Latency type	Interleaved
Noise margin (Down/Up)	12.9 dB / 20.0 dB
Line attenuation (Down/Up)	52.0 dB / 25.5 dB
Output power (Down/Up)	16.5 dBm / 11.9 dBm
Loss of Framing (Local)	0
Loss of Signal (Local)	99
Loss of Power (Local)	0
FEC Errors (Down/Up)	7062336 / 118
CRC Errors (Down/Up)	16695 / N/A
HEC Errors (Down/Up)	N/A / 59
Error Seconds (Local)	4391

So it seems that it can hold a 2.1 Mbs UL, which is a slight improvement but I don't like how many error seconds that are there. Also, with more than 3 days of stable sync, I can ask for an SNR reset, right?

Routerstats Lite doesn't work with BT HH2 so I can't track stats for now. Lame.

Re: Lower than expected speeds due to high SNR

dcwt2010 — Sat, 14 Apr 2012 11:25:38 GMT

Requested an SNR reset via tech support on the phone. Pretty easy although the guy kept insisting that the best my line could do was 500kbs to 2Mbs! I wouldn't mind but I told him point blank that nearby houses could get ~3.6Mbs, although I'm only aiming for ~3 Mbs which, with a 52 db downstream attenuation, I should be totally able to do so.

I put in a new router TD-W8960N and guess what? The Homehub 2 was lying, I seem to have a 60 db downstream attenuation now so 2 Mbs really is my max capacity... unless the new router is wrong?

Re: Lower than expected speeds due to high SNR

MHC — Sat, 14 Apr 2012 18:39:35 GMT

There is no consistency in the way downstream received power and noise is measured - and some use the absolute figure, others the margin allowing for the 6dB needed for sync ... Then the termination impoedance is not always te same which can further affect the figure ...

If you can find a 2wire2700HGV-C on ebay at a reasonable price, go for it. They are very stable on long / hi atten lines and may give a little more speed. They also sync at 3dB once a line is seen as stable and will hold down to 0dB.

Re: Lower than expected speeds due to high SNR

dcwt2010 — Sat, 14 Apr 2012 20:13:46 GMT

I think I will keep my TP link for now but thanks for the suggestion. It's certainly more sturdy than the HH2! Below you can see where the SNR just dives to 0 db but the connection doesn't seem to have broken! Also, the SNR hasn't dropped even though we are now well into the night.

I do find it frustrating that these stats are not comparable to the Homehub...

So how the heck can I work out line length if not from downstream attenuation? HH2 and this TP link router show 8 db difference... that's pretty significant, no?

Re: Lower than expected speeds due to high SNR

kuerten — Sun, 15 Apr 2012 12:19:08 GMT

8db sounds normal to me but it should be better than that though.

Re: Lower than expected speeds due to high SNR

dcwt2010 — Sun, 15 Apr 2012 14:18:37 GMT

I think you misunderstood what I said;

HH2 shows downstream attenuation as 52db

TP link TD-W8960N shows it as 60/61db.

The difference in potential sync speed is really significant and seeing as with the HH2 I never got better than 2.3 Mbs sync I'm inclined to believe that the attenuation is ~60 db which is really quite disappointing.