Speed

[ichilton]

Hi,

We just moved a few weeks ago and are having to move to ADSL as this street isn't cabled, even though it's only round the corner from our old house.

I've had a bit of a nightmare getting a BT line in - the previous people had their phone with Sky and said they'd cancelled it but it's still working. BT were supposed to be taking it over and it would take 10 working days but after 2 weeks they cancelled the order and said they couldn't do it so i've ordered a brand new line which is getting installed on Thursday, at which point i'm going to order O2 Premium.

Anyway, i'll post my proper stats when i'm connected but this is what i'm seeing from the previous owner's Sky connection and thought it would be interesting to see how good this is as i'm assuming i'll get similar results on O2.

The full output is in the image attached to this post but it's sync'd at: 5280kbps and 416kbps. Line attenuation is 53db and 31.5db and noise margin 7.3db and 14db (all downstream then upstream).

What's the quality of my line like?

Are those sync speeds good for this line or could it be improved?
(if so, how?)

The exchange checker on this site is showing 1.57 miles direct and 1.9 miles by road. Are the above numbers about right for that distance?

The speed test on this site is showing: 4392kbps and 308kbps - is that about right for the above sync speed?

I'd particularly like to get better upstream if possible?

The router is connected to the master socket with an ADSL Nation filtered faceplate.

Thanks,

Ian

[Saturday]

Your attenuation of 53db would indicate a line length approaching 4km so a bit more than the road distance (not unusual). It would also suggest a maximum sync of ~5meg is possible - which is what you are currently seeing i.e. your line quality is good but your line length is fairly long.

Expect a similar downstream sync with O2 but an upstream sync of a bit over 1meg.

[ichilton]

Hi Saturday,

Excellent - so you would agree on those numbers that everything is in order and there is nothing I can do to improve it?

Wow - 1mb upstream? - i'll be happy with that!!

How come so much better than Sky?

Thanks,

Ian

[ichilton]

Hi Again,

Just another question - if I were to go for the Pro package which has 2.5Mbps upstream instead of 1.3Mbps, what would I likely get on that line?

Would I not really get much better because of the line length or would I get just over 2Mbps? (and will that affect my downstream?)

Thanks!

Ian

[Saturday]

Sky cap the upstream to below what ADSL2+ is capable of - though there are rumours that this will soon be changing.

O2 will set you up with a 1.3meg upstream sync. In practice you'll get a shade under that. This won't affect your downstream.

If you were to go for the Annex M option then the upstream would rise to a potential 2.5meg. However, the full 2.5 demands a good quality, fairly short line. My guess is that you'd see more like 1.8 or 2meg with your line. The other consequence is that your downstream sync would be slightly lower to allow for the higher upstream.

Yes, indications are that your line is in as good a condition as is possible. You won't know for sure though until you actually have the new connection.

[ichilton]

Hi Saturday,

Thanks for all your help.

It sounds like it's worth just sticking with Platinum as £10-£17 is quite a jump to go from say 1.2Mbps to say 1.8Mbps and get a static ip (especially when I read a comment from you in another thread saying that O2 IP's are very sticky).

Out of interest though, when you say that going to Annex M will decrease the downstream slightly to give the higher upstream - by how much is that roughly? - If 5280kbps was my downstream sync for example, what would that likely drop to with Annex M?

Does Annex M give any other advantage apart from up to 2.5Mbps instead of 1.3Mbps upstream?

My line is supposed to be installed tomorrow afternoon so as soon as the new number is recognised by O2's line checker i'll be placing an order and hoping for an activation date as soon as possible so i'll post back here all my stats when I get up and running.

Thanks again,

Ian

[Saturday]

A copper phoneline is capable of carrying a wide range of frequencies other than those needed for a voice call - it's those higher frequencies that are used for ADSL. The usable frequencies available depends on the line length and condition (attenuation and induced noise).

In simple terms, ADSL takes the available non voice frequency bandwidth and divides it into two unequal parts. The first part above the frequencies used for voice are used for the upstream signal. The remainder is used for the downstream.

Annex M, again in simple terms, takes a slightly bigger chunk for the upstream and so offers a higher upstream sync. If the line is long and/or poor quality then this can mean that the downstream sync is lower as there isn't enough "spare" frequency left. How big this effect is will depend on the frequency carrying characteristics of your line so I'm afraid it's not possible to predict the exact loss (if any) that you'd see on your line. I offered a guess but that's all it is I'm afraid.

I can't think of any other advantage to Annex M than the increased upstream. It's just ADSL2+ with a different apportionment as loosly described above.

[ichilton]

Hi,

Ah, that's very useful - thanks!

Shame you can't take up some of the voice frequencies for extra data bandwidth :-)

Ian

[ichilton]

Hi,

Router arrived today - just plugged it in and it's working and online - whoo!
(activation date is Wednesday and it's only Monday today).

Here are the stats:

Uptime: 0 days, 0:22:34
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 1,144 / 6,036
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 19.0
Line Attenuation (Up/Down) [dB]: 31.0 / 53.0
SN Margin (Up/Down) [dB]: 6.5 / 6.5
Vendor ID (Local/Remote): TMMB / BDCM
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 0 / 0
FEC Errors (Up/Down): 21 / 7,794
CRC Errors (Up/Down): 21 / 53
HEC Errors (Up/Down): 6 / 41


Does that all look ok?

Speed is better than the old owner's sky connection was at the moment but i'm guessing it will drop if there are too many re-connects in the next few days...

Thanks,

Ian

[Saturday]

Wow, you have been connected early!

O2 tends to sync ~10% faster downstream than Sky, not always but it seems to be quite common. Whilst that may partly be down to the slightly lower target noise margin (6.5 v 6.9db) I think they just have a better set up network/hardware/firmware. O2 will set a 3db profile on good lines if asked. I think that may be pushing it though with your line length. Try it yourself once line testing (DLM) has finished - you'll need a router that can take custom firmware or will work with the DMT tool.

6meg is very good for your attenuation.

No reason why your connection should drop, your errors aren't particularly high, though the measurement period was only 22min.

I think you can expect a good, reliable connection. I hope it lives up to its promise for you.