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[colin79666]

Posted this on the BT community forums but since discovered this site. What an excellent resource! 

We have had BT infinity 2 (up to 78 Mbps) for nearly 4 years and since the day of connection until a month or two ago any speed test indicated we pretty much got the headline rate. Now seeing 58Mbps down and 14Mbps up. When it was installed the BT engineers gadget showed our line was more than capable for 80/20. Of late however I noticed some activity was a bit slower, especially my backups to Azure. Unfortunately I don't have any line stats to go back to.

From the info found on here I discovered we have a Huawei cabinet but a ECI modem so couldn't get stats. I've never used the BT Home Hub, preferring an Asus RT-AC68U for the past 2 years. I've acquired a HG612 from eBay and had that running a couple of days, installing the unlocked firmware. Since installing it I've had to disconnect the phone line once as the modem seems to run hotter than the ECI and I needed to move it for more ventilation, other than that the connection has been stable (and going back weeks the router logs don't show any disconnections).

I've got a better modem/phone cable on order but currently using standard flat cable the modem came with (don't think it will be twisted). Modem is connected direct to the NTE5 socket. Line is underground from the cabinet to the DP in the street and from the DP to the house. Distance from the house to the cabinet is about 200m as the crow flies but unsure how long a path the line takes. In the house the old master socket wasn't in a good position so the original line was extended by the engineer about 10cm into a new NTE5 master socket also into which there is a phone extension running from upstairs. I've made no changes to extensions or phone handsets since. No noise on the line to be heard when conducting a quiet line test.

With the background out the way I'm hoping someone more experienced than I might be able to shed some light on the possible reasons for the performance to have dropped?

[skyeci]

probably due to cross talk if the speed has reducded over time (new subscribers). 80/20 is up to so full speed never guaranteed. your sync is actually 62mb so you have lost a bit. Looks like dlm has you on a 3db snr so  not likely to gain anymore at the moment.

with attenuation of 16 you are over 200m from the cab.

[ktz392837]

With an attenuation of 16 I would estimate a length of around 350m. 

If you are a member of MDWS you can view other user stats.  I would say you are probably at the lower range of sync speeds for that db especially with ginp and 3db active.  I think this points more to just high take up at your cabinet rather than a fault though but check if you are below the handback speed for your line at the checker if you want to risk reporting a fault to see if BT will pair swap you.

Signing up to mdws and recording stats for a few days may be beneficial as I am sure the more experienced stats experts will give their opinion if they believe there is a fault.

[colin79666]

Thanks both for the advice. I've signed up for MyDSLWebStats (colin79666) so that might help keep a track although I won't be able to leave my PC running 24/7. Handback is 53.7Mbps so I'm above that threshold for now. Quite happy with current service but worried it might drop further, especially if cause is unknown.

The drop of around 10Mbps for DL appeared to be quite sudden rather than a gradual decline. Is that expected with cross talk caused by more FTTC activations?

[ktz392837]

You tend to get three kinds of crosstalkers, 1) makes little difference (1% loss), 2) makes a small amount of difference (5% loss) and 3) a major disturber (15% loss).  Just plucked these three educated guess % figures from thin air just to give you an idea.

You get loads of 1, several 2 and a couple of 3.  Crosstalk normally costs you 30-40% on a full cabinet (seems to be the accepted % figure, vectoring really helps offset this but only deployed on a few cabinets).

If you find mdws useful I recommend getting a RPI so you can keep stats running 24/7.  I think there is a link somewhere for All User Stats and you get a table of all user data so you can sort on the data like cabinet type and attenuation - very useful.

Hopefully a friendly expert will comment on your qln, hlog and other stats.

[colin79666]

Thanks for the info. I've got a Raspberry Pi Zero on order so that can be left gathering stats once I get it configured.

Was across the road at a neighbours this afternoon to help with her PC. Did a quick speed test while I was there and she was getting 72 down, 16 up with the HG612 and Home Hub 3 so I'm more convinced than every that my line has been affected by some internal or external factor.

[burakkucat]

I've taken a quick look, via MDWS, at your Hlog and QLN plots.

We can see from the Hlog plot that the US2 and DS3 bands show some slight, abnormal, undulations. I am unable to say what could be the cause of that effect.

The QLN plot also shows signs of abnormality in the US2 and DS3 bands. That could be the result of one (or more) cross-talkers coupling into your circuit.

Overall, the circuit appears to be quite good and I would suggest that you examine the local wiring within your premises to ensure that best principles prevail.

[ktz392837]

As noted by bcat definitely ensure you are testing from the master socket to ensure your local wiring is having no impact.

Also worth mentioning trying a different modem may give positive results either speed or much lesser errors wise.  Can be expensive as may make no difference so unless you are looking to change to a combined unit or using your current as a spare you need to have accommodating friends.

I use the decent Zyxel 8324 can't remember if its the A or D model (and it does make a difference).  I think there is a thread mentioning newer models (1312?) that has the same chipset though - again be careful you get the correct variant though.  Definitly confirm first as I am not 100% sure on model numbers (someone may post details?).

[colin79666]

Thanks again.

Performance dropped with the ECI modem and appears much the same with the HG612. Unfortunately I don't have another VDSL modem to try but I guess having tried two with different chipsets that probably rules out a failed modem.

I haven't made any other changes internally but will disconnect the phones (including extension) tomorrow along with the NAS that sits next to the modem and see if there is any improvement.

[ktz392837]

I wasn't really trying to say a dodgy modem more the original HG612 & ECI modems are very old and use old chipsets, a newer modem with the correct newer chipset can make a difference. Also can make no difference.

Not sure what else to suggest apart from let your stats gather a bit more and ask if someone else is happy to give a 2nd opinion.

I still think you are certainly a bit unlucky not to be getting a better sync speed especially on a huewai cabinet with ginp and 3db at your line attenuation.

[colin79666]

Raspberry Pi Zero should be turning up today or tomorrow so I'll be able to get stats over a bigger timeframe soon. That might help establish a pattern or at least give me something to wave in-front of BT should the sync drop again.

Took the NTE5 apart this morning and tried the HG612 straight into the test socket. Also powered off both DECT phones in the house. Got a slight improvement of sync rate and slightly less of a drop in the SNR around tones 400-500 but nothing significant so that can probably be put down to time of day/weather/random chance.

I should have my hands on a Zyxel VMG1312-B10D by the weekend. I don't expect it will magically get the profile back to where it was but as you say with the more modern Broadcom chip it might improve things a little and probably won't make it worse anyway. Apparently it supports vectoring so if my issues are indeed crosstalk and BT enable the functionality at my cabinet then I will have the equipment to take advantage of it.

Thanks for your help 

[ktz392837]

The main thing I value my Zyxel for is it keeps the ES very low for my line and as I am on an ECI cab that is good news as it has no ginp. 

I cross fingers your new modem syncs faster.  The better chipset (?) will hopefully play better with the dlm so it should be positive.  Even if not immediate sync increase less errors may allow the DLM to adjust power and bit loading over a few days?

Also good you will have before and after mdws.  Be careful I am not sure how long stats are kept if you do not donate though!

[colin79666]

Hmm connected up the ZyXEL VMG1312-B10D yesterday around 1700. Had a few issues getting the RPi reconfigured so it wasn’t monitoring quite straight away.

Stats don’t paint a pretty pictures. Errors (of all kinds) have shot up!

Now the question this raises is the ZyXEL just bad for my particular line or was the HG612 not reporting the truth? I’ve afraid the leave things as they are as DLM may well kick in with this.

[ktz392837]

Have you gained any sync speed?  If your FEC errors have shot up I think that is fine as these are automatic error corrections.  Work out your estimated ES/hr is it reasonably within the amber range for a 24h period?

I think someone who knows the stats better than me is going to have to suggest next steps?

You can look at the forum yourself for others singing praises of the Zyxel modems (did you check the D variant was the better one?) so you must be very unlucky for it to be worse than a hg612!

[colin79666]

Slightly lost sync speed  E/S hour have gone well into the red (almost zero recorded on the HG612)

I've actually got two ZyXEL VMG1312-B10Ds and have tried both. Each has much the same stats after an hour of running so I think I'm perhaps just unlucky that they don't agree with my particular line. I've seen plenty positive comments from others about their performance although one reviewer on Amazon did comment that the B10D did give them more errors than their HG612.