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ADSL speed problems

Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

ADSL speed problems

Hello,

 

I have had some major problems this past month with my router not authenticating. I replaced the router and was getting decent speeds for a few days until last night.

The highest I've seen this line sync with any router was around 21000kbps this has been slowly decreasing over the past few months, the line syncs at around 16368kbps with this router but throughput to any device wired or wireless is around 6500kbps if I'm lucky.

Could anyone shed some light on this problem?

ADSL line status

Connection information

Line state Connected
Connection time 0 days, 0:41:58
Downstream 16,368 Kbps
Upstream 1,178 Kbps

 

ADSL settings

VPI/VCI 0/38
Type PPPoA
Modulation ITU-T G.992.5
Latency type Interleaved
Noise margin (Down/Up) 15.2 dB / 7.3 dB
Line attenuation (Down/Up) 2.0 dB / 2.3 dB
Output power (Down/Up) 18.8 dBm / 12.3 dBm
Loss of Framing (Local) 0
Loss of Signal (Local) 0
Loss of Power (Local) 0
FEC Errors (Down/Up) 469 / 5
CRC Errors (Down/Up) 2 / 2147480000
HEC Errors (Down/Up) nil / 179481
Error Seconds (Local) 1
 
18 REPLIES 18
Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

Recent speed test on a wired connection

Rising Star
Posts: 376
Thanks: 32
Fixes: 1
Registered: ‎12-02-2014

Re: ADSL speed problems

Interesting. I'm merely an 'amateur' here but my observation is that those line losses (2.0 dB / 2.3 dB) are very low - you must be almost living in the exchange! - and those speeds, though pretty good, should indeed be higher with such low line losses. (I used to get speeds somewhat higher on line losses of ~28/14 dB)  The original 21,000 Kbps sounds right to me. 

The 15.2 dB/7.3 dB noise margin is the restriction. The default noise margin on download nowadays is ~6 dB, not 15 dB as in your case. So either the speed is being limited - and 15dB is the corresponding noise margin, or some problem somewhere is causing a high noise margin and that is limiting the download speed.

Have you checked your line and connections using the 17070 Option 2, Quiet Line Test? If OK, I would try a reboot of the router early in the morning to see if it can renegotiate a lower noise margin and higher speed. But, with the low throughput something is likely wrong somewhere. Possibly line noise or RF interference on phone line? The HEC errors seem high, mine are usually zero.

Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

I live about 30m from the exchange. The speeds since moving to ADSL 2+ have been pretty stable around the 21000 kbps mark with a download noise margin of 8db usually resulting in 18000 kbps in throughput as expected sometimes higher.


The noise has been slowly creeping up and the lowest sync was around 15500kbps at 12db but throughput has always been about 90% of the sync speed.

I've checked all connections, replaced filters and cables. The line test comes back clean.

Rising Star
Posts: 376
Thanks: 32
Fixes: 1
Registered: ‎12-02-2014

Re: ADSL speed problems

Sounds like possibly rising RF interference on telephone line. You could use a portable Medium Wave radio tuned to 612 KHz to check (no idea why this frequency is used).

I use the program DSLstats (freely available) on my PC to see what is going on, display errors and look at BitLoading Bitswaps etc. This could show if there are any 'holes' in your ADSL spectrum.

Quite a few years ago now, I used to get a very reliable 18 Kbps download (at 3dB NM I think) but I seem permanently on ~15 Kbps at 6dB now. My impression is that, where I am, the general electrical/RF environment has deteriorated over the years.

Superuser
Superuser
Posts: 16,659
Thanks: 6,848
Fixes: 63
Registered: ‎22-08-2007

Re: ADSL speed problems

Before delving into the complexities of REIN & SHINE the basics need to be investigated here.  This line is being managed for stability and looking at the error counts, I am wondering if the issue is upstream transmission giving rise to the line being deemed unstable and the DS (the usual culprit) being slowed down to attain stability.

Have you been through the basic checks - replaced the filter, run in the test socket, raised a fault report?  I would suspect that your authentication problems were related to line error rates, the new router simply being more tolerant of the line's throughput (not to be confused with sync rate).

On a line this short you should see 24mbps, not 21mbps.  The links below will be useful in assisting you with self diagnosis.  Going through the fault reporting process will ensure that all of the proper line checks are performed.

Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

I've done all basic checks, I've watched the line get slower and less stable over the last few months, the ticket i have open is taking a long time to progress.

Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

ADSL line status

Connection information

Line state Connected
Connection time 4 days, 2:52:04
Downstream 16,510 Kbps
Upstream 1,186 Kbps

 

ADSL settings

VPI/VCI 0/38
Type PPPoA
Modulation ITU-T G.992.5
Latency type Interleaved
Noise margin (Down/Up) 15.1 dB / 7.1 dB
Line attenuation (Down/Up) 2.0 dB / 2.1 dB
Output power (Down/Up) 18.8 dBm / 12.3 dBm
Loss of Framing (Local) 0
Loss of Signal (Local) 0
Loss of Power (Local) 0
FEC Errors (Down/Up) 36266 / 25
CRC Errors (Down/Up) 0 / 2147480000
HEC Errors (Down/Up) nil / 179747
Error Seconds (Local) 0
 
Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

Basic Speed Test
Broadband Speed Test
Executed Successfully
PING

81

Ms
DOWNLOAD

12.93

Mbps
UPLOAD

1.21

Mbps
 

Results

[CLOSE][RESET]

 

 
 
 
Summary of Performance Test
Timestamp
Sunday 3 January 2021 | 20:33:58
Ping
81 Ms
Download
12.93 Mbps
Upload
1.21 Mbps
Advance Test
Download Test
Download speed achieved during the test was 12.93 Mbps
For your connection, the acceptable range of speeds is 4 - 21 Mbps
IP Profile for your line is 14.57 Mbps
12.93 Mbps
 
 
21 Mbps
Upload Test
Upload speed achieved during the test was 1.21 Mbps
IP Profile for your line is 0.83 Mbps
1.21 Mbps
 
 
0.83 Mpbs
 

 

 
Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

@Townman Could the IP profile be holding it back? The line has been stable for a few days now but still nothing like it was.

Superuser
Superuser
Posts: 16,659
Thanks: 6,848
Fixes: 63
Registered: ‎22-08-2007

Re: ADSL speed problems

No. The profile is correct for the line speed.

The issue is the line speed, consequent to the elevated SNRM which is more than likely caused by a line fault.
Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

Thanks I was thinking that.

Plusnet don't believe there is a fault on the line.

Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

After doing more tests the phone line is noisy when connected directly to the master test socket.

Superuser
Superuser
Posts: 16,659
Thanks: 6,848
Fixes: 63
Registered: ‎22-08-2007

Re: ADSL speed problems

Have you put a filter into the test socket?

If there’s noise on the line, then that’s the source of your problem.
Grafter
Posts: 28
Thanks: 1
Registered: ‎07-12-2020

Re: ADSL speed problems

@Townman No just the phone connected straight to it with nothing else connected.