Acceptable Noise Margin

[Black_Infinity]

As per the title , what is an acceptable noise margin in HH5 stats ?

Mine was always running at around 6.3/6.0 but now suddenly it has gone to 6.3/9.8  😞

Accordingly my connection speed has dropped too.

[imjolly]

normal is about 6db so if you have now jumped to 9.8db and dropping connection it appears there is a line noise problem and errors which have resulted in DLM increasing noise margin.  the result of higher noise margin is as you say reduced conenction speed

try quiet line test

[Black_Infinity]

Quiet line test seems normally quiet tbh.

Connection had been very stable since last Openreach visit. The increase in noise margin has dropped my connection speed from 32 to 24.

[pippincp]

Can you post lines 1-12 from the HH stats page?

[Black_Infinity]

Looks like this may have been a temporary glitch.

Things seem to be returning to normal. Noise margin 6.0/6.7

Obviously I'll monitor this and see if things stabilise back to where they were.

[Black_Infinity]

Oops , spoke too soon. Noise margin back to 8.4 and connection speed dropped again 😞

Can anything be done about this ?

Why would the noise margin begin fluctuating instead of staying around 6 ?

[Black_Infinity]

1. Product name:	BT Home Hub
2. Serial number:	+068543+NQ51128943
3. Firmware version:	Software version 4.7.5.1.83.8.204.1.11 (Type A) Last updated 08/07/15
4. Board version:	BT Hub 5A
5. DSL uptime:	0 days, 02:40:36
6. Data rate:	4877 / 26947
7. Maximum data rate:	4851 / 30493
8. Noise margin:	6.4 / 8.4
9. Line attenuation:	33.2 / 28.8
10. Signal attenuation:	33.2 / 25.3
11. Data sent/received:	4.6 MB / 23.8 MB
12. Broadband username:	bthomehub@btbroadband.com

[imjolly]

Your connection has reset hence the noise margin increase. Is there any noise on quiet line test as there is an underlying problem causing the resets

[Black_Infinity]

Quiet line test is indeed very quiet 🙂

[umpire]

There is a relationship between SNR margin (noise margin) and connection speed. The connection speed is set at sync time (reconnection time) and stays fixed for the duration of the connection up time. If you look in the Troubleshooting > Event Log > WAN section you will be able to see the sync time noise margin that was associated with your current connection speed.

From that initial starting point at sync time the noise margin can vary as the capability of the line varies due to noise fluctuations but the connection speed remains constant.

It's useful to be aware of the sync time noise margin compared to the current level. The sync time noise margin is usually set to a value around a target that the DLM sets for your line. The default sync time target is 6dB, hence you will see that mentioned as the normal level.