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High RS Uncorrectable Errors

2: Seeker
2: Seeker

I've been with Vodafone now for a few years, and over that time my speed has slowly degraded from ~54mbps to 40mbps today (I have actually been stuck on a 35mbps profile for the past 12 months but that recently got lifted to 40mbps, however my line was previously capable of much more).


I am seeing a very high number of RS Uncorrectable Errors and Super Frame errors, see below for an example. These stats are about 10pm last night when I reset them:

Line Quality

  Downstream Upstream
Current Rate39998 kbps9995 kbps
Maximum Rate47584 kbps11306 kbps
Signal-to-Noise Ratio5.8 dB6.4 dB
AttenuationDS1 16.9 dB, DS2 42.1 dB, DS3 64.9 dBUS0 3.2 dB, US1 31.4 dB, US2 48.0 dB
Power6.7 dBm6.6 dBm
CRC Errors in last 940 minute(s)3031
K (number of bytes in DMT frame)00
R (number of bytes in RS code word)1616
S (RS code word size in DMT frame)0.04610.7508
D (interleaver depth)7011
Delay8 ms0 ms
  Downstream Upstream
Super Frames253756654771053
Super Frame Errors3031
RS Words577160530300517282
RS Correctable Errors716715106
RS Uncorrectable Errors3340


Clearly there is something noisy on the line somewhere but it's not my end as far as I can determine. I have the router plugged directly into a filtered faceplate with no other devices connected to the landline at all.


Any suggestions on further investigation that can be done to identify the cause here as a 30% reduction in speed over a couple of years is pretty frustrating?


16: Advanced member
16: Advanced member

I would assume that there is no FTTP/Full Fibre at your location.  If that's the case, as more people have over time signed up to xDSL connections the speeds especially for those furthest away from the cabinet tend to drop.  When the POTS (Plain Old Telephone System) gets turned off, leaving just FTTC/xDSL you should see it at least plateau if not improve a little.

It might be worthwhile using the BT ADSL checker (I know the name is out of date) to just check that your speeds are in, or at least close to those expected.

Here's a link to that explains those "errors" a little.  When is an error, not an error?  When it a recoverable without the need to send any additional data!  So over the period of a day, that number of retransmissions while not great is not exactly appalling either!  And if you are "resetting" the count by restarting your router every night at 10 pm, that can have a detrimental effect on your speed.

Good luck, though my suspicion is that the is little you can do (other than switch to FTTP) in the short term.

Thanks @CrimsonLiar, sadly no FTTP here yet or I'd have it already, I need decent broadband for work and 40/10 in this day and age just doesn't cut it. The OpenReach fibre checker currently tells me I should get FTTP by December 2026. Woo. At least I only have to wait 2 years for the POTS switch off I guess.

I think you're probably right that there's nothing I can do, I sit at the lower end of what the BT wholesale checker tells me I should get on an impacted line, and I'm well above the handback threshhold of 28mbps, it just frustates me when I used to get 55/14 not so long back, although I appreciate and understand that crosstalk is a thing.

Just to be clear, I'm not rebooting my router every night, I can reset the stats via the web interface on the router, I did that last night as I wanted to get an idea from a fixed point in time because I planned on posting this today. I almost never reboot my router, it frequently has an uptime measured in months.

16: Advanced member
16: Advanced member

As you obviously understand, the speed is dependant on the length and condition of the line.

Over time the line can degrade (corroded joints, water ingress etc) so only Openreach can investigate those, and Vodafone would need to call them out.

As the copper service is being phased out they seem less willing to spend money keeping it in "tip-top" condition, so as long as you have a working service that is possibly the best you can hope for.

However I would start by trying a line test from Vodafone, if that finds problems it can call an engineer out.

My broadband is slow | Vodafone Home Broadband