Cisco ECP3212 Cablemodem Signal Strength needed for good internet access

As described in my last blog-entry I had a very unstable internet connection. After complaining many times Vodafone had send a technician who adjusted the gain of the cable amplifier.

After that adjustment my internet connection has been much better, but we still faced intermittent issues. The Downlink and the Uplink quality varied very much. It took Vodafone again multiple escalations over multiple month until they fixed the issue completely. It turned out that the amplifier had to be exchanged.

It took Vodafone 10 month and many escalations to fix this issue!

I would like to share the how the situation has to look like for a working configuration.

The gain for the channels has to be in the following ranges:

Downstream Channels

  • QAM 64: 50-66 dBuV
  • QAM 256: 56-72 dBuV

Upstream Channels:

  • 96 – 110 dBuV

I found in some forums that the Signal to Noise values for the Download channels should be larger than 34dB. A snapshot of the modem values show that all requirements are met at the moment.

So this looks fine.

But there is another very important aspect which has to be ensured so that the internet connection works fine:

  • the gain and signal to noise has to be stable over the time !

In this setup the cable modem shows

  • a ratio of “Correctable Codewords”/”Unerrored Codewords” less than 0,0001
  • a ratio of “Uncorrectable Codewords”/”Unerrored Codewords” less than 0,00001
Signal Stats(Codewords) Bonding Channel ID
Channel ID 1 2 3 4 17 18 19 20
Total Unerrored Codewords 2028181539 2026089866 2026088914 2026092832 445805463 445803690 445805601 445805767
Total Correctable Codewords 8766 9986 11675 9220 12279 14709 12038 13012
Total Uncorrectable Codewords 1156 1189 608 111 915 854 933 586

A single iperf3 stream then shows the expected results (200Mbit/12MBit)

iperf3 -c -p 5002 -R -t 30
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-30.00  sec   681 MBytes   191 Mbits/sec                  receiver
iperf3 -c -p 5002
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-10.00  sec  14.3 MBytes  12.0 Mbits/sec                  receiver

For your reference I have attached the charts where the difference of the amplifier is shown.

As you would have guessed the amplifier was exchanged on Thursday 😉



Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.