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Archive for July, 2014

Cable Internet: Connection Metrics to Monitor

July 5, 2014 Leave a comment

Material in this post came from FAQ: Acceptable cable modem signal levels and Cable Modem Signal Levels.  Please refer to the source materials for additional details and recommendations on fixes to issues you can try from your end.

There are three connection metrics that you can use to monitor the stability of your cable Internet connection.  Access these metrics by going to http://192.168.100.1/ from your browser and look at the following values reported by the modem:

Metric Range Remarks
Downstream (Rx) Receive Power Level -15 dBmV to +15 dBmV maximum Recommended range between -12 dBmV to +12 dBmV

 

“Optimal” level at 0 dBmV

Upstream (Tx) Transmit Power, a.k.a. Return Signal Level +8 dBmV to +58 dBmV maximum for QPSK (DOCSIS 1.x)

 

+8 dBmV to +55 dBmV maximum for 8 QAM and 16 QAM (DOCSIS 1.x)

 

+8 dBmV to +54 dBmV maximum for 32 QAM and 64 QAM (A-TDMA DOCSIS 2.0)

 

+8 dBmV to +53 dBmV maximum for S-CDMA DOCSIS 2.0 modulation rates

Recommended range between +35 dBmV to +52 dBmV

 

Values in the 40+ dBmV range are common and considered normal

SNR (Signal-to-Noise Ratio) Level QPSK: 12 dB minimum; 15 dB or higher recommended (often used in upstream channels)

 

16 QAM: 18 dB minimum; 21 dB or higher recommended (often used in upstream channels)

 

64 QAM: 24 dB minimum; 27 dB or higher recommended (often used in downstream channels)

 

256 QAM: 30 dB minimum; 33 dB or higher recommended (often used in downstream channels)

SNR should be 30 dB or higher; the higher the better

If your metrics are not within the ranges then your Internet connection is not stable.  If you are consistently close to either the minimum or maximum limits (except where noted for the SNR) then consider this a warning that something might be wrong.

Recommendations on what can be done from your end are beyond the scope of this post.  Suffice it to say, you can try referring to the two source materials mentioned at the start of this post.  Contact your Cable ISP for assistance in troubleshooting risks or issues encountered as per monitoring these particular metrics.

Speaking from my own experience, I’ve been monitoring these metrics every time I’m online and before doing anything else on the network.  This has helped me set my expectations on the reliability of my connection, which for the most part has been stable.  For the times I suddenly lose my connection or it acts sluggish, I consult these metrics to see if there’s something wrong in the line; I found the information I got useful in reporting problems with my ISP, though they can actually monitor the same from their end.

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