How to calculate good or bad levels from the modem

[thecubefarm]

So at work there is a small battle going on on how to automatically calculate levels output from a modem.

Here is a sample from Hitron CODA45 using my script:

Upstream (Tx): 45.8 45.3 45.0 44.8
Downstream (Rx): -3.9 -2.7 -2.4 -2.5 -2.4 -2.2 -3.0 -3.0 -3.2 -3.5 -3.5 -4.2 -3.0 -3.2 -2.7 -3.0 -3.0 -3.0 -3.0 -3.4 -3.2 -3.4 -3.2 -3.5 -3.7 -3.7 -3.5 -3.5 -3.7 -3.7 -4.2
SNR
38.9 38.9 38.9 38.9 38.9 38.9 38.6 38.9 38.9 38.6 38.9 38.9 38.9 38.6 38.6 38.6 38.6 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9 38.9

Upstream(TX): Low: 44.8 High: 45.8 Avg: 45.22 Levels = GOOD (Range = 1 dB)
Downstream(RX): Low: -4.2 High: -2.2 Avg: -3.23 Levels = GOOD (Range = 2 dB)
SNR: Low: 38.6 High: 38.9 Avg: 38.84 Levels = EXCELLENT (Range = 0.3 dB)


What I have learned so far.

1. Downstream (Rx) Power Levels:
Acceptable Range: -8 dBmV to +10 dBmV
Low Limit: -15 dBmV
High Limit: +15 dBmV
Spread between channels: Maximum of 3 dB difference between channels
2. Upstream (Tx) Power Levels:
Acceptable Range: 35 dBmV to 52 dBmV
Low Limit: 35 dBmV
High Limit: 52 dBmV
Spread between channels: Maximum of 2-3 dB difference between channels
3. Signal-to-Noise Ratio (SNR):
Acceptable Range: 30 dB to 50 dB
Low Limit: 30 dB (Below 30 dB is considered poor)
High Limit: 50 dB (Higher is generally better)
4. Modem Spread Between Channels:
Downstream Spread: No more than 3 dB difference between any two channels.
Upstream Spread: No more than 2-3 dB difference between channels.

I have created a script that checks these ranges and "spreads" and ranks each channel as excellent/good/fair/poor/bad

How much weight should be given to the db difference (spread) between any two channels?

Interestingly, I can find very little references about channel difference and what happens if a channel is not in use (NOT LOCKED)

As the project moves along I am discovering that there are several other factors (several I've discovered here from various reading), some which include

Modem manufactuer
Docsis Level
Carrier
etc

In general, is the above a reasonable set of ranges to base an evaluation on a level or am stepping into a big pile of much that ultimately will just turn out to be a big headache?

Thank you for your input.

[Philip]

Welcome to SG. Interesting work, thanks for sharing.

I don't know exactly "how much weight" should be given to the db difference between channels. I imagine it would depend on the width of the ingress frequencies, it may affect a couple of channels, and not others. Modem manufacturer and DOCSIS level sure will play a role, some work betters than others in marginal conditions, and with high upstream power.

Here is the general guideline I look at usually for acceptable signal levels:
https://www.speedguide.net/faq/what-cab ... ed-good-78