How to find downstream and upstream signal levels?

On almost all the Cable Modems or Cable Modem Routers, you can find your signal level by logging into the modem diagnostic GUI page via http://192.168.100.1/ and username/password (unless you have changed credentials on the device, default credentials should be located on label on the device bottom or side).

What are optimum signal levels for my modem?

Downstream (Rx) Signal Levels:

This is the amount of signal received by the modem from your ISP. For all modems DOCSIS 3.0 / 3.1:

  • -7 dBmV to +7 dBmV are “Recommended” values. 
  • -8 dBmV to -10 dBmV / +8 dBmV to +10 dBmV are “Acceptable” values but out of spec from ISP. A technician should still fix this to get to recommended levels.
  • -11 dBmV to -15 dBmV / +11 dBmV to +15 dBmV are “Maximum” values but out of spec from ISP. A technician should still fi this to get to recommended levels. It is strongly recommended for you to force ISP tech to fix it since your power levels are close to edge.
  • Lower than -15 dBmV & Higher than +15 dBmV are out of DOCSIS 3.0 specifications and modems may not work at all or cause lot of problems

SNR (signal to noise ratio) levels:

This is how clear the signal is at the modem receiver (downstream SNR) .

DOCSIS specifications list minimum CNR (carrier to noise ratio) levels not SNR levels. The SNR levels listed here are based on commonly recommended MER levels for digital cable signals.

  • 256 QAM: 30 dB minimum. 33 dB or higher is recommended. Most ISPs run 256-QAM downstream.
  • 64 QAM: 24 dB minimum. 27 dB or higher recommended. Some ISPs have 64-QAM in downstream but rare
  • 16 QAM: 18 dB minimum. 21 dB or higher recommended. It is very rare for ISPs to use 16-QAM on newer DOCSIS 3.0 networks.
  • QPSK: 12 dB minimum. 15 dB or higher recommended. It is very rare for ISPs to use QPSK as performance on this modulation is very low.

Upstream (Tx) Transmit Power level:

This is the amount of signal transmitted by the modem to reach the receiver in the cable company head-end. This is a problem in most homes and the most common cause of internet disconnects.

These are generic recommended power levels

Recommended Upstream signal levels are +35 dBmV to +49 dBmV (DOCSIS 3.1) Recommended Upstream signal levels are +35 dBmV to +49 dBmV (DOCSIS 3.0)

However, Upstream power levels depend on the number of upstream bonded channels and type of upstream modulation (64-QAM, 16-QAM, etc). Most ISPs use either 3 or 4 bonded channels and are mostly 64-QAM.

Number of Bonded US Channels 1 2 3 4
DOCSIS 3.0 Specification for 64-QAM channel 57 dBmV 54 dBmV 51 dBmV 51 dBmV
Recommended Value for good operations 35-49 dBmV 35-49 dBmV 35-49 dBmV 35-49 dBmV