Nova Hologram Modem Signal data


#1

When you run the signal command for the modem with the hologram python I am getting 2 numbers seperated by comma for my signal strength, however I don’t know what the rating is. IE if I get something like 10,99 is that good or bad. Can we get a simple way to either just display a percentage, or db rating?


#2

I had the same question about the two number result, and found the following in the Hologram-CLI reference document:

Signal strength:,

Properties:
rssi (int) – The rssi value here ranges between 0-31 and 99.
qual (int) – The qual value here ranges between 0-7 and 99.

Elsewhere on hologram.io, I found the following (dBm closer to 0 is better):

Signal Strength Code:
0: -113 dBm or less
1: -111 dBm
2 to 30: -109 to -53 dBm with 2 dBm steps
31 to 98 – -51 dBm or greater
99 – No signal


#3

Thanks very much for this. Sorry for not reading the documentation.


#4

If I get this right, a RSSI of 14 mean -85dBm
But in
31 to 98 – -51 dBm or greater
Could you please explain? Does it mean there is no more dBm measurement below -51dBM, meaning like “all good, don’t worry about it?”. Isn’t it a difference between -51dBm and -30dBm in term of signal strength?
Thank you!


#5

Hello everyone!

Thanks @tnunnster for the great answers on this thread. To make sure this is clear I wanted to dive into this a bit more.

The signal command used in the Python SDK is the standard AT command signal request AT +CSQ this command will return two values the received signal strength indicator (RSSI) and the Bit Error Rate (BER) or Qual.

The values for RSSI are between 0-31 and 99 where the larger the value the better the signal and 99 is not known or not detectable

The value for BER or Qual is between 0 and 7 and 99 where the larger the value the higher the bit error rate and 99 is not known or not detectable.

Therefore you want the RSSI to be as large as possible, but not 99 and the BER to be as low as possible, but also not 99.

Ideally you want your RSSI to be 10 or above as anything below it is marginal signal.

I’d also focus on the scale provided by the signal command as opposed to dBm and BER % given that these vary by radio access technology so for example an RSSI of 10 maps to -90.5 dBm in UMTS and -93.5 dBm in LTE.

Once you get 31 as the RSSI the dBM value wouldn’t have a noticeable effect on signal strength.

For more information I would recommend checking out the modem manufacturer’s information on the AT+CSQ command. Here is the link for the AT Command Set for the u-blox Sara U201 used in the 2G/3G Nova.

Best,
Maiky