Signal strength on Linux

timtech · EVDO Newbie Joined: 17 Jan 2007 Posts: 1

I haven't seen this any where and wanted to post for others.

If you have a communications program like minicom, you can point the modem to your device (in my case ttyACM0)

Then query the modem with

AT+CSQ

This will return two numbers xx,xx

The first number is the signal strength difference from the base of -109dBm

For example, if you get a return of 14,99

you take -109+14 which gives you -95dBm

You can also query the firmware revision with:
AT+GMR

djmay · EVDO Newbie Joined: 22 Dec 2006 Posts: 2

I have been trying to find a way to do that, but this doesn't look right.

I have a 720S on a MB6000 router, which uses linux inside.
The MB6000 provides a AT Command interface.

AT+CSQ

74, 99

OK

So according to your formula that would mean I have a signal strength of
-109+74 = -35dBm

I could only wish...

You know that 74 looks about right for me.... could this be different for different cards?

MB6000 doesn't let me send AT commands while connected, but I would really like to find a way to monitor this while connected.

Also if I could determine the connection type, or check the signal strength for each EVDO Rev 0, EVDO Rev A, and 1xRTT, I would be really happy.

glenozzy · EVDO User Joined: 03 Jan 2007 Posts: 49

first number is RSSI
second number is FER or SQE
99 means your not on a call or unsupported

tamasrepus · Posted: Sat Jan 20, 2007 8:27 pm Post subject:

djmay · EVDO Newbie Joined: 22 Dec 2006 Posts: 2

I usually get somewhere between -72dBm to -85dBm
Since the numbers I got were 74, 99
I think it looks more like this particular card is reporting the abs(dBm)

I would think it is telling me I am currently measuring -74dBm

If this was RSSI then my understanding is that I would have -34dBm
according to this white paper

http://www.wildpackets.com/elements/whitepapers/Converting_Signal_Strength.pdf

KriminalMinded · Posted: Wed Mar 07, 2007 2:57 am Post subject:

Any possibility of getting this to work on a mac?
_________________
Kriminal Minded

timmerk15 · EVDO Fledgling Joined: 21 Jul 2007 Posts: 13

plor · EVDO Newbie Joined: 09 Oct 2007 Posts: 5

I also get measurements between 65 and 85, which would make the dBm make sense. I've seen lower numbers (<31) on other cards, which would probably use a different scale. Does anyone know of a place that would show the card and what the +CSQ command returns?