How to corelate the signal strength with the numbers

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Sankar - 25 Aug 2006 10:26 GMT

Dear friends

I aquired the signal strength of GSM network through a wavecom modem. I
got 15 at "A" place, 14 at "B" place and so on. I would like to know
this 15 or 14 corresponds to what db or how to come to a conclusion for
this this conservrsions.

Sankar Prasad

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John Henderson - 25 Aug 2006 22:12 GMT

> I aquired the signal strength of GSM network through a wavecom
> modem. I got 15 at "A" place, 14 at "B" place and so on. I
> would like to know this 15 or 14 corresponds to what db or how
> to come to a conclusion for this this conservrsions.

What command are you using to read signal strength?

For the serving cell, Wavecom modems typically have two commands
to do this: "AT+CSQ" and "AT+CCED". The results from these
commands require different manipulation to convert to dBm.

From a "+CSQ: " result, I convert the extracted number (variable
"nbr") to dBm with:

rxlv = (2 * nbr) - 113

and from a "+CCED: " result with:

rxlv = nbr - 110

John

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Sankar - 26 Aug 2006 10:44 GMT

Dear John

Thank you for the reply. we are using AT+CSQ commands. as you have
given the formula we will be able to extract the upper level of the
signal strength (considering at absolute permitivity), what about to
know the lower level of the db (considring relative permitivity)?

Regards

K Shankar Prasad

> > I aquired the signal strength of GSM network through a wavecom
> > modem. I got 15 at "A" place, 14 at "B" place and so on. I
[quoted text clipped - 17 lines]
>
> John

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John Henderson - 26 Aug 2006 11:16 GMT

> Thank you for the reply. we are using AT+CSQ commands. as you
> have given the formula we will be able to extract the upper
> level of the signal strength (considering at absolute
> permitivity), what about to know the lower level of the db
> (considring relative permitivity)?

Are you asking the possible range of values from the "AT+CSQ"
command? If so, it's from -113 to -51 dBm, as per GSM 07.07

0, -113 dBm or less
1, -111 dBm
2 to 30, -109 to -53 dBm
31, -51 dBm or greater
99, not known or not detectable

The result relevant to "+CCED: " is discussed in GSM 05.08,
section 8.1.4, where a base range of -110 to -48 dBm is given.

John

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Sankar - 28 Aug 2006 06:31 GMT

Dear John

Thank you for the reply.

Regards

K Shankar Prasad

> > Thank you for the reply. we are using AT+CSQ commands. as you
> > have given the formula we will be able to extract the upper
[quoted text clipped - 15 lines]
>
> John

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