Distinction between "Rx Level" and "RSSI&quot


#1

AT+CCED reports signal strength as “Rx Level” on a scale of 0-63;
AT+CSQ reports signal strength as “RSSI” on a scale of 0-30.

I’m sure this is general, and nothing specifically to do with Wavecom, but is there any significance to these two different scales?
Why couldn’t they both use the same scale?

BTW: the 0-63 scale for “Rx Level” is not described in any of the Wavecom documnetaion - you have to go to the FAQ to find it! :angry:


#2

CSQ is 0-31


#3

Oops - so it is! :blush:

However, this doesn’t answer the original question: “is there any significance to these two different scales? Why couldn’t they both use the same scale?”


#4

CSQ and RXlev in cced are equal to some signal level in dbm

CSQ is 0-31
as wavecom doc says
0 -113 dbm (absolute signal level)
1 -111 dbm

31 >= -51dbm
and so … that means every CSQ equals 2 dbm change

CCED is 0-63

0 -111 dbm
1 -110 dbm
2 -109 dbm

63 >=48 dbm

every Rxlev is equal to 1 dbm change

if you want to convert

CSQ = (Rxlev+1)/2 if there is module round to upper integer

note keep in mind that rxlev go upper that -51 dbm (it will be 31 CSQ)
the formula it is rigth when the limits are the same for both measures


#5

Yes, I know all that - but it still doesn’t answer the question:

“is there any significance to these two different scales?” :question:

and:

Why couldn’t they both use the same scale?” :question: :question:

Or, to put it another way:

Why should we have to do two different conversions - one for CSQ, and a different one for CCED? What’s the point in that?! :question:

Is there, perhaps, some historical reason…?


#6

as you can see in my last post CCED RXlev is more accurate since you can see diferences of 1 dbm, in CSQ the minimun step is 2 dbm, that is the only diference.


#7

You are still missing the point!

I know that they are different - I am asking why are they different?

What is the point in having two different scales?

Why does CSQ use 2dBm steps when CCED uses 1dBm steps?

Surely, they must both come from the same underlying data - so why two different scales for the same reading?


#8

well the two measures are signal strength,
the underlaying data as you say it is the data that measure the signal strength,

dbm is the absolute signal strength for P dbm = 10 * log (Pin/1mW)
csq and RXlev are only equivalents leves to dbm

i do not why they are using one or another ,but seems to me Rxlev it is an evolution since it is more accurate. anyway both of them give you an equivalent signal level in dbm


#9

Also, AT+CCED seems to be a Wavecom-specific command; whereas AT+CSQ is standard GSM…


#10

at+cced seems to be wavecom specific command out of AT standard, rigth, but cced gives you a measure of Rxlev.

RxLev it is a standar signal scale and it is provide by a lot of manufactures in another ways diferent than at+cced, RxLev it is not a wavecom specific scale.


#11

We are going to study on a project of measuring GSM network parameters. In this project, we will produce about 500 devices that can collect important parameters (RxLev, RxQual, SQI-Speech Quality Index, C/I-Carrier/Interference, CI: Cell Identify, MS power control, BER-Bit Error Rate, FER-Frame Error Rate). These parameters accompanied with the position of the device (via GPS) will be sent to the operating center. I wonder if you could let me know if you have product that can meet the requirements of this project?

Btw, I would like to know what are included in the 16 bytes of the parameter in the reponse of “AT+WLOC” command?

Thanks and best regards,
kkk


#12

Yes I would also like to know that!
Unfortunately, as is all too common, Wavecom do not document it. :angry: