My application uses GPRS data (GE865 v10.5 fw). I have noticed that even when registered, but the signal is rather weak, lets say -95db or worse, the data connection cannot be established. That is to say, the PDP context cannot be activated.
Is this expected? What are the criteria, in terms of signal level, for establishing a data connection.
Hi, for a GPRS connection , the signal strength should be greater or equal to -100dBm, so that means CSQ greater or equal to 7 . so -95dBm is a sufficient strength signal. Maybe you had temporary fading and while you attempted to activate the PDP contest the signal was too low.
So is it the case that a text (SMS) would go through at a slightly lower dBm ? i.e -103 or whatever? And what about placing a voice call, what is the level there?
In these cases the parameter is the receiver sensitivity.
Sensitivity is the fundamental measure of receiver performance.
It specifies the minimum signal level for a specified percentage of errors (not free of errors) in the demodulated information.
ETSI Specifications define required sensitivity levels in different radio propagation conditions
For handheld GSM900 and GSM1800 modules the reference sensitivity level is – 104dBmYou can find the sensitivity level for our modules in our datasheet (e.g. for GE865 is -106/7 dBm (typ.))
Obvioulsy you should be able to measure continuously the level of signal to be sure that this level is stable at receiver, because you could have e.g -103dBm when you issue an AT commmands like at#moni and immediately after you could have a strong fading due the environment
Thank you Luca,
Yes, good point about the environment. I am aware that the radio environment is ever- changing!
Just one further question : we have observed that signal level often appears to drop during a call (as reported by CSQ). Is this a valid observation and if so, what is the cause?
Is your measurement carried our with antenna connected to an instrument (UMTS/GSM tester) or in a free environment? in second case the fading is the most probable cause
In a free environment. Are you saying this is probably random fading that normally happens or is it something related to making the call?
random fading that normally happens
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