3G Signal Strength Query | Thales IoT Developer Community
May 3, 2016 - 9:13pm, 4359 views
EHS6T: From various forums it was recommended that for satisfactory 3G GSM transmissions, there were recommendations to disable 3G transmissions if signal strength was below -105 dbm and -5db S/N. However if the 3G levels remain at this level, you can end up waiting for a long time before you can do any GSM transmissions in poor signal areas. Is it possible to force the modem to try and use 2G transmission, if signal strength adequate, if the 3G remains too low for a timeout period?
Are the above 3G signal, S/N levels practical in practice - or can lower levels still provide satisfactory transmission??
Bobg
Hello,
The values that you have cited seem really poor. If you mean RSSI as signal strength it is not enough for 3G while there can be a strong signal with big noise resulting in the poor quality. You should rather use RSCP and EC/n0, you could also consider SQual and SRxLev values.
An algorithm for cell reselection is based on 3GPP documentation and there is no way of modifying it directly. You would need to implement some network monitoring on your own and select the radio access technology or bands.
Regards,
Bartłomiej
Hi
I am using RSCP > -105dbm and EC/No > -14db (excuse wrong limit given previously). However this does not always give reliable transmissions, which is why I am looking at what are acceptable limits for reliable 3G transmission. Your answer above suggests that even if RSCP and EC/No are within limits that this is not necessarily the only values that I should be monitoring to determine if the conditions are acceptable for transmission.
I have seen RSCP on a number of occassions being at -109dbm and stayed there for quite some time - although on other occassions the level can be in the -80's to -90's dbm - evidently the local transmitted is occassionally being operated at low signal levels.
The modem is being used on the move and in different locations and transmissions may occur at any time and thus separate network monitoring would be impractical.
What values for RSCP, EC/No, SQual, SRsLev would be accepatble for reliable transmission ?
Bobg
Hello,
These first parameters do not look good but could be worse. However there's no straight answer which values are good and which not. Especially that there are also other factors that can matter here and which you can't measure like number of devices that are using the same cell.
In your case there is also another issue that matters - the device is moving so the parameters are constantly changing and there are also handovers.
So if your device is moving and if it's moving in most cases in the countryside and if the device doesn't send big amounts of data, maybe it would be worth trying 2G only for better reliability, at least for test.
Regards,
Bartłomiej
Pleas, take a look in this thread
https://iot-developer.thalesgroup.com/threads/atsmoni-vs-atcsq-ehs6-signal-strength-detection
Regards
ALopez
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