Encouraging modems to switch from 2G to 3G


We use a large number of modems in embedded mobile devices across various territories. Often these devices will be passing a continuous flow of traffic for extended periods whilst moving between areas of varying network coverage.

We are experiencing issues where the modems will stay locked on to a 2G signal rather then switch to a 3G one, even in areas with very good 3G coverage. Specifically we see modems such as the MC8705 stay in EDGE mode rather than switching to HSPA, and the MC5728V stay in 1xRTT rather than switching to EV-DO. However we also see that at other times the same appear to be able to switch from 2G to 3G even while actively passing data.

From reading the literature I’m still not clear if it is possible for modems to handover from 2G to 3G whilst actively passing data, or whether they need to first be in idle/dormant mode when in GPRS/1xRTT. Also I’m not clear whether this is ability is dependant on the capabilities of the cell towers the modems are connected to.

Do you know what conditions have to be met to allow a modem to switch from 2G to 3G and whether it’s dependent on the cell towers? Are there any parameters or techniques we can use with the modem to force/encourage them to switch to an available 3G network?

Thanks very much.


Switching from 2g to 3g is possible while the data session is still active. Anyhow, network also should support this feature.
For MC8705 you can use the command AT!SELRAT while for MC5728V you can use :

AT!SWI=97 – to Unlock the internal command
AT!NV=10,9 – set modem to CDMA only
AT!NV=10,10 – set modem to HDR only.

But, yes switching should be supportef by network also.


Thanks for your response.

I’ll give that a try.