I am a little curious about a few things. We have a 3G tower on our building and 2G repeaters in certain areas that don't have good coverage. My question is if you are on a 3G call and drop to a 2G is it supposed to be a smooth handoff or does the call drop? Also if you are on 2G will the call step back up to 3g or does it just stay at 2G? I am really unsure of this and not sure if this is the right place to post this question or not.
Yes, your phone call (or data session) can handover seamlessly between 2G and 3G. But it's a compilcated procedue between the phone and the network. In short, your phone measures the 2G and 3G signals it receives and sends a report back to the network. The network can "force" you to one network or the other (eg: if one network is congested) by penalizing one network and sending back altered reports to the phone. The phone reads this returned report and then decides to handover or not. Of course the network has to allow and "pre-approve" it, as the network has to set up and secure the channel in advance for the handover. Here's a good read, a little old (2003) but still valid: http://www.ericsson.com/ericsson/corpinfo/publications/review/2003_01/files/2003011.pdf
