I'm currently working on an experimental Android Kernel (Research). I'actually trying to find some ways to preserve battery charge by implementing a kind of power management tool on the kernel level. I'm working on the msm-hammerahead kernel (used by the nexus 5 running Android 5.0).
I'm trying to figure out if there exists a way to switch between network types (2G,3G,Wifi) at runtime. I know that there exist the possibility to switch the default network type within the build.prop file(ro.telephony.default_network).
Does anybody know if it is even possible to achive this?
The android kernel is not the place to look for network switching. build.prop is also useless for this because it just contain the default boot values. Switching network interfaces is a very bad idea, because the android framework need to be synchronized with the lower linux layer state.
I would suggest checking the ConnectivityManager.java in the android framework to understand better how the network switching works.