There are a bunch of modules in Linphone SDK (Also, you must consider if you need to work with a standard SDK build, or a custom one if you only need some specific codecs.)
Before wrapping, in order to better understand how it works and integrates with the specific OS. I'd recommend to take a look at the free Linphone sample app for Android: you'll see that most of the functions needed for the high-level, are in the LinphoneManager Class. Also see the manifest for the required permissions and the services needed to work in background.