Hi Babudass,
Migration from 2.5G to 3G is not corelated with each other because both are working on different transport tech. As 3G works on WCDMA, the access network become totally change.We can share only the antennae.Different RBS,different BSC(RNC),Separated control & payload layers are needed.Its actually migration towards all IP solution as transport. We can use media gateways for transformation of access technologies.
Much more later………….
bye
ARSHAD