We present PROTON, a policy-based solution for 4G mobile devices – it allows users to seamlessly connect to highly integrated heterogeneous wireless networks. The key motivation behind PROTON stems from the statement that handover process complexity will increase in 4G systems, creating the need for augmented knowledge about context, as well as more flexibility. This paper demonstrates (1) how a flexible policy-based approach is suitable for 4G scenarios, and (2) how to incorporate richer context into policies and still maintain a light weight solution appropriate for mobile devices.