Heterogeneous environment in next-generation wireless networks poses several challenges in terms of mobility management includes the seamless mobility and the handover. Network slicing appears as a promising technology to meet different network requirements. Due to the diversity of future network application scenarios and users density in the access network, new mobility management is needed to control seamless handover for user mobility in different access network. In this paper, we introduce a new mobility architecture based on the slicing network paradigm to empower user mobility in different Radio Access Technologies (RATs). Simulation results demonstrate that the proposed architecture successfully manages the seamless handover in LTE and WiFi networks for a user under a slice control. In other words, it means that the user moves between different access networks under the same slice control.