In this paper we discuss the major modifications required in the current LTE network to realize a decentralized LTE architecture and develop a novel IP mobility management solution for it. The proposed solution can handle traffic redirecting and IP address continuity above the distributed anchor points in a scalable and resource efficient manner. Our approach is based on the NAT (Network Address Translation) mechanism, which is a well- known and widely used procedure in the current Internet. We extend the NS3-LENA to implement a decentralized LTE network as well as the proposed scheme. The evaluation results show that the proposed solution efficiently fulfills the functionality and performance requirements (e.g., latency and signaling load) related to the mobility management.