The world is undergoing a major telecommunications revolution that will provide ubiquitous communication access to citizens, wherever they are. Seamless roaming across different wireless networks which has different types of services and quality of service guarantees has becomes a major topic for the past several years in the research area. With the integration of different technologies, the signaling protocol of mobility management must be designed to support seamless roaming for both intra and interdomain system. In this paper, we designed a simplified system architecture, called enhanced system architecture evolution (eSAE) to support mobility between multiple heterogeneous wireless system. eSAE contains fewer network nodes and is reduced to only the enhanced node B (eNB) and access gateway (aGW) that comprise Mobility Management Entity (MME) and User Plane Entity (UPE). We designed a signaling protocol for the location registration due for intersystem roaming in next generation wireless systems. Performance analysis has been carried out and based on this proposed architecture, it is shown that this enhancement can reduce the signaling cost and latency of location registration.