The limited IPv4 address space has driven the cellular industly to start using IPv6 addresses for mobile users in 3G-networks. However, there is a potential threat to the success of 3G-network deployment, as the success will depend on the services offering to the end users. Currently, the overwhelming proportion of services resides in the IPv4 address space, which makes them inaccessible to users in the IPv6 address space. Thus, users cannot directly communicate with and access services without an intermediate translation mechanism. Previous studies on network address translation methods have shown that REBEMH-IP with Port Extension, RPX is promising in that it provides excellent theoretical maximum scalability while supporting all types of services without limitations for the users in the network.

However, the initial RPX proposal does not support host mobility to different networks, despite the fact that mobility is the most important feature of a wireless communication system. In this paper, we propose to extend the RPX scheme with a mobility support scheme based on Mobile IP. RPX allows more than one host to use a single IPv4 address and therefore we have augmented Mobile IP with a new tunneling mechanism called IP-in-FQDN tunneling. The mechanism allows for unique mapping despite the sharing of IP addresses while maintaining the scalability of RPX. In addition, we present simulation results that indicate that the proposed scheme pe$orms well in terms of scalability, connection request delay and packet transmission delay compared to Mobile IP.