Roaming between heterogeneous 3rd generation wireless networks

As existing wireless networks, systems, and standards migrate and evolve to 3rd generation wireless capability, the ability to roam between these networks increases in importance. The ITU-T has taken on the challenge to provide this roaming capability. This paper addresses the difficult network issues facing ITU-T and standards organizations in their attempt to achieve the vision of seamless international roaming between 3rd generation wireless networks. In particular this paper addresses the key network-to-network (NNI) interface issues and outline an evolution solution that will facilitate the vision