The future of wireless communications beyond the third generation

In this paper, we develop a vision for the future of wireless communications beyond the third generation, which consists of a combination of several optimized access systems on a common IP-based medium access and core network platform. Different access systems interwork via horizontal (intra-system) and vertical (inter-system) handover, service negotiation, and global roaming. These complementary access systems are optimized for different applications and environments. They are allocated to different cell layers in the sense of hierarchical cells with respect to cell size, coverage, and mobility to provide globally optimized seamless services for all users. New air interfaces can also be incorporated to satisfy demands for higher data rates, increased mobility, and reduced cost per bit. This vision requires international research and standardization activities to solve many technical challenges. Key issues include the global interworking of different access systems on a common platform. advanced antenna concepts. and the implementation of multi-mode and multi-band terminals as well as base stations via software-defined radio concepts. (C) 2001 Published by Elsevier Science B.V.