Heterogeneous Networks to Support User Needs with Major Challenges for New Wideband Access Systems

Third generation mobile radio systems are currently being deployed in different regions of the world. Future systems beyond the third generation are already under discussion in international bodies and forums such as ITU, WWRF and R&D programs of the European Union and in other regions. These systems will determine the research and standardization activities in mobile and wireless communication in the next years. Based on the experience from the third generation future systems will be developed mainly from the user perspective with respect to potential services and applications including traffic demands. This is directly related to the paradigm shifts from the first generation to systems beyond third generation. International bodies are already discussing basic system requirements. The basic system architecture of heterogeneous networks with different complementing access systems is from the today's perspective the most economic approach for systems beyond 3G to satisfy user and operator needs for reasonable cost. Such system architectures enable the deployment of system capacity according to the traffic requirements with the user experience ``Optimally Connected, Anywhere and Anytime'' with seamless service provision between different access systems. New radio interface components with high data rate as additional components of systems beyond 3G are being proposed in international bodies. Key issues of such systems are coverage due to reduced range and the huge spectrum demand. In this paper the international context, the user perspective, revenue and traffic expectations are presented. This results in the basic system requirements and the potential system architecture of heterogeneous networks. Major challenges for the new wideband radio interfaces are the impact on range and spectrum demand. Basic investigations are presented on these issues to critically review requirements on future systems.