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Overlapping coverage of multiple radio access technologies provides new multiple degrees of freedom for tuning the fairnessthroughput tradeoff in heterogeneous communication systems through proper resource allocation. This paper treats the problem of resource allocation in terms of optimum air interface and cell selection in cellular multi-air interface scenarios. We find a close to optimum allocation for a given set of voice users with minimum QoS requirements and a set of best-effort users which guarantees service for the voice users and maximizes the sum utility of the best-effort users. Our model applies to arbitrary heterogeneous scenarios where the air interfaces belong to the class of interference limited systems like UMTS or to a class with orthogonal resource assignment such as TDMA-based GSM or WLAN. We present a convex formulation of the problem and by using structural properties thereof deduce two algorithms for static and dynamic scenarios, respectively. Both procedures rely on simple information exchange protocols and can be operated in a completely decentralized way. The performance of the dynamic algorithm is then evaluated for a heterogeneous UMTS/GSM scenario showing high-performance gains in comparison to standard load-balancing solutions.

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Abstract. In this article, we present a multi-radio management (MRM) architecture for intelligent access selection and load balancing over multiple radio access technologies. We discuss possible implementations of this MRM architecture and analyze to what extent the IEEE 802.21 'Media Independent Handover' framework can be applied here. Starting from the fundamental building blocks of the multi-radio management architecture, we find several issues with respect to the integration with and the interworking between today's 3GPP and non-3GPP networks. Because support of 802.21 can largely differ from one access technology to another, we propose ways to compensate for these differences and finally present an adapted MRM architecture.