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The work reported here has been funded by the Delft University of Technology DIOC research programme. DIOC programmes are an initiative of the ARTD ("Advisory Council Technology T.U. Delft"), and aim at solving, in a multi-disciplinary way, specific technological problems with engineering and social significance. Ubiquitous Communications AbstractMobile systems operate in a resource-scarce environment and thus must adapt to external conditions; all layers must make cost-based decisions about what mode of operation to use in response to performance feedback. This paper focuses on the generic interface between adjacent layers (client and server) in a multi-level hierarchy. The Adaptive Research Contracts (ARC) framework uses a bottom-up approach in which the server exposes a range of quality/cost modes to the client above. This allows the client to trade off various algorithms generating different workloads for multiple resources. A case study shows that control can be distributed effectively over multiple layers with ARC; global cost-effective solutions can be obtained with exchanging a small fraction of all possible control settings.