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Abstract. Directed diffusion is a prominent example of data-centric routing based on application layer data and purely local interactions. In its functioning it relies heavily on network-wide flooding which is an expensive operation, specifically with respect to the scarce energy resources of nodes in wireless sensor networks (WSNs). One well-researched way to curb the flooding overhead is by clustering. Passive clustering is a recent proposal for on-demand creation and maintenance of the clustered structure, making it very attractive for WSNs and directed diffusion in particular. The contribution of this paper is the investigation of this combination: Is it feasible to execute directed diffusion on top of a sensor network where the topology is implicitly constructed by passive clustering? A simulation-based comparison between plain directed diffusion and one based on passive clustering shows that, depending on the scenario, passive clustering can significantly reduce the required energy while maintaining and even improving the delay and the delivery rate. This study also provides insights into the behavior of directed diffusion with respect to its long-term periodic behavior, contributing to a better understanding of this novel class of communication protocols.

Abstract. Component-based architectures are the traditional approach to reconcile application specific optimization with reusable abstractions in sensor networks. However, they frequently overwhelm the application designer with the range of choices in component selection and composition. We introduce a component framework that reduces this complexity. It provides a well-defined content-based publish/subscribe service, but allows the application designer to adapt the service by making orthogonal choices about: (1) the communication protocol components for subscription and notification delivery, (2) the supported data attributes and (3) a set of service extension components. We present TinyCOPS, our implementation of the framework in TinyOS 2.0, and demonstrate its advantages by showing experimental results for different application configurations on two sensor node platforms in a large-scale indoor testbed.

Simulating the physical layer of wireless communication remains a challenge. Communication standards like OFDM or MIMO systems go beyond the simple single narrow frequency band, single antenna model used in popular simulators. Yet, these technologies gain popularity, since they provide researchers with a plethora of possibilities that can be explored to invent new protocols or improve existing ones. However, building a detailed and sufficiently accurate model for such complex systems is a tremendous task that takes a lot of time. In this paper we present the physical layer model of MiXiM, which tackles this task. It provides the researcher with an easy to use interface to the wireless transmission medium. It models the wireless medium in all three dimensions (time, space and frequency) supporting the implementation of future wireless communication standards, but at the same time also supports easy modeling and simulation of traditional single frequency systems.