Abstract-In tree-structured data collection sensor networks, packets are routed towards a sink node by iteratively choosing a node's immediate parent node as the next hop. It is however beyond the scope of these routing protocols to transfer messages along the reverse path, i.e., from the sink to individual nodes in the network. In this paper, we present CBFR, a novel routing scheme that builds upon collection protocols to enable efficient point-to-point communication. We propose the use of spaceefficient data structures known as Bloom filters to efficiently store routing tables on the networked devices. In particular, each node in the collection tree stores the addresses of its direct and indirect child nodes in its local Bloom filter. A packet is forwarded down-tree only if the node's local filter indicates the presence of the packet's destination address among the node's descendants. In order to cater for the presence of mobile nodes, we apply the concept of counting Bloom filters to allow for the removal of elements from the filter by means of gradual forgetting. The effectiveness of our approach in achieving both high delivery rates and low overhead is demonstrated by means of simulations and experiments.

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The logistics domain constitutes a promising application area for wireless sensor network technology. Wireless sensor nodes can be deployed for example in containers or trucks' load areas to monitor environmental parameters relevant to the condition of transported goods in real time. Exploiting their computation and communication capabilities, wireless sensor nodes can locally detect the occurrence of critical situations, so-called events, and send corresponding alarm messages to responsible decision makers via the network and corresponding gateway nodes in real time. Within this paper, we present a fully working solution and corresponding prototypical implementation of how such real-time monitoring and event detection can be realized in a context-dependent and user-specific way. As such a system requires transmitting alarm messages and sensor data from the wireless sensor network deployment to users' backend systems, we furthermore explore means to interconnect wireless sensor nodes and smartphones. In particular, we present findings from field tests concerning the link quality of such connections for different technological approaches for which we realized prototypical implementations.