Abstract-Vehicular sensor networks are emerging as a new network paradigm of primary relevance, especially for proactively gathering monitoring information in urban environments. Vehicles typically have no strict constraints on processing power and storage capabilities. They can sense events (e.g., imaging from streets), process sensed data (e.g., recognizing license plates), and route messages to other vehicles (e.g., diffusing relevant notification to drivers or police agents). In this novel and challenging mobile environment, sensors can generate a sheer amount of data, and traditional sensor network approaches for data reporting become unfeasible. This paper proposes MobEyes, an efficient lightweight support for proactive urban monitoring based on the primary idea of exploiting vehicle mobility to opportunistically diffuse summaries about sensed data. The reported experimental/analytic results show that MobEyes can harvest summaries and build a low-cost distributed index with reasonable completeness, good scalability and limited overhead.

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Abstract-In this paper we study multi-hop ad hoc routing in a scalable Underwater Sensor Network (UWSN), which is a novel network paradigm for ad hoc investigation of the world below the water surface. Unlike existing Underwater Acoustic Networks (UAN), the new UWSN paradigm dispatches large number (in the thousands) of unmanned low-cost sensor nodes to locally monitor and report otherwise not easily accessible underwater events in a time-critical manner. Due to the large propagation latency and very low bandwidth of the acoustic channel, a new protocol stack and corresponding models are required as conventional approaches fail. In particular, we show that neither proactive routing message exchange nor reactive/on-demand flooding is adequate in the challenging new underwater environment. Unlike the terrestrial scenarios, on-demand flooding cannot be both reliable and efficient due to widespread collisions caused by the large propagation delay. On the other hand, as in terrestrial scenarios, proactive routing is more expensive and less efficient than on-demand routing in typical underwater environments. We propose a "conservative" communications architecture that minimizes the number of all packet transmissions to avoid possible acoustic collisions. This is implemented in the nonintrusive Under-Water Diffusion (UWD), which is a multi-hop ad hoc routing and in-network processing protocol with no proactive routing message exchange and negligible amount of on-demand floods. To achieve its design goal, UWD does not rely on GPS or power hungry motors to control currents. Instead, UWD is designed in a minimalist's framework, which assumes homogeneous GPS-free nodes and random node mobility. Our simulation study verifies the effectiveness and efficiency of our design.

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