Hock-Beng Lim

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Sensor networks are widely used in many applications for collecting information from the physical environment. In these applications, it is usually necessary to track the relationships between sensor data readings within a time window to detect events of interest. However, it is difficult to detect such events by using the common aggregate or selection(More)
Coverage is an important performance metric for many applications such as surveillance in wireless sensor networks (WSNs). Coverage control is used to select as few active nodes as possible from all deployed sensor nodes such that sufficient coverage of the monitored area can be guaranteed, while reducing the energy consumption of each individual sensor(More)
Wireless sensor networks have emerged as an exciting technology for a wide range of important applications that acquire and process information from the physical world. Grid computing has evolved as a standards-based approach for coordinated resource sharing. Sensor grids combine these two promising technologies by extending the grid computing paradigm to(More)
In energy-limited wireless sensor networks, network clustering and sensor scheduling are two efficient techniques for minimizing node energy consumption and maximizing network coverage lifetime. When integrating the two techniques, the challenges are how to select cluster heads and active nodes. In this paper, we propose a coverage-aware clustering(More)
When there are multiple queries posed to the resource-constrained wireless sensor network, it is critical to process them efficiently. In this paper, we propose a two-tier multiple query optimization (TTMQO) scheme. The first tier, called base station optimization, adopts a cost-based approach to rewrite a set of queries into an optimized set that shares(More)
In this paper, we study the problem of processing multiple queries in a wireless sensor network. We focus on multi-query optimization at the base station level to minimize the number of radio messages in the sensor network. We adopt a cost-based approach, and develop a cost model to study the benefit of exploiting common subexpressions in queries. We also(More)
In this paper, we consider a large scale sensor network comprising multiple, say K, base stations and a large number of wireless sensors. Such an infrastructure is expected to be more energy efficient and scale well with the size of the sensor nodes. To support a large number of queries, we examine the problem of allocating queries across the base stations(More)
The middleware for a cyber-physical system is crucial as it tightly integrates computation with physical processes to achieve better reliability, distributed coordination, higher precision and efficiency, and better autonomous control. In this work, we design and develop the cyber-physical middleware framework for a large-scale water distribution system(More)