If you want to see what Zigbee and low-cost, low-power micros can do, then check out Wireless Sensor Networks: An Information Processing Approach by Feng Zhao and Leonidas Guibas.The book is actually very general and addresses things such as infrastructure, tracking of multiple objects, and network databases. Network databases provide a way to gather sensor information, allowing the aggregate computing power to be employed in processing the information.
Zhao and Guibas address a range of issues, including routing methods such as attribute-based routing and geographic, energy-aware routing. They present various algorithms for the localization services needed in large sensor environments.
The book presents some system implementations like Berkely’s Motes, the TinyOS, and a dataflow-style language: TinyGALS. It is a good teaching book, although its coverage of real-world examples does not go into much detail. Still, it’s an excellent book to read if you need an overview of this type of technology.
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