PicoRadio: Self-Configuring Wireless Sensor Networks

Distributed, large-scale sensor information networks combine a number of seemingly contradictory implementation requirements. On the one hand the networks have to be versatile, self-organizing, dynamically reconfigurable, and multi-functional. This implies that the communication and computational components of the sensor nodes need to be adaptive and programmable. On the other hand, extensive large-scale coverage (which implies large numbers) requires that the sensor nodes be inexpensive, have a very small footprint, and consume a minimum amount of energy to extend their operational lifetimes.

Consider for instance the following scenario. A science museum for children (to be more particular, the San Francisco Exploratorium) presents a collection of exhibits that feature a combination of data measurements and cause-and-effect experiments. To make the museum exciting, a close interaction with the visitors in terms of controlling the exhibits and providing feedback on the experiments is mandatory. In an even more aggressive scenario, the children can be an active part of the experiments themselves. Keeping the exhibits flexible and easily modifiable is hence desirable. The availability of cheap and easily-deployable wireless sensor (and monitor) networks may create a true revolution in how these museums operate. In addition to the functions of sensing/control/monitoring, the ad-hoc wireless networks could also provide paging, intercom, and localization functionality.

This is only one single example of the potential of wireless sensor networks. Others include the smart home (integrating environment control, security, identification, inventory, and smart tagging), the industrial building control and management, and the emerging world of interacting and evolvable toys.

The ever-evolving scaling of the semiconductor technology has enabled new opportunities to provide both flexibility and efficiency, as needed for these self-configuring and adaptive wireless networks, at a low cost and small size. When reducing the minimum feature sizes into the deep sub-micron realm (0.25 mm and below), it becomes possible to integrate more than one million gates on a single die, enabling the co-integration of the interfacing, computation, position location and communication functions into a single silicon circuit. This system-on-a-chip approach not only maximally reduces the size of the sensor node, but also allows the use of advanced circuit architectures which provide the optimal trade-off between flexibility and energy-efficiency. The tight integration of communication and computation functions into a single chip (which we will call a PicoNode from now on), will provide the desired functionality at the lowest possible cost and energy.

The PicoRadio project strives to develop the range of technologies necessary for the realization of ultra-low energy wireless sensor networks. These include the study of multi-hop networks, and media-access layers that support low (but variable)-rate data transmission, while ensuring energy-consumption levels that are close to the theoretical limits. Other issues involve the choice of the implementation platforms and chip architectures that enable the implementation of these advanced algorithms. A heterogeneous combination of programmable, configurable, and fixed components seems to be a probable solution. Mapping the advanced networking and communication algorithms onto such an architecture presents a real design methodology problem. Ensuring and verifying that these distributed and embedded systems will behave in a correct manner is especially hard. Finally, implementing an RF front-end that meets the demands of variable bit-rates and energy-efficiency opens some interesting new venues for research. In the coming paragraphs, a number of research projects will be described that attempt to tackle the issues raised above.

Last Update: 11/29/01 07:27:55 PM