Emerging Challenges-Mobile Networking for Smart Dust
Large scale networks of wireless sensors are becoming increasingly tractable. Advances in hardware technology and engineering design have led to dramatic reductions in size, power consumption and cost for digital circuitry, wireless communications and Micro ElectroMechanical Systems (MEMS). This has enabled very compact, autonomous and mobile nodes, each containing one or more sensors, computation and communication capabilities, and a power supply. The missing ingredient is the networking and applications layers needed to harness this revolutionary capability into a complete system. We review the key elements of the emergent technology of “Smart Dust” and outline the research challenges they present to the mobile networking and systems community, which must provide coherent connectivity to large numbers of mobile network nodes co-located within a small volume.
As the research community searches for the processing platform beyond the personal computer, networks of wireless sensors have become quite interesting as a new environment in which to seek research challenges. Many researchers have recently shown that it is possible to integrate sensing, communication, and power supply into an inch-scale device using only off-the-shelf technology. These have been enabled by the rapid convergence of three key technologies: digital circuitry, wireless communications, and Micro ElectroMechanical Systems (MEMS). In each area, advances in hardware technology and engineering design have led to reductions in size, power consumption, and cost. This has enabled remarkably compact, autonomous nodes, each containing one or more sensors, computation and communication capabilities, and a power supply. Fig. 1 shows two examples of this off-the-shelf sensor technology. The device on the left contains a microprocessor, temperature sensor, light sensor, 900 MHz radio, and battery (hidden underneath). The radio range is about 10 m. The device on the right consists of a microprocessor and four sensors, and the radio has been replaced with a laser pointer driven by the microprocessor. Transmitting at 4 bps to a small CCD camera attached to a PCMCIA frame grabber in a laptop computer, that device is capable of sensing and communicating weather information at a distance of over 20 km. Communication was demonstrated from San Francisco to the authors’ building in Berkeley, across the San Francisco Bay. Both devices have a full-duty lifetime of about a day