Wireless Sensing Spawns The Connected World

WIRELESS NODES GET A BOOST
The power problem goes beyond available sensor output power levels and high power-dissipation levels. The power needed for wireless transceiver nodes also is a concern. BitWave Semiconductor proposed using software-defined radio (SDR) to deal with this problem. The company points to its Softransceiver concept as an example of a viable SDR solution that enables seamless global wireless connectivity (Fig. 5). The SDR concept minimizes circuit hardware costs. Instead, it relies on software changes to program or "tune" a circuit to a specific application.

A group of researchers at the University of California at Berkeley came up with a 2.4-GHz wireless transceiver that dissipates only 200µW. Kris Pister, founder and chief technology officer of Dust Networks (and who coined the term "smart dust" while heading R&D efforts at Berkeley), lauds this work as an important step toward low-cost wireless sensing hardware. Dust Networks is working on low-cost wireless sensing software to complement the technology.

"Berkeley's work is all about low-cost hardware. At Dust Networks, we're working on low-cost software," says Pister. "We came up with communications protocols that keep wireless radios off 99.995% of the time. Low-power software running on low-power hardware is what we're looking for. At that point, power consumption goes down into the single-digit microampere range."

To give users better tools so they can move quickly while developing their core applications, Jennic Ltd. recently showed off its IEEE 802.15.4/ZigBee transceiver modules. The JNS5121MOxxx devices provide minimum bill-of-materials (BOM) costs with minimum engineering time spent on RF circuit design and test development.

Yet the world of ubiquitous sensing, computing, and communications lacks standard software platforms. Adoption of the Tiny Operating System (TinyOS) developed at the University of California at Berkeley has helped, but it's only the beginning.

Now, sensor network designers are starting to build on the TinyOS concept. Crossbow Technology's MoteWorks software/hardware wireless mesh development platform uses TinyOS. It supports rapid, flexible, and open designs based on the IEEE 802.15.4/ZigBee standard.

At WINLAB, the open-access research testbed (ORBIT) system facilitates a broad range of experimental research on next-generation protocols and application concepts for wireless networks. A 64-node radio-grid emulator was already released. A full 400-node radio grid is being tested indoors; an outdoor system will be operational shortly. The project involves Rutgers University, Princeton University, Columbia University, Thomson SA, IBM, and Lucent Technologies.

WINLAB also fabricated and tested a novel wireless sensor network known as SOHAN (self-organizing hierarchical adhoc network). The laboratory says that this network, which has been prototyped, offers significant capacity improvements over conventional ad-hoc wireless sensor networks.

LOOKING FORWARD
Wireless sensor techniques eventually will mature to permit the seamless interconnection of the physical and virtual worlds. Wireless network technologies like WiMedia Ultra-Wideband (UWB) will enable users to do things like download an entire television show in just one minute. Demonstrations of such capabilities already have proven feasible, so it's only a matter of time before there's wide-scale market acceptance.

With Qualcomm's MediaFLO service, users can receive TV broadcasts on cell phones with a TV decoder. The decoder can also decode video from other sources, such as digital video recorders. Users will be able to download programs from other sources onto their phones and watch them when they're on the go.

The rapid proliferation of low-cost, low-power, radio-frequency identification (RFID) tags in industrial, medical, and agricultural applications only adds to the seamless pervasiveness of connectivity. All-plastic—instead of silicon—RFID tags have aided RFID advances. Many such tags will debut this year.

Even still, there's a need for new software development and deployment approaches. The industry also must develop the right networking protocols, the organization of network-based services, and techniques for self-organization, self-configuration, and self-maintaining large distributed systems.

Privacy and security issues must be resolved as well. "If a wireless network's architecture is not planned for privacy and security from the beginning, it will never succeed," warns Rutgers University's Raychaudhuri.

New business models are needed, too, so that there's interoperability between devices and services. This will ensure the flexibility consumers demand. Ultimately, though, technology must be shaped to address a wide range of user needs.

The impact of ubiquitous sensors may create some surprises in the long term. Some technology forecasters predict a greater emphasis on analog computing and networking to faithfully interact with the real world of analog sensors. After all, the realworld variables detected by sensors are all analog in nature.

"A modest indicator of this trend is visible today in the audiophile world," says Paul Saffo, director of the Institute for the Future (IFTF). "The most sophisticated audiophile stereo systems available today still rely on old-fashioned vacuum-tube technology. Audiophiles can tell the difference between sound that has been deconstructed into bits and reconstructed as an analog waveform and sound that has remained in analog form all along."

Ubiquitous sensing will rely on computing and communications. In turn, these technologies will depend on the wide-scale deployment of actuators that enable total closed-loop system control. MEMS technology can fulfill this need.