POWER AND ENERGY MANAGEMENT

Power and energy management issues came up in a variety of contexts including software radios.

Addressing the issue of power management in a broader context, Marcel Pelgrom at Philips noted the trend towards higher energy per weight and size through the evolution of batteries from NiCd to Lithium-ion to Lithium-polymer and beyond. Hans Hofstraat, also at Philips, discussed polymer batteries, which in 5-10 years could be widely deployed and reduce costs dramatically. However, Hofstraat, who passed around a working polymer display driven by a polymer battery, believes that substantial research is still needed, particularly multidisciplinary research.

The success of untethered, mobile communications depends critically on portable energy sources that enjoy a long life. Longer battery life can be effected directly through the development of higher capacity cells but, so far, advances in battery technology have failed to keep up with the rapid pace of developments in other aspects of mobile communications. Thus, energy savings may more likely be found through more efficient management of available battery energy.

Pelgrom claimed that the best research area for power management was better power management through protocols. Pelgrom also observed that RF power consumption often dominates software power consumption. He felt that long-term research should emphasize RF and packaging research and software improvements that have a direct effect on RF power consumption. Nokia representatives pointed out that the drivers of technologies in the future will be service and application protocols and not more capacity (as is the current driver) and identified battery and energy management as one of the technologies needed to achieve these applications. Mitsubishi Electric Corporation's overarching concern for reducing the size and weight of handsets induced them to explore battery technologies to extend life or reduce weight. U.S. companies that are interested in the topic include IBM, Hughes, Rockwell Collins, and Maxim.

Assessment

Development of higher capacity electrochemical cells has failed to keep pace with the demand. Therefore it is desirable to develop energy efficient architectures, systems, protocols, algorithms, and circuits for the efficient management of available battery energy.

Currently, the energy consumed in RF processing dominates digital processing. Technology areas in the critical path include (1) RF and packaging advances, (2) software that reduces RF power consumption, (3) energy efficient modulation formats and protocols, and (4) power efficient hardware-software co-design. Low cost polymer batteries appear to be an innovative development on the battery technology side, but the need for more extensive multidisciplinary research on the topic persists.

As networks reach deeper, penetrating home and commercial control applications, many simple non-computing nodes will need to be networked. Such an approach is expected to result in new services and applications. Current initiatives, such as Bluetooth, HomeRF, and sensor networks, are early precursors of this trend. In sensor networks or any largely dormant segment of a network, battery powered nodes will be mostly asleep and consequently consume most of their energy while asleep. Therefore research on ways to reduce energy consumption in sleep modes is critical. This means that RF energy consumption is not the only limiting factor.

The panel agreed that United States and European companies were on par with regard to their interest in energy efficient system designs. The Japanese companies that the panel visited did not articulate any special concern in this regard. Many of the leading suppliers of batteries for portable devices are currently Japanese.


Published: July 2000; WTEC Hyper-Librarian