It's done to an extent today with clock gating and voltage scaling, but it could be done much more if each component -- the antenna, receiver, and so on -- were designed in concert, Magarshack said.
"The holy grail is that the system only expends power and energy when needed. This is definitely not possible with the tools we have today. We need the next generation of tools and methods," he said.
He and Sun also proposed a so-called wide I/O architecture, which would allow multiple components to share an input/output device. A DRAM chip could be stacked on a baseband processor, for example, and do parallel instead of serial I/O operations, Magarshack said.
Dobberpuhl, the former DEC engineer, said the biggest gains can be made from improved algorithms and architectures, including more efficient parallel designs.
Herman Eul, president of Intel Mobile Communications, said the key is moving functions handled by analog processors into digital. Digital circuits are easier to shrink, he said, and they can be reprogrammed -- so a single transceiver could be used for all five frequency bands in a 3G phone, for example, instead of the five separate chips used today.
"The most power effective transistor is the transistor which is not there," Eul said.
In general the panelists seemed optimistic, if only because engineering persistence has broken through many barriers in the past.
"In general, engineers never give up," Eul said.