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In big wireless networks, little things matter big time when it comes to power. That was the message from Elad Alon, a UC Berkeley professor (pictured left) involved in research at the university’s Berkeley Wireless Research Center. Alon kicked off the day-long Low-Power Technology Summit at Cadence’s San Jose headquarters.
“Unlike performance, where you are looking for the max—meaning the worst-case path—power is set by the sum of everything,” Alon said. “From a design standpoint, this changes things in a dramatic way. Every small piece can matter quite substantially.”
And engineers can often focus on optimizing a portion of a system and end up creating problems for themselves they didn’t anticipate.
By way of example, he pointed to a sample RF front-end system he worked on, a 60GHz wireless transceiver. The team built a 4mW power amplifier (“the stage you think is the most important part”) that was 20 percent efficient, good by many standards.
But then when considering components around the PA, trouble set in. The mixer and phase rotator consumed 9mW, buffers burned another 8mW and some baseband logic at 1mW.
“By the time I’m done, I’ve taken this 20-ish percent efficient power amplifier and my overall transmitter is maybe 3-4 percent efficient. There's always the first thing you think of to optimize, then as soon as you do that, everything else is now actually the thing you should have optimized.”
He added, “What this really means is you're going after an energy-efficient (design)… you have to think about the entire system as a whole.”
To demonstrate tradeoffs and system-level thinking, Alon walked the audience through two research projects—one a 5G cellular system, the other electronics for brain-machine interfaces.
You can see Alon’s fascinating presentation here (Cadence Community login required) and access his presentation here.
In addition, click here for a complete roster of Low-Power Summit presentations.
- Low-Power Summit Presentation: Why Cadence Has “Passion” for Power
- Panel: Engineers Debate Progress of Low-Power Design