Letting Wi-Fi Do More With Less Energy

Atheros, G2, and ZeroG are trying to make Wi-Fi work more efficiently by off-loading functions to their chips, opening up new mobile functions

In the quest for a truly mobile device, we've managed to cut the phone cord and the Ethernet cable, but the power cord? Well, that's still a problem. While some innovators are working on better batteries and alternative power sources, such as methanol fuel cells and motion-powered mobile phones, investing in expensive power sources without paying attention to device efficiency is sort of like buying a closet full of new suits just before going on a diet.

Earlier this year, we looked at a few of the reasons why mobile devices power down quickly, among them gorgeous displays, cold weather, and needy chips and applications that keep the processor hopping even when your device isn't in use. One such culprit is Wi-Fi, something chipmakers have long recognized and are now responding to with low-power offerings. While these won't all keep your iPhone running longer, they could play a role in boosting the efficiency of a growing number of new devices (BusinessWeek.com, 8/15/08).

Letting sleeping dogs lie

In most of the how-to's that litter the Web with advice about extending mobile battery life, a top recommendation is to disable Wi-Fi when it isn't actively being used. That's fine for some users, but for anyone interested in mobile VoIP applications—or any of the social applications that use Wi-Fi to pinpoint their location—having Wi-Fi continuously enabled is a must.

One solution is to reduce Wi-Fi's power consumption when it's inactive. This can be done using Atheros's AR6002 family of low-power Wi-Fi chips that launched last year. The AR6002 chips, which are beginning to appear in handsets made by both LG and HP, operate a lot more autonomously than previous generations of Atheros chips, off-loading some of the simple operations from the host processor onto the Wi-Fi chip's own processor.

For example, even when Wi-Fi is not actively transmitting data, it's constantly polling for the presence of a network, using an assist from the host processor. While most manufacturers have reduced the power required to perform this polling function, Atheros says its chips go one better: Instead of waking up the host processor to see if a wireless access point is still around, Atheros's chips check in unassisted. This saves a substantial amount of power because it allows the phone (or other battery-powered device) to remain asleep while the Wi-Fi is awake. "The goal here really is to leave Wi-Fi always on," said Tim Peters, manager of mobile communications and marketing at Atheros.

G2 Microsystems, a four-year-old asset-tracking technology company in Campbell (Calif.), which launched a low-power Wi-Fi system earlier this year, praised Atheros's low-power chips. "We benchmark our power against them in part because their data is in the public domain, but also because they've put the most effort there," said Lisa Payne, G2's vice-president of marketing.

Ubiquitous, if not powerful

G2's Wi-Fi chips offload even more functions than Atheros's chips.

The company's Wi-Fi "system on a chip" (SoC) hosts the processor and networking protocols, completely eliminating the need for an external 32-bit processor. While that means G2's products aren't suited for such high-end mobile devices as smartphones, they allow product manufacturers to bring Wi-Fi to devices that require longer battery life more than advanced processing power.

As Payne noted; "The minute you add Wi-Fi, people start worrying about power consumption." G2's products aim to bring Wi-Fi to where it's useful without burdening devices with power-hungry processors. While G2's Wi-Fi-enabled products aren't capable of handling the high throughput necessary for big data, such as streaming video, they do support audio and simple data transmission. "I can't give you a perfect picture of where our technology fits," Payne said. That's not, however, because there it lacks a market, but because potential applications are so numerous and diverse.

As Wi-Fi becomes increasingly ubiquitous, the market for such chips will only grow. Investors are taking note. ZeroG Wireless, a Cisco-backed startup contending in this area, is set to announce today that it has closed a $17 million Series B round of financing from Battery Ventures, Morgenthaler Ventures, and Greylock Partners. ZeroG previously raised a $13 million Series A round in June 2007. GainSpan—which was spun out of Intel in 2006 and offers SoC products with embedded Flash memory—closed a $20 million Series B round last December.

G2 showed off a Wi-Fi-enabled remote with Philips Electronics at the Consumer Electronics Show earlier this year. Payne said that other uses for low-power, low-bandwidth Wi-Fi include applications in health care (such as Wi-Fi-enabled scales to automatically share health data with doctors) and building management (Wi-Fi-equipped sensors to detect the temperature and to initiate heating or cooling responses wirelessly). Such low-power chips could also make Internet-enabled appliances targeting energy efficiency (BusinessWeek.com, 9/24/08) a reality. GainSpan is particularly interested in this market: Earlier this year, the company announced an energy-monitoring partnership with Hitachi.

G2's all-in-one approach is enough to convince some consumer device manufacturers to make the switch—even when they're not battery dependent. Payne says one of G2's clients is swapping out an efficient Atheros Wi-Fi chip for a G2 chip, although its product plugs into the wall. While Payne wouldn't disclose exactly how the chip will be used, she referred in her description to in-home electronic displays for Internet-connected data such as news and weather. "They didn't need the processing power," she said of the client.

While a "use-only-what-you-need" philosophy may not help our smartphones just yet, it's an efficiency lesson that could come in handy for the rest of our Wi-Fi-wired lives.

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