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

By Celeste LeCompte

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.