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Broadcom cuts WiFi power burn to phone levels

The prospect of seeing mobile phones using WiFi as a matter of course looms nearer; Broadcom has designed a chipset which will work on the tiny phone battery typical of a cellphone. But why? The answer is: IP telephony.

It's perfectly possible, even today, to plug a microphone and earpiece into a personal computer, and use that to chat to friends over the Internet. For someone connected to broadband at a flat rate, the voice call is effectively free.

It's also possible, using software from people like net2phone and Callserve, to place calls from a computer, to an ordinary phone.

But when you're out and about, your only Internet connection is likely to be GPRS telephone (costly) or WiFi hotspot; and to connect to that, you need something with a powerful battery. The typical WiFi circuit burns 0.6W of power - enough to flatten a phone battery in hours. That same phone can run for a week if it only needs to talk to GSM transmitters.

That's bizarre, because GSM cellphones are typically restricted to a maximum power of 100 mW while WiFi transmissions (in Europe, at least) are not allowed to exceed 1 mW - and there's a simple reason for the fact that WiFi is power hungry: when it was originally designed, nobody foresaw people using it in anything less than a notebook computer.

Broadcom has fixed that. Its AirForce One chip set "is the size of a postage stamp and consume up to 97 percent less power than other Wi-Fi solutions on the market," said the announcement. All the circuitry is on a single silicon chip, all-CMOS wireless LAN transceiver.

"While competing products require multiple chips and many discrete components, Broadcom's AirForce One single-chip integrates a 2.4 GHz radio, power amplifier, IEEE 802.11b baseband processor, medium access controller (MAC), Tx/Rx and diversity switches and all other radio components onto a single silicon die," the release claims. "This unprecedented level of chip integration eliminates more than 100 discrete components and makes the one-chip module 87 percent smaller than traditional mini-PCI WiFi solutions."

As to when or whether such things appear on the market in mobile phones, depends on many factors. In theory, anybody offering a WiFi hotspot could add a Bluetooth access point for a total cost of $50 odd by plugging a bluetooth dongle into the computer - as was done at the Progress Bar in North London, using a Meshbox as the host, for example.

With the right software, a Bluetooth phone could connect to the Internet over that, and voice calls could be placed over broadband. But that won't work, because the phone providers have rigorously opposed the design of mobile phones with that capability.

Dam the stream at one place, and it overflows somewhere else; and the overflow could be WiFi. There are already thousands of WiFi hotspots, and all it takes is a phone with a WiFi capability on top of its normal wireless, plus that IP telephony software, and we can stop placing calls over the cellular networks.

Broadcom's one-chip solution also offers a comprehensive power management scheme to extend the battery life of small mobile devices.

"This power management approach consumes an average of 70-97% less power than existing solutions and leverages the benefits of extreme integration, innovative hardware design and Broadcom's new SuperStandby software," says the company.

SuperStandby wakes the minimum amount of circuitry for the shortest possible period of time, allowing the one-chip module to consume up to 97 percent less power than the Intel Centrino wireless LAN solution in standby mode, according to internal tests carried out by Broadcom. Pocket-sized mobile devices spend a majority of their time in standby mode.

"The power savings offered by the AirForce One chip solution can add several days of battery life to a WiFi-enabled PDA," the company added.

More data - an audio presentation and from Broadcom's own web site.