Wi-Fi Direct vs. Bluetooth 4.0: A Battle for Supremacy

Who's got the power?

Both the Bluetooth SIG and the Wi-Fi Alliance are claiming their specifications will use power-saving technology for battery-powered devices. The Bluetooth SIG says the new low-energy technology (PDF) feature means that Bluetooth 4.0 chips are optimized to run on a coin cell battery for a year or longer. But low-energy technology is only meant to be used when transferring short bursts of data. It also won't work if you are trying to talk to an older Bluetooth device that lacks the low-energy feature. That means laptops and mobile phones with Bluetooth 4.0 will have to switch between the new low-energy technology and so-called classic Bluetooth technology depending on the device they are talking to and how much data they are transferring. The bottom line is that while Bluetooth 4.0's power-saving feature sounds impressive, it's not clear how often you will get to take advantage of it in the real world.

The Wi-Fi Alliance says Wi-Fi Direct devices can support the WMM Power Save program that promises to improve a device's battery life by 15 to 40 percent.

Backward compatibility?

Wi-Fi Direct devices will be able to communicate with legacy Wi-Fi devices. That means if your next laptop has a Wi-Fi Direct chip, you will be able to create a device-to-device connection with your old wireless printer or wireless digital picture frame.

As I've already said, Bluetooth 4.0's new low-energy technology means that compatibility with older Bluetooth devices could get a bit messy. Some Bluetooth 4.0 devices such as pedometers and glucose monitors will only come with Bluetooth's low-energy feature using a single-mode Bluetooth radio. Since these single-function devices are meant to be small and mobile, they use the new power-saving feature to save space and battery power. But that means they are also incompatible with, say, an older PC equipped with Bluetooth 2.1.

More complex devices using Bluetooth 4.0, such as PCs and mobile phones, will use a dual-mode radio to take advantage of all three Bluetooth 4.0 technologies - low-energy, high-speed transfers and classic Bluetooth. This will make it possible for newer Bluetooth 4.0 devices to communicate with legacy Bluetooth tech.

It's also important to note that so-called "streaming devices" such as hands-free headsets for mobile phones or stereo equipment cannot use Bluetooth low energy technology. That means new Bluetooth headsets for your iPhone 4, Droid X or Samsung Focus should not be affected by Bluetooth 4.0's use new low-energy technology. For more information, check out the Bluetooth SIG's FAQ about low energy technology (PDF).

Availability

Bluetooth 4.0 products should start hitting the market before the end of the year or early 2011. But it looks like Wi-Fi Direct may be first out the gate. The Wi-Fi Alliance recently announced that five wireless networking PC cards from Atheros, Broadcom, Intel, Ralink and Realtek are Wi-Fi Direct ready and should be available before the end of the year.

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