Category: Bluetooth

A while back the Wi-Fi Alliance announced a new certification program, Wi-Fi Direct, which enables a PC to connect directly with other Wi-Fi devices without having to go through an Access Point.

The Wi-Fi certification process for Wi-Fi Direct is scheduled to be launched by the end of 2010, but there are already two pre-standard implementations of this concept, My Wi-Fi, an Intel product which ships in Centrino 2 systems, and Wireless Hosted Network which ships in all versions of Windows 7.

The Wi-Fi Direct driver makes a single Wi-Fi adapter on the PC look like two to the operating system: one ordinary one that associates with a regular Access Point, and a second acting as a “Virtual Access Point.” The virtual access point (Microsoft calls it a “SoftAP”) actually runs inside the Wi-Fi driver on the PC (labeled WPAN I/F in the Intel diagram below).

To the outside world the Wi-Fi adapter also looks like two devices, each with its own MAC address: one the PC just like without Wi-Fi Direct, and the other an access point. Devices that associate with that access point join the PC’s PAN (Personal Area Network).

This yields several benefits in various use cases.

I wrote a couple of years ago about how a company called Ozmo planned to use a Wi-Fi PAN to connect peripherals to PCs, replacing Bluetooth and proprietary wireless technologies. That plan has now come to fruition. Earlier this month Ozmo announced that it had received $10.8 million in additional funding, and this week it announced two major customers: Primax, a leading ODM of wireless mice, and NMB Technologies, a leading ODM of wireless keyboards.

Here’s a slide from one of their promotional presentations giving a comparison with Bluetooth and proprietary technologies:

The essence of Ozmo’s approach is low cost, multi-device, low bandwidth and low power consumption. Wi-Fi Direct has another use case that is high bandwidth, with no requirement for low power.

If you want to stream video from your PC to a monitor using traditional Wi-Fi (“infrastructure mode”) each packet goes from the PC to the access point, then from the access point to the TV, so it occupies the spectrum twice for each packet. Wi-Fi Direct effectively doubles the available throughput, since each packet flies through the ether only once, directly from the PC to the TV. But it actually does better than that. Supposing the PC and the TV are in the same room, but the access point is in a different room, the PC can transmit at much lower power. Another similar Wi-Fi Direct session can then happen in another room in the house. Without Wi-Fi direct the two sessions would have to share the access point, taking turns to use the spectrum. So we get increased aggregate throughput both from halving the number of packet transmissions, and from allowing simultaneous use of the spectrum by multiple sessions (if they are far enough apart).

A Wi-Fi buff would point out that you can already do all this with ad-hoc mode, but Wi-Fi Direct purports to be usable by mortals, and to work interoperably, neither of which could be said for ad-hoc mode until recently. In January Infinitec announced a new point-to-point video streaming product that claims to be easy to use and universally interoperable, that Engadget implies uses ad-hoc mode, though Google can’t find the words “ad hoc” on the Infinitec website.

Between the bandwidth extremes of mice and TVs, lie numerous other potential uses, like headsets (which Ozmo also supports); syncing phones, cameras and media players; and wireless printers.

A while back I wrote about Ozmo, a company that plans to replace Bluetooth with Wi-Fi in certain applications.

Ozmo’s pitch is that their special version of Wi-Fi is faster, less prone to interference, cheaper and more power efficient than Bluetooth. Though slow for Wi-Fi, Ozmo’s data rate of 9 Mbps is way better than the 3 Mbps of Bluetooth 2.1 plus EDR. Concerning interference, Bluetooth transmissions are in the same 2.4 GHz frequency range as Wi-Fi, so careful engineering is always needed for coexistence; but coexistence is not an issue for Ozmo, because it is a flavor of Wi-Fi. The lower-cost part of the story is that while an Ozmo chip for a peripheral is roughly the same price as a Bluetooth chip, it saves the need for a Bluetooth chip in the host device. So if Ozmo’s claims of double the battery life of Bluetooth turn out to be valid when tested, the pitch holds water.

Bluetooth is unshakably incumbent in the billion-unit-per-year mobile phone market; most phones are now shipping with Bluetooth. But in laptops the Bluetooth attach rate is still well under 50%, while the Wi-Fi attach rate is close to 100%. So it makes sense that Ozmo is focusing initially on the computer market. Ozmo enables a laptop to use wireless peripherals like mice, keyboards, game controllers and headsets with a software modification to the Wi-Fi rather than having to include a USB wireless receiver in the package.

Ozmo is also focusing on the Consumer Electronics market, where Wi-Fi is gaining traction, and where the ability to support wireless remotes and similar peripherals can be added ‘free of charge’ to a device that already has Wi-Fi.

Since this is a compelling proposition, OEMs in these markets are likely to fall into line relatively easily, and indeed Ozmo has already secured the support of the biggest fish in the PC pond, Intel.

It may be a harder sell to the peripheral manufacturers. For them it’s not just a software upgrade. It is a new product line, one that depends on a single source for a key component and that sells into a currently non-existent base of host devices.

On the other hand, the peripheral device manufacturers may not be oposed to a new product line – they already have a plethora of products, using a variety of connectivity technologies including proprietary ones. Adding another one may not be too arduous, especially if it removes the need for a USB part. Ozmo could overcome the non-existent base issue by supplying, or convincing Intel and the other PC Wi-Fi chip vendors to supply, upgraded drivers for legacy Wi-Fi devices.

The Bluetooth SIG put out a press release the other day saying that by mid-2009 a specification that includes Wi-Fi as an “alternate MAC/PHY” will be released.

This is the relevant part of the release:

What we’re doing is taking classic Bluetooth connections – using Bluetooth protocols, profiles, security and other architectural elements – and allowing it to jump on top of the already present 802.11 radio, when necessary, to send bulky entertainment data, faster. When the speed of 802.11 is overkill, the connection returns to normal operation on a Bluetooth radio for optimal power management and performance.

So this innovation specifies an interface above the Bluetooth MAC layer that enables Bluetooth session data to flow through a Wi-Fi radio instead of a Bluetooth one.

The press release says that the Alternate MAC/PHY will be used to do things like:

Wirelessly bulk synchronize music libraries between PC and MP3 player.
Bulk download photos to a printer or PC.
Send video files from camera or phone to computer or television.

But the new specification will only be useful in devices that already have both Wi-Fi and Bluetooth, and Wi-Fi can do these things without any assistance from Bluetooth. So the increment in value may be small; but Bluetooth can still bring something to the table. According to Wikipedia,

The Bluetooth Radio will still be used for device discovery, initial connection and profile configuration, however when lots of data needs to be sent, the high speed alternate MAC PHY’s will be used to transport the data.

It seems oddly limiting not to go the whole way, and enable Bluetooth applications to run on top of Wi-Fi even when there is no Bluetooth radio.