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« Wi-Fi Alliance Peers into the Future with Ad Hoc Replacement | Main | Going the Distance with Wi-Fi Direct »

October 14, 2009

Is Wi-Fi Gunning for Bluetooth? Not Precisely

Wi-Fi Direct is both parallel to and complementary of Bluetooth. Discuss: Today's announcement of Wi-Fi Direct, a peer-to-peer Wi-Fi transfer method, might seem to be firing across Bluetooth's bow. But it isn't quite. Intel's My WiFi is a much more direct threat, and even then may not materialize in quite the way that's being predicted. (Read my coverage, "Wi-Fi Alliance Peers into the Future with Ad Hoc Replacement.")

To review, Bluetooth is a PAN (personal area networking) technology in which devices under the control of the same person or computer communicate over short ranges and relatively low speeds. Bluetooth can create peer-to-peer connections or piconet networks, which comprise a host and up to seven clients. In a very standard configuration, a cell phone might use Bluetooth to communicate with a laptop, sharing its 3G mobile broadband connection, while at the same time a Bluetooth earpiece is paired with the phone to handle audio.

Bluetooth requires a pairing process, in which devices authenticate to each other and agree through a handshake (with optional encryption) to talk to one another. The SIG, device makers, and desktop and mobile OS developers have done a great job of simplifying this process down to typically entering a PIN--one of several options with the current security system, Secure Simple Pairing--instead of having 20 to 25 steps as it used to be.

Bluetooth's current release (2.1+HDR [high data rate]) encompasses a wireless spec for 3 Mbps data transfer (raw) using the 2.4 GHz band. The spec also includes application-layer elements, which are called profiles, and which define a large array of end-to-end tasks, like printing, file transfer, or acting as a modem. This allows any manufacturer to make a Bluetooth keyboard that talks the HID (human interface device) profile, and which is tested and certified as such, to talk to any other Bluetooth device with the HID profile.

The Bluetooth SIG, which maintains and develops the spec, isn't tied to its physical medium. It's tried to partner with other specs in process to extend itself, notably tying its cart at one point to both major ultrawideband (UWB) encodings, and then picking WiMedia, which was the "winner" in UWB. WiMedia disbanded, but handed off the Bluetooth component to the SIG; there may still be life in it. (Originally, Intel et al. wanted to stick one UWB radio in computers and devices, but have many different protocols run over that radio, such as Bluetooth, TCP/IP, Wireless USB, and video. UWB is currently shipping only as an instantiation of Wireless USB.)

While UWB fiddled and burned, however, the SIG worked on Bluetooth 3.0+HS (High Speed), which incorporates a high-speed transfer mode that allows a Bluetooth device to coordinate with a peer switching to use 802.11 for a bulk transfer, useful for large files or high-speed video streaming. The session is still within the structure of a Bluetooth PAN, and the use of 802.11 is entirely under the control of the Bluetooth session. The devices don't suddenly become ad hoc nodes or soft access points. Note the use of 802.11: this is a particular use of that protocol outside of any current Wi-Fi spec.

Wi-Fi Direct is an outgrowth of the interest by Intel and others in reducing the number of radio technologies and the level of complexity in devices, which can correspondingly reduce battery usage, while also developing a spec that's to their liking. Intel has a board seat on the Wi-Fi Alliance and the Bluetooth SIG, but still enjoys charting its own course.

Wi-Fi Direct is a peer-to-peer technology, at least the way it's being described initially. Wi-Fi devices that have services to offer (like printing, file sharing, etc.) can advertise those in a way that other equipped devices can access directly. This new method offers the speed and security of an infrastructure Wi-Fi network with an access point at the center without the overhead of joining such a network or making such networks public to allow access to specific resources. That is, someone can print to your printer without you giving them a key to your network. Wi-Fi Direct is built on top of 802.11n, so it can work in both 2.4 and 5 GHz, too.

The simplicity of Wi-Fi Direct is supposed to aid in devices without keyboards or easy data entry methods, much as Wi-Fi Protected Setup (WPS) was supposed to offer a one-click secure connection. With a peer-to-peer approach, a camcorder could hook up with a laptop to transfer data directly without you needing to enter a WPA2 Personal passphrase or even connect at all to an existing Wi-Fi network.

Beyond speed and security, Wi-Fi Direct will allow an adapter to be scanning and accessing peers while also maintaining a full infrastructure connection to a network. It's this feature that allows devices to ostensibly cut the Bluetooth "cord," although I'm still dubious about that as a general element, as I'll explain.

The My WiFi technology that Intel developed (apparently at least in part with Ozmo Devices) emphasizes more of the PAN aspect, talking about having eight devices associated with a laptop, for instance.

So, the question at the outset was whether Wi-Fi Direct is a competitor to Bluetooth?

Bluetooth and Wi-Fi Direct definitely compete head to head on trying to make the simplest network connection between two devices for a variety of straightforward purposes.

However, Wi-Fi Direct won't be backward compatible to the hundreds of millions of devices on the market that already have Bluetooth 1.x or 2.x. Bluetooth's later flavors (2.x and 3.x) are backwards compatible with those older devices.

And while Wi-Fi with a PAN mode could reduce circuit counts, most Wi-Fi chips that are being sold in the mobile market, and I believe in the desktop/laptop market, are integrated Bluetooth/Wi-Fi modules that often throw in other radios and circuitry as well.

Wi-Fi may eventually be appropriate to build into keyboards, mice, wireless headsets, earpieces, and other low-battery peripherals, but that's not really the case today. Bluetooth dominates there in hundreds of millions of installed devices.

Bluetooth's profiles also seem like an advantage to me. Kelly Davis-Felner, the Wi-Fi Alliance's marketing director, said that Wi-Fi Direct would not have application or task overlays, but would be focused on the networking and communication level, as with other Wi-Fi certifications.

Which means that if I connect my mobile phone with my computer to transfer music over, I still need an application on both sides that handles the file transfer. With Bluetooth, the profiles still need an interface on top, but a universally supported file-transfer method already exists. I can use a Bluetooth program under Windows and on the Mac and within various mobile phones to transfer files today.

If I want a method that synchronizes stored files and handles it automatically, then OS makers or third-party developers still do have to build an application on top of that. But with Bluetooth, they can rely on leveraging a well-supported mechanism. It's asymmetric, in that a desktop OS program for syncing MP3 files or photos doesn't require a corresponding program to be installed on a mobile phone that allows access to its storage via the Bluetooth profile.

Now, of course, I'm being a little disingenuous about profiles, because Wi-Fi Direct will create an IP-based network between the two parties, allowing existing service discovery methods to work just as they do over a wireless LAN today--including Apple's Bonjour and whatever the current name of Microsoft's technology. But none of these methods are supported across gadgets (like cameras). mobile operating systems, and desktop/laptop operating system platforms. That's going to be the challenge for Wi-Fi Direct.

In the end, I certainly see Wi-Fi Direct as provoking additional industry efforts to figure out precisely what's useful about PANs and sell those capabilities to consumers as solutions for frustration or a way to accomplish tasks they're unaware they need to accomplish.

The best thing about Wi-Fi Direct is that it enables a secure, high-speed ad hoc mode that will actually work among different devices, something that's long been needed.

One of the most interesting aspects of Wi-Fi Direct is that it could be used with Bluetooth, since many manufacturers participate actively in the Bluetooth SIG and Wi-Fi Alliance. Beyond Bluetooth 3.0+HS, there could be a convergence path for hand-in-hand networking, playing to each standard's strengths.


thanks for clearing up the issue of profiles, as that is imo what makes bluetooth the superior, no matter the lack pf speed.

still, i guess obe could stack the bluetooth profiles on top of this, no?

Yes, I don't mean to harp too much on Bluetooth profiles, but the difference between "you can do anything you want" and "you can do this whole set of particular things" is fairly large.

Just as Bluetooth profiles could have been overlaid onto UWB, I don't see any practical reason that they couldn't be used with Wi-Fi Direct, either.

Glenn, you say "the best thing about Wi-Fi Direct is that it enables a secure, high-speed ad hoc mode that will actually work among different devices, something that's long been needed." However, isn't this exactly what the 802.11s mesh standard set out to do? Why the sudden duplication of effort?

Mesh architecture is as different from a personal area network as, well, the IEEE is from the Wi-Fi Alliance. The mesh proposal, still not finalized, is a way to create a network path among many devices, particularly at the edge. It would potentially have the benefit of allowing device-to-device communication, but that doesn't seem to be its primary goal.

Wi-Fi Direct is precisely focused on a market need and a market failing, and is being pushed outside of the IEEE standards, a first for the trade group. In this case, there's a crying need for a simple way to move data among devices without a base station, since ad hoc networking was never standardized, doesn't offer simplicity, and lacks robust security.

It's possible that 802.11s and Wi-Fi Direct could merge into one kind of standard to serve both masters.

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