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Wi-Fi Direct and Bluetooth – battle to the death?

October 25th, 2009 |  Published in Wireless Connectivity  |  4 Comments

The media lapped up the recent press release from the Wi-Fi Alliance, announcing the birth of Wi-Fi Direct.  Almost to a man, they decided once again that it would kill Bluetooth.  I suspect that Bluetooth will prove to have something in common with Mark Twain, being able to sit back and calmly repeat that “the report of my death is an exaggeration”.

For many of the reports, that analysis seems to be based on little more than the relative number of press releases that the two organisations send out.  For some reason known only to itself, the Bluetooth SIG is remarkably reticent about publicising its technology, preferring to sit quietly on its laurels of shipments of over a billion chips per year (1,050 million in 2008 – IMS).  Wi-Fi tends to be more vociferous about its plans, possibly stung by the fact that it manages to ship only just over a third of that (387 million in 2008 – Instat).  As is often the case with young pretenders, noise can be rather more noticeable than actions.  (Incidentally, no other short range standard gets within an order of magnitude of the lower of these figures.)

A few articles dug down a bit more into the technology itself, and came to less of a conclusion as a result.  None of them thought about what really matters, which is what the user experience will look like.  So let’s do exactly that…

First, what are the features of each?  Bluetooth has always used to solve the issue of ad-hoc connections between mobile devices, typically letting users connect phones to headsets and also to transfer content such as photos and music between phones.  The first use case has largely sold to professional users who want to make calls when driving.  The second, of impromptu content transfer, is widely used by kids and students.  (Anyone over the age of twenty-five would probably think of email as the obvious first choice for sharing data.)

In comparison, Wi-Fi’s core ability is to connect laptops and devices pretending to be PCs to the internet via a fixed access point.  The underlying technology – 802.11 has always been able to make ad-hoc connections, but in practice they have not been very compatible and lacked any form of security. 

The problem with ad-hoc content sharing is that the content on mobile devices keeps on getting bigger.  In the early days of Bluetooth, pictures were typically only a few tens of kilobytes, which fitted well with Bluetooth’s 723 kbit/s maximum data throughput.  Today with 10 Mpixel cameras, images have grown to several Mbytes, which take an appreciable time to transfer, even with Bluetooth’s Enhanced Data Rate of 2.1 Mbit/sec. 

Both standards would like to “own” the space of ad-hoc content transfer.  And both sees an opportunity if it can increase its real data transfer throughput, or in the case of Wi-Fi Direct, make ad-hoc connections work.  Earlier this year, Bluetooth made a pre-emptive foray with the release of the Bluetooth 3.0+HS standard.  The HS stands for High Speed (or possibly Hope Springs eternal…).  This is quite a clever approach.  It has not changed the basic Bluetooth radio – that still runs at 2.1Mbps.  But it has worked out a way for Bluetooth to take control of the underlying 802.11g radio within a device and use that just for the data transfer, upping the data throughput to around 24Mbps.  (All of the figures I’m giving are real figures which you might hope to get after all of the protocol overheads have been taken into account.  The headline 54Mbps of 802.11g is a technical fiction as far as real world performance is concerned.) 

The Bluetooth approach has some neat features:

  • The security is still covered by the underlying Bluetooth link.  That makes it easy and secure to make new connections to your friend’s device.
  • The 802.11 radio is only turned on when it’s needed to increase the data rate, so it doesn’t eat up the phone battery the rest of the time, and
  • In theory it’s still possible to use the 802.11 radio for a simultaneous Wi-Fi connection to an access point.

We don’t know much else about Wi-Fi direct, as the announcement is just that – a piece of PR to say it’s coming.  But it has its roots in Ozmo Devices’ Ultra Low Power wireless technology, which has revisited the ad-hoc aspect of the 802.11 standard to fill in the holes and done a good job of that, as well as adding security and reducing the power consumption.   The Wi-Fi direct standard appears to be based on this and is due to appear early in the second half of 2010.  The transfer speed of Wi-Fi Direct is… 

As you can see, there are still a number of technical questions surrounding Wi-Fi direct.  Such as what the transfer speed is, how will it manage ad-hoc security in an easy to use way, will it allow hotspot connections at the same time and what will it do to power consumption?  We won’t really know the answers to these questions until we see the first demos, when we will be able to do a like-for-like comparison.  And Bluetooth will probably have evolved some more in the meantime.  It will be interesting to get that that point.  I suspect there will not be a lot to choose between them in terms of performance.

When that will be is an interesting question.  Like any other standards group, the Wi-Fi Alliance is a group of companies all of whom a vested interest in the standard.  There’s nothing wrong with that, as it brings the industry together.  But in the course of developing a standard many of those companies want to add their own Intellectual Property to it. Partly that’s to improve the standard, by incorporating as many of the best ideas as possible.  And partly that’s to ensure that no one company has an overwhelming technical advantage.  Today I suspect that Ozmo might be in the position of having that overwhelming technical advantage, so it would not surprise me to see the deadline for Wi-Fi Direct slipping from the promise of mid-2010 as competitors try to “improve” the specification to their advantage.

Whether or not that happens is probably irrelevant, because technology is not going to win this battle.  At the end of the day both Bluetooth 3.0+HS and Wi-Fi are just transports.  In other words, they are standards that define how the radios put bits of information over the air and how the protocol stack formats that information.  They’re just the wheels on the car.  Neither defines how the operation is presented to the user.

Bluetooth goes a little further in this respect, by defining application profiles which tell devices how to manage the content transfer, but they don’t extend up into the user interface. 

And this is where we come to the real battleground.  A user does not care how the data gets from one device to another, as long as it’s quick and intuitive.  Today on a phone they will typically select the “Send” function and then choose “via Bluetooth” if they’re under 25, or “via email” if they’re not.  That gives Bluetooth 3.0+HS an advantage, as the user interface remains the same – the underlying specification is responsible for seeing if both devices support the use of 802.11 and if they do, it uses it.

I don’t think users will want to see another option “via Wi-Fi direct”.  But with the way interfaces work today it would need that.  That’s the biggest challenge for Wi-Fi Direct – to get onto the phone’s menu.

What makes this a phony battle is that there’s another stalking technology out there – the femtocell.  If femtocells take off and users get used to using the network itself for transferring data between devices, then ad-hoc transfers may lose out altogether.  It may also signal a change to the way that phone interfaces are written.  I would argue that the Send function on a phone should only need one option – the contact you want to send it to, not the technology used to send it.  Today that’s not there, because the networks are not reliable enough for it to be the only option.  In the future it may be. 

There’s no reason why the phone should not look to see whether the recipient device is close enough to use a Bluetooth or Wi-Fi connection instead, but that should be up to the phone.  Which means that although they’re there, Bluetooth and Wi-Fi Direct become invisible.  Neither Standards body wants to hear that message, but users would probably be elated to get something that just works.

One final thought.   If either succeeds, they will drive a cart and horses through DRM by making it really easy to share content.  But that’s another story…

4 comments ↓

#1 Vince Holton on 10.25.09 at 7:16 pm

From the evidence I’ve picked up at my Bluetooth BiteBack events (see the movie at http://www.incisor.tv), the vast majority of Bluetooth uses have already kicked DRM into touch. File sharing is by far the most active application for Bluetooth.

#2 Nick on 10.25.09 at 7:24 pm

Hoorah for that. If Bluetooth can play a small part in bringing twenty first century reality to the nineteenth century mentality of Hollywood and Music industry lawyers it will have served users well.

#3 Femtocell market update for week of 26 October 2009 « 3G In The Home on 11.01.09 at 10:25 pm

[…] WiFi Direct vs Bluetooth – but will femtocells beat them both? […]

#4 WiFizz on 05.08.10 at 2:09 am

Thanks for the post! Looking forward to many new developments in Wi-Fi Direct in the very near future! To keep up to date with the latest developments, visit http://www.wifizz.com.

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About Creative Connectivity

Creative Connectivity is Nick Hunn's blog on aspects and applications of wireless connectivity. Having worked with wireless for over twenty years I've seen the best and worst of it and despair at how little of its potential is exploited.

I hope that's about to change, as the demands of healthcare, energy and transport apply pressure to use wireless more intelligently for consumer health devices, smart metering and telematics. These are my views on the subject - please let me know yours.

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