Microsoft Researchers have been working on a technology that would let mobile phones and other 3G devices automatically switch to public WiFi even while the device is traveling in a vehicle. The technology is dubbed Wiffler and earlier this year, researchers took it for some test drives in Amherst, Mass, Seattle and San Francisco.
Mind you, WiFi was available only about 11 percent of the time for a mobile device in transit, the team discovered, compared to 87% of the time 3G was available. So it would stand to reason that, at best, the mobile device wouldn't only be able to use WiFi a tiny bit of the time. However, the Wiffler protocol allowed the device to offload nearly half of its data from 3G to WiFi.
How so? Wiffler is smart about when to send the packets. It doesn't replace 3G, it augments it and transmits over WiFi simultaneously, allowing users to set WiFi as the delivery method of choice when it is available -- and when an application can tolerate it. Not every application can handle even a few seconds delay in the stream (VoIP) -- and WiFi tends to drop more packets than 3G does. But many apps can handle even a minutes-worth of delay perfectly well (messaging).
Wiffler uses what researchers call "prediction based offloading" in which it determines how likely it is to travel within the area of an acceptable WiFi hotspot within a certain time frame.If the car is moving in an urban area, discovering frequent hotspots, it predicts it will find another one quickly. If it is traveling on a highway and hasn't run across a hotspot in a while, it figures it won't find another one soon. If the the device doesn't find a hotspot within a predicted maximum delay time it goes ahead and fires up the 3G.
"We try to ensure that application performance requirements are met. So, if some data needs to be transferred right away (e.g., VoIP) we do not wait for WiFi connectivity to appear. But if some data can wait for a few seconds, waiting for WiFi instead of transmitting right away on 3G, that can reduce 3G usage," Ratul Mahajan told me in an e-mail interview. Mahajan is a researcher with the Networking Research Group at Microsoft Research Redmond. Mahajan worked on the project with two teammates, Aruna Balasubramanian and Arun Venkataramani, both of whom are researchers at the University of Massachusetts Amherst.
"The second feature is that we may actually use both connections in parallel instead of using only one. So, if we deem that some data cannot be transferred using WiFi alone within its latency requirement, we will use both 3G and WiFi simultaneously. This parallel use is different from a handoff from one technology to the other, and it better balances the sometimes conflicting goals of reducing 3G usage and meeting application constraints," Mahajan explained.
The results of the test was presented in a paper, Augmenting Mobile 3G Using WiFi (PDF), presented in June 2010 at the eighth annual International Conference on Mobile Systems, Applications and Services.
The test consisted of running Wiffler units on 20 buses in Amherst, MA as well as in one car in Seattle and one in San Francisco at SFO. The Wiffler unit itself was a proxy device that included a small-from factor computer, similar to a car computer (no keyboard), an 802.11b radio, a 3G data modem, and a GPS unit. The 3G modem was using HSDPA-based service via AT&T.
Interestingly, the researchers didn't actually use Wiffler with mobile phones during their tests. They ran phone-like applications on the embedded computer. But the project team does envision Wiffler as a technology for smartphones, perhaps embedded directly into the smartphone. It could also be adapted to run in an in-vehicle infotainment system.
While this research focused on using free WiFi in a moving vehicle, Mahajan says Wiffler could be used in other ways. Carriers may want it to for private WiFi services that augment their 3G/4G data networks. It could be used by pedestrians who might get even higher WiFi offload rates if they were wandering in a city with their Wiffler-equipped smartphones. It could be valuable in a stationary setting, too, like hanging out at Starbucks.
"Today, the WiFi/3G combo management is highly suboptimal. Today, smart phones tend to use WiFi connectivity only when they are stationary and not use WiFi connectivity when they are on the move. At the same time, they experience poor application performance when the WiFi connectivity is poor because they happen to be far from the AP (access point) or because the WiFi network is congested. This experience occurs because the devices insist on using WiFi whenever they are connected, largely independent of the performance of WiFi. Our technology provides an automatic combo management that is aware of application performance," Mahajan says.
Next up, the crew plans to test the Wiffler protocol in other uses, including the 3G savings "in a setting when users have Wiffler running all the time rather than just driving. Another is to understand current smartphone traffic workloads to get a sense of how much traffic individual applications generate; this is important because data for some of the applications can be delayed and for some it cannot be delayed," Mahajan explains.
There is no association of Wiffler to Windows Phone 7 at this time. I hope it stays that way. Wiffler could be of best use if it were something that any handset on any phone could have. Plus, by the time a commercial product came to market based on Wiffler, Windows Phone 7 will either have found its niche, or died.
At this time it's unclear how or when Wiffler will formally come to market. Neither the researchers nor Microsoft PR would comment on that, and in truth, I got the sense that it hadn't yet progressed to that point anyway. Despite the long road to commercial use, now that the world knows that WiFi offloading from 3G is worthwhile, even from a car, it's only a matter of time before someone creates the first product.
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