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Peer-to-Peer Phones
Benefit: Image sharing on cell phones

By Patric Hadenius

Peer-to-peer computing has become an enormously popular way to share digital data, enabling, among other applications, music downloads via the now defunct sharing service Napster. Now Nokia, the Finnish telecom giant, is working to bring it to multimedia mobile phones.

Why is the world’s largest maker of cell phones suddenly interested in the technology that made Napster a household name and an industry villain? The sale of more and more smart phones, camera phones, and game phones is driving a constant search for new applications to support them. Indeed, the killer application for all those camera phones has yet to be found – but peer-to-peer could help. With file-swapping technology, you and your friends could easily share photos you take with your phones. Or when you have a colleague on the phone, you could share a document and even edit it at the same time.

At least, that’s what Nokia is betting on. With one-third of the mobile-phone market, $36.2 billion in net sales, and $6.3 billion in profit last year, Nokia is indisputably the world’s leader in mobile communication. But it’s an increasingly competitive business. So the pressure is on Nokia’s research departments to devise cell-phone improvements that will distinguish their products from competitors’.

To help reinvigorate the company’s technology, Jukka Nurminen at Nokia’s research center in Helsinki, Finland, recruited Balázs Bakos at its site in Budapest to start investigating the possibilities of moving peer-to-peer from the wired world to the mobile world. Any peer-to-peer system sends information between computers with a minimum of hierarchy, using few, if any, servers and databases. So at first glance, the technology might seem a natural for the mobile world: isn’t talking on the phone already a kind of peer-to-peer networking? In fact, there are plenty of servers and directories needed to connect two phones and keep a line open between them. And mobile phones have other limitations that typical wired devices don’t, including far less processing power and memory, a short battery life, and limited bandwidth.

One of the first questions Nurminen and his Hungarian partner addressed was whether a typical mobile network could support a widely used file-sharing protocol called Gnutella. The experiment proved a dead end. “I think of it as an important finding,” argues Nurminen, “but we saw that it didn’t scale above 10,000 phones.” The problem was that peer-to-peer applications use a lot of bandwidth as they hunt for information. And the demand for bandwidth multiplies rapidly as more computers join the network. On the Internet this is less of a problem, since there is plenty of bandwidth, and most service providers charge their users flat rates, regardless of the number of bits they send. But on the mobile networks, where bandwidth is limited, and the pricing is per connection and per bit sent, users need a protocol that skyrocketing traffic won’t overwhelm.

So Nurminen and Bakos focused on reducing bandwidth requirements. The first step was to restrict search traffic by dividing the whole network into smaller clusters. Each phone in the network keeps a list of the images and other files stored within its cluster and can respond to queries from outside on behalf of the whole cluster. In a simulated mobile network, this approach proved ideal, enabling fast searching without sacrificing network resilience.

Having solved a key technical challenge, the researchers took their work to the company’s business units. But here the project ran into a hitch: concerns about digital rights management. With the fate of Napster still fresh in everyone’s mind, the business side didn’t want to start promoting technology that could facilitate the exchange of copyright-protected material. Erich Hugo, Nokia’s technology marketing manager, says, “The technology is still in development.”

Maybe so, but if the Napster phenomenon is any indication, once potential users understand the possibilities of peer-to-peer cell phones, it might be next to impossible to go back. Peer-to-peer technology, after all, has always distinguished itself by a very strong reluctance to be controlled.

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Tagged: Computing, Business

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