The advantage of this is not only that you are using less bandwidth to send information, and thus avoiding bottlenecks, but also that you don’t have to keep track of which node sent what, says Médard.
Surprisingly, even the means of combining data into a single packet at the source node doesn’t have to be shared. If the packets contain enough clues, the destination nodes can reconstruct the contents of packets that have been created randomly. You’re not sending data, per se, says Lauer, you’re sending pieces of algorithms for assembling data.
Network coding is an offshoot of a field called information theory, which has already been put to use in data-compression software. But it’s only relatively recently that people have started looking at how network coding could be used to send data. “It turns out it can be extremely powerful,” Médard says.
As part of a program funded by DARPA, BAE and MIT used network-coding principles to develop protocols that could be used to send information to multiple destinations. In a conventional network, each node would act like a router, steering specific information toward specific destinations. But in BAE and DARPA’s network, all nodes broadcast all information to all other nodes.
In the DARPA simulations, where a tactical mobile network was emulated on an Ethernet network, the researchers experimented to see how much they could reduce the bandwidth of the network while maintaining the same standard of communication. The simulations involved all forms of military data, from voice and video streams to tactical data, and all kinds of conditions, such as interference and poor connectivity.
The researchers found that they could reduce the bandwidth to just one-fifth of that required by a conventional network, with no loss of quality. The upcoming field tests, on the other hand, will investigate whether the protocols can be used to send more data over existing radio networks than standard protocols can, says Lauer.
Network coding is an exciting new area that has attracted a lot of interest, says Christina Fragouli, an expert in network coding at the École Polytechnique Fédérale de Lausanne in Switzerland. And mobile wireless networks are precisely the kind of application that network coding can help with, she says. “It’s a very difficult kind of network to deal with,” she says, because of its intrinsic interference problems and limited bandwidth.
The protocols have also been tested on a standard Wi-Fi network as a way to stream video, and the results were very promising, says Médard. Further down the line, network coding could help perform security functions. “There are ways to tell if someone has messed around with your data,” Médard says.