Using FM to mitigate Wi-Fi interference

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RESEARCHERS at Northwestern University's McCormick School of Engineering have found a way to use FM radio to mitigate interference between different wireless networks.

According to Aleksandar Kuzmanovic, associate professor of electrical engineering and computer science, the varying performance of wireless Internet connections can be attributed to interference between different wireless networks. The higher the density of networks, for example, in large urban apartment buildings, the greater the potential for interference.

Kuzmanovic and his PhD students Marcel Flores and Uri Klarman found that they can resolve the interference by using FM radio.

According to the researchers, current wireless networks have no way of communicating with each other, resulting in a hodge-podge of data packets being sent at various times. When network data are sent at the same time, they interfere with each other, requiring the packets to be re-sent.

Called “Wi-FM,” the team’s technique enables existing wireless networks to communicate through ambient FM radio signals. Most smartphones and mobile devices are already manufactured with an FM chip hidden inside. FM is also able to pass through walls and buildings without being obstructed. This means existing devices would be able to take advantage of Wi-FM with simply a software upgrade.

Wi-FM works by allowing the device to “listen” to the network and select the quietest time slots according to FM radio signals.

“It will listen and send data when the network is quietest,” Flores said. “It can send its data right away without running into someone else or spending any time backing off. That’s where the penalty happens that wastes the most time.”

Wi-FM identifies the usage patterns of other networks in order to detect times with lightest and heaviest traffic, helping to harmonize Wi-Fi signals that are transmitting on the same channel. And it can adapt as those patterns change with very little effort.