Wi-Fi connections are great when they work quickly and efficiently, but when they suddenly slow down inexplicably it can be very frustrating. Surprisingly, this isn't usually caused by a slow connection from your ISP, rather it occurs when two physically close Wi-Fi connections interfere with each other. Now researchers from the McCormick School of Engineering at Northwestern University have come up with a simple way to prevent this – and improve Wi-Fi speeds – by using Frequency Modulation (FM) and a smart time-sharing system that maximizes data throughput.
Dubbed Wi-FM by its creators, the system aims to prevent a person's network data from competing with a neighbor's data when packets of network data are transmitted at the same time. This is because data packets "bump into" each other if two networks transmit at the same time. Slow Internet speeds are the result, because both packets automatically back off when this occurs and stop moving toward their destinations.
"Most people think it's a mystery," says Aleksandar Kuzmanovic, associate professor of electrical engineering and computer science at Northwestern. "They get upset at their routers. But what's really happening is that your neighbor is watching Netflix."
The protocols built into Wi-FM, on the other hand, allow the device to monitor the network and choose the least busy time slots in which to transmit FM radio signals.
"It will listen and send data when the network is quietest," says PhD student Marcel Flores. "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."
The team's method enables existing wireless networks to communicate through current commercial FM radio signals, constantly transmitted through the spectrum from 87.5 Mhz to 108 Mhz. To do this, the device effectively transmits signals that are synchronized with the digital information transmitted on the RDS (Radio Data System) section of a transmitted FM signal.
Designed to improve the usability and versatility of FM radio, the RDS is a method by which digital information pertaining to the content – such as station information for display on modern receiver displays, program information, and traffic alerts – is relayed on a sub-carrier to the main transmission frequency. This information also contains time signals regarding the broadcast, and it is these signals that the McCormick Engineering team uses to allow their system to determine the "quiet" intervals in which the WiFM can transmit with the least interference.
As such, as the device monitors the network, it also monitors the traffic in that network and considers the volume of data flow occurring in physically nearby signals. In this way, it times data packet transmissions into slots of time within the best frequency space to avoid cross-talk and interference with other signals. Happening at exceptionally fast speeds, though, the network itself sees no gap in transmission or reception as each data packet is transferred and, in the case of streaming music or video, continuously cached on a local machine.
FM was also chosen for its ubiquity; most smartphones and other mobile devices already come standard with an embedded FM chip. FM is also very reliable in its transmission and reception behaviors and, at the frequencies transmitted, is more easily able to travel through solid obstructions such as buildings. According to the team, minor software upgrades to connected devices may also be possible by using the Wi-FM system to carry them.
"Our wireless networks are completely separate from each other," says Flores. "They don't have any way to talk to each other even though they are all approximately in the same place. We tried to think about ways in which devices in the same place could implicitly communicate. FM is everywhere."
Because the Wi-FM system also sees the usage patterns of other nearby networks so as to detect times of light and heavy traffic, it can also adapt its behavior automatically as those patterns change. "Our system can solve these problems without involving real people," says Kuzmanovic. "Because are you going to knock on 30 doors to coordinate your wireless network with your neighbors? That is a huge management problem that we are able to bypass."
The results of this research were recently presented in a paper to the 23rd Annual IEEE International Conference on Network Protocols in San Francisco. Source: Northwestern University
