Surge in mobile data usage puts Wi-Fi performance under severe test

According to the policies of communication regulatory agencies such as the FCC, wireless routers can use unlicensed "white label spectrum" within a limited range. However, in recent years, cellular mobile network operators have also begun to adopt it. Embarrassingly, researchers at the University of Chicago found that spectrum competition between networks will have a negative impact on Wi-Fi performance.

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LAA base station in the University of Chicago campus (Photo: Monisha Ghosh)

SCI Tech Daily points out that when you try to transfer a lot of data on your smartphone but the network speed is slow, you can scroll through how many Wi-Fi networks there are nearby that you can switch to.

"Unrestricted white-label spectrum means anyone can use it freely within the limits set by the FCC," said Monisha Ghosh, a member of the University of Chicago's computer science department and a research professor at the Pritzker School of Molecular Engineering.

However, in fact, this excessive choice is a big problem in itself. Due to the competition between networks, each network cannot provide the ideal operating speed.

For mobile network operators, they mainly rely on a completely independent spectrum band obtained through auction. For example, when T-Mobile or AT&T obtains a license from the FCC, they can exclusively use a specific spectrum.

This approach allows operators to build fast and reliable services and avoid interference caused by spectrum competition. However, as the demand for cellular data continues to grow, conflicts under limited bandwidth are also emerging.

For example, on the University of Chicago campus, LAA base stations allow cellular network operators to access frequency bands shared with Wi-Fi.

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Monisha Ghosh pointed out that the user base and data volume of cellular mobile networks have skyrocketed in the past five years. Operators are already facing a shortage of available spectrum, and the purchase of licenses often costs billions of dollars.

To boost bandwidth without causing harm, some operators have tried combining white-label spectrum, a model called licensed-assisted access (LAA), which lets base stations operate in the same frequency bands as Wi-Fi.

So Ghosh's team began to study the impact of this spectrum sharing strategy on the actual experience, such as measuring the performance of the Wi-Fi network near an LAA base station pole in front of a bookstore on campus.

During the experiment, computer science graduate student Muhammad Rochman and postdoctoral researcher Vanlin Sathya configured five laptops and smartphones and connected them using local Wi-Fi and cellular data networks.

In various application environments (such as low-demand website text access and high-demand streaming video transmission), the research team concluded that spectrum contention would reduce the actual performance experience by accessing multiple networks simultaneously.

Regardless of the amount, speed, or signal quality of data transmission, when various devices compete for the spectrum at the same time, the interference generated will result in a blockage of information.

And this competition is particularly bad for Wi-Fi, which sees its data rate drop by 97% when LAA is also active. Conversely, LAA base stations only see a 35% performance drop.