The WiFi performance is being affected by increased cell phone data usage.

Researchers at the University of Chicago find that competition among networks reduces performance.

Try scrolling through your network options to see how many WiFi networks you have. If you experience slow service when sending an email from your smartphone, it is possible to browse your network options. This is the problem. These networks compete with each other, which limits the speed at all can work.

Researchers at the University of Chicago have shown that increased network competition can negatively impact internet service for everyday consumers.

When networks operate in the same spectrum bands or frequency ranges, they compete. WiFi, in particular, uses a spectrum that is “unlicensed.” This means any device or network can use this spectrum provided specific transmission rules are adhered to by the Federal Communications Commission.

Monisha Ghosh is an associate member of the Department of Computer Science at Chicago and a research professor at the Pritzker School of Molecular Engineering.

Cellular phone service relies heavily on a separate spectrum band, which provides licenses through spectrum auctions from the FCC. However, that has changed with the growing demand for cellular data and limited bandwidths.

T-Mobile and AT&T are the only ones who can license a spectrum band from FCC. Networks operating in licensed bands are, therefore, not affected by interference. However, this allows providers to provide reliable and fast service.

Ghosh stated that the number of users in the cellular network has increased over the past five years. He also said that they had seen an increase in the data required. “Cellular service providers are running out of spectrum, and licensed spectrum costs billions.”

These providers can now use unlicensed spectrum through cellular networks via licensed assisted access (LAA) mode. This allows them to increase bandwidth without having to break the bank. Ghosh’s team set out to study how coexistence (shared use of unlicensed spectrum) affected WiFi users and cellular users.

Ghosh stated that they found an LAA station on UChicago’s campus. It was located on a pole right in front of the bookstore. WiFi access is also available in this space. We started measuring from that platform, which was an experimental one in our backyard.

Muhammad Rochman, a computer science graduate student, and Vanlin Sathya, a postdoctoral researcher, set up five smartphones and laptops outside the bookstore. They used them to connect to LAA via cellular data or to access local WiFi networks. They used different types of data to adjust the demand on these networks, such as text access on a website or streaming a video. The group could monitor the quality of each connection on each device by using applications.

By accessing multiple networks simultaneously, the group found that competition decreased performance–reducing the amount of data transmitted, the speed of transmission, and the signal quality.

This could have been better for WiFi. Data transmissions by WiFi users fell to 97% when LAA was active. However, LAA data showed a 35% decrease in messages when WiFi was available.

Ghosh explained that incompatibility between WiFi and LAA is partly due to the different protocols used to handle heavy internet traffic.

Ghosh stated that if everyone uses the spectrum simultaneously, it causes interference, and all information is lost. “But WiFi, cellular and other networks have different ways of dealing with this problem.”

WiFi relies on an unlicensed spectrum and therefore uses a protocol tailored to unpredictable demand. Listen-before-talk is a protocol that mimics the behavior of polite party-goers. Participants wait until there is a pause in the conversation before speaking. Two people can talk simultaneously, so one person politely backs away to allow the other to speak. Then, the other person chimes in after. Like the above, multiple WiFi users trying to access the network simultaneously are given a short wait time. The randomness of these wait times decreases the chance of collisions.

Cellular providers, however, can predict user demand based on cellular access and assign each user a transmission time. LAA users behave more like speakers at a well-planned colloquium than at an informal party.

These protocol differences were not a problem when cellular providers had to use licensed spectra. However, as LAA has moved to an unlicensed spectrum, it is difficult for WiFi users to access the medium equally. Even though LAA has modified the strict scheduling in cellular bands to allow listen-before-talk, its parameters are still different. The most crucial difference between the two systems is how long they hold the medium after it has access to it: LAA transmits for up to 10ms while WiFi transmits only 4ms.

The shared spectrum is a competition between WiFi providers and cellular service providers and between each type of network.

Ghosh stated that WiFi/WiFi coexistence was compared with WiFi/LAA in their experiments. The listen-before-talk process makes WiFi/WiFi coexistence easy, so this was used as a measure of fairness. WiFi/LAA behaves worse, and we were shocked at how much worse.

In future research, she hopes to continue her studies and examine the competition between LAA networks provided by different cellular carriers.

Ghosh also advised regulatory agencies about how to align better protocols for network networks based on her research.

“These changes have led to better coexistence and improved sharing mechanisms. She said that there was still much to be done.