PhD Students Win Best Student Paper Award at 2024 WiOpt Conference

Northwestern Engineering’s Kangle (Phil) Mu and Zongyun Xie earned the Best Student Paper Award at the 22nd International Symposium on Modeling and Optimization in Mobile, Ad hoc, and Wireless Networks (WiOpt) last month in Seoul, South Korea.

Mu and Xie are PhD students in electrical and computer engineering and members of the Communications and Networking (Commnet) Laboratory.

The annual WiOpt conference showcases state-of-the-art, theoretical, experimental, and empirical research related to the modeling, performance evaluation, and optimization of networks.

“It is a great honor to receive the Best Student Paper award. This recognition reflects not only my efforts but also the invaluable contributions of my coauthors, to whom I am deeply grateful,” Mu said. “The award underscores the importance of studying markets with spectrum sharing involved, and I am thrilled that our work has been appreciated and recognized in this way.”

The winning paper, titled “Impact of Geographical Separation on Spectrum Sharing Markets,” is coauthored by advisers Randall Berry, John A. Dever Chair of Electrical and Computer Engineering at the McCormick School of Engineering, and Igor Kadota, assistant professor of electrical and computer engineering.

In the work, the team examined mechanisms for spectrum sharing to accommodate the increasing demand for wireless services. They considered a scenario where two competing wireless service providers (SPs) share the same spectrum band. Each SP has an access point in a distinct location with some overlapping customer coverage.

Mu and Xie proposed a method to model such markets and study the dynamics of SP competition when coverage is divided into dedicated areas served exclusively by one SP’s access point and an overlapping area served by both. The pool of customers is spread across the three areas. Service congestion costs vary across the areas, which occur when too many devices access the same frequency bands at the same time, resulting in a lack of available bandwidth.

Their findings demonstrate that market outcomes exhibit complex behaviors that are influenced by the sizes of coverage areas and the bandwidth of the shared spectrum.

With limited shared bandwidth, for instance, SPs might avoid overlapping zones to prevent potential revenue losses.

“Serving users in the overlap may increase the congestion to the entire market. Thus, service providers might strategically choose to avoid these customers,” Mu said.

Depending on the size of the overlap, Mu explained that increasing the bandwidth — allowing SPs to enter the overlapping market — might still reduce revenue and adversely affect wireless service (e.g., Wi-Fi) to customers. This is an example of Braess's paradox, whereby injecting more resources into the system in turn makes it less efficient.

The team also demonstrated the impact of strategic cooperation among SPs that agree to withhold service in the overlapping areas. While exclusive-SP zone customers may benefit from the supply surplus, the overlapping areas become Wi-Fi deserts.

As a next step in the research, the team is building a more general competition model to capture more complicated market settings.

“It is a tremendous honor for our team and me to receive this award,” Xie said. “I sincerely appreciate all the efforts everyone has devoted to this project. This award is significant for our work, and we hope it will draw greater attention to the economic perspective within the communications field, helping us address practical problems in the real world.”