Aircraft communications and radar have historically been separate systems, each operating in their own frequency bands. With telecommunications companies now spending millions or billions of dollars for exclusive access to narrow frequency bands, autonomous vehicles that transport people or transmit data may find themselves limited with limited bandwidth. Husheng Li, professor of aeronautics and astronautics, is working on a solution.

"Historically, a cellular phone was used for communications, but not radar. You might additionally have radar in an autonomous vehicle," Li says. "Our project is to integrate both: When you send out a signal in forward propagation, you can do communications, and as it bounces back, you can do some sensing."

Funded by three grants from the National Science Foundation, Li is pursuing mathematical methods and physical implementations to combine radar and cellular communications into one signal. Reducing bandwidth in this way could reduce costs for urban air mobility (UAM) operators, and improve drone-based wireless services in remote areas.

Combining wireless systems through mathematical models

Li joined the School of Aeronautics and Astronautics in fall 2022, bringing his experience as a senior engineer at a San Diego-based telecom giant in addition to degrees from Tsinghua University and Princeton University.

"At Qualcomm I designed wireless systems," he says. "Adhoc networks with no high base stations, no large towers and access points everywhere. We created simulations and testbeds, and a lot of those ideas went into 5G standards."

Husheng Li, Professor of Aeronautics and Astronautics

Li even has a legacy within the 5G world: Friends in the industry shared that they’d spotted his name in pieces of professional 5G simulation source codes.

For the 15 years after leaving Qualcomm, Li conducted research on cybersecurity of physical systems and wireless communications as a professor at the University of Tennessee. He was motivated to shift into sensing and communications for unmanned aerial vehicles (UAVs) in part because of the implications it has for the upcoming 6G wireless standard.

"One of the major features we’ll have is a ubiquitous network. Satellites, airliners, UAVs, boats on the ocean will all be connected," he says. "UAV and airliner communications will become one of the critical parts."

Li says coverage, rather than data throughput, is one of the major concerns of 6G. That’s something he has experienced personally in the sparsely populated Great Smoky Mountains: Telecommunications companies are hesitant to invest in base stations to serve a small number of users, he says.

"Most of the coverage in low-density areas will be done using satellites and UAVs. So the study of communications and sensing becomes very important in engineering for 6G," he says.

Li hopes to find solutions in part through his love for mathematics.

"Control and communications for urban air mobility is very dangerous and difficult," he says. "We need robust sensing, agile controls and to integrate these historically separate areas together. With mathematics, we can figure out a unified framework to have all these subsystems in the same system."

That’s part of what has drawn him to this project — the integration of theory and practice. When a system becomes too complicated, he says, you can’t just rely on math. The challenge is to find an essential problem, then devise a mathematical tool that can analyze that problem and give insight that can be applied back to the practical design for experimentation.

"You sometimes have some theoretical framework that doesn’t work in practice, so you have to find some compromise. It’s quite challenging to integrate theories and practical design."