Building wireless infrastructure

Lingjia Liu has a deep understanding of society’s dependence on wireless connections – for work, play, and survival. He conducts critical research on wireless network security, the prevention of outages caused by natural disasters, and the future of telecommunications.

“Wireless is everywhere. It’s an essential, critical infrastructure you only feel when it’s gone,” said Liu, director of Wireless@Virginia Tech. “When we look at what happened with the 2023 wildfires in Hawaii, hundreds of people died because of disconnected power and communications. This is one of the many reasons we need to maintain a secure, connected infrastructure.”

A professor in the Bradley Department of Electrical and Computer Engineering, Liu has a research portfolio that currently spans more than $10 million, including support and collaboration from agencies such as the U.S. Department of Defense, National Science Foundation, and National Telecommunications and Information Administration. The goals of those projects include the following:

• Developing the next generation of wireless networks to help close the Digital Divide – the gaps in internet and technology availability and accessibility 

• Creating a secure, seamless connection for cellular vendors looking to leverage and help advance open radio access networks

• Contributing to, and defining, the standards for 6G

From his earliest days in industry, it was not only Liu’s technical expertise, but also his ability to rally others around common goals that elevated his work.

“Lingjia’s energy and passion toward technology and innovation really set him apart,” said Charlie Zhang, senior vice president Samsung Research America. “And he was able to communicate and explain complex technology and solutions in simple and intuitive ways.”

Today, Liu’s research impact knows no boundaries, even without his direct involvement. Collaborators from Samsung Research recently built a test bed that verified the theoretical analysis in one of Liu’s published papers on nonlinear distortion and its limitations on the applications of higher order modulation. The paper introduces an artificial intelligence-enabled signal distortion compensation method that aims to avoid the performance degradation from unknown nonlinear distortion. This enables opportunities to utilize higher order quadrature amplitude modulation (QAM) signals, such as 256QAM, 1024QAM and 4096QAM, for NextG systems and networks.

“It’s not from an award-winning paper or something high profile,” said Liu, who is part of the inaugural cohort of Virginia Tech Innovation Campus faculty. “They built a prototype, and they found it very useful in their own system. It made me happy because that’s what my work has been – it's not about me, it’s about the whole field. I’m glad to see the work I’m doing has meaningful impact that goes beyond papers or number of citations.” 

The test bed is just one example of the type of connections and collaborations Liu has built throughout the telecommunications community, during the last two decades.

It all began with his first engineering role at Samsung Research America.

Setting the standard

It was 2008. Apple launched the App Store to pair with its new product, the iPhone. And Liu started his dream job as a standards engineer at Samsung Research America.

Hired by Zhang, who is also the head of the Samsung Research America’s Standards Mobility and Innovation Team, Liu spent his first days as a standards delegate not in sunny Dallas, Texas, but Kansas City, Missouri  –the location for a meeting of the 3rd Generation Partnership Project.

The project is an international collaboration between seven wireless global standardization groups, including the United States Alliance for Telecommunications Industry Solutions. As a collective, it is responsible for the following:

• Developing technical specifications for 2G, 3G, 4G, 5G, and beyond

• Ensuring interoperability – making sure mobile phones and networks from different manufacturers and operators work together seamlessly

• Focusing on future technologies

During the meeting, Liu served as a standards delegate. He attended different working group meetings to share ideas and contribute to the technical specifications.

Zhang said Liu’s passion for innovation and clear, effective communication shined during his time working with the group.

“These thought leadership qualities are important for success in 3GPP [3rd Generation Partnership Project] work, as the ability to convey these passions and technical ideas to other delegates from around the world was critical,” Zhang said.

At Samsung, Liu was essential in developing, verifying, and advocating for the company’s proposals on multi-user, multiple-input multiple output and coordinated multi-point for 4G LTE-Advanced, which allow multiple cellular base stations to work together to serve multiple users at the same time, despite challenging signal conditions. Some aspects of Liu’s proposal were adopted as part of today’s 4G LTE-Advanced standards.  

“I learned so much during the four years I was there,” Liu said. “I started to understand that my work needed to be folded into the bigger picture, to think about the whole industry and solve relevant problems. It wasn’t just about Samsung. It was about all of us working together to push forward.”

For Liu and Zhang, the bigger picture included future work that went beyond them, and that’s where they ran into some issues. When hiring engineers to work at Samsung Research, there weren’t enough potential engineering candidates, and the ones available often didn’t share Liu’s vision for the future of wireless technology. The solution was simple for Liu: He needed to jump in himself.

“That was a bit surprising initially, as he was doing very well here in the industry,” Zhang said, “But then I understood his passion for more forward-looking research in academia, and I also liked his idea of bringing his industry experience with him to universities and try to bridge the gap between industry and academia research. I thought it was good timing and he was the right person to do that.”

During the last decade, Liu and Zhang have continued their collaborations, whether on research, Liu sending students to Samsung for internships, or connecting at conferences such as the the Institute of Electrical and Electronics Engineers.

Building the future at Virginia Tech

At an Institute of Electrical and Electronics Engineers conference nearly 10 years ago Liu met wireless researcher and future Virginia Tech colleague Jeffrey Reed. 

“Lingjia and I connected right away on our industry experiences,” said Reed, who is the founding director of Wireless@Virginia Tech and founder of the Ted and Karyn Hume Center for National Security and Technology. “I had a good impression of him being very oriented toward solving industry problems, and he expressed his interest in joining Virginia Tech because of the wireless group’s reputation.”

Since joining his fellow Virginia Tech researchers in 2017, Liu has collaborated with Reed and other colleagues on millions of dollars’ worth of projects that work to secure the global wireless infrastructure, including work that connects back to his time in industry. Some of these highlights include the following:

• A $9 million grant from the U.S. Department of Defense, one of the largest awards ever received by a College of Engineering faculty member, to support work focused on mobile distributed multiple-input, multiple-output systems. The team will make technical contributions to 3rd Generation Partnership Project to help define 6G and FutureG standards.
  
  

• Learning-Based O-RAN [Radio Access Networks] Testing, which is a $2 million project supported by the Public Wireless Supply Chain Innovation Fund from the National Telecommunications and Information Administration that utilizes reservoir computing – a machine learning method – to develop efficient and accurate tests for cellular vendors looking to leverage open radio access networks for wireless operations.
  
  

• Nearly $1 million from the National Science Foundation  to support bridging the Digital Divide by creating the next generation mobile broadband networks. This work will increase access to users by providing seamless wireless coverage and supporting varying service requirements. 

In 2022, Liu took over as the director of Wireless@Virginia Tech from Michael Buehrer, with an eye on national and international recognition for the group and Virginia Tech.

“We’re building a strategy for how we want to work together on a national and global level, what our signature will be, what we want to uniquely do,” Liu said. “As a university, we’re trying to harmonize together – Wireless@Virginia Tech, the Commonwealth Cyber Initiative, the Virginia Tech National Security Institute, and the Innovation Campus – to work together on advancing wireless and positioning Virginia Tech as a global leader."