Lingjia Liu, professor of electrical and computer engineering who is also an inaugural faculty member at the Virginia Tech Innovation Campus, has been awarded the Mobile Distributed Multiple-Input, Multiple-Output (Mobile dMIMO) project by the U.S. Department of Defense’s (DoD’s) Office of the Under Secretary of Defense for Research and Engineering (OUSD(R&E) as part of its flagship FutureG program. The Mobile dMIMO project consists of three phases, with $9 million total planned funding -- $1.5 million is for Phase 1 of the project. The Mobile dMIMO project represents one of the largest single awards received by a faculty member at the College of Engineering at Virginia Tech.  

Through the award, Liu, the Bradley Senior Faculty Fellow in the College of Engineering and the director of Wireless@VT, will lead a team researching Mobile dMIMO-facilitated complex and large-scale wireless networks to help define and set the standards for FutureG technology.

Leading the push for FutureG

Virginia Tech already is leading the push into FutureG wireless technology through Wireless@Virginia Tech  and the Innovation Campus in Alexandria, VA, set to open in 2024. Liu was awarded an $800,000 grant from the National Science Foundation (NSF) earlier this year to help create next generation (NextG) mobile broadband networks that increase the availability of access to users by providing seamless wireless coverage and supporting varying service requirements. This research is part of the NSF’s Resilient and Intelligent NextG Systems program, which combines resources and support from U.S government agencies such as the NSF, OUSD(R&E), and the National Institute of Standards and Technology (NIST), along with funding from major U.S.-based telecommunications companies such as Apple, Google, IBM, Nokia, and Microsoft.

The goal is to focus exclusively on NextG wireless, networking, and computing systems that may have potential impacts for the future of NextG standards. As the director of Wireless@Virginia Tech, Liu oversees a center of more than 30 faculty that already focus on research and development in wireless communication and networking.

“If we can develop and demo the technology, we have a very good chance of achieving many features of 6G,” said Liu. “Furthermore, we anticipate making technical contributions to 3GPP, which is the standard body set to define the technical specifications for 6G and beyond standards. If so, we would literally be contributing to the 6G standards and would be defining what 6G is. Virginia Tech would help to drive the standardization specifications, which is extremely rare for an academic institution to have the opportunity to do so.”

The OUSD(R&E) FutureG program aims to accelerate the adoption of new wireless networking technologies to ensure that DoD military forces can operate effectively anywhere.

Since coming to Virginia Tech in 2017, Liu has been “a tremendous asset and force in the department. His work on 6G networks and machine learning for wireless is highly topical right now,” said Luke Lester, the Roanoke Electric Steel Professor and head of the Bradley Department of Electrical and Computer Engineering. “This comprehensive 6G initiative will represent pioneering research and impressive teaching opportunities in connecting massive traditional terrestrial fiber networks wirelessly using MIMO. I have no doubt he will lead his team to success in this critically important project.”

Scope of work

MIMO is an antenna technology for wireless communications in which multiple antennas are used at both the source, or transmitter, and the destination, or receiver. The antennas at each end of the communication circuit are combined to minimize errors, optimize data speed, and improve the capacity of radio transmissions by enabling data to travel over many signal paths at the same time using varied broadband messaging.

MIMO is the enabling technology for 4G LTE-Advanced. Its extended version, called massive MIMO, is the enabling technology for 5G new radio systems. Traditionally, MIMO antennas are co-located, such as at a base station. For this project, Liu and his team will work to bring MIMO technology to the next level, leveraging mobile distributed MIMO networks where distributed antenna arrays are wirelessly connected.

Distributed MIMO has multiple advantages over its co-located counterparts:

  • Improved coverage: Distributed MIMO can utilize multiple antennas that are spread out over a larger geographical area, covering a larger space.
  • Improved scalability: Because antennas in distributed MIMO are not co-located at the base station, they circumvent the form factor limitation at the base station to improve the scalability of the number of antennas utilized in the system.
  • Reduced interference: In co-located MIMO, antennas are deployed at the base station, which can sometimes interfere with each other’s signals. Distributed MIMO spreads antennas geographically, reducing this interference.
  • Enhanced reliability: With antennas deployed in different locations, distributed MIMO can provide more reliable connections to users irrespective of their geolocations. It's like having multiple pathways to walk from a starting point to the destination. If one path has obstacles, you can choose another path to reach your destination.

Future impact of mobile distributed MIMO networks

Designing mobile distributed MIMO networks is complicated and challenging, but the work is expected to result in applications that unlock technologies for 6G and beyond. These include

  • Commercial communications: 6G is expected to provide higher data rates with more reliable services.
  • Reduced operating expenses: Mobile distributed MIMO networks use wireless connections instead of fiber, meaning it operates with less costly infrastructure.
  • Military communications: 6G could dramatically improve situational awareness and decision-making for military operations and shorter conflicts. Wireless connections are more agile and could be set up and dismantled quickly in the field.
  • Improved location services: 6G is expected to detect locations accurately within centimeters, meaning drones or other unmanned vehicles could be sent into dangerous environments without risking human lives.
  • Cybersecurity: 6G would incorporate advanced security features to minimize or eliminate cyberattacks. By distributing antennas in various locations, mobile distributed MIMO networks avoid the common issue of single point of failure.

As the initiative develops, additional opportunities and applications will become “real and relevant for FutureG,” said Liu. “Harnessing wireless technology through mobile distributed MIMO networks means developing an enabling technology that has so far been unrealized or imperfect at best. It will have profound impacts for FutureG networks.”

According to industry experts, the 6G network is expected to be 100 times faster than the current 5G network, offering data speeds of up to 1 terabyte per second. 6G networks will be able to use higher frequencies than 5G networks and provide faster response times without delays or lags.

Teamwork is key

According to Liu, collaboration and teamwork will be critical to the effort.  Not only are the Office of the Under Secretary of Defense for Research and Engineering and Lockheed Martin Advanced Technology Laboratories involved as partners, but various organizations across the university — including Wireless@Virginia Tech, the Bradley Department of Electrical and Computer Engineering, the Virginia Tech National Security Institute, the Innovation Campus, and Commonwealth Cyber Initiative Southwest Virginia – are also involved.

The research team led by Liu includes electrical and computer engineering Professors Mike Buehrer, Jeff Reed, Nishith Tripathi, and Yang “Cindy” Yi as well as Daniel Jakubisin from the National Security Institute, who will serve as the deputy co-principal investigator for the project award.

Lockheed Martin Advanced Technology Laboratories will serve as a subcontractor to assist the team on transition and field demonstration. 

“This is a true team effort,” Liu said. “It’s not ever just one person leading the charge, but rather multiple smart and talented stakeholders who collaborate to make the breakthrough discoveries that change the status quo. It’s wonderful to watch and exceptionally rewarding to be part of this type of a team.”

As an academic institution, Virginia Tech’s primary goal is to teach students, a role Liu prioritizes. Over the course of the award period, numerous Virginia Tech graduate students will have the opportunity to support the research.

“We conduct fundamental theoretical analysis and design the prototypes,” Liu said. “And we teach future professionals how to apply what we discover in the real world. We are quite literally building a pipeline of talent to industry, academia, and to the government. The students will learn by doing, and we simultaneously lay the foundation for future career professionals who will go on to make a real, true, meaningful difference in the world.”


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