Catching up with NYU WIRELESS Director Tom Marzetta

Thomas Marzetta

When Tom Marzetta was elected to the National Academy of Engineering in 2021, the Academy cited his contributions to the wireless technology Massive MIMO (multiple-input multiple-output). Similarly, when he garnered the 2022 Association for Computing Machinery's Special Interest Group on Mobility of Systems, Users, Data and Computing (SIGMOBILE) “Test of Time” award and, more recently, the 2023 IEEE SPS Donald G. Fink Overview Paper Award, those laurels were given in honor of his seminal work to prove the ability of numerous small, individually controlled, low-power antennas to direct streams of information, selectively and simultaneously, to many users. Massive MIMO is the most spectrally efficient wireless technology yet devised. It provides high-quality service throughout the cell, simplicity and scalability, and outstanding radiated energy efficiency.

Marzetta had developed the idea for Massive MIMO during his decades at Bell Labs, where he directed the Communications and Statistical Sciences Department within the former Mathematical Sciences Research Center. By the time he arrived in Brooklyn in 2017, he was ready to move on to other projects. “Massive MIMO was in very good hands,” he explains. “Very competent industry engineers were on the job, and there was really no reason for further input from academia; they were already leveraging Massive MIMO about as far as possible, and as an academic researcher I wanted to find out what the next great innovation in wireless would be. Could I invent something that would improve spectral efficiency by a factor of 10? By a factor of 100? With spectrum as expensive as it is, improving efficiency would be transformative for the field.”

To that end, Marzetta and his graduate students have been working on several research projects based on a closer union of the physics of wireless channels and communication theory. For example, they are studying the phenomenon of heat conduction, which is typically considered too slow to be of use in communication. But what if they thought on the micron scale, rather than the centimeter scale? “The temperature response is eight orders of magnitude faster, and that might mean that it can be used for intra-silicon chip purposes,” Marzetta predicts. Another research project originated when Marzetta posed the question: “Why do engineers work so assiduously to create a system that performs well in a given propagation environment? Why not, instead, simply create the most favorable possible environment?” For certain applications the answer might be found in a resonant chamber – taking the form of a copper box completely isolated from the exterior, which would present a rich scattering environment that facilitates numerous propagation paths. “If we’re successful, it might be possible to build data centers in which thousands of servers are linked together wirelessly, factories manned by robots requiring no communication or power cables, or
other similarly ambitious facilities,” he says.

Yet another project seeks to find ways to make “super-directivity” practical. (The directivity of an antenna is the ratio of the radiation intensity in a given direction to the radiation intensity averaged over all directions; as the name implies, “super-directivity” refers to a ratio higher than that obtained with the a conventional transmit array.) S.A. Schelkunoff of Bell Labs had discovered the concept of the super-directive beam back in 1943, but no one has succeeded in scaling up the technology for more than a handful of antennas. Now, Marzetta and his team are resurrecting the concept, with the hope that it will one day help make it possible to power a drone wirelessly across long distances, among other feats.

He admits that such research projects are risky, with no guarantees of success. NYU WIRELESS, which he has directed since 2019, is fortunate to receive funding from not only traditional government sources like the National Science Foundation and DARPA, but from a robust roster of industry affiliates willing to back ambitious projects with the potential to be groundbreaking. “This is the opposite of incremental research, and I think it’s better for industry and better for the nation,” he says. “It’s certainly of enormous benefit to our Ph.D. candidates: even if their research does not ultimately yield transformative inventions, they will have learned the importance of being intellectually curious, scientifically rigorous, and confident to take on fresh challenges,” he asserts. At NYU WIRELESS, he and other faculty members are working to educate a new breed of engineer. “People who understand communications and information theory are different from those actually building the circuits and antenna arrays, and getting to 6G and beyond is going to take bridging that gap,” Marzetta, who is currently co-authoring a new textbook, says. “NYU WIRELESS is the bridge, and our students are going to be ready to do it all.”