Trunks of fiber optic cable make up most of the Internet’s backhaul–the network that links smaller networks across the globe together into the World Wide Web. But installing fiber between remote locations can get expensive. Electrical and Computer Engineering Professor Akbar Sayeed (left) and Assistant Professor Nader Behdad (right) have developed a new communication architecture that could offer those same connection speeds wirelessly, employing an improved form of multiple-input and multiple-output communications (MIMO) technology.
Similar to how fiber optics pack thousands of data streams into a single cable, high-frequency MIMO communications can pack more wireless data streams into a single antenna array by arranging them in tightly packed beams, a concept pioneered by Sayeed’s research group. While the core concept has been around since the early 2000s, Sayeed observed that conventional MIMO systems running at millimeter-wave frequencies left a lot to be desired—most designs either contained inefficient gaps between antennas, or an efficient but prohibitively complex array containing thousands of antenna elements. “I thought we could do better than that,” says Sayeed.
Leveraging Behdad’s antenna expertise, the pair of researchers have developed a system that uses a lens array to steer data-bearing beams quasi-optically, rather than depending on hardware and software to direct them. That significantly decreases the computational and hardware complexity required to transmit data at very high frequencies.
Steering high-frequency beams with lens antennas also allows for more active beams per array, meaning more users, and more importantly, more data. “Current systems run below five gigahertz,” says Sayeed. “This system runs at 10 to 20 times higher frequencies, with much more bandwidth.”
The Wisconsin Alumni Research Foundation is helping Sayeed and Behdad realize the technology as a commercial product through its accelerator program. The technology eventually could be used in mobile broadband networks, but for now, the most logical market for the system is in the backhaul, where it could bring the speed of fiber to areas too remote to lay cable. “Rather than digging and putting fiber in, you could have a couple of towers with these millimeter wave systems,” says Sayeed.