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Doubling Wireless Bandwidth: Just the Tip of the Iceberg

By Negar Reiskarimian and Paula Reinman

“I have a great respect for incremental improvement, and I’ve done that sort of thing in my life, but I’ve always been attracted to the more revolutionary changes … because they’re harder. They’re much more stressful emotionally. And you usually go through a period where everybody tells you that you’ve completely failed.”

— Steve Jobs

The Marconi Society stands for creativity, vision and change that benefits humankind.  Marconi Fellows have pioneered the Internet, wireless communications, security, GPS and other technologies that make today’s connected world possible.

The Marconi Society Young Scholars (nominations are open now!) show the potential to develop the next generation of ground-breaking discoveries.

So when 2017 Young Scholar Negar Reiskarimian decided what to focus on, she was not satisfied with developing integrated circuits that performed incrementally better. She wanted to find a fundamentally different way to design new circuits to power upcoming 5G and IoT applications.

Direction From the Intersection

As tomorrow’s applications diverge – from uses that will require more data and lower latency to support technologies such as the next generation of wireless communication systems (5G), augmented reality (AR) and virtual reality (VR) to Internet of Things (IoT) applications demanding lower power, smaller sizes and flexibility to tag everything – design ideas can come from many places across the scientific and engineering spectrum.  Negar’s research focuses on the intersection of fundamental physics, applied electromagnetics and nanoelectronics to design new integrated circuits (ICs) for these applications.

One key concept in overcoming current network design constraints is to create “full duplex” communications, enabling transmitters and receivers to function at the same time on the same frequency band. Full duplex capability doubles the capacity on existing networks and opens the door for 5G applications (click here for more information about full duplex and the ICs being developed at Columbia’s CoSMIC Lab).

Most of the prior full duplex demonstrations either used antenna pairs or nonreciprocal magnetic circulators to route the transmit and receive signals, which exist concurrently at the same frequency band. This is not the most efficient approach in terms of the area and cost of the overall system.

Negar’s challenge was to achieve non-reciprocal behavior without magnets.  She investigated prior approaches using modulation of material properties.  However these attempts could not meet the stringent requirements of full-duplex systems.

Combining her skills in IC design with her knowledge of the prior art, Negar created a different approach and a new modulation scheme based on switching transistors that is on a much smaller scale than anything that has been done before.  The intersection of this newly developed concept and CMOS platform produced a totally new type of design.

Beyond Doubling Capacity

While much of the initial interest around this innovation stems from its ability to double wireless network capacity, Negar believes that there are more fundamental and far-reaching applications for her work.

There are a number of government-funded programs to investigate and enhance the performance of nonreciprocal devices. DARPA’s SPAR (Signal Processing at Radio Frequency) program includes various groups working on nonreciprocal devices and circulators designed for high-performance wireless communication systems.  Negar and her team at CoSMIC Lab also have funding from the NSF to continue creating compact and low cost nonreciprocal devices that will support tomorrow’s applications.

Many of applications that seem to be right on the horizon will benefit from breaking reciprocity in a light, inexpensive and scalable way.  Most optical and electrical systems require nonreciprocal devices for protection against reflections. Self-driving cars need nonreciprocal devices in their radar systems to see objects and sense where they are on the road.

At a broader level, there is more that can be done with spatial and temporal modulation schemes beyond achieving nonreciprocity.  Since it is difficult to analyze and build these time varying systems, this work is just the beginning of endless opportunities.

New Rules for Building Game-Changing Technology

Solving the complex problems that will enable the next generation of connected communications and applications is an interdisciplinary sport.  Researchers need to look at how expertise in different fields and connecting ideas from these domains will result in new approaches to solve these problems. Scientists and engineers need to understand enough about the work and language of adjacent spaces to identify the promise of relevant ideas from other disciplines.

As basic scientific research continues to power consumer and business experiences, we will see more recognition of this research.  The 2017 Forbes 30 Under 30 List included two Marconi Society Young Scholars, Negar Reiskarimian and Dinesh Bharadia, who are creating big impact through fundamental research.

We hope to see more of this kind of innovation in the 2018 Young Scholar nominees.  Please click here for more information on nominating a deserving young innovator.