Electrical and Computer Engineering
Dean of Engineering
Faculty Host: Ashu Sabharwal
Associate Professor, Electrical Engineering
ECE Seminar Series: Integrated Full-Duplex Radios: From Fundamental Physics and Integrated Circuits to Complex Systems and Networking(698/699)
Friday, April 28, 2017
1064 Duncan Hall
6100 Main St
Houston, Texas, USA
Full duplex wireless has attracted significant research attention in the last five years due to its ability to potentially double network capacity at the physical layer, while offering numerous benefits at the higher layers. The basic challenge in full duplex is the tremendous transmitter self-interference at the receiver, which can be one trillion times more powerful than the desired signal and must be dealt with in all domains. There has been significant work on prototype full-duplex radios using off-the-shelf components and showing the feasibility of self-interference cancellation, and on network-layer implications of full-duplex operation.
However, the implementation of integrated full-duplex radios in commercial CMOS processes, necessary for widespread deployment, particularly in small-form-factor devices, is fraught with several fundamental challenges. Integrated CMOS electronics typically exhibit much lower dynamic range than off-the-shelf components, leading to several challenges related to full-duplex operation, including noise and distortion added by the transceiver or by the cancellers, and the bandwidth associated with the cancellation. Furthermore, shared antenna interfaces for full-duplex, such as circulators, are either impossible to integrate on chip due to a reliance on magnetic (ferrite) materials, or exhibit prohibitive loss and/or linearity penalties.
This talk will introduce several generations of integrated full-duplex transceivers developed at Columbia University that address these problems. I will discuss RF self-interference cancellation concepts that add minimal noise and distortion penalty, and are able to achieve wideband cancellation across antenna interfaces with significant frequency selectivity. At the electromagnetic (i.e. antenna) interface, I will talk about our recent work on breaking Lorentz Reciprocity using time-variance to realize the first integrated magnetic-free non-reciprocal circulator. I will also discuss how polarization can be utilized to achieve robust self-interference suppression by embedding complex signal processing functionalities like wireless channel equalization in the antenna domain. Finally, I will discuss how joint self-interference suppression across the antenna, RF/analog and digital domains can enable achievement of the 90-100dB self-interference suppression levels in integrated full-duplex radios .
Biography of Harish Krishnaswamy:
Harish Krishnaswamy received the B.Tech. degree in electrical engineering from the Indian Institute of Technology, Madras, India, in 2001, and the M.S. and Ph.D. degrees in electrical engineering from the University of Southern California (USC), Los Angeles, CA, USA, in 2003 and 2009, respectively. In 2009, he joined the Electrical Engineering Department, Columbia University, New York, NY, USA, where he is currently an Associate Professor.
His research interests broadly span integrated devices, circuits, and systems for a variety of RF, mmWave and sub-mmWave applications.
Dr. Krishnaswamy serves as a member of the Technical Program Committee (TPC) of several conferences, including the IEEE International Solid-State Circuits Conference (2015/16-present) and IEEE RFIC Symposium (2013-present). He was the recipient of the IEEE International Solid-State Circuits Conference (ISSCC) Lewis Winner Award for Outstanding Paper in 2007, the Best Thesis in Experimental Research Award from the USC Viterbi School of Engineering in 2009, the Defense Advanced Research Projects Agency (DARPA) Young Faculty Award in 2011, a 2014 IBM Faculty Award and the 2015 IEEE RFIC Symposium Best Student Paper Award - 1st Place. He is serving as a Distinguished Lecturer of the IEEE SSCS over 2017-2018.