Keynote: Full-Duplex MIMO – Prospects and Enabling Technologies
In this talk we present enabling technologies for full-duplex (FD) MIMO. For self-interference cancellation, we have introduced adaptive echo cancellation concept which is based on adaptive filter theory. First, open loop technique is compared to closed loop technique. Closed loop technique such as adaptive echo cancellation continuously updates the system parameters even without requiring special training signal and synchronizations such as OFDM boundary, resulting fast and continuous tracking even during random data transmission. In addition, even in the presence of stronger desired received signal than self-interference, it provides stable tracking and continuous self-interference cancellation. Secondly, in MIMO, the SIC complexity increases exponentially. We propose simpler architecture for RF cancellation which requires only one extra downcoverter regardless of the number of taps without performance loss. For digital cancellation, bilinear architecture is proposed. RF components can be modeled by a linear combination of kernels. In non-bilinear, an adaptive filter is applied at each kernel. Hence, parallel adaptive filters are required. However, in bilinear architecture, two adaptations are cascaded: one for non-linear RF component modeling and the other for echo channel. Although this architecture significantly reduces the complexity, it has stability issues and creates too large dynamics of intermediate variables which prevent from efficient HW implementation. We have solved these short comings and will show demo videos of 2x2 MIMO FD system exhibiting that residual self-interference is below noise.
Yang-Seok Choi received the B.S. degree from Korea University, Seoul, South Korea in 1990, the M.S.E.E. degree from the Korea Advanced Institute of Science and Technology, Taejon, South Korea, in 1992, and the Ph.D. degree from Polytechnic University, Brooklyn, NY, in 2000, all in electrical engineering. From 1992 to 1996, he was with Samsung Electronics, Co., Ltd., Suwon, Korea, where he developed 32-QAM modem for HDTV and QPSK ASIC for DBS. During 2000 summer he held a Summer intern position at AT&T Labs-Research Shannon Lab, Florham Park, NJ. In 2000, he joined National Semiconductor, East Brunswick, NJ, where he was involved in the development of W-CDMA. During 2001–2002, he was a Senior Technical Staff Member at AT&T Labs-Research, Middletown, NJ where he researched on MIMO systems, OFDM systems and information theory. From 2002 to 2004, he had been with ViVATO, Inc., Spokane, WA, working on MIMO OFDM systems, smart antenna systems, Lens and antenna/beam selection techniques. He researched on Smart antenna applications to CSMA protocol and co-invented Complementary Beamforming. In 2004, he joined Intel Corporation, Hillsboro, OR where he studied on Broadband Wireless communications systems and led Standards team. Since 2013, he has been with Intel Labs where he researches on future wireless communications. He holds 60+ U.S. patents.
Shilpa Talwar received the Ph.D. degree in applied mathematics from Stanford University, in 1996, and the M.S. degree in electrical engineering. She held several senior technical positions in the wireless industry. She has over 15 years of experience in wireless. She is currently a Principal Engineer with the Wireless Communications Laboratory, Intel Corporation, where she is conducting research on mobile broadband technologies. She has authored numerous technical publications and patents.
Harish Krishnaswamy
Keynote: Full Duplex Wireless: From Fundamental Physics and Integrated Circuits to Complex Systems and Networking
Mobile data traffic in 2014 was nearly 30 times the size of the entire global Internet in 2000. Next generation wireless networks are targeting 1000x increase in capacity to meet the insatiable demand for more data. Such a tremendous increase in wireless data will require a complete rethinking of today’s wireless communication systems and networks from the physical layer to the network and application layer. Several new wireless communication paradigms, including full-duplex wireless, massive MIMO and millimeter-wave wireless, are being considered as candidates for "5G". However, full duplex wireless places requirements on the radio front-end circuitry that are orders of magnitude more challenging than what we have seen in the past on metrics such as interference tolerance and mitigation, dynamic range and power consumption. Such requirements force us to rethink how we have traditionally architected radios, blurring/breaking the functional boundaries that have traditionally existed between the electromagnetic (EM), radio-frequency (RF), analog and digital domains, and bringing sophisticated signal processing functionality traditionally implemented in digital into the RF and EM domains. In this talk, I will focus on recent research in CoSMIC lab in this space. The fundamental 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. This powerful self-interference is susceptible to uncertainties of the wireless channel (for instance, frequency selectivity and time variance) and the imperfections of the transceiver electronics (nonlinear distortion and phase noise to name a few), making it even harder to deal with. I will describe RF self-interference cancellation concepts that use frequency-domain equalization to obtain wideband cancellation across highly-selective antenna interfaces. In the electromagnetic domain, 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 that are required for practical full-duplex wireless links.
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 currently serves as a Distinguished Lecturer for the IEEE Solid-State Circuits Society.