Columbia electrical engineering PhD alumnus Linxiao Zhang and his thesis advisor Professor Harish Krishnaswamy have received the Best Demo Award for their demonstration at ISSCC 2017 of an innovative integrated MIMO (multiple-input- multiple-output) receiver array. They received the award at ISSCC 2018, which took place February 11–15, in San Francisco. ISSCC (International Solid-State Circuits Conference) is the foremost global forum for the presentation of advances in solid-state circuits and systems-on-a-chip.
Existing wireless communication technologies such as cellular and WiFi typically rely on a time domain and/or frequency domain to enable access by multiple users. This is analogous to groups of speakers in an audience holding multiple conversations simultaneously. A time domain solution allows one conversation at a time to take place, while a frequency domain solution requires that different groups speak at different pitches, so as not to interfere with one another.
A new technology called massive MIMO relies on a third domain to increase wireless link capacity: direction. The technology allows people in the same space—say, an auditorium—to converse only in certain directions, blocking out conversations from other directions. The success of the technology can be defined as how well one can hear a person in the back of the audience speaking softly, while someone seated in the front row screams from a different direction.
Zhang and Krishnaswamy’s prototype integrated circuit (IC) can receive and demodulate a weak signal in the presence of multiple strong interfering signals, using only directional information. This is akin to hearing a whisper from afar while blocking out nearby screams. Attendees at the 2017 conference were able to interact with their prototype, to compare signal quality with and without the novel function.
Zhang received his PhD from Columbia in 2017. His thesis focused on architectures and ICs for radio frequency (RF) MIMO transceivers and systems. He is currently an IC design engineer at Broadcom Limited.
Krishnaswamy, who joined Columbia in 2009, after receiving his PhD from the University of Southern California, is director of the Columbia High-Speed and Millimeter-Wave IC Laboratory (CoSMIC). In 2017, he co-founded MixComm Inc., a venture-backed startup, to commercialize CoSMIC Laboratory’s advanced wireless research.
