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Title : “Distributed Beam and Nullforming for Distributed MIMO”

Speaker : Prof. Soura Dasgupta, University of Iowa, USA

Venue : Golden Jubilee Seminar Hall, ECE Dept., Indian Institute of Science, Bangalore

Time/Date : 4pm, Monday, Aug. 26, 2013

Tea : 3.45 pm


Multi-antenna, or MIMO, technology has revolutionized wireless communication in terms of both power and spectral efficiency, and is now a part of commercial wireless standards (e.g., WiFi and cellular). MIMO techniques today, however, are fundamentally constrained by form factor and carrier wavelength, both of which limit the number of antennas that can be accommodated on a transceiver.

In recent years proposals have been made for distributed MIMO where groups of transceivers self-organize into virtual arrays that are indistinguishable in their functionality from a centralized antenna array and scale to an arbitrary number of nodes. Such distributed MIMO (DMIMO) concepts have been analyzed by theorists and dismissed by practitioners because of fundamental synchronization bottlenecks. Unlike centralized antennas, distributed MIMO involves nodes each of which has its own oscillator. The frequency and phase of these oscillators undergo drift modeled by Brownian motion. Even expensive oscillators starting in perfect synchrony, become virtually incoherent within tens of milliseconds.

This talk will focus on synchronization issues involving two basic building blocks of DMIMO: distributed beamforming and distributed nullforming. In the former N-nodes collaborate to achieve a coherent beam whose power is N^2-fold (as opposed to N-fold) higher than that due to a single node. Incoherence only results in an N-fold increase. In nullforming, nodes achieve a null at a prescribed location. It assists in achieving spatial-multiplexing and also secure communication. The key ingredient is scalable feedback by cooperating receivers.


Soura Dasgupta is a Professor of Electrical and Computer Engineering at the University of Iowa, U.S.A. He is a past Associate Editor of the IEEE TRANSACTIONS ON AUTOMATIC CONTROL, IEEE Control Systems Society Conference Editorial Board, and the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS-II. He is a co-recipient of the Gullimen- Cauer Award for the best paper published in the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS for the calendar years of 1990 and 1991, and a member of the editorial boards of the International Journal of Adaptive Control and Signal Processing, and the EURASIP Journal of Wireless Communications.

He received the University Iowa Collegiate Teaching award in 2012. In the same year he was selected by the graduating class for an award on excellence in teaching and commitment to student success. In 1993 he was a selected as a US National Science Foundation Presidential Faculty Fellow, an award given annually to 15 early career engineers and 15 early career scientists for excellence in research and teaching.

His research interests are in Controls, Signal Processing and Communications. He was elected a Fellow of the IEEE in 1998.

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