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Dissertation Defense

WHAT:
Benjamin Vigoda:
Continuous-Time Analog Circuits for Statistical Signal Processing in Multiuser Communication

WHEN:
Monday, July 21, 2003, 12:00 PM EST

WHERE:
E15-070
Bartos Theatre [map]
Wiesner Building
20 Ames Street
Cambridge, MA

WEBCAST:
tv icon http://helix.media.mit.edu/ramgen/encoder/highlive.rm
The link will become active on the date and time scheduled for this event.

DISSERTATION COMMITTEE:
Neil Gershenfeld
Professor of Media Arts and Sciences
MIT Media Laboratory

Anantha Chandrakasan
Associate Professor of Electrical Engineering and Computer Science
MIT

Hans-Andrea Loeliger
Professor of Signal Processing
ETH, Zurich, Switzerland

Jonathan Yedidia
Research Scientist
Mitsubishi Electronics Research Laboratory

ABSTRACT:
This thesis proposes that it is a good idea to build some computers using continuous-time analog circuits. Digital computation squanders continuous degrees of freedom. A principled approach to recovering them is to view analog circuits as propagating probabilities in a message passing algorithm. Within this framework, analog continuous-time circuits can perform robust, programmable, high-speed, low-power, cost-effective, statistical signal processing. This methodology offers the possibility of adaptable/programmable radio front-ends at frequencies where software radio would be cost and power prohibitive. Other potential application areas include ultra-wide-band, high-speed interconnect, optical communications, and communications for distributed computing.

Many problems must be solved before the new design methodology can be shown to be useful in practice: continuous-time signal processing is not well understood. Analog computational circuits known as "soft-gates" have been previously proposed, but a complementary set of analog memory circuits is still lacking. Analog circuits are usually tunable, rarely reconfigurable, but never programmable.

The thesis develops an understanding of the convergence and synchronization of statistical signal processing algorithms in continuous time, and explores the use of linear and nonlinear filters and wave-guides for analog memory. An exemplary embodiment called the Noise Lock Loop (NLL) using these design primitives is demonstrated to perform direct-sequence spread-spectrum acquisition and tracking functionality and promises order-of-magnitude wins over digital implementations. A building block for the construction of programmable analog gate arrays, the "soft-multiplexer" is also proposed.


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