[CPCC] SEMINAR: Interference Alignment 3/9 Mon 10 AM

[Ender Ayanoglu]

                                 SEMINAR

        Interference Alignment and the Capacity of Wireless Networks

                             Prof. Syed Jafar
                                UC Irvine

                            Monday March 9, 2009
                                   10 AM
                            Engineering Tower 331


                                 ABSTRACT

The talk will present new insights into the capacity of wireless networks
with a finite number of interfering nodes. A widely held belief in network
design, and also a formal conjecture, is that for an interference network
with K users competing for the same spectrum, at high SNR (when both
signal and interference powers are strong), it is capacity-optimal to
divide the network degrees of freedom (bandwidth) among the users in a
cakecutting fashion so that each user gets a fraction 1/K of the total
spectrum. We disprove this conjecture and establish that even with K > 2
users competing for the same spectrum, each user is able to access a
fraction 1/2 of the total spectrum free from interference - i.e. everyone
gets half the cake. To prove this result we introduce a new scheme, called
interference alignment, where signals are designed to cast overlapping
shadows at the receivers where they are not desired while they remain
distinct at the receivers where they are desired. Interference alignment
is shown to be the capacity optimal scheme for a wide variety of wireless
interference networks at high SNR and for certain classes of networks at
any SNR. Examples are provided for different types of interference
alignment schemes that exploit the relativity of alignment in space, time,
frequency and code dimensions.


                             SPEAKER'S BIOGRAPHY

Syed Ali Jafar received the B. Tech. degree in Electrical Engineering
from the Indian Institute of Technology (IIT) Delhi, India in 1997, the
M.S.  degree in Electrical Engineering from California Institute of
Technology (Caltech), Pasadena USA in 1999, and the PhD degree in
Electrical Engineering from Stanford University, Stanford, CA in 2003. His
industry experience includes positions at Lucent Bell Labs, Qualcomm Inc.
and Hughes Software Systems. He is currently an Assistant Professor in the
Department of Electrical Engineering and Computer Science at the
University of California Irvine, Irvine, CA USA. His research interests
include multiuser information theory and wireless communications.

Dr.  Jafar received the NSF CAREER award in 2006 and the ONR Young
Investigator Award in 2008. He received the UC Irvine Engineering Faculty
of the Year Award in 2006 and EECS Professor of the Year 2009 for
excellence in teaching. He is a corecipient of the DARPA ITMANET Young
Investigator Team Award. Dr. Jafar serves as Associate Editor for IEEE
Communications Letters.