[CPCC] SEMINAR: OFDM Optimization and Reconfigurable Antennas 4/12 Mon 10 AM

[Ender Ayanoglu]

                               CPCC SEMINAR

   Link Enhancement for Reconfigurable Software Defined Radio (SDR) Systems

                                   by

                        Chitaranjan Pelur Sukumar

                         April 12, 2010, Monday
                                  10 AM
                        Engineering Gateway 3161


                               ABSTRACT

Orthogonal Frequency Division Multiplexing (OFDM) has become a
modulation of choice for many state-of-the-art wireless standards due
to its inherent ability to combat multipath. However, one area that
has not received sufficient attention is the means by which power is
divided between pilots and subcarriers. If too much power is invested
in pilots, then there is insufficient energy in the data subcarriers
for decoding. Conversely, if there is not enough power in the pilots,
then channel estimation becomes unreliable and equalization becomes
hard. In this work, three modes of multiple antenna transmission were
modeled: a) Multiple Input Single Output (MISO) b) Single Input
Multiple Output (SIMO) and finally, c) Multiple Input Multiple Output
(MIMO) spatial multiplexing. For the cases where the channel rank is
unity (i.e., for MISO and SIMO) systems, we demonstrate how to split
the power between data and pilot subcarriers optimally using the
symbol MSE metric. However, for higher rank channels, because of the
difficulty in solving the joint optimization, we demonstrate how to
design the training symbols, provided the precoder has already been
defined. Through simulations, it will be shown that the proposed
technique performs better (in a symbol error rate sense) than the
conventional technique. In the second part of the talk, we will
discuss the improvements in capacity and bit error rate performance
that can be achieved by beam tilting reconfigurable antennas. The
architecture of such an antenna that utilizes Micro Electrical
Mechanical System (MEMS) switches to reconfigure the antenna will be
discussed. Training techniques used to train such an antenna will be
presented with simulations results documenting the training overhead
and performance improvements.

                            SPEAKER'S BIOGRAPHY

Chitaranjan Pelur Sukumar was born in Chennai, India in 1981. He
received his Bachelor of Engineering degree from the University of
Madras in the area of Electrical and Communication Engineering in 2003
and Master of Science in Electrical Engineering from North Carolina State
University in 2005. Currently he is a PhD candidate at the University
of California, Irvine. His research interests include wireless system
design and signal processing. He was a recipient of the Center for
Pervasive Communications and Computing (CPCC) Fellowship in 2007.