John C. Koshy, Ph.D.
Recently, for multiple-input multiple-output (MIMO) systems, space-time bitinterleaved
coded modulation (ST-BICM) using iterative detection has been recognized
as a method for achieving near-capacity performance, and thus, enabling the best possible
trades between spectral-efficiency and energy-efficiency. However, due to the
complexity of the demapper (or the inner detector, in BICM parlance), this method is not
amenable to practical implementation for high-rate MIMO systems targeting rates
exceeding 8 bps/Hz. This is because the conventional ST-BICM iterative receiver
requires the demapper to compute the per-bit a posteriori probability (APP) by
considering all possible realizations of the simultaneously transmitted symbol streams.
Consequently, the demapper complexity associated with the per-bit APP computation is
exponential in the product of the number of simultaneously transmitted streams and the
bits per symbol. With a view to enabling practical implementations of high spectralefficiency
near-capacity wireless communications, this talk introduces a novel detection
approach based on soft-cancellation and soft-spatial-filtering.
Relative to the conventional APP detector, the proposed method is shown to have a
superior performance-complexity trade. Results are presented demonstrating the
robustness of the proposed demapper in overloaded conditions (where there are fewer
receive antenna elements devoted to signal separation than there are transmitted streams)
and correlated channels (for example, due to the presence of a strong line-of-sight path).
John C. Koshy received the M.S. and Ph.D. degrees in electrical engineering from Drexel University, Philadelphia, PA.
He joined Bellcore in 1997, and is currently, a research scientist in the advanced wireless
signal processing group in Telcordia Technologies (formerly, Bellcore), Red Bank, NJ.
His areas of work include MIMO, UWB, wireless channel characterization, 2G and 3G+
wireless network planning and optimization, and radio-on-fiber technologies. Some of his
more recent investigations are in the areas of iterative MIMO, resource allocation and
analysis of MIMO networks, and performance analysis of UWB localization and
communication systems. He is currently also pursuing new research avenues in Optical
MIMO, and bio-informatics.
Dr. Koshy is a technical area lead for the "Signal Processing for Secure Communications
and Networking" program under the Communications and Networks Collaborative
Technology Alliance (CTA) consortium of the Army Research Laboratories (ARL). He is
also the industry PI for the MIMO area of the CTA program. In these roles, in addition to
being an individual technical contributor, he assists the ARL program managers in
steering the work of the industry and university researchers. For the past several years, he
has also involved with the DARPA Networking in Extreme Environments (NETEX)
program, where he is currently leading the investigation on the modeling of localization
performance of a UWB sensor network. Dr. Koshy has several patents filed and pending
in the areas of MIMO signal processing and wireless network optimization. He has
published papers in topics that include MIMO, spatio-temporal channel modeling,
Bluetooth, and radio-on-fiber transmission. In 2005, Dr. Koshy and his team were
recipients of the Telcordia CEO award in recognition of their work for the Army
Friday, February 24th at 2 p.m.