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    Electrical and Computer Engineering Department


    Low Complexity Detectors for Near-Capacity Extreme-Rate MIMO Communications

    February 24, 2006
    2 p.m.
    Bossone 303

    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 Research Laboratories.

    Friday, February 24th at 2 p.m.

    Bossone 303