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Presenter: Mr. Hong-Chuan Yang - Dept. of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota
Supervisor:

Date: Mon, March 3, 2003
Time: 14:30:00 - 15:30:00
Place: EOW 430

ABSTRACT

Abstract

Multipath fading has a deleterious impact on the performance of wireless communication systems. Diversity combining is one of the most effective fading mitigation techniques. In general, the more the available diversity paths, the larger the potential diversity benefits. As such, most emerging wireless communication systems tend to employ physical layer solutions operating in a diversity-rich environment. Examples include wideband code division multiple access (W-CDMA) systems, millimeter-wave systems, and ultra-wideband (UWB) systems. However, when the number of diversity paths is large, the optimal maximum ratio combining (MRC) scheme, while delivering the best performance, becomes very complex to implement. Therefore, reduced-complexity combining schemes that can render near optimal performance are highly desired.

In this talk, starting from the traditional dual-branch switch and stay combining (SSC) scheme, we develop and analyze several low-complexity diversity combining schemes. More specifically, we first present a Markov chain-based analytical framework for the performance analysis and comparison of various dual-branch SSC strategies. Then we investigate the performance of switched combining schemes in multi-branch scenario. Noting the deficiency of the pure switching-based combining schemes in taking advantage of available diversity paths, we generalize multi-branch switched diversity and develop effective low-complexity combining solutions for diversity-rich environments. For most of these schemes, we obtain the closed-form expressions for the statistics of the combiner output, including the moment generating function, cumulative distribution function and probability density function. The resulting expressions allow for accurate performance analysis of these combining schemes over most fading models of interest. In addition, the complexity savings of the proposed schemes with respect to the optimal combining scheme are also quantified. Finally, the tradeoffs of performance versus complexity are further illustrated with selected numerical examples.

For Further Information Contact
Dr. N.J. Dimopoulos (721-8902)