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FIFTH ANNUAL
ASAP '97 WORKSHOP


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STAP in Wireless
Communications:
Performance Analysis

A.M. Haimovich and A. Shah
New Jersey Institute of Technology
Center for Communications and Signal Processing
Department of E.C.E.
University Heights, Newark, NJ 07102-2982

Abstract
In wireless communications, degrees of freedom provided by space-time processing can be used to combat both fading and interferences. In this presentation we are concerned with spatial processing and STAP in a Rayleigh channel model with cochannel interference. STAP is applicable to both narrowband (TDMA), and wideband (CDMA) communications. With TDMA, temporal degrees of freedom are applied to equalization in addition to their role in interference cancellation, while in CDMA, temporal processing is also used for diversity. While couched in terms of a specific multiple access method, the analysis is quite generic and may be extended to the other method. For narrowband communications, new closed-form expressions are presented for the distribution of the signal-to-noise and interference ratio (SNIR), and for bounds on the error probability for spatial processing in a Rayleigh channel with multiple cochannel interferences. Reduced-rank methods are studied for their ability to provide better performance through improved statistical stability. Finally, STAP is analyzed with respect to the rejection of narrowband interferences in CDMA communications. This situation arises either when narrowband communications share the spectrum with the CDMA signal, or when the interferences are intentional. The conventional approach to rejecting narrowband interferences in direct sequence spread spectrum signals, has been to whiten the received signal containing the interference prior to spread spectrum demodulation. In this presentation it is shown that STAP is much more robust with respect to the interference bandwidth. New closed-form expressions are obtained that characterize the performance of STAP in rejecting narrowband interferences in CDMA communications.

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