Gradient estimation for sensitivity analysis and adaptive multiuser interference rejection in code-division multiple-access systems

In this paper, we consider a direct-sequence code-division multiple-access (DS-CDMA) system in the framework of a discrete-event dynamic system (DEDS) in order to optimize the system performance. Based on this formulation, we develop infinitesimal perturbation analysis (IPA) for estimating the sensi...

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Bibliographic Details
Published in:IEEE transactions on communications Vol. 45; no. 7; pp. 848 - 858
Main Authors: Mandayam, N.B., Aazhang, B.
Format: Journal Article
Language:English
Published: IEEE 01.07.1997
Subjects:
Detectors
Error correction
Frequency estimation
Interference
Multiaccess communication
Power control
Sensitivity analysis
Stochastic processes
Stochastic systems
System performance
ISSN:0090-6778
Online Access:Get full text
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Summary:In this paper, we consider a direct-sequence code-division multiple-access (DS-CDMA) system in the framework of a discrete-event dynamic system (DEDS) in order to optimize the system performance. Based on this formulation, we develop infinitesimal perturbation analysis (IPA) for estimating the sensitivity of the average probability of bit error to factors ranging from near-far effects to imperfections in power control. The above estimates are shown to be unbiased, and this technique is then further incorporated into a stochastic gradient algorithm for achieving adaptive multiuser interference rejection for such systems, which is also subject to frequency nonselective slow fading. We use an IPA-based stochastic training algorithm for developing an adaptive linear detector with the average probability of error being the minimization criterion. We also develop a practical implementation of such an adaptive detector where we use a joint estimation-detection algorithm for minimizing the average probability of bit error. A sequential implementation that does not require a stochastic training sequence or a preamble is also developed.
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ISSN:0090-6778
DOI:10.1109/26.602590