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

Narayan B. Mandayam, Behnaam Aazhang

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)848-858
Number of pages11
JournalIEEE Transactions on Communications
Volume45
Issue number7
DOIs
StatePublished - 1997

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering

Keywords

  • Adaptive detection
  • Direct-sequence cdma
  • Infinitesimal perturbation analysis
  • Stochastic gradient algorithm

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