M.-A.R. Baissas

Texas Instruments Inc., Dallas, Texas, United States

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Publications (5)5.63 Total impact

  • Source
    M.-A.R. Baissas, A.M. Sayeed
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    ABSTRACT: Reliable coherent wireless communication requires accurate estimation of the time-varying multipath channel. This paper addresses two issues in the context of direct-sequence code-division multiple access (CDMA) systems: (i) linear minimum-mean-squared-error (MMSE) channel estimation based on a pilot transmission and (ii) impact of channel estimation errors on coherent receiver performance. A simple characterization of the MMSE estimator in terms of a bank of filters is derived. A key channel characteristic controlling system performance is the normalized coherence time, which is approximately the number of symbols over which the channel remains strongly correlated. It is shown that the estimator performance is characterized by an effective signal-to-noise ratio (SNR)-the product of the pilot SNR and the normalized coherence time. A simple uniform averaging estimator is also proposed that is easy to implement and delivers near-optimal performance if properly designed. The receivers analyzed in this paper are based on a time-frequency RAKE structure that exploits joint multipath-Doppler diversity. It is shown that the overall receiver performance is controlled by two competing effects: shorter coherence times lead to degraded channel estimation but improved inherent receiver performance due to Doppler diversity, with opposite effects for longer coherence times. Our results demonstrate that exploiting Doppler diversity can significantly mitigate the error probability floors that plague conventional CDMA receivers under fast fading due to errors in channel estimation
    IEEE Transactions on Signal Processing 09/2002; · 2.81 Impact Factor
  • M.-A.R. Baissas, A.M. Sayeed
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    ABSTRACT: Reliable coherent communication over multipath wireless channels requires accurate estimation of time-varying channel parameters. For coherent estimation, a key channel characteristic is the coherence time that approximately corresponds to the interval over which the channel parameters remain strongly correlated. We address linear MMSE estimation of code division multiple access (CDMA) multipath channels based on a pilot transmission. We derive a simple characterization of the estimator in terms of a bank of filters. We show that the estimator performance is primarily governed by an effective SNR that is proportional to the coherence time. We also propose two suboptimal estimators that are easy to implement and demonstrate that they deliver near-optimal performance if properly designed
    Acoustics, Speech, and Signal Processing, 2000. ICASSP '00. Proceedings. 2000 IEEE International Conference on; 02/2000
  • M. Baissas, A.M. Sayeed
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    ABSTRACT: This paper studies the impact of channel estimation errors and Doppler diversity on the performance of coherent CDMA receivers under fast fading. A key channel characteristic controlling performance is the coherence time over which the channel remains strongly correlated. We analyze a time-frequency RAKE receiver structure that exploits joint multipath-Doppler diversity. Modeling of channel estimation errors is based on the performance of pilot-based estimators tailored to the receiver structure. It is shown that the overall performance is controlled by two competing effects: shorter coherence times lead to degraded channel estimation but inherently higher (Doppler) diversity, with opposite effects for longer coherence times. Our results demonstrate that Doppler diversity gains dominate under certain conditions and can significantly mitigate the error probability floors that plague the performance of conventional CDMA receivers under fast fading.
    Signals, Systems and Computers, 2000. Conference Record of the Thirty-Fourth Asilomar Conference on; 02/2000
  • M. A. R. Baissas, A. M. Sayeed
    IEEE Transactions on Signal Processing - TSP.
  • M.A.R. Baissas, Akbar M. Sayeed
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    ABSTRACT: This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
    IEEE Transactions on Signal Processing · 2.81 Impact Factor

Publication Stats

66 Citations
5.63 Total Impact Points

Institutions

  • 2002
    • Texas Instruments Inc.
      Dallas, Texas, United States
  • 2000
    • University of Wisconsin, Madison
      • Department of Electrical and Computer Engineering
      Madison, MS, United States