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Published July 2006 | public
Journal Article Open

Analysis and optimization of pilot symbol-assisted Rake receivers for DS-CDMA systems

Abstract

The effect of imperfect channel estimation (CE) on the performance of pilot-symbol-assisted modulation (PSAM) and MRC Rake reception over time- or frequency-selective fading channels with either a uniform power delay profile (UPDP) or a nonuniform power delay profile (NPDP) is investigated. For time-selective channels, a Wiener filter or linear minimum mean square error (LMMSE) filter for CE is considered, and a closed-form asymptotic expression for the mean square error (MSE) when the number of pilots used for CE approaches infinity is derived. In high signal-to-noise ratio (SNR), the MSE becomes independent of the channel Doppler spectrum. A characteristic function method is used to derive new closed-form expressions for the bit error rate (BER) of Rake receivers in UPDP and NPDP channels. The results are extended to two-dimensional (2-D) Rake receivers. The pilot-symbol spacing and pilot-to-data power ratio are optimized by minimizing the BER. For UPDP channels, elegant results are obtained in the asymptotic case. Furthermore, robust spacing design criteria are derived for the maximum Doppler frequency.

Additional Information

© Copyright 2006 IEEE. Reprinted with permission. Manuscript received May 13, 2005; revised September 19, 2005 and December 4, 2005. [Posted online: 2006-07-17] This work was supported in part by the Natural Sciences and Engineering Research Council of Canada, the Informatics Circle of Research Excellence, and the Alberta Ingenuity Fund. This paper was presented in part at the IEEE Global Telecommunications Conference 2004, TX, November 2004. The review of this paper was coordinated by Dr. O. C. Ugweje.

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August 22, 2023
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