DocumentCode :
775307
Title :
Semiblind maximum-likelihood demodulation for CDMA systems
Author :
Míguez, Joaquín ; Castedo, Luis
Author_Institution :
Dept. Electronica e Sistemas, Univ. da Coruna, Spain
Volume :
51
Issue :
4
fYear :
2002
fDate :
7/1/2002 12:00:00 AM
Firstpage :
775
Lastpage :
781
Abstract :
This correspondence addresses the problem of channel estimation and symbol detection in wireless direct-sequence code-division multiple-access (DS-CDMA) communication systems. We introduce a novel multiuser demodulation scheme that proceeds in two steps. First, the multiaccess channel parameters are estimated according to a suitable modification of the maximum-likelihood (ML) criterion using the expectation maximization (EM) algorithm. Subsequently, this estimate and other useful side information are employed to perform ML detection of the transmitted symbols with the Viterbi algorithm. Our main contribution is the development of a novel stochastic ML method for channel estimation that takes advantage of all the available statistical information referred to the transmitted signals and channel noise. Additionally, it can incorporate the knowledge of a fraction of the transmitted symbols; hence, the term semiblind. Computer simulation results are presented that show how close-to-optimum performance is achieved in time-dispersive fading channels using remarkably short training sequences
Keywords :
Viterbi detection; code division multiple access; demodulation; dispersive channels; fading channels; maximum likelihood detection; maximum likelihood estimation; mobile radio; multiuser channels; optimisation; parameter estimation; random noise; spread spectrum communication; statistical analysis; stochastic processes; time-varying channels; ML detection; ML estimation; Viterbi algorithm; channel estimation; direct-sequence code-division multiple-access; expectation maximization algorithm; maximum-likelihood criterion; multiuser demodulation; parameter estimation; semiblind maximum-likelihood demodulation; symbol detection; third-generation mobile communication; time-dispersive fading channels; training sequences; wireless DS-CDMA; Channel estimation; Computer simulation; Demodulation; Fading; Maximum likelihood detection; Maximum likelihood estimation; Multiaccess communication; Parameter estimation; Stochastic resonance; Viterbi algorithm;
fLanguage :
English
Journal_Title :
Vehicular Technology, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9545
Type :
jour
DOI :
10.1109/TVT.2002.1015357
Filename :
1015357
Link To Document :
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