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Two-stage ML-based Group Detection for Direct-sequence CDMA Systems
Buzzi, Stefano,Lops, Marco The Korea Institute of Information and Commucation 2003 Journal of communications and networks Vol.5 No.1
In this paper a two-stage maximum-likelihood (ML) detection structure for group detection in DS/CDMA systems is presented. The first stage of the receiver is a linear filter, aimed at suppressing the effect of the unwanted (i.e., out-of-grout) users' signals, while the second stage is a non-linear block, implementing a ML detection rule on the set of desired users signals. As to the linear stage, we consider both the decorrelating and the minimum mean square error approaches. Interestingly, the proposed detection structure turns out to be a generalization of Varanasi's group detector, to which it reduces when the system is synchronous, the signatures are linerly independent and the first stage of the receiver is a decorrelator. The issue of blind adaptive receiver implementation is also considered, and implementations of the proposed receiver based on the LMS algorithm, the RLS algorithm and subspace-tracking algorithms are presented. These adaptive receivers do not rely on any knowledge on the out-of group users' signals, and are thus particularly suited for rejection of out-of-cell interference in the base station. Simulation results confirm that the proposed structure achieves very satisfactory performance in comparison with previously derived receivers, as well as that the proposed blind adaptive algorithms achieve satisfactory performance.
Linear--Quadratic Detectors for Spectrum Sensing
Ezio Biglieri,Marco Lops 한국통신학회 2014 Journal of communications and networks Vol.16 No.5
Spectrum sensing for cognitive-radio applications mayuse a matched-filter detector (in the presence of full knowledge ofthe signal that may be transmitted by the primary user) or an energydetector (when that knowledge is missing). An intermediatesituation occurs when the primary signal is imperfectly known, inwhich case we advocate the use of a linear–quadratic detector. Weshow how this detector can be designed by maximizing its deflection,and, using moment-bound theory, we examine its robustnessto the variations of the actual probability distribution of the inaccuratelyknown primary signal.
ECM and GLR Based Multiuser Detection with I-CSI
Maio Antonio De,Episcopo Roberto,Lops Marco The Korea Institute of Information and Commucation 2005 Journal of communications and networks Vol.7 No.1
This paper deals with the problem of multiuser detection over a direct-sequence code-division multiple access (DS-CDMA) channel with incomplete channel state informations (I-CSI). We devise and assess two novel recursive detectors based on the expectation conditional maximization (ECM) algorithm and the generalized likelihood ratio (GLR) principle, respectively. Both receivers entail an affordable computational complexity. Moreover, the performance assessment, conducted via Monte Carlo techniques, shows that they achieve satisfactory performance levels and outperform linear detectors.