Multi-user Detection of Nonlinearly Distorted MC-CDMA Symbols by Microstatistic Filtering |
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Authors: | Jozef Krajňák Marc Deumal Pavol Pavelka Du?an Kocur Joan Lluís Pijoan Pavol Galajda |
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Affiliation: | (1) Department of Electronics and Multimedia Communications, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Košḱe, Slovak Republic;(2) Grup de Recerca en Electromagnetisme i Comunicacions, Enginyeria i Arquitectura La Salle, Universitat Ramon Llull, Barcelona, Spain |
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Abstract: | Multi-carrier code division multiple access is a powerful modulation technique that is being considered in many emerging broadband
communication systems. In a downlink scenario orthogonal spreading sequences are used since they reduce multiple access interference
compared to non-orthogonal. However, the nonlinear amplification of the transmitted signal destroys the orthogonality and,
thus, reduces the system performance. In order to avoid performance degradation without requiring large back-offs in the transmitter
amplifier, it becomes necessary to use multi-user detection techniques at the receiver side. Conventional multi-user detectors
(MUD) are designed for linear environments and, as a result, might not exhibit enough performance improvement. In this paper
a new MUD based on microstatistic filtering is proposed. The presented MUD uses piece-wise linear filtering in conjunction
with threshold decomposition of the input signal, which introduces a nonlinear effect, to improve performance when a nonlinearity
is present. Maximum performance improvement compared to conventional MUD is achieved for low spreading factors and user loads
no greater than 50%.
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Keywords: | MC-CDMA Nonlinear distortion Multi-user detection Microstatistic filter |
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