Multi-user Detection of Nonlinearly Distorted MC-CDMA Symbols by Microstatistic Filtering

  • Authors:
  • Jozef Krajňák;Marc Deumal;Pavol Pavelka;Dušan Kocur;Joan Lluís Pijoan;Pavol Galajda

  • Affiliations:
  • Department of Electronics and Multimedia Communications, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Koške, Slovak Republic;Grup de Recerca en Electromagnetisme i Comunicacions, Enginyeria i Arquitectura La Salle, Universitat Ramon Llull, Barcelona, Spain;Department of Electronics and Multimedia Communications, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Koške, Slovak Republic;Department of Electronics and Multimedia Communications, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Koške, Slovak Republic;Grup de Recerca en Electromagnetisme i Comunicacions, Enginyeria i Arquitectura La Salle, Universitat Ramon Llull, Barcelona, Spain;Department of Electronics and Multimedia Communications, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Koške, Slovak Republic

  • Venue:
  • Wireless Personal Communications: An International Journal
  • Year:
  • 2008

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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%.