e&i Elektrotechnik und Informationstechnik

, Volume 119, Issue 11, pp 395–402 | Cite as

Multi-user detection in multicarrier-CDMA systems

  • V. Kühn
  • R. Böhnke
  • K. D. Kammeyer
Originalarbeiten

Abstract

The upcoming third generation mobile radio system in Europe is based on UMTS (Universal Mobile Telecommunications Standard). In order to supply access to a common transmission channel for several users, UMTS incorporates Code Division Multiple Access (CDMA). Besides a lot of practical advantages, CDMA suffers from multi-user interference limiting spectral efficiency dramatically. However, bandwidth is a very valuable resource and should be used as efficiently as possible. One appropriate mean to increase spectral efficiency of CDMA systems is multi-user detection. This paper gives an overview of different multi-user detection techniques and compares them with the conventional single-user detection including channel coding. Specifically, linear as well as nonlinear multi-user detectors are considered. Efficient realizations of linear detectors are presented and extended to improved nonlinear techniques. It is shown that nonlinear MUD including channel decoding can achieve a spectral efficiency twice as high as that of the well-known GSM standard (Global System for Mobile Communications) employing TDMA and FDMA.

Keywords

CDMA OFDM-CDMA multi-user detection turbo principle channel coding 

Mehrnutzerdetektion in Mehrträger-Codemultiplex-Systemen

Zusammenfassung

Die dritte Mobilfunkgeneration in Europa basiert auf dem Standard UMTS (Universal Mobile Telecommunications Standard), der als Vielfachzugriffsverfahren CDMA (Code Division Multiple Access) verwendet. Neben einer Vielzahl praktischer Vorteile besitzt das Codemultiplex den gravierenden Nachteil, dass sich die Teilnehmersignale gegenseitig stören (Mehrnutzerinterferenz), wodurch die spektrale Effizienz solcher Systeme dramatisch reduziert wird. Aufgrund der hohen Preise der Frequenzbänder sollten diese aber so effizient wie möglich genutzt werden. Eine Möglichkeit zur Erhöhung der spektralen Effizienz von CDMA-Systemen stellt dabei die Mehrnutzerdetektion dar. Dieser Artikel gibt einen Überblick über die diversen Ansätze zur Mehrnutzerdetektion und vergleicht sie mit der konventionellen Einnutzerdetektion. Insbesondere werden lineare und nichtlineare Verfahren betrachtet sowie effiziente Realisierungen basierend auf iterativen Strategien diskutiert. Anhand von Simulationsergebnissen wird gezeigt, dass mit der nichtlinearen Mehrnutzerdetektion inklusive Kanaldecodierung eine doppelt so hohe spektrale Effizienz wie in klassischen Zeit- und Frequenzmultiplexsystemen (GSM: Global System for Mobile Communications) erzielt werden kann.

Schlüsselwörter

CDMA OFDM-CDMA Mehrnutzerdekektion Turbo-Prinzip Kanalcodierung 
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Copyright information

© Springer 2002

Authors and Affiliations

  • V. Kühn
    • 1
  • R. Böhnke
    • 1
  • K. D. Kammeyer
    • 1
  1. 1.Department of Communications EngineeringUniversität BremenBremen

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