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Comparing Multicarrier Based Broadband Systems for Higher Modulation Cardinalities

Raulefs, R. and Dammann, A. and Kaiser, S. and Auer, G. (2004) Comparing Multicarrier Based Broadband Systems for Higher Modulation Cardinalities. In: Proceedings VTC 2004-Fall. IEEE Vehicular Technology Conference (VTC 2004 - Fall), Los Angeles, CA, USA, 26-29 September 2004, Los Angeles, USA. ISBN 0-7803-8522-5.

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Abstract

In this paper coded multicarrier systems, like the MC-CDMA, the time-frequency-localized (TFL) (or variablespreading factor CDMA) and the OFDMA system in the downlink are discussed with different modulation cardinalities and different detection techniques. The effect of the multiple-access interference (MAI) is addressed by using different detection schemes like a carrier-based MMSE and a soft parallel interference cancellation (PIC) scheme. The multiple access interference is a major drawback that reduces the performance for MCCDMA considerable and for TFL-CDMA slightly. It was shown in recent papers that this could be tackled by using a soft PIC for MC-CDMA. For 4-QAM modulation the loss due to MAI can be reduced through a soft PIC and allows to exploit the available diversity. However, our investigations show that it is no longer a dominant advantage for systems with a 64-QAM alphabet. Therefore, considering the lower complexity, simple OFDMA is a reasonable choice for 64-QAM and higher. In addition we propose to keep the length of the spreading sequence flexible depending on the system load. The flexible approach of spread spectrum for one user combining with OFDMA offers the use of the simple MRC detector. Therefore we name that scheme SSMRC-OFDMA. The CDMA based systems need more complex detectors to decrease the effect of MAI. The SS-MRC-OFDMA outperforms the MC-CDMA scheme even with a channel code rate of 3 4 and the complex soft PIC for the 64-QAM modulation scheme in a half loaded system by more than half a dB.

Document Type:Conference or Workshop Item (Paper)
Additional Information: LIDO-Berichtsjahr=2005,
Title:Comparing Multicarrier Based Broadband Systems for Higher Modulation Cardinalities
Authors:
AuthorsInstitution or Email of Authors
Raulefs, R.UNSPECIFIED
Dammann, A.UNSPECIFIED
Kaiser, S.UNSPECIFIED
Auer, G.DoCoMo Eurolabs, München
Date:2004
Journal or Publication Title:Proceedings VTC 2004-Fall
Refereed publication:Yes
In ISI Web of Science:No
ISBN:0-7803-8522-5
Status:Published
Keywords:Multivarrier, Broadband, Modulation
Event Title:IEEE Vehicular Technology Conference (VTC 2004 - Fall), Los Angeles, CA, USA, 26-29 September 2004
Event Location:Los Angeles, USA
Event Type:international Conference
Organizer:IEEE
HGF - Research field:other
HGF - Program:other
HGF - Program Themes:other
DLR - Research area:no assignement
DLR - Program:no assignment
DLR - Research theme (Project):other
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Communication and Navigation
Deposited By: elib DLR-Beauftragter
Deposited On:09 Oct 2005
Last Modified:14 Jan 2010 12:51

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