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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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)|
|Title:||Comparing Multicarrier Based Broadband Systems for Higher Modulation Cardinalities|
|Journal or Publication Title:||Proceedings VTC 2004-Fall|
|In ISI Web of Science:||No|
|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|
|HGF - Research field:||no assignement|
|HGF - Program:||no assignment|
|HGF - Program Themes:||no assignment|
|DLR - Research area:||no assignement|
|DLR - Program:||no assignment|
|DLR - Research theme (Project):||other|
|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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