Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System
Raulefs, R. and Dammann, A. and Sand, S. and Kaiser, S. and Auer, G. (2004) Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System. EURASIP Journal on Wireless Communications and Networking - Special Issue on Innovative SignalTransmission and Detection Techniques for Next Generation Cellular CDMA Systems, Vol. 2004 (No. 1), pp. 74-83.
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We investigate rotated Walsh-Hadamard spreading matrices for a broadband MC-CDMA system with robust channel estimation in the synchronous downlink. The similarities between rotated spreading and signal space diversity are outlined. In a multiuser MC-CDMA system, possible performance improvements are based on the chosen detector, the channel code, and its Hamming distance. By applying rotated spreading in comparison to a standard Walsh-Hadamard spreading code, a higher throughput can be achieved. As combining the channel code and the spreading code forms a concatenated code, the overall minimum Hamming distance of the concatenated code increases. This asymptotically results in an improvement of the bit error rate for high signal-to-noise ratio. Higher convolutional channel code rates are mostly generated by puncturing good low-rate channel codes. The overall Hamming distance decreases significantly for the punctured channel codes. Higher channel code rates are favorable for MC-CDMA, as MC-CDMA utilizes diversity more efficiently compared to pure OFDMA. The application of rotated spreading in an MC-CDMA system allows exploiting diversity even further. We demonstrate that the rotated spreading gain is still present for a robust pilot-aided channel estimator. In a well-designed system, rotated spreading extends the performance by using a maximum likelihood detector with robust channel estimation at the receiver by about 1 dB.
|Title:||Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System|
|Journal or Publication Title:||EURASIP Journal on Wireless Communications and Networking - Special Issue on Innovative SignalTransmission and Detection Techniques for Next Generation Cellular CDMA Systems|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 74-83|
|Keywords:||code division multiaccess, Walsh-Hadamard spreading sequences, multicarrier, fading channels, concatenated channel coding|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Space|
|HGF - Program Themes:||W KN - Kommunikation/Navigation|
|DLR - Research area:||Space|
|DLR - Program:||W KN - Kommunikation/Navigation|
|DLR - Research theme (Project):||UNSPECIFIED|
|Institutes and Institutions:||Institute of Communication and Navigation|
|Deposited By:||elib DLR-Beauftragter|
|Deposited On:||16 Sep 2005|
|Last Modified:||06 Jan 2010 21:42|
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