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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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Abstract

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.

Document Type:Article
Additional Information: LIDO-Berichtsjahr=2005,
Title:Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System
Authors:
AuthorsInstitution or Email of Authors
Raulefs, R.UNSPECIFIED
Dammann, A.UNSPECIFIED
Sand, S.UNSPECIFIED
Kaiser, S.UNSPECIFIED
Auer, G.DoCoMo Eurolabs Germany
Date:2004
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
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:Vol. 2004
Page Range:pp. 74-83
Status:Published
Keywords:code division multiaccess, Walsh-Hadamard spreading sequences, multicarrier, fading channels, concatenated channel coding
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W KN - Kommunikation/Navigation
DLR - Research area:Space
DLR - Program:W KN - Kommunikation/Navigation
DLR - Research theme (Project):UNSPECIFIED
Location: Oberpfaffenhofen
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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