Distortions Inherent to Spread-Spectrum
Multiple-Access Systems Applied to
Mobile Radio Transmission

Michael Schnell

Dr.-Ing. Michael Schnell
German Aerospace Center (DLR)
Research Site Oberpfaffenhofen
Institute for Communications Technology
P.O. Box 1116
D-82230 Wessling, Germany
Phone: +49 8153 282858
Fax: +49 8153 281442
E-mail: Michael.Schnell@dlr.de
Web Site: http://www.op.dlr.de/ne/nt/NT-S/Schnell

Thesis Defence: June 19, 1997
Supervisor: Prof. Dr.-Ing. A.J. Han Vinck, University of Essen, Germany
Advisor: Prof. Dr.-Ing. J. Lindner, University of Ulm, Germany

Keywords: Spread-spectrum transmission, direct-sequence CDMA, multicarrier CDMA, mobile radio channel, intersymbol interference, equalization, multiple-access interference, multiuser detection


The growing demand for mobile communications has been the initiator for discussions about third generation mobile radio systems known as "Future Public Land Mobile Telecommunications System" (FPLMTS) and "Universal Mobile Telecommunications System" (UMTS). Increased user capacity as well as the possibility to transmit not only low rate speech data but also high rate digital data of any kind are the main requirements for FPLMTS and UMTS. For achieving these goals spread-spectrum multiple-access is a promising transmission scheme and discussed in several proposals for third generation mobile radio systems.

In this thesis, two spread-spectrum multiple-access schemes are discussed for use in third generation mobile radio systems - direct-sequence CDMA and multicarrier CDMA. Especially, the distortions inherent to these spread-spectrum multiple-access systems are investigated, namely intersymbol interference and multiple-access interference. First, the distortions are determined and described using theoretical considerations as well as Monte-Carlo simulations. Subsequently, several countermeasures for reducing the distortions are investigated. Finally, suitable countermeasures are identified and proposed for use in direct-sequence CDMA and multicarrier CDMA systems.

Ph.D. thesis available only in German:

M. Schnell, "Systeminhärente Störungen bei `Spread-Spectrum'-Vielfachzugriffsverfahren für die Mobilfunkübertragung", Fortschrittberichte VDI, Reihe 10: Informatik/Kommunikationstechnik, Nr. 505, VDI Verlag GmbH, Düsseldorf 1997

Parts of Ph.D. thesis available in English:

M. Schnell, M. Werner, "Comparison Between Different Transmission Schemes for Mobile Radio Channels", Proc. of ISSSE'92, Paris, France, September 1992, pp. 705-708

U.-C. Fiebig, M. Schnell, "Correlation Properties of Extended M-Sequences", IEE Electronics Letters, Vol. 29, No. 20, September 1993, pp. 1753-1755

M. Schnell, "Hadamard Codewords as Orthogonal Spreading Sequences in Synchronous DS CDMA Systems for Mobile Radio Channels", Proc. of ISSSTA'94, Oulu, Finland, July 1994, pp. 505-509

M. Schnell, A.J. Han Vinck, "Low Complexity Equalization with an Efficient Coding Scheme for Broadband Mobile Radio Systems", Proc. of Globecom'94, San Francisco, California, November 1994, pp. 16-21

K. Fazel, S. Kaiser, M. Schnell, "A Flexible and High Performance Cellular Mobile Communications System Based on Orthogonal Multi-Carrier SSMA", Wireless Personal Communications, Vol. 2, Nos. 1&2, 1995, pp. 121-144

M. Schnell, "Interference Calculations for MC-SSMA Systems in Mobile Communications", Proc. of PIMRC'95, Toronto, Cananda, September 1995, pp. 158-163

M. Schnell, S. Kaiser, "Diversity Considerations for MC-SSMA Systems in Mobile Communications", Proc. of ISSSTA'96, Mainz, Germany, September 1996, pp. 131-135

M. Schnell, A.J. Han Vinck, "A Low Complexity Equalization Concept for Frequency-Selective Mobile Radio Channels", AEÜ International Journal of Electronics and Communications, Vol.50, No. 6, November 1996, pp. 343-352