The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Advanced Receivers for High Data Rate Mobile Communications

Maarit Melvasalo

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 8th of December, 2006, at 12 noon.

Overview in PDF format (ISBN 951-22-8487-1)   [620 KB]
Dissertation is also available in print (ISBN 951-22-8486-3)

Abstract

Improving the spectral efficiency is a key issue in the future wireless communication systems since the spectrum is a scarce resource. Both the number of users as well the demanded data rates are increasing all the time. Furthermore, in mobile communications the wireless link is required to be reliable even when the mobile is in a fast moving vehicle. Using Multiple-Input Multiple-Output (MIMO) antennas is a well known technique to provide higher spectral efficiency as well as better link reliability. Additionally, higher order modulation methods can be used to provide higher data rates. In order to benefit from these enhancements in practise, sophisticated signal processing methods as well as accurate estimates of time-varying wireless channel parameters are needed.

This thesis addresses the problem of designing multi-antenna receivers in high data rate systems. The case of multiple transmit antennas is also considered. System specific features of High Speed Downlink Packet Access (HSDPA) which is part of 3rd generation (3G) Wideband Code Division Multiple Access (WCDMA) evolution are exploited in channel estimation methods and in MIMO receiver design. Additionally, complexity reduction methods for Minimum Mean Square Error (MMSE) equalization are addressed.

Blind channel estimation methods are spectrally efficient, since no extra resources are needed for pilot signals. However, in mobile communications accurate estimates are needed also in fast fading channels. Consequently, semi-blind channel estimation methods where the receiver combines blind and pilot based channel estimation are an appealing alternative. In this thesis blind and semi-blind channel estimation methods based on knowledge of multiple spreading codes are derived. A novel semi-blind combining scheme for code multiplexed pilot signal and blind estimation is proposed.

Another important factor in receiver design criteria is the structure of interference in the received signals. Interference mitigation techniques in MIMO systems have been shown to be potential methods for providing improved performance. A chip level inter-antenna interference cancellation method has been developed in this thesis for HSDPA. Furthermore, this multi-stage ordered interference canceler is combined with the semi-blind channel estimation scheme to enhance the system performance further.

This thesis consists of an overview and of the following 7 publications:

  1. M. Melvasalo and V. Koivunen. Blind channel estimators for multicode transmission in long code CDMA systems. In Proceedings of the 36th Conference on Information Sciences and Systems, CISS 2002, Princeton, New Jersey, USA, CD-ROM proceedings, March 2002.
  2. M. Melvasalo and V. Koivunen. Blind channel estimation in multicode CDMA system with antenna array. In Proceedings of the 3rd IEEE Workshop on Sensor Array and Multichannel Signal Processing, SAM 2002, pp. 565-569, Virginia, USA, August 2002. © 2002 IEEE. By permission.
  3. M. Melvasalo and V. Koivunen. Blind channel estimation in multicode CDMA using multiantenna receiver. In Wireless Personal Communications, Kluwer, vol. 28, pp. 163-178, 2004.
  4. M. Melvasalo and V. Koivunen. Semi-blind channel estimation in HSDPA systems. In Conference Record of the 39th Asilomar Conference on Signals, Systems and Computers, pp. 1292-1296, California, USA, 2005. © 2005 IEEE. By permission.
  5. M. Melvasalo, P. Jänis and V. Koivunen. Low complexity space-time MMSE equalization in WCDMA systems. In Proceedings of the 16th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2005, pp. 306-310, Berlin, Germany, 2005. © 2005 IEEE. By permission.
  6. M. Melvasalo, P. Jänis and V. Koivunen. MMSE equalizer and chip level inter-antenna interference canceler for HSDPA MIMO systems. In Proceedings of the 63rd IEEE Vehicular Technology Conference, VTC Spring 2006, vol. 4, pp. 2008-2012, Melbourne, Australia, 2006. © 2006 IEEE. By permission.
  7. M. Melvasalo, P. Jänis and V. Koivunen. Low complexity semi-blind channel estimation in HSDPA systems. Helsinki University of Technology, Signal Processing Laboratory, Report 55, 2006. Submitted for publication.

Errata of publications 1, 2, 3, 4 and 6

Keywords: MIMO, multi-antenna receivers, High Speed Downlink Packet Access, HSDPA, Wideband Code Division Multiple Access, WCDMA, channel estimation, Code Division Multiple Access, CDMA

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© 2006 Helsinki University of Technology

Last update 2011-05-26