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.

Methods and Criteria for Performance Analysis of Multiantenna Systems in Mobile Communications

Pasi Suvikunnas

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 S5 at Helsinki University of Technology (Espoo, Finland) on the 25th of August, 2006, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-8297-6)   [849 KB]
Dissertation is also available in print (ISBN 951-22-8296-8)


Multiple-input multiple-output (MIMO) technique is one of the most promising solutions for increasing reliability and spectral efficiency of the radio connection in future mobile communication systems. The performance potential of MIMO systems is well established from theoretical point of view. However, much effort is still needed in the experimental verification of those systems using realistic antennas and channels. It is widely accepted that the antenna properties are of significant importance regarding the performance of single-input single-output (SISO) systems. However, the effect of the antennas on MIMO systems has not been thoroughly studied. Due to the complexity of MIMO systems, evaluation of MIMO antennas becomes increasingly cumbersome and time-consuming process in comparison to simpler systems.

In the first part of this work an advanced antenna evaluation technique called experimental plane-wave based method (EPWBM) is generalized and validated to cover MIMO systems. This work is the extension of the previous work where the method has been used in the analysis of SISO systems. The EPWBM is based on the measured or simulated complex 3-D radiation patterns of the antennas and measured directional radio channel data. The EPWBM simplifies antenna evaluation process in comparison to traditional means since the same channel library can be utilized in the evaluation of several antenna systems without performing the same measurements for each prototype antennas separately. It is verified that the EPWBM is sufficiently reliable in comparing the performance of prototype antennas.

In the second part of the work new quality factors for MIMO system evaluation enclosing traditional systems as special cases have been developed. The MIMO channel correlation matrix is formulated so that it reveals the ability of MIMO antenna systems to transfer signal power from a transmitter to a receiver and to utilize parallel spatial channels. It is also verified that correct normalization of the channel matrices is of significant importance in the MIMO antenna evaluation. This approach gives comprehensive framework for MIMO antenna evaluation, which takes into account both realistic antenna and channel properties.

In the last part of the work insight into the performance of different antennas in different signal propagation environments is given. The performance of the antennas depends on the signal-to-noise-ratio and on the outage probability level considered. Although MIMO systems are based on the utilization of parallel spatial channels, the capability of the system to transfer signal power plays a significant role especially with small MIMO systems. In the realistic dynamic channels the capacity variation is larger than in the ideal channels, which are based on the identically and independently distributed (iid) channel assumption. Large performance variations occur in the realistic channels with directive antennas, when antennas are rotated in the usage environment, whereas omnidirectional ones are more robust but are difficult to realize in practice. The largest differences between the antennas are found at the low outage probability levels due to different radiation properties of the antennas. The systems with the cross-polarized antennas have smaller eigenvalue dispersion and are more robust in performance for the variations of the channel than the systems with co-polarized antennas. On the other hand, the co-polarized antennas possess better capability to transfer signal power and are more robust in performance for the antenna array orientation. From practical point of view, the dual-polarized antennas seem to be the most feasible candidates to be used in MIMO antenna systems due to compact structure, and indoor seems to be the most suitable for MIMO applications due to typically scatter-rich channel.

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

  1. K. Sulonen, P. Suvikunnas, L. Vuokko, J. Kivinen, and P. Vainikainen, Comparison of MIMO antenna configurations in picocell and microcell environments, IEEE Journal on Selected Areas in Communications, vol. 21, no. 5, pp. 703-712, June 2003. © 2003 IEEE. By permission.
  2. P. Suvikunnas, J. Villanen, K. Sulonen, C. Icheln, J. Ollikainen, and P. Vainikainen, Evaluation of the performance of multi-antenna terminals using a new approach, IEEE Transactions on Instrumentation and Measurement, accepted for publication. © 2006 IEEE. By permission.
  3. P. Suvikunnas, J. Salo, L. Vuokko, J. Kivinen, K. Sulonen, and P. Vainikainen, Comparison of MIMO antenna configurations: methods and experimental results, Helsinki University of Technology, Radio Laboratory Publications, Report S 277, Espoo, Finland, June 2006, 27 p. © 2006 by authors.
  4. P. Suvikunnas, J. Salo, J. Kivinen, and P. Vainikainen, Comparison of MIMO antennas: performance measures and evaluation results of two 2x2 antenna configurations, Nordic Radio Symposium 2004, Oulu, Finland, August 16-18, 2004, CD-ROM (ISBN 951-42-7419-9), paper WEDAM7_1.pdf.
  5. P. Suvikunnas, K. Sulonen, J. Kivinen, and P. Vainikainen, Effect of antenna properties on MIMO-capacity in real propagation channels, in Proceedings of the 2nd COST 273 Workshop on Broadband Wireless Local Access, Paris, France, May 21-22, 2003, pp. 1-6. © 2003 COST 273. By permission.
  6. P. Suvikunnas, I. Salonen, J. Kivinen, and P. Vainikainen, A novel MIMO antenna for laptop type device, in Proceedings of the Antenna Measurement Techniques Association, 26th Annual Meeting and Symposium (AMTA 2004), Atlanta, USA, October 17-22, 2004, pp. 118-123. © 2004 Antenna Measurement Techniques Association (AMTA). By permission.
  7. J. Salo, B. Badic, P. Suvikunnas, H. Weinrichter, M. Rupp, and P. Vainikainen, Influence of antenna configurations on performance of STBC in urban microcells, Electronics Letters, vol. 41, no. 21, pp. 1157-1158, October 2005. © 2005 The Institution of Engineering and Technology (IET). By permission.

Keywords: multiple-input multiple-output (MIMO), antenna evaluation, multielement antennas, channel measurements

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© 2006 Helsinki University of Technology

Last update 2011-05-26