## 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. | |

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 7^{th} of July, 2003, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-6666-0) [1759 KB]

Dissertation is also available in print (ISBN 951-22-6627-X)

Results of this thesis contribute in modeling and characterization of radio channels for future mobile communications. The results are presented mainly in three parts: a) modeling of propagation mechanisms, b) methodology of developing a propagation model, c) characterization of urban radio channel.

One of the main propagation physical phenomena that have an important role in diverting signals to non line of sight scenarios is the diffraction process. This thesis proposes diffraction coefficients that have better agreement with finite difference time domain solution and rigorous diffraction theory than the coefficient commonly used in propagation predictions for mobile communications. The importance of diffuse scattering has also been investigated and showed that this physical process may have a key role in urban propagation, with a particular impact on the delay spread and angular spread of the signal at the receiver.

This thesis proposes wideband propagation models for main and perpendicular streets of urban street grids. The propagation models are ray-based and are given in explicit mathematical expressions. Each ray is characterized in terms of its amplitude, delay, and angle of arrival, angle of departure for vertical and horizontal polarizations. Each of these characteristics is given in a closed mathematical form. Having wideband propagation model in explicit expression makes its implementation easy and computation fast. Secondary source modeling approach for perpendicular streets has also been introduced in this thesis.

The last part of the thesis deals with characterization of urban radio channels for extracting parameters that help in successful design of mobile communication systems. Knowledge of channel characteristics enables reaching optimum trade off between system performance and complexity. This thesis analyzes measurement results at 2 GHz to extract channel parameters in terms of Rake finger characteristics in order to get information that helps to optimize Rake receiver design for enhanced-IMT2000 systems. Finger life distance has also been investigated for both micro- and small cell scenarios. This part of the thesis also presents orthogonality factor of radio channel for W-CDMA downlink at different bandwidths. Characterization of dispersion metrics in delay and angular domains for microcellular channels is also presented at different base station antenna heights. A measure of (dis-) similarity between multipath components in terms of separation distance in delay and angular domains is introduced by the concept of distance function, which is a step toward in development of algorithm extraction and analysis multipath clustering.

In summary, the significant contributions of the thesis are in three parts. 1) Development of new diffraction coefficients and corrections of limitations of existing one for accurate propagation predictions for mobile communications. 2) Development of wideband propagation models for urban street grid. The novelty of the model is the development in explicit mathematical expressions. The developed models can be used to study propagation problem in microcellular urban street grids. 3) Presenting channel parameters that will help in the design of future mobile communication systems (enhanced-IMT2000), like number of active fingers, finger life distance, and orthogonality factors for different bandwidths. In addition, a technique based on multipath separation distance is proposed as a step toward in development of algorithms for extraction and analysis of multipath clusters.

This thesis consists of an overview and of the following 10 publications:

- El-Sallabi H. M., Liang G., Bertoni H. L., Rekanos I. T. and Vainikainen P., 2002. Influence of diffraction coefficient and corner shape on ray prediction of power and delay spread in urban microcells. IEEE Transactions on Antennas and Propagation 50, No. 5, pages 703-712. Special Issue on Wireless Communications, May 2002.
- El-Sallabi H. M., Rekanos I. T. and Vainikainen P., 2002. A new heuristic diffraction coefficient for lossy dielectric wedges at normal incidence. IEEE Antennas and Wireless Propagation Letters 1, pages 165-168.
- El-Sallabi H. M. and Vainikainen P., 2003. Improvement in heuristic UTD diffraction coefficient. IEE Electronics Letters 39, No. 1, pages 10-12.
- Degli-Esposti V., El-Sallabi H. M., Guiducci D., Kalliola K., Azzi P., Vuokko L., Kivinen J. and Vainikainen P., 2002. Analysis and simulation of the diffuse scattering phenomenon in urban environment. Proceedings of the XXVIIth General Assembly of the International Union of Radio Science (URSI 2002). 17-24 August 2002, paper no. 1734 in CD, 4 pages.
- El-Sallabi H. M. and Vainikainen P., 2000. Physical modeling of line-of-sight wideband propagation in a city street for microcellular communication. Journal of Electromagnetic Waves and Applications 14, pages 905-927.
- El-Sallabi H. M. and Vainikainen P., 2003. Radio wave propagation in perpendicular streets of urban street grid for microcellular communications. Part I: Channel modeling. Progress In Electromagnetics Research (PIER) 40, pages 229-254, an abstract version in Journal of Electromagnetic Waves and Applications 17, No. 8, pages 1157-1158.
- El-Sallabi H. M., 2000. Fast path loss prediction by using virtual source technique for urban microcells. Proceedings of the IEEE Vehicular Technology Conference (VTC'2000). Tokyo, Japan, May 2000, Vol. 3, pages 2183-2187.
- El-Sallabi H. M. and Vainikainen P., 2003. Influence of chip frequency on characterizing radio channels for Rake receiver fingers for CDMA systems in microcellular environment. Accepted for publication in IEICE Transaction on Fundamentals of Electronics and in Communications and Computer Sciences, to appear in October 2003.
- El-Sallabi H. M., Bertoni H. L. and Vainikainen P., 2002. Channel characterization for CDMA Rake receiver design for urban environment. Proceedings of the IEEE Communication Conference (ICC2002). NYC, USA, April 2002, Vol. 2, pages 911-915.
- El-Sallabi H. M., Bertoni H. L. and Vainikainen P., 2002. Experimental evaluation of Rake finger life distance for CDMA Systems. IEEE Antennas and Wireless Propagation Letters 1, pages 50-52.

Errata of publications 5 and 6

**Keywords:**
propagation model, urban radio channel, diffraction process, diffuse scattering, Rake receiver design, finger life distance

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© 2003 Helsinki University of Technology

Last update 2011-05-26