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Papers Published in Technical Journals and Conferences


Statistical Analysis and Characterization of Doppler Spectrum in Large Office Environment

W. Yamada, K. Nishimori, Y. Takatori, and Y. Asai

The 2009 International Symposium on Antennas and Propagation (ISAP 2009), Proc., pp. 564–567, Bangkok, Thailand.

Doppler spectra in a typical large office environment were measured during working hours and multiple Doppler spectra were statistically evaluated on the basis of a bell-shaped spectrum model. The results show that the channel in this measurement environment can be considered to be more quasi-static than described in TGn channel models. In addition, empirical formulas for Doppler spectra in large office environments are proposed.

Plane-wave and Vector-rotation Approximation Techniques for Reducing Computational Complexity in Simulating MIMO Propagation Channel by Ray-tracing

W. Yamada, N. Kita, T. Sugiyama, and T. Nojima

Trans. IEICE Jpn., Vol. E92-B, No. 12, pp. 3850–3860, 2009.

This paper proposes techniques for simulating a multiple-input multiple-output (MIMO) propagation channel by ray-tracing to decrease the computational complexity. These techniques simulate a MIMO propagation channel by substituting the propagation path between a particular combination of transmitter and receiver antennas. Their estimation accuracy was evaluated through comparison with results calculated using imaging algorithms. They were found to simulate a MIMO propagation channel with low computational complexity, and better estimation accuracy was achieved using the proposed vector-rotation approximation technique than using the imaging algorithms.