The physics and mathematics of signal propagation mechanism in cellular wireless communication system



Speaker: Prof. Tapan Sarkar, Syracuse University, US (12.8., Espoo, Finland)


The objective of this short course is to introduce a new physics based visualization of the Electromagnetic wave propagation mechanism in cellular wireless communication systems. We also illustrate from a mathematical point of view that an electromagnetic macro model can accurately predict the dominant component of the propagation path loss in a cellular wireless communication. The reason a macro model can provide accurate results that agree with experiments is because the trees, buildings, and other man made obstacles contribute second order effects to the propagation path loss as the dominant component is the free space propagation of the signal and the effect of the Earth over which the signal is propagating. It is demonstrated using both measurements and an analytical theoretical model that the propagation path loss inside a cellular communication cell is first about 30 dB per decade of distance and later on, usually outside the cell, it is about 40 dB per decade of distance between the transmitter and the receiver irrespective of their heights from the ground. This implies that the electric field decays first at a rate of ρ─1.5 inside the cell and later on, usually outside the cell, as ρ─2, where ρ stands for the distance between the transmitter and the receiver. It will also be illustrated that the so called slow fading is due to the interference between the direct wave and the ground wave as introduced by Sommerfeld over a hundred years ago. All these statements can be derived from the approximate integration of the Sommerfeld integrals using a modified path for the steepest descent method and also using an accurate purely numerical methodology. An optical analog model will be presented based on the image theory developed by Van der Pol to illustrate the mechanism of radio wave propagation in a cellular wireless communication system where the path loss is 30 dB per decade or the field decays as ρ─1.5. This macro model is used to refine the experimental data collection system for the propagation path loss and it is also illustrated how the antenna tilt both mechanical and electrical can be incorporated in the macro model to predict the propagation path loss. Finally, an observation is made on how to further improve the propagation mechanism by observing the second channel from the mobile to the base station. Numerical and Experimental data will reveal that the proposed methodology is a much better way to deploy base station antennas.



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