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A Complete Physics-Based Channel Parameter Simulation for Wave Propagation in a Forest Environment
Final rept. 16 Aug 1999-15 May 2000
MICHIGAN UNIV ANN ARBOR RADIATION LAB
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At HF through UHF frequencies, wave propagation in a forest environment is mainly attributed to a lateral wave which propagates at the canopy-air interface. Due to the existence of tree trunks, significant multiple scattering also occurs which is the dominant source of field fluctuations. Basically the current induced in the tree trunks by the source and the lateral wave re-radiate and generate higher order lateral waves and direct scattered waves. Using a full-wave analysis based on the method of moments in conjunction with Monte Carlo simulations, the effect of multiple scattering among a very large number of tree trunks is studied. It is shown that only scatterers near the source and the observation points contribute to the field fluctuations significantly. This result drastically simplifies the numerical complexity of the problem. Keeping about 200 tree trunks in the vicinity of the transmitter dipole and the receiver point, a Monte Carlo simulation is used to evaluate the statistics of the spatial and spectral behavior of the field at the receiver. Using a wideband simulation, the temporal behavior impulse response is also studied as is performance of antenna arrays and the effects of different spatial diversity combining schemes in such a multi-path environment.
APPROVED FOR PUBLIC RELEASE