Application of the fast far-field approximation to the computation of UHF pathloss over irregular terrain

Abstract

The recent availability of fast numerical methods has rendered the integral-equation approach suitable for practical application to radio planning and site optimization for UHF mobile radio systems. In this paper, we describe a conceptually simple scheme for the efficient computation of UHF radial propagation loss over irregular terrain, which is based on the fast far-field approximation. The method is substantially faster than conventional integral-equation (IE) solution techniques. The technique is improved by incorporating the Green's function perturbation method and we outline a way in which the formulation can be made more exact. Computational issues such as terrain profile truncation and the effect of small-scale roughness are addressed. The method has been applied to gently undulating terrain and compared to published experimental results in the 900-MHz band. It has also been successfully applied to more hilly terrain and to surfaces with buildings added.

Application of the spectral acceleration forward-backward method for propagation over terrain

“…It is also worth mentioning that, the empirical methods are run on the surfaces Green's function with measurement data or Hata model have been presented [18], [20]. However, those IE methods do not dicretize the surface profile as much as FBSA does and also they use additional approximations, such as neglecting the backscatter.…”

“…As in the previous case, this method remains computationally complex, although a parallel implementation of the method allows the solution of some practical problems in the VHF band. A more efficient solution can be found in [20], where the fast far field approximation (FAFFA) was introduced and modified in an integral equation formulation for the terrain propagation problem. The FAFFA reduces the operational cost of the previous IE methods from O(N 2 ) per iteration to O(N 4/3 ).…”

“…Diffraction losses over 'secondary' obstacles are added to the diffraction loss over the main obstacle [49]. [18], [20]. In this work, using the FBSA as reference solution, the most common propagation prediction models are examined.…”

An efficient solution of an integral equation applicable to simulation of propagation along irregular terrain

“…This could become a serious constraint to many propagation applications. They also observed that a number of time-saving measures [5] could be developed to deal with this aspect of integral equations, even though this was not within the goals of their paper.…”

Multilevel tabulated interaction method applied to UHF propagation over irregular terrain

“…Backscattering could be Manuscript received April 6, 1998 explicitly accounted for and the whole computation took a matter of seconds on a modest computational resource such as an HP workstation. The fast far-field algorithm (FAFFA) [9], which is related to the well-documented fast multiple method [10], was combined with the Green's function perturbation method (GFPM) [11], [12] and offers large computational savings over a wider range of problems than those amenable to rapid NBS solution. Though not as fast as the NBS, the FAFFA was further specialized (via the incorporation of certain assumptions, described in Section II, about the problem geometry and incident field) into an extremely rapid scheme namely the tabulated interaction method (TIM) [13] which, for terrain problems, combined the robustness of the FAFFA with the speed of the NBS.…”