Viability of Numerical Full-Wave Techniques in Telecommunication Channel Modelling

In telecommunication channel modelling the wavelength is small compared to the physical features of interest, therefore deterministic ray tracing techniques provide solutions that are more efficient, faster and still within time constraints than current numerical full-wave techniques. Solving fundamental Maxwell's equations is at the core of computational electrodynamics and best suited for modelling electrical field interactions with physical objects where characteristic dimensions of a computing domain is on the order of a few wavelengths in size. However, extreme communication speeds, wireless access points closer to the user and smaller pico and femto cells will require increased accuracy in predicting and planning wireless signals, testing the accuracy limits of the ray tracing methods. The increased computing capabilities and the demand for better characterization of communication channels that span smaller geographical areas make numerical full-wave techniques attractive alternative even for larger problems. The paper surveys ways of overcoming excessive time requirements of numerical full-wave techniques while providing acceptable channel modelling accuracy for the smallest radio cells and possibly wider. We identify several research paths that could lead to improved channel modelling, including numerical algorithm adaptations for large-scale problems, alternative finite-difference approaches, such as meshless methods, and dedicated parallel hardware, possibly as a realization of a dataflow machine.

Computational Electrodynamics - A Powerful Tool for Nanophotonics and Microscopy

ABSTRACTComputational electrodynamics simulations provide a critical complement to experimental investigations for the understanding of light-matter interaction in complex systems. Its success is due in part to its relative simplicity and ease of use, coupled with its broad applicability to many material systems and optical processes. First, we will review our recent work in nanophotonics. While computational electrodynamics has been, and continues to be, very widely used in plasmonics, there are significant issues in convergence and accuracy, which we have studied in detail, and which sometimes point to the need for parallel computing. With access to large computational resources, we are able to study complex arrangements of dielectric and plasmonic objects, including metallic nanoparticle distributions for color production, hybrid dielectric/plasmonic nanoantennas for enhancement of third harmonic generation, and metasurfaces for nonlinear light control and structuring. Second, we will discuss our computational electrodynamics simulations of nonlinear optical microscopy experiments. Our tool includes high numerical aperture light sources, propagation through heterogeneous media, nonlinear near-field interaction, subsequent propagation to the far field, and integration over a collecting lens. We have used this to unravel the image formation mechanisms in nonlinear optical microscopy, such as CARS and SHG microscopy. We find that the images are not a one-to-one density map of the object, but rather that the sub-micrometer to nanometer structure of the object, along with the coherence of parametric nonlinear optical processes, can be imprinted in the image in surprising ways.