This study explores the application of GPU-based algorithms in radiowave propagation modeling, specifically through the scope of solving parabolic wave equations. Radiowave propagation models are crucial in the field of wireless communications, where they help predict how radio waves travel through different environments, which is vital for planning and optimization. The research specifically examines the implementation of two numerical methods: the Split Step Method and the Finite Difference Method. Both methods are adapted to utilize the parallel processing capabilities of modern GPUs, harnessing a parallel computing framework known as CUDA to achieve considerable speed enhancements compared to traditional CPU-based methods.Our findings reveal that the Split Step method generally achieves higher speedup factors, especially in scenarios involving large system sizes and high-frequency simulations, making it particularly effective for expansive and complex models. In contrast, the Finite Difference Method shows more consistent speedup across various domain sizes and frequencies, suggesting its robustness across a diverse range of simulation conditions. Both methods maintained high accuracy levels, with differences in computed norms remaining low when comparing GPU implementations against their CPU counterparts.

The advent of Internet based digital services, and bandwidth-intensive business and personal applications has necessitated deployment of broadband network access technologies. Research analysts project that the U.S. market for broadband wireless networking will grow to nearly $2 billion by 2004 and Local Multipoint Distribution Services (LMDS) have enormous potential to emerge as the most reliable and cost-effective solution. However, in order to design and deploy LMDS systems, it is vital for system designers to be able to predict the behavior of mm-waves (28, 38 and 60GHz) during different weather conditions, especially rain. This research attempts to characterize the performance of pico-cell scenario broadband wireless channels by measuring path loss statistics during different weather conditions. Hardware and software components of a wideband direct-sequence spread spectrum (DSS) channel sounding system, used extensively throughout measurement campaigns, are discussed in detail in this dissertation. The measurement plan comprehensively describes the methodology, logistics, equipment setup, and calibration procedures for propagation measurement campaigns. Power Delay Profile (PDP) snapshots recorded during measurement campaigns are thoroughly analyzed using the 'Channel Imaging Analysis Suite' and Path Loss as well as Rain Attenuation statistics, calculated from recorded PDP data files, are classified and tabulated on the basis of measurement locations, propagation frequencies and antenna polarizations. Path Loss Exponent values are also calculated and Rain Attenuation statistics are compared with popular rain models. Results from Frequency Diversity measurement campaigns are also presented. / Master of Science

Approved for public release, distribution is unlimited / In urbanized terrain, radiowave propagation is subjected to fading on large-scales and smallscales that would impede on the quality and reliability of data link transmission. This would have implications in many military applications. One example is the performance of unmanned aerial vehicle (UAV) data and communications links in complex urban environments. The purpose of this research is to study the effectiveness of diversity techniques on the performance of urban UAV data and communications links. The techniques investigated were spatial, polarization, and angle diversities. The ray tracing software, Urbana Wireless Toolset, was used in the modeling and simulation process. The various combinations of diversity techniques were simulated using a realistic urban city model. For the few transmit-receive geometries examined, it was found that angle diversity with a directive antenna provided the greatest increase in signal strength relative to the no diversity case. / Civilian, Singapore DOD

This Thesis is devoted to theoretical investigation of the effective magnetic properties of nonlinear metamaterials, based on resonant conductive elements.A general expression for the effective bulk ermeability in the microwave frequency range is derived. Frequency dispersion of the permeability is studied and recommendations for optimisation of metamaterials with negative permeability are given. The results are supported with numerical simulation of the finite metamaterial sample.Next, a metamaterial possessing nonlinear magnetic responseowing to nonlinear electronic components, inserted into resonant conductive elements, is proposed. For the limit of low nonlinearity, the arising quadratic nonlinear susceptibility is calculated; it is shown how it is controlled by the properties and arrangement of the structure elements as well as by the type and characteristics of the insertion.For the insertions operating in essentially nonlinear regime, when a nonlinear magnetic susceptibility cannot be introduced, an approach is developed for analyzing three-wave coupling processes with a strong pump wave and two weak signals. Peculiarities of coupling, arising from use the insertions with variable resistance or variable capacitance are discussed. Estimates are given that extremely strong nonlinear coupling can be achieved using typical diodes reported in literature.Finally, it is demonstrated how the metamaterial band gap can be tuned, and the resulting metamaterial switching between transmitting, reflecting and absorbing states is described. The details appear to depend drastically on the type of nonlinear components inserted into the resonant conductive elements. Relying on practical estimates, it is predicted that the transmittance of a metamaterial slab can be modulated by several orders of magnitude already using a slab with thickness equal to one microwave wavelength in vacuum.