By simulating the radar pulses directed at buildings, engineers can better understand complex scattering mechanisms. They also can provide benchmark data for evaluating imaging algorithms. Previous work on wall-imaging algorithms has been rooted in techniques like synthetic-aperture-radar (SAR) imaging, time reversal, the boundary scattering transform, and beamforming with nonlinear inverse scattering algorithms. More recently, large-scale, fullwave simulations using the finite-element timedomain (FETD) method have been performed by Mark L. Stowell, Benjamin J. Fasenfest, and Daniel A. White from Lawrence Livermore National Laboratory (Livermore, CA). These researchers had two goals: to simulate a highly detailed building model consisting of more than 10 billion mesh elements and to investigate various wall materials. To investigate wall materials, the researchers modeled a twostory building with concrete walls and cinder block and rebar construction. The hypothetical radar is a pulsed system with 1-GHz bandwidth and 700-MHz center frequency.

Most of the simulations were conducted on the ZEUS Linux computer cluster at Lawrence Livermore National Laboratory. This cluster comprises 288 computational nodes, which each contain four AMD (www.amd.com) dualcore Opteron processors. See "Investigation of Radar Propagation in Buildings: A 10-Billion Element Cartesian-Mesh FETD Simulation," IEEE Transactions on Antennas and Propagation, August 2008, p. 2241.