Preliminary Simulation Study of Doppler Reflectometry
A preliminary simulation study of Doppler reflectometry is performed. The simulations solve Maxwell's equations by a finite difference time domain (FDTD) code method in two dimensions. A moving corrugated metal target is used as a plasma cutoff layer to study the basic features of Doppler reflectometry. We examined the effects of the full width at half maximum (FWHM) of the electromagnetic waves and the corrugation depth of the metal target. Furthermore, the effect of a nonuniform plasma is studied using this FDTD analysis. The Doppler shift and velocity are compared with those obtained from FDTD analysis of a uniform plasma.
We assume a CDMA downlink multiuser scenario, where the base station is equipped with multiple transmit antennas, and each user has multiple receive antennas. For this setup we propose a new, computationally effective MIMO multiuser detector for frequency selective channels. We exploit the fact that the interference mainly comes from the spatial domain, while the residual interference is due to temporal dispersion and multiuser interference. This motivates us to suppress the residual interference in a linear fashion, while combating the spatial interference iteratively. This approach is an efficient performance-complexity tradeoff between fully iterative and linear detectors.