부산대학교 도서관

This contribution presents results from an application of the SAGE (space-alternating generalized expectation-maximization) algorithm published in Fleury et al. (2002) to measurement data collected in a selected propagation environment. The scheme jointly estimates the delay, the direction (i.e. azimuth and coelevation) of departure, the direction of incidence, as well as the Doppler frequency of waves propagating from the transmitter to the receiver. An improved initialization and search procedure is proposed which enhances the probability of identifying weak paths and therefore allows for a more comprehensive and detailed characterization of the propagation mechanisms. In order to relate the estimated waves to the propagation environment, a simple method based on ray tracing attempts to reconstruct the propagation paths based on the estimated wave parameters while assuming oneand two-bounce scattering. Significant objects can be identified in the environment that coincide with the interaction points of the calculated paths. The same conclusions can be drawn from similar analyses of other environments. The presented results demonstrate the high potential of high-resolution estimation techniques performing true joint estimation of delay, direction of departure, and direction of incidence for detailed investigations of dispersion in the radio channel jointly in delay and in direction at both transmitter and receiver sites. These studies are of paramount importance for an accurate characterization of MIMO (multiple-input multiple-output) systems operating in these channels.