Realistic channel models are crucial in developing future wireless systems. Channel sounding and consequently propagation parameter estimation are key tasks in creating such models. In this paper we present an estimator for the angular distribution of the diffuse scattering component that is frequently observed in channel sounding measurements. Finding the Cramer-Rao lower bound and comparing the variances study the large sample performance of the estimator. The simulations show that the variance of the proposed estimation technique closely reaches the Cramer-Rao lower bound for small sample size and for any number of antennas.
The increased popularity of array antennas for wireless communication, has inspired investigations of the spatio-temporal properties of the radio channel, among others the azimuthal shape of the scattering clusters. Based on a statistical analysis, we show that trying to estimate the shape of the scattering is an ill-posed problem and that the heavy-tailed power azimuth spectra reported in the literature may be an artifact stemming only from the measurement procedure.
We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero.