Cluster Angular Spreads in a MIMO Indoor Propagation Environment

An important parameter of MIMO channel models is the cluster root-mean-square (rms) directional spread. In this paper we determine this parameter in the azimuth-of-arrival/azimuth-of-departure (AoA/AoD) domain based on comprehensive indoor MIMO measurements at 5.2 GHz in a cluttered office environment. This is done in a four-step procedure: (i) the SAGE algorithm is used to extract propagation paths, (ii) clusters of estimated paths in the double-azimuth domain are defined, (iii) the estimated propagation paths are allocated to the clusters, (iv) the cluster directional spreads are estimated based solely on propagation paths within the clusters. We found that the spreads are different when seen from transmitter or receiver due to different propagation conditions resulting in AoD rms cluster spreads lying in the range from 2 to 9 degrees and AoA rms cluster spreads in the range from 2 to 7 degrees.