On Spectral Efficiency in Spatially Clustered MIMO Radio Channels

Multi-antenna transmission with multi-antenna reception brings significant improvement in spectral efficiency for wireless communication systems. The degree of improvement is directly proportional to the correlation properties of the related MIMO (multiple-input, multiple-output) radio channel. Recently, it has been noticed that signal propagation paths appear as clusters both in the delay and spatial (azimuth) domains. Depending on the number of clusters and their directions and the corresponding angular spreading the MIMO channel characteristics, especially the correlation properties, can vary significantly. Therefore, the achievable spectrum efficiency of a MIMO channel can differ considerably from the expected maximum values. In the current study a geometry based stochastic radio channel model employing signal clustering was used as a starting point for evaluation of the spectral efficiency of MIMO channels in realistic radio environments. In order to enable double-directional radio channel modeling, uniform linear arrays were employed both at the mobile terminal and at the base station. Simulation results indicate that the degree of propagation path clustering has a significant impact on the spectral efficiency of MIMO channels