Cluster-based radio channel emulation for over-the-air testing of automotive wireless systems

More and more radio systems are incorporated in modern automobiles e.g. multiple mobile communication standards for car-to-car or car-to-infrastructure communications like LTE, ITS G5, satellite navigation, radar detection, and so on. Due to the intimate relation between wireless information and the automotive state of operation, these complex systems need to be tested extensively and under realistic conditions. Due to the rapidly increasing integration of antennas and RF frontends, new test procedures need to be established, as conducted tests are not possible if the RF ports of the antennas are inaccessible. This paper discusses a modular approach for antenna constellations for over-the-air tests in the virtual road simulation and test area (VISTA) of the Thuringian Center of Innovation in Mobility at the Technische Universität Ilmenau, with a focus on mobile communications. The goal is to reproduce multipath clusters, in terms of the angular spread of arrival and, as a consequence, the spatial correlation of received signals, as a key parameter to parameterize the complex wave propagation effects of mobile communication channels. This paper amplifies the scope of current research on modular antenna configurations and analyzes the influence of array design parameters on the spatial correlation and, hence, on their suitability for reliable channel emulation. The criterion adapted to evaluate the quality of the emulation is the spatial correlation of the received signals in the theoretical case as well as in the emulated case.