On Channel Emulation Methods in Multiprobe Anechoic Chamber Setups for Over-the-Air Testing

Multiple-input multiple-output (MIMO) over-the-air (OTA) testing gives a way to evaluate the radio performance of MIMO-capable devices under realistic propagation channels as an alternative to expensive and uncontrollable drive testing. In this paper, we review two major channel emulation methods for MIMO OTA testing under the multiprobe anechoic chamber setup, i.e., the prefaded signals synthesis (PFS) and the plane wave synthesis (PWS). The target channel model for emulation is the geometry-based stochastic channel model (GSCM). The signal models for both channel emulation methods for the whole link from the transmitter (Tx) side to the receiver (Rx) side are given. The comparison analysis gives some new insights into the two channel emulation methods. The analytic expression of the joint space-time correlation function is derived for both methods in comparison to that of the target channel. It shows the clusterwise channel emulated by the PFS method is Kronecker structured, which is different from the general definition of GSCMs. In contrast, the channel emulated with the PWS method is consistent with GSCMs. Moreover, the emulation accuracy for the two methods are compared under different target channel settings, i.e., different cluster angular spreads. The simulation results demonstrate the advantage of the PWS method over the PFS method, especially when cluster angular spreads are small.