Abstract: An apparatus comprises a receiver receiving wireless transmission of a real radio system from at least one base station of a radio system as a function of reception direction. The transmission comprises predetermined data. The apparatus comprises also a processing unit that forms taps of a delay profile on the basis of comparison between the data that is received and corresponding predetermined data. The processing unit estimates direction for the taps of the delay profile on the basis of a reception direction of the transmission, and forms radio channel data by associating the taps of the delay profile with the estimated direction. The radio channel data is for a radio channel model of a MIMO emulation in an OTA chamber having a plurality of antennas around a test zone where a device-under-test may be placed.

Abstract: A testing system comprises a noise source coupled to at least two antenna elements. The noise source forms a total noise power on the basis of a total signal power received by the emulator, a gain of at least one antenna-specific channel between the emulator and the antenna elements, and a desired signal-to-noise ratio. The noise source transmits noise at the total noise power from the at least two antenna elements to the device under test wirelessly.