A user allocating apparatus and method in a multiple antenna mobile communication system supporting multi-user diversity is provided. A first validation circuit determines if the received signal is a valid type signal, and if so the microprocessor counts the channels from the channel on which the signal is first detected to the channel on which the signal can no longer be detected is reached. Measured too is a third calibration standard, symmetrical with regard to its reflection parameters and designed as a two-port standard or a double one-port standard and is connected between the same test ports of the network analyzer. The method further comprises distributing, with the control unit, the total radiation dose among the individual radiation doses such that the strongest individual radiation doses are emitted by the source in positions corresponding to the beginning of an imaging session of the series of medical images. A blank function generator in this case randomly produces blank functions in the data processing unit, thus making an eavesdropping attack by analysis of leakage information considerably more difficult or preventing it.