A transmitter-side estimation of the complex channel influence between function variable value transmitters and function receivers is limited to the estimation of the magnitude of the channel influence, so that a pre-distortion of the symbols of the symbol sequences depends on an inverse of the magnitude of the channel influence, but is independent of a phase of the channel influence. Easing the channel estimation does not change the central tendency of the calculated function results transmitted over the multiple channel. Alternatively, on the side of the function receiver, a statistical quantity describing the multiple-access channel is determined. For this purpose, it is sufficient when the function variable value transmitters transmit constant power signals over the multiple-access channel in a channel estimation phase. Thus, the channel estimation effort is transferred to the function receiver and hence occurs less frequently, which again reduces the overall energy expenditure.