Fade margin measurement in a radio system

Abstract

The invention relates to a method for measuring the fade margin in a radio system. The system comprises at least one transmitter (11,; 11,) and at least one receiver (12,; 12,) which in an operational situation establish a fixed radio connection. In the method, the receiver is calibrated by supplying the receiver with an input signal at several different power levels and determining the correspondence between the supplied signal level and a quantity detected by the receiver. To enable the fade margin to be determined as simply as possible, (a) the calibration is carried out in such a way that at least one supplied power level is close to the noise level of the receiver, (b) in a situation where substantially mere noise is suued into the payload signal, a threshold value (PTH1) for the received signal level, corresponding to a predetermined bit error ratio, is determined for the receiver (c), in an operational situation of the radio system, the signal level arriving at the receiver is determined without payload signal, (d) on the basis of the calibration data and the level determined in step (c), that threshold value for the received signal level which corresponds to said predetermined bit error ratio in the operational situation of the radio system is determined, and (e) the fade margin is determined on the basis of the threshold value for the operational situation and the signal level measured in the operational situation of the system.