When a dynamic channel allocation method based on monitoring of signal levels is used for channel allocation, the results of signal level measurements must be averaged in order to achieve a sufficient reliability. Averaging causes a delay in measurement results, for which reason such a channel may be allocated the interference level of which has just changed e.g. because another connection has been set up which functions nearby on the same channel. According to the invention, allocation of a channel causing excessive interference with a connection already set up is limited.