A data transmission method in a telecommunication system utilizing frequency hopping and the system having a limit for allowable interference. The method includes performing at least two frequency hopping layers, each layer comprising one or more frequency hopping areas, the frequency hopping layers having frequency hopping parameters divergent from each other, setting the frequency hopping layers one on the other in such a way that the overlapping of the border zones of the frequency hopping areas is minimized, estimating interference in the system or in a predetermined part of the system, and if the interference is too high, transferring one or more users to another frequency hopping layer.