A method is provided for arranging transmissions on a downlink carrier c, spanning a frequency range Fc, in a mobile radio communications system, wherein a bandwidth of Fc belongs to a set of predefined channel bandwidths in the communications system, and wherein the carrier c comprises a reference signal defined in the communications system. A configurable frequency range FRS comprising a set of time-frequency resources for comprising the reference signal of the carrier c is provided. Information associated with the configuration of the frequency range FRS is signaled to a receiver in the communications system, such that c can be deployed over a frequency range F smaller than Fc when the frequency range FRS is configured within F and any other transmissions on the carrier c are arranged to be within F.