Methods, apparatus and computer program products define additional resource elements of a physical resource block (PRB) to be allocated for the provision of channel state information reference signals in a manner that does not create issues relating to backwards compatibility for legacy mobile terminals. A method may include receiving a definition of a plurality of resource elements of a PRB to be allocated for provision of channel state information reference signals. At least some of the plurality of resource elements of the PRB that are allocated for the provision of channel state information reference signals correspond in position to resource elements of the PRB that are interpreted by a different type of mobile terminal to be muted. The method also causes channel state information reference signals to be received via the plurality of resource elements of the PRB that are allocated for the provision of channel state information reference signals.