The set of resource aggregation levels available for forming an enhanced control channel message may vary from one subframe to another, based on the level of puncturing in the transmitted subframes. An example method begins with determining (2710) members of a set of aggregation levels usable to aggregate the non-overlapping subsets of resource elements for transmitting downlink control information. This determining is based on a puncturing level to be used for the transmission of the downlink control information. Downlink control information for the given subframe is mapped (2720) to one or more non-overlapping subsets of resource elements in the at least one block of time-frequency resources, according to an aggregation level selected from the determined set, and then transmitted (2730), in the one or more non-overlapping subsets. This method may be repeated for each of several subframes, where the puncturing may differ from one subframe to another.