In a general aspect, a User Equipment (UE) in a cellular communications network receives a Radio Resource Control (RRC) signaling message from a base station communicatively coupled to the UE over a communications channel. The UE accesses a search space in the RRC signaling message. The UE identifies a fallback Downlink Control Information (DCI) Information Element (IE) included in the search space. The UE determines whether an aggregation factor is indicated in the fallback DCI IE for shared channel communications with the base station, over multiple slots in the communications channel. The UE determines an uplink/downlink (UL/DL) configuration for transmission on the communications channel. The UE schedules an aggregated transmission over multiple slots in the communications channel based on the aggregation factor and the uplink/downlink configuration.