A User Equipment (UE) is described. The UE includes a processor and instructions stored in memory that is in electronic communication with the processor. The UE receives signaling to configure the UE with multiple serving cells wherein each of the multiple serving cells is configured with a first uplink/downlink (UL/DL) configuration. The UE also determines a downlink (DL)-reference UL/DL configuration for a serving cell. The UE further sends Physical Downlink Shared Channel (PDSCH) Hybrid Automatic Repeat Request Acknowledgement/Negative Acknowledgement (HARQ-ACK) information based on the DL-reference UL/DL configuration. In a case that the serving cell is a secondary cell and is configured with additional information enabling dynamic UL/DL reconfiguration, then the DL-reference UL/DL configuration is determined based on a pair formed by a primary cell UL/DL configuration and a secondary cell UL/DL configuration, wherein the secondary cell UL/DL configuration is determined based on at least a UL/DL configuration included in the additional information for the serving cell.