Technology for reporting periodic channel state information (CSI) is disclosed. One method can include determining a reporting period (Npd) of a user equipment (UE) for a serving cell. A Time-Division Duplex (TDD) uplink-downlink (UL-DL) configuration of a primary cell of the UE can be identified. A periodic CSI report for the serving cell can be transmitted, from the UE to the eNB, using a physical uplink control channel (PUCCH) on the primary cell according to the reporting period. The reporting period of Npd=1 can be used for the serving cell if the TDD UL-DL configuration of the primary cell is one of 0, 1, 3, 4, or 6 and all UL subframes of the primary cell in a radio frame are used for periodic CSI reporting.