Some techniques are disclosed for determining downlink control information for use in each cell in carrier aggregation using a FDD cell and a TDD cell together. One aspect of the present invention relates to user equipment, comprising: a transmission and reception unit configured to transmit and receive a radio channel to/from a base station via multiple cells configured for carrier aggregation in accordance with a frequency division duplex (FDD) mode and a time division duplex (TDD) mode; a cell management unit configured to manage the multiple cells; and a communication control unit configured to determine whether a duplex mode applied to a primary cell in the multiple cells is either the FDD mode or the TDD mode and receive and demodulate downlink control information compliant with the determined duplex mode for each carrier aggregation implemented cell.