A base station used as a first base station of a Long Term Evolution, LTE, radio communication system including the first base station , a second base station communicating with the first base station, and user equipment communicating with the first base station, the base station comprising: an obtainer adapted to obtain, from the second base station, a first parameter used for generation of a signal of a physical downlink control format indicator channel, a second parameter used for generation of a signal of a physical downlink HARQ indicator channel, or a third parameter used for generation of a signal of a physical downlink control channel; a generator adapted to generate the signal of the physical downlink control format indicator channel, the signal of the physical downlink HARQ indicator channel, or the signal of the physical downlink control channel using the first parameter, the second parameter, or the third parameter; and a transmitter adapted to transmit the generated signal of the physical downlink control format indicator channel, the generated signal of the physical downlink HARQ indicator channel, or the generated signal of the physical downlink control channel; characterized by a storage adapted to store a plurality of preamble IDs used for a physical downlink control channel order in advance, wherein the obtainer is adapted to obtain the third parameter that does not include a preamble ID used for a notification of the physical downlink control channel order, and the generator is adapted to select one of the plurality of preamble IDs stored in the storage and generate the signal of the physical downlink control channel using the selected preamble ID and the third parameter that does not include the preamble ID used for the notification of the physical downlink control channel order. an obtainer adapted to obtain, from the second base station, a first parameter used for generation of a signal of a physical downlink control format indicator channel, a second parameter used for generation of a signal of a physical downlink HARQ indicator channel, or a third parameter used for generation of a signal of a physical downlink control channel; a generator adapted to generate the signal of the physical downlink control format indicator channel, the signal of the physical downlink HARQ indicator channel, or the signal of the physical downlink control channel using the first parameter, the second parameter, or the third parameter; and a transmitter adapted to transmit the generated signal of the physical downlink control format indicator channel, the generated signal of the physical downlink HARQ indicator channel, or the generated signal of the physical downlink control channel; characterized by a storage adapted to store a plurality of preamble IDs used for a physical downlink control channel order in advance, wherein the obtainer is adapted to obtain the third parameter that does not include a preamble ID used for a notification of the physical downlink control channel order, and the generator is adapted to select one of the plurality of preamble IDs stored in the storage and generate the signal of the physical downlink control channel using the selected preamble ID and the third parameter that does not include the preamble ID used for the notification of the physical downlink control channel order. <EOS>