A user equipment apparatus in a radio communication system in which uplink communication and downlink communication are dynamically changed includes a reception unit configured to receive, from a base station, control information indicating a resource for an uplink demodulation reference signal in a subframe used for transmitting uplink data; and a transmitting unit configured to transmit the uplink demodulation reference signal according to the control information; wherein the resource for the uplink demodulation reference signal is multiplexed into a part of resources corresponding to one or more symbols at a beginning of a data segment in the subframe used for transmitting the uplink data.