A base station includes: an area information generation unit which generates information for a determined second area by determining an additional assignment of the second area different from a first area to a component carrier (CC) of the first area having a bandwidth smaller than a bandwidth of a maximum assignable CC; a mapping control unit which controls an assignment of a reference signal to a frequency band including the first and second areas by generating the reference signal for channel estimation in the first and second areas; a signal generation unit which generates the information for the second area and the reference signal as a wireless signal; and a transmission unit for transmitting the generated wireless signal and is characterized by transmitting data to a user terminal and receiving the data from the user terminal by assigning the resources to the first and second areas.