serving radio terminal ue 2 different frequency bands srs transmission frequency bands that are used when the serving radio terminal ue 2 transmits srs at a timing of a predetermined special subframe at that time the radio base station enb 1 1 sets the srs transmission frequency band such that a bandwidth of a frequency band an srs transmission frequency band available for the transmission of srs in the serving radio terminal ue 2 is larger as priority setting priority of setting of the srs transmission frequency band which is determined according to a communication state of the serving radio terminal ue 2 is higher and transmits information on the set srs transmission frequency band to a radio terminal accordingly as setting priority corresponding to the serving radio terminal ue 2 is higher the serving radio terminal ue 2 increases an option of a frequency available for the transmission of the srs thereby easily avoiding interference from another radio base station enb 1 2 at the time of the transmission of the srs in other words easily reducing the interference furthermore the serving radio terminal ue 2 uses a frequency hopping scheme and transmits the srs at each special subframe timing while switching the srs transmission frequency band furthermore a common switching sequence is applied to each serving radio terminal ue 2 accordingly different srs transmission frequency bands at the timing of the predetermined special subframe are set to each serving radio terminal ue 2 so that srs transmission frequency bands at each special subframe are different for each serving radio terminal ue 2 accordingly each serving radio.