An apparatus comprising: a communication unit configured to perform radio communication; and a control unit configured to - determine a filter length of a filter, which is applied to transmission data, in accordance with at least one of a frequency resource and a time resource for the radio communication, wherein the control unit is configured, - in case a guard interval is added to the transmission data after application of the filter, to determine the filter length and a guard interval length of the guard interval such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - in case a guard interval is not added to the transmission data after application of the filter, to determine the filter length such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - perform control such that control information regarding the filter length of the filter for limiting a width of a guard band in a frequency band to be used in the radio communication is transmitted to an external apparatus through the radio communication as part of radio resource control signaling, as part of system information or as part of downlink control information. a communication unit configured to perform radio communication; and a control unit configured to - determine a filter length of a filter, which is applied to transmission data, in accordance with at least one of a frequency resource and a time resource for the radio communication, wherein the control unit is configured, - in case a guard interval is added to the transmission data after application of the filter, to determine the filter length and a guard interval length of the guard interval such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - in case a guard interval is not added to the transmission data after application of the filter, to determine the filter length such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - perform control such that control information regarding the filter length of the filter for limiting a width of a guard band in a frequency band to be used in the radio communication is transmitted to an external apparatus through the radio communication as part of radio resource control signaling, as part of system information or as part of downlink control information. - determine a filter length of a filter, which is applied to transmission data, in accordance with at least one of a frequency resource and a time resource for the radio communication, wherein the control unit is configured, - in case a guard interval is added to the transmission data after application of the filter, to determine the filter length and a guard interval length of the guard interval such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - in case a guard interval is not added to the transmission data after application of the filter, to determine the filter length such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - in case a guard interval is added to the transmission data after application of the filter, to determine the filter length and a guard interval length of the guard interval such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - in case a guard interval is not added to the transmission data after application of the filter, to determine the filter length such that a resulted data length in a time direction of transmission data is equal to a data length in the time direction of the transmission data to which a guard interval is added but the filter is not applied, and - perform control such that control information regarding the filter length of the filter for limiting a width of a guard band in a frequency band to be used in the radio communication is transmitted to an external apparatus through the radio communication as part of radio resource control signaling, as part of system information or as part of downlink control information.