An infrastructure equipment forming part of a mobile communications network for transmitting signals to or receiving signals from communications devices, the infrastructure equipment comprising a transmitter configured to transmit signals to one or more of the communications devices in accordance with a wireless access interface formed by the infrastructure equipment, and a receiver configured to receive signals transmitted by one or more of the communications devices in accordance with the wireless access interface, a controller configured to control the transmitter and the receiver to transmit data to one or more of the communications devices via a downlink of the wireless access interface or receive data from the one or more communications devices via an uplink of the wireless access interface, wherein the wireless access interface includes communications resources for allocation to the communications device on the uplink and the downlink, the communications resources comprising frequency resources of a predetermined number of subcarriers, one or more of which can be allocated to the communications device, and time resources in which the wireless access interface is divided into predetermined time units, and the controller is configured in a combination with the transmitter and the receiver to identify a requirement to provide communications resources of the wireless access interface to one of the communications devices on the uplink or on the downlink, to determine a number of the subcarriers of the wireless access interface to be allocated to the communications device, to determine a transmission time interval for transmitting data to or receiving data from the communications device as a function of the number of the one or more subcarriers allocated to the communications device, and to transmit an indication on a downlink of the wireless access interface of the one or more subcarriers allocated to the communications device for receiving or transmitting the data, and the transmission time interval representing a number of the time units within which a transport block of the data is to be transmitted or to be received, the transmission time interval varying as a number of the time units. a transmitter configured to transmit signals to one or more of the communications devices in accordance with a wireless access interface formed by the infrastructure equipment, and a receiver configured to receive signals transmitted by one or more of the communications devices in accordance with the wireless access interface, a controller configured to control the transmitter and the receiver to transmit data to one or more of the communications devices via a downlink of the wireless access interface or receive data from the one or more communications devices via an uplink of the wireless access interface, wherein the wireless access interface includes communications resources for allocation to the communications device on the uplink and the downlink, the communications resources comprising frequency resources of a predetermined number of subcarriers, one or more of which can be allocated to the communications device, and time resources in which the wireless access interface is divided into predetermined time units, and the controller is configured in a combination with the transmitter and the receiver to identify a requirement to provide communications resources of the wireless access interface to one of the communications devices on the uplink or on the downlink, to determine a number of the subcarriers of the wireless access interface to be allocated to the communications device, to determine a transmission time interval for transmitting data to or receiving data from the communications device as a function of the number of the one or more subcarriers allocated to the communications device, and to transmit an indication on a downlink of the wireless access interface of the one or more subcarriers allocated to the communications device for receiving or transmitting the data, and the transmission time interval representing a number of the time units within which a transport block of the data is to be transmitted or to be received, the transmission time interval varying as a number of the time units.