Enhanced Machine Type Communications (eMTC) is a wireless communication technology with reduced system bandwidth. To improve spectral efficiency, user equipment (UE) is configured to receive first downlink control information (DCI) from a base station. The first DCI indicates a resource block (RB) sized frequency allocation for the UE. Additionally, the UE is configured to receive second DCI from the base station. The second DCI indicates a sub RB sized frequency allocation for the UE. The UE is configured to transmit a plurality of uplink data transmissions to the base station in a variable frequency allocation such that the plurality of uplink data transmissions switches between using the RB sized frequency allocation and the sub RB sized frequency allocation. Thus, by using the sub RB sized frequency allocation, more UEs can be allocated to the same RB without lowering the data rate thereby improving total uplink capacity.