A method of scheduling data transmission of transport blocks in an Orthogonal Frequency-Division Multiple Access communication system, wherein each of the transport blocks is transmitted with a respective transmission format and transmission power in a set of physical resource blocks in the frequency domain. The method identifies the relationship between transmission power and the block error rate for a set of transmission formats, and evaluates alternative transmission formats and different numbers of physical resource blocks for at least one of the transport blocks. The method determines a set of alternative transmission formats with different numbers of physical resource blocks, and determines a value indicating the total power difference required to transmit the transport block, while maintaining a target block error rate. The transport block is then transmitted with the alternative transmission format and different number of physical resource blocks if the value indicates that the total transmission power is less.