A method in a Multiple-Input Multiple-Output (MIMO) transmitter includes selecting a transmission mode from a group of modes including a spatial multiplexing mode and a transmit diversity mode. A rate matching parameter is set depending on at least the selected transmission mode. Data for transmission is formatted in one or more transport blocks, each transport block including multiple code blocks having respective lengths, in symbols, that are respective integer multiples of the rate matching parameter. The code blocks of a given transport block are mapped onto time-frequency resource elements in accordance with the selected transmission mode, such that each resource element contains data originating from only a respective one of the code blocks of the given transport block. The code blocks of the given transport block are transmitted over the time-frequency resource elements to a receiver.