Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive downlink control information that indicates a transmit precoding matrix indicator, that identifies a precoding matrix, and a set of demodulation reference signal (DMRS) antenna ports. A first association may be between a first set of antenna indices of the precoding matrix, that form a first transmission group, and a first code-division multiplexing (CDM) group of the set of DMRS antenna ports, and a second association may be between a second set of antenna indices of the precoding matrix, that form a second transmission group, and a second CDM group of the set of DMRS antenna ports. The UE may transmit an uplink transmission according to the first association and the second association. Numerous other aspects are provided.