Methods and apparatus for signaling scheduling information in a spatial multiplexing wireless communications system (700), as well as corresponding methods and apparatus for processing such signaling information, are disclosed. An exemplary method for signaling scheduling information comprises scheduling (310, 420) first and second transport blocks (110) for simultaneous transmission during a first transmission interval on first and second data substreams, respectively, and further comprises assigning (320, 430) a single re-transmission process identifier for the first transmission interval and transmitting (330, 440) first scheduling information for the first transmission interval. The first scheduling information comprises the re-trans-mission process identifier and first disambiguation data. The method further comprises scheduling (360, 470) at least one of the first and second transport blocks (110) for re-transmission during a second transmission interval and transmitting (370, 495) second scheduling information for the second transmission interval, the second scheduling information comprising the re-transmission process identifier and second disambiguation data. The first and second disambiguation data indicate whether the re-transmission of the retransmitted transport block (110) is scheduled for the first or second data substream and may be used by a receiver to determine the same