HARQ in spatial multiplexing MIMO system

A method and apparatus for signaling scheduling information in a spatial multiplexing wireless communications system, as well as corresponding methods and apparatus for processing such signaling information, are disclosed. Signaling scheduling information includes scheduling first and second transport blocks for simultaneous transmission during a first transmission interval on first and second data substreams, respectively, and assigning a single re-transmission process identifier for the first transmission interval and transmitting first scheduling information for the first transmission interval. The first scheduling information includes the re-transmission process identifier and first disambiguation data. Additionally, at least one of the first and second transport blocks is scheduled for re-transmission during a second transmission interval. Second scheduling information for the second transmission interval is also transmitted; the second scheduling information including the re-transmission process identifier and second disambiguation data.