A method for controlling the allocation of hybrid automatic repeat request, HARQ, resources during a semi-persistent scheduling session, the method comprising: a wireless transmit/receive unit, WTRU, reserving a subset of a plurality of HARQ process identification, IDs, for semi-persistent scheduling; the WTRU determining a HARQ process ID for a downlink, DL, transmission associated with an allocation of a semi-persistent resource and a system frame number, SFN, wherein the HARQ process ID is one of the subset of the plurality of HARQ process IDs reserved for semi-persistent scheduling and the SFN is used to determine that the HARQ process ID is to be used for processing the DL transmission; the WTRU receiving a dynamic allocation that includes the HARQ process ID via a physical downlink control channel, PDCCH, when semi-persistently scheduled data associated with the determined HARQ process ID has been successfully transmitted and before the HARQ process associated with the determined HARQ process ID will be used at a subsequent transmission opportunity that is associated with the allocation of the semi-persistent resource corresponding to a subsequent SFN; the WTRU determining to suspend HARQ processing for the dynamic allocation that includes the HARQ process ID based on: reaching the subsequent transmission opportunity; and data associated with the dynamic allocation that includes the HARQ process ID not being successfully transmitted; the WTRU replacing any data in a buffer configured to store the data associated with the dynamic allocation that includes the HARQ process ID upon the data associated with the dynamic allocation that includes the HARQ process ID not being successfully transmitted; and the WTRU using the HARQ process to process data received at the subsequent transmission opportunity associated with the allocation of the semi-persistent resource. a wireless transmit/receive unit, WTRU, reserving a subset of a plurality of HARQ process identification, IDs, for semi-persistent scheduling; the WTRU determining a HARQ process ID for a downlink, DL, transmission associated with an allocation of a semi-persistent resource and a system frame number, SFN, wherein the HARQ process ID is one of the subset of the plurality of HARQ process IDs reserved for semi-persistent scheduling and the SFN is used to determine that the HARQ process ID is to be used for processing the DL transmission; the WTRU receiving a dynamic allocation that includes the HARQ process ID via a physical downlink control channel, PDCCH, when semi-persistently scheduled data associated with the determined HARQ process ID has been successfully transmitted and before the HARQ process associated with the determined HARQ process ID will be used at a subsequent transmission opportunity that is associated with the allocation of the semi-persistent resource corresponding to a subsequent SFN; the WTRU determining to suspend HARQ processing for the dynamic allocation that includes the HARQ process ID based on: reaching the subsequent transmission opportunity; and data associated with the dynamic allocation that includes the HARQ process ID not being successfully transmitted; reaching the subsequent transmission opportunity; and data associated with the dynamic allocation that includes the HARQ process ID not being successfully transmitted; the WTRU replacing any data in a buffer configured to store the data associated with the dynamic allocation that includes the HARQ process ID upon the data associated with the dynamic allocation that includes the HARQ process ID not being successfully transmitted; and the WTRU using the HARQ process to process data received at the subsequent transmission opportunity associated with the allocation of the semi-persistent resource.