In a wireless communication system including a wireless transmit/receive unit (WTRU) which transfers data to a Node-B, data transmission parameters such as modulation and coding scheme (MCS) and transport block set (TBS) size are dynamically adjusted on a transmission time interval (TTI) basis, and hybrid-automatic repeat request (H-ARQ) processes used to control the transfer of data between the WTRU and the Node-B are initiated and released, as required. The WTRU transmits and retransmits data to the Node-B through an enhanced uplink (EU) dedicated channel (E-DCH) in accordance with data feedback information received from the Node-B. The WTRU queues data for transmission, and determines a transmission status of the data. The transmission status is set to one of “new transmission,” “successful transmission,” “retransmission” and “restarted transmission.” For each TTI, the WTRU initiates an EU transmission to the Node-B which identifies the assigned H-ARQ process, TBS size and MCS.