Method and apparatus for maintaining uplink synchronization and reducing battery power consumption

A wireless transmit/receive unit (WTRU) comprising:

• a transceiver, and
• a processor coupled to the transceiver, the processor configured to:
• receive discontinuous reception (DRX) control information from a wireless network, the DRX control information indicating a time interval that the WTRU should monitor a downlink control channel;
• receive a control message on the downlink control channel while monitoring the downlink control channel according to the DRX control information, wherein the control message is associated with an identifier of the WTRU, the control message indicating that the WTRU should transmit a random access preamble to the wireless network;
• transmit the random access preamble to the wireless network in response to receiving the control message;
• and
• receive a timing adjustment command from the wireless network.

A wireless transmit/receive unit (WTRU) comprising:

• a transceiver, and
• a processor coupled to the transceiver, the processor configured to:
• receive discontinuous reception (DRX) control information from a wireless network, the DRX control information indicating a time interval that the WTRU should monitor a downlink control channel;
• receive a control message on the downlink control channel while monitoring the downlink control channel according to the DRX control information, wherein the control message is associated with an identifier of the WTRU, the control message indicates that the WTRU should transmit a random access preamble to the wireless network, and the control message is indicative of a time and resource for the WTRU to transmit the random access preamble;
• transmit the random access preamble to the wireless network in response to receiving the control message;
• and
• receive a timing adjustment command from the wireless network.