Method and apparatus for random access in multicarrier wireless communications

A wireless transmit/receive unit (WTRU) capable of transmission via a multi-carrier uplink, the WTRU comprising:

• a processor, a receiver, and a transmitter;
• the receiver operably coupled to the processor, the receiver configured to:
• receive an indication of a threshold value associated with path loss;
• and
• receive random access channel (RACH) configuration information including an indication of one or more frequency resources;
• the processor configured to:
• select an uplink carrier of a plurality of uplink carriers as a selected uplink carrier, wherein, on a first condition that a measurement result is below the threshold value, a first uplink carrier of the plurality of uplink carriers is selected, and on a condition that the measurement result is not below the threshold value, a second uplink carrier of the plurality of uplink carriers is selected;
• and
• the transmitter operably coupled to the processor, the transmitter configured to send a random access preamble in a physical random access channel (PRACH) transmission using at least a portion of the one or more frequency resources of the selected uplink carrier;
• wherein a random access radio network temporary identifier (RA-RNTI) is associated with the PRACH transmission, and wherein the RA-RNTI is a function of:
• a carrier ID of the selected uplink carrier, a time index associated with the PRACH transmission, and an index of the at least a portion of the one or more frequency resources.