Method and apparatus for accessing a random access channel by selectively using dedicated or contention-based preambles

A method implemented in a wireless transmit/receive unit (WTRU) for random access during handover from a source base station to a target base station, the method comprising:

• receiving, from the source base station, a handover command, the handover command having dedicated preamble configuration information including an indication of a dedicated preamble, a dedicated preamble period, and a dedicated preamble reservation, wherein the dedicated preamble is used for contention free random access in a cell during available random access channel (RACH) opportunities of the dedicated preamble period, and wherein the dedicated preamble reservation indicates a subset of the available RACH opportunities of the dedicated preamble period during which the dedicated preamble is reserved for the WTRU;
• initiating a timer in response to the handover command;
• transmitting, to the target base station on a condition that the timer has not expired, the indicated dedicated preamble during a RACH opportunity selected from the indicated RACH opportunities for the dedicated preamble based on the dedicated preamble reservation;
• and
• transmitting, to the target base station subsequent to expiration of the timer and on a condition that RACH access using the dedicated preamble was not successful, a contention based preamble during a RACH opportunity selected from RACH opportunities for the contention based preamble.

A wireless transmit/receive unit (WTRU) configured for random access during handover from a source base station to a target base station, the WTRU comprising:

• a receiver configured to receive, from the source base station, a handover command, the handover command having dedicated preamble configuration information including an indication of a dedicated preamble, a dedicated preamble period, and a dedicated preamble reservation, wherein the dedicated preamble is used for contention free random access in a cell during available random access channel (RACH) opportunities of the dedicated preamble period, and wherein the dedicated preamble reservation indicates a subset of the available RACH opportunities of the dedicated preamble period during which the dedicated preamble is reserved for the WTRU;
• a timer configured to initiate in response to the handover command;
• and
• a transmitter configured to:
• transmit, to the target base station on a condition that the timer has not expired, the indicated dedicated preamble during a RACH opportunity selected from the indicated RACH opportunities for the dedicated preamble based on the dedicated preamble reservation;
• and
• transmit, to the target base station subsequent to expiration of the timer and on a condition that RACH access using the dedicated preamble was not successful, a contention based preamble during a RACH opportunity selected from RACH opportunities for the contention based preamble.

A communication station configured to manage random access of a wireless transmit/receive unit (WTRU), the communication station comprising:

• a transmitter configured to:
• transmit preamble configuration information including an indication of a preamble and a preamble period, wherein the preamble is used for random access by the WTRU during a random access channel (RACH) opportunity of the preamble period, wherein the preamble period spans a plurality of RACH opportunities;
• and
• transmit a preamble reservation to the WTRU, wherein the preamble reservation indicates a subset of the plurality of RACH opportunities during which the preamble is reserved for the WTRU.