METHOD AND APPARATUS FOR CELL RESELECTION
A method and wireless transmit receive unit (WTRU) are disclosed that is configured to perform cell reselection to another cell when the WTRU is in a CELL_FACH state using an Enhanced-Dedicated Channel (E-DCH). The cell reselection is based on internal measurements by the WTRU. Alternatively, the cell reselection can be WTRU based on the WTRU measurements reported to the network.
1 . A method performed by a wireless transmit/receive unit (WTRU), the method comprising:
communicating with a source cell;
performing measurements on a plurality of neighboring cells;
transmitting, via the source cell, information from the measurements;
receiving, via the source cell, a message indicating that the WTRU is to communicate via a target cell, the target cell being one of the plurality of neighboring cells; and
after receiving the message:
ceasing using an enhanced radio network terminal identifier (E-RNTI) associated with the source cell;
resetting a medium access control;
receiving, via the source cell, an E-RNTI associated with the target cell; and
communicating, via the target cell, using the received E-RNTI.
2 . The method of claim 1 , further comprising receiving resource allocation information via the target cell.
3 . The method of claim 2 , wherein the communicating via the target cell includes communicating over an enhanced dedicated channel in accordance with the resource allocation information.
4 . The method of claim 1 , further comprising:
initiating a timer in response to the received message.
5 . The method of claim 1 , wherein the received message is a handover message.
6 . The method of claim 1 , wherein the received message includes an identification of the target cell.
7 . The method of claim 1 , wherein the resetting of the medium access control includes flushing a hybrid automatic retransmission request buffer in the WTRU.
8 . The method of claim 1 , wherein the resetting of the medium access control includes resetting a transmission sequence number in the WTRU.
9 . The method of claim 1 , further comprising:
transmitting, in response to the received message, a random access preamble via the target cell.
10 . The method of claim 1 , wherein the received E-RNTI is assigned to the WTRU by a radio network controller.
11 . A wireless transmit/receive unit (WTRU) comprising:
a transmitter;
a receiver; and
a processor to:
perform measurements by the receiver on signals received from a plurality of neighboring cells;
cause the transmitter to transmit, via a source cell, information from the measurements;
process a message received by the receiver via the source cell, the message indicating that the WTRU is to communicate via a target cell, the target cell being one of the plurality of neighboring cells; and
after processing the message, reset a medium access control, cease using an E-RNTI associated with the source cell, and cause the WTRU to communicate, via the target cell, using an enhanced radio network temporary identifier (E-RNTI) associated with the target cell and received by the receiver via the source cell.
12 . The WTRU of claim 11 , wherein the processor processes resource allocation information received by the receiver via the target cell.
13 . The WTRU of claim 12 , wherein the WTRU communicates, via the target cell, over an enhanced dedicated channel in accordance with the resource allocation information.
14 . The WTRU of claim 11 , wherein the processor initiates a timer in response to the message received by the receiver.
15 . The WTRU of claim 11 , wherein the message received by the receiver is a handover message.
16 . The WTRU of claim 11 , wherein the message received by the receiver includes an identification of the target cell.
17 . The WTRU of claim 11 , wherein the resetting of the medium access control by the processor includes the processor flushing a hybrid automatic retransmission request buffer in the WTRU.
18 . The WTRU of claim 17 , wherein resetting of the medium access control by the processor includes the processor resetting a transmission sequence number in the WTRU.
19 . The WTRU of claim 11 , wherein the received E-RNTI is assigned to the WTRU by a radio network controller.
20 . The WTRU of claim 11 , wherein the processor, in response to the message received by the receiver, causes the transmitter to transmit a random access preamble via the target cell.