Method and apparatus for cell reselection

Abstract

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.

What is claimed is: 
     
         1 . A method of operating a wireless network to communicate with a wireless transmit/receive unit (WTRU), the method comprising:
 receiving, via a source cell, a message sent from the WTRU, the message including information from measurements made on a plurality of neighboring cells by the WTRU;   transmitting, to the WTRU via the source cell, a handover message indicating that the WTRU is to change to a target cell, the target cell being one of the plurality of neighboring cells, and the handover message including i) a command that the WTRU is to cease using an enhanced radio network terminal identifier (E-RNTI) associated with the source cell and ii) a command that the WTRU is to reset at least one medium access control resource;   transmitting, to the WTRU via the source cell, an E-RNTI associated with the target cell; and   transmitting, to the WTRU via the target cell, resource allocation information to establish an enhanced dedicated channel for communication with the WTRU via the target cell.   
     
     
         2 . The method of  claim 1 , further comprising:
 releasing a resource allocated to the WTRU after the handover message is transmitted via the source cell.   
     
     
         3 . The method of  claim 1 , further comprising:
 receiving a random access preamble from the WTRU via the target cell.   
     
     
         4 . The method of  claim 1 , further comprising:
 assigning the transmitted E-RNTI by a radio network controller.   
     
     
         5 . A wireless network operable to provide a source cell and a target cell with respect to a wireless transmit/receive unit (WTRU), comprising:
 a first base station associated with the source cell to receive, via the source cell, a message sent from the WTRU, the message including information from measurements made by the WTRU on a plurality of neighboring cells, and to transmit, to the WTRU via the source cell, a handover message indicating that the WTRU is to change to the target cell, the target cell being one of the plurality of neighboring cells and the handover message including i) a command that the WTRU is to cease using an enhanced radio network terminal identifier (E-RNTI) associated with the source cell and ii) a command that the WTRU is to reset at least one medium access control resource; and   a second base station associated with the target cell,   wherein the first base station transmits, to the WTRU via the source cell, an E-RNTI associated with the target cell; and   wherein the second base station transmits, to the WTRU via the target cell, resource allocation information to establish an enhanced dedicated channel for communication with the WTRU via the target cell.   
     
     
         6 . The wireless network of  claim 5 , wherein the first base station releases a resource allocated to the WTRU after the handover message is transmitted via the source cell. 
     
     
         7 . The wireless network of  claim 5 , wherein the second base station receives a random access preamble from the WTRU via the target cell. 
     
     
         8 . The wireless network of  claim 5 , further comprising a radio network controller, wherein the transmitted E-RNTI is assigned to the WTRU by the radio network controller. 
     
     
         9 . A base station, comprising:
 a receiver; and   a transmitter;   wherein the receiver receives, via a source cell, a message sent from a wireless transmit/receive unit (WTRU), the message including information from measurements made by the WTRU on a plurality of neighboring cells, and   wherein the transmitter:
 transmits, to the WTRU via the source cell, a handover message indicating that the WTRU is to change to a target cell, the target cell being one of the plurality of neighboring cells and the handover message including i) a command that the WTRU is to cease using an enhanced radio network terminal identifier (E-RNTI) associated with the source cell and ii) a command that the WTRU is to reset at least one medium access control resource, and 
 transmits, to the WTRU via the source cell, an E-RNTI associated with the target cell. 
   
     
     
         10 . The base station of  claim 9 , wherein the base station releases a resource allocated to the WTRU after the handover message is transmitted via the source cell. 
     
     
         11 . The base station of  claim 9 , wherein the receiver further receives a random access preamble from the WTRU via the target cell. 
     
     
         12 . The base station of  claim 9 , wherein the transmitted E-RNTI is assigned to the WTRU by a radio network controller. 
     
     
         13 . The base station of  claim 9 , wherein the base station is one of a Node-B, an access point, a site controller, and an interfacing device.