Method and apparatus for efficient handling of the updates of serving/neighbor cell information

A method performed by a wireless transmit receive unit (WTRU), the method comprising:

• receiving configuration information including information regarding a change in an identity of a serving cell, one or more conditions for the change in the identity of the serving cell, and associated WTRU behavior, wherein the configuration information includes a new identity or a set of equivalent new identities;
• monitoring the one or more conditions for the change in the identity of the serving cell;
• on a condition that the one or more conditions for the change in the identity of the serving cell are fulfilled:
• determining that the WTRU does not detect a cell with an identity of a current serving cell;
• in response to the determining, searching for a cell with the new identity or one of the equivalent new identities;
• and
• on a condition that the WTRU detects a cell with the new identity or one of the equivalent new identities, changing the identity of the serving cell to the new identity, or one of the equivalent new identities;
• deriving one or more new security keys based on the new cell identity;
• and
• using the one or more new security keys according to a configured security key handling behavior.