Control of Time Alignment Timer in Wireless Device Timing Advance Measurement for Mobility

A wireless device comprising:

• one or more processors;
• and
• memory storing instructions that, when executed by the one or more processors, cause the wireless device to:
• receive one or more radio resource control (RRC) messages comprising configuration parameters of a layer-1 or layer-2 triggered mobility (LTM) candidate configuration for an LTM procedure, wherein the configuration parameters comprise:
• a configuration index of the LTM candidate configuration;
• and
• a physical cell identifier (PCI) of a cell for the LTM procedure;
• receive an LTM cell switch command medium access control (MAC) control element (CE), wherein the LTM cell switch command MAC CE:
• comprises the configuration index of the LTM candidate configuration;
• and
• does not comprise a timing advance command (TAC) with a timing adjustment value for a primary timing advance group (PTAG) of the cell;
• and
• measure a timing advance of the cell;
• and
• in response to the receiving the LTM cell switch command not comprising the TAC with the timing adjustment value for the PTAG and after the measuring of the timing advance, start a time alignment timer associated with the PTAG.