Abstract: A base station transmits an RRC message to modify a first cell group index of a first cell. If the first cell is a primary cell, the RRC message reconfigures the primary cell as a secondary cell with an updated first cell group index and the RRC message comprises mobility control information. If the first cell is a secondary cell, the RRC message releases the secondary cell and adds the secondary cell with an updated first cell group index without employing mobility control information.

Abstract: A wireless device receives a control command causing transmission of a random access preamble on a reference secondary cell in a secondary cell group. The reference secondary cell is employed as a timing reference to transmit first uplink signals in the secondary cell group. The wireless device receives a random access response comprising a timing advance command for the secondary cell group. The wireless device, autonomously and when a predefined condition is met, selects a new activated secondary cell in the secondary cell group as the timing reference.