US Patent 9763203 Cell timing in a wireless device and base station

A plurality of cells are grouped into a primary cell group and a secondary cell group. The wireless device receives a timing advance command comprising a time adjustment value and an index of the secondary cell group. The wireless device applies the time adjustment value to uplink transmission timing of the secondary cell group. The wireless device triggers an action when the difference between primary cell group timing and secondary cell group timing is greater than a value.