US Patent 11412422 Handover in unlicensed band

A wireless device receives a radio resource control message from a base station that indicates a handover from a first cell of the first base station to a second cell of a second base station. During the handover, a DCI from the second base station is received that indicates a random access channel occasion. The random access channel occasion is determined and used to transmit a preamble to the second base station. Once a response to the preamble is received, the wireless device transmits a message to the second base station to indicate a completion of the handover.