A method and a base station are disclosed. The base station includes a receiver and a transmitter. The base station transmits, to a primary downlink cell, a first scheduling assignment for a first uplink transmission and receives first data in the first uplink transmission to at least a primary uplink cell using a first hybrid automatic repeat request (HARQ) process. The base station transmits, to the primary downlink cell, a second scheduling assignment indicating, the second scheduling assignment indicating a hybrid automatic repeat request (HARQ) process identification of the first HARQ process, a modulation and coding set (MCS), and a transmission time opportunity; and receives the first data in a second uplink transmission using the first HARQ process, the MCS, and the transmission time opportunity, wherein the first data is received in a transmission based on the HARQ process identification.