Method, base station and user equipment are disclosed for uplink transmission and control thereof. A base station transmits to a user equipment a first grant that schedules a first uplink transmission in a first at least one subframe over a first carrier. In response to a trigger event, the base station determines a second grant that schedules a second uplink transmission over the first carrier. The base station transmits the second grant to the UE over a second carrier that has a different frequency than the first carrier.