Systems and methods of signaling uplink control information in a mobile communication network using carrier aggregation are provided. In one exemplary embodiment, a method may include scheduling downlink transmissions to a first user terminal on a single downlink component carrier (CC) associated with a primary cell and scheduling downlink transmissions to a second user terminal on multiple downlink CCs or on a downlink CC associated with a non-primary cell. Further, the method may include receiving, on a first set of radio resources, control information associated with the downlink transmissions to the first user terminal. In addition, the method may include receiving, on a second set of radio resources, control information associated with the downlink transmissions to the second user terminal.