This disclosure relates to carrier aggregation using separate RLC entities for different component carriers. According to one embodiment, a base station and a wireless device may establish a primary component carrier and at least one secondary component carrier according to a first radio access technology. Separate radio link control entities may be established for the primary component carrier and the secondary component carrier. Data communicated between the base station and the wireless device may be routed by way of the primary component or the secondary component carrier based on differing characteristics of the component carriers, and the RLC entities may treat downlink data differently on the primary component carrier and the secondary component carrier based on the differing characteristics of the component carriers.