A network device in a wireless communication system includes a first communication circuit that receives a first control-plane message from a base station (BS) over a first communication link; a second communication circuit that transmits user-plane data to a user equipment (UE) over a second communication link established responsive to the first control-plane message; and a third communication circuit that receives the user-plane traffic data from a server over a third communication link. The UE communicates user-plane data with the BS and the network device simultaneously at a predetermined time. The first communication circuit receives a second control-plane message from the BS. The second communication circuit transmits a pilot signal to the UE responsive to the second control-plane message to enable the UE to measure a radio link quality of the second communication link using the pilot signal. The second communication link is maintained, at least in part, based on the radio link quality of the second communication link.