Synchronizing uplink and downlink transmissions by a wireless user equipment (UE) device. A connection with a network may be established via a wireless link with a cell. The UE may operate in an active state during first periods of time in which uplink or downlink communications may be performed between the UE and the network. The UE may operate in a reduced-power state during second periods of time in which uplink and downlink communications are not performed. The first periods of time may alternate with the second periods of time in a repeating manner. Uplink data generated by the UE may be buffered during second periods of time and transmitted during first periods of time. Buffering uplink data in this manner may prevent the UE from immediately transitioning from the reduced-power state to the active state to transmit uplink data, which may conserve battery of the UE.