According to one embodiment of the present invention, a method and a device for improving communication quality in a mobile communication network are provided, and the method further comprises the steps of transmitting downlink packets for IP-based voice traffic to a terminal in a radio link unacknowledged mode (RLC UM) and storing at least one packet among the downlink packets for retransmission. In addition, the present invention provides a communication method and device of a target base station for retransmitting the stored packet to the terminal. Furthermore, the present invention provides a method and a device of a terminal that receives a packet from the target base station.