Method, transmitter, receiver and system for data back-transmission

A method and system for data back-transmission are provided in the present invention. The method includes the following steps: the source enhanced Node B (eNB) fills the COUNT comprising the SN and HFN corresponding to the first one of the second type packets into the DL COUNT Value of a SN Status Transfer message, transmits the SN Status Transfer message and transmits the first type packet with its own SN; the target eNB receives the SN Status Transfer message, which is transmitted from the source eNB and filled with the COUNT, and receives the first type packet with its own SN, wherein the first type packet is transmitted from the source eNB; the target eNB analyzes the received first type packet to obtain the SN carried by the first type packet, analyzes the DL COUNT Value in the SN Status Transfer message to obtain the SN and HFN corresponding to the COUNT, and allocates the SN and HFN to the first type packet by comparing the SN carried by the first type packet with the SN corresponding to the COUNT obtained from the DL COUNT Value of the SN Status Transfer message. The system comprises a transmitter and a receiver. The method and system of the present invention ensure correct processing of packets, increase the success rate of decryption after UE receives packets, and ensure the data continuity during the handover process.