Patent ID: 8891485

Claim:
A mobile station, comprising: a receiving means for receiving first Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) from a source base station and second PDCP-PDU from a target base station, in which the second PDCP-PDU being created by using sequence number and Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) that are transferred from the source base station to the target base station by a user plane message which includes the user plane message header, one PDCP SDU, and the corresponding sequence number of the PDCP SDU; a storage means for storing PDCP SDUs corresponding to the first PDCP PDU and to the second PDCP PDU; and a reordering means for performing in-sequence delivery of the stored PDCP SDUs based on the sequence numbers, wherein the user plane message is transferred via a user plane from the source base station to the target base station.