Patent ID: 8331316

Claim:
A mobile communication system comprising a plurality of nodes, hierarchically connected to each other, including a source base station wirelessly connected to a mobile terminal, and a target base station to which the mobile terminal connects after moving, a U-plane management station defined as a high-order node connected to both of the source base station and the target base station and managing a user plane, including: a first processor which executes processes comprising: detecting a handover for the mobile terminal; and transmitting, when detecting the handover for the mobile terminal, the same user data addressed to the mobile terminal toward both of the source base station and the target base station, the target base station including: a second processor which executes processes comprising: receiving the user data addressed to the mobile terminal, which is transmitted by the U-plane management station, and retaining the user data; and a wireless transmitter to wirelessly transmit, when receiving, from the mobile terminal, a handover confirm message including at least one identification number specifying the user data desired by the mobile terminal, the user data desired by the mobile terminal in the user data retained by the second processor and addressed to the mobile terminal, a third processor of the source base station executing: managing, when receiving the user data and identifying information specifying the user data wirelessly transmitted from the mobile terminal after detecting the handover for the mobile terminal, a sequence of the received user data based on the identifying information specifying the user data; and forwarding, if the third processor determines that the received user data is received in a due sequence, the received user data to the U-plane management station, and, whereas if the third processor determines that the received user data is not received in the due sequence, does not forward but retains the received user data.