Communication system

Abstract

In a communication system according to the present invention, a UE and an MeNB perform both a direct communication and a communication through a SeNB. Along with moving of the UE, a handover process of switching the MeNB to which the UE is connected, from an S-MeNB to a T-MeNB is performed. The connection between the UE and the SeNB is maintained during the handover process. The UE starts transmitting data to the SeNB before a communication path between the UE and the MeNB is changed from a path formed by the S-MeNB and the UE to a path formed by the T-MeNB and the UE.

1 . (canceled) 
     
     
         2 . A communication system comprising:
 a user equipment; and   a plurality of base stations configured to perform radio communication with the user equipment,   wherein the plurality of base stations include:
 a first master base station and a secondary base station that provide a dual connectivity for the user equipment; and 
 a second master base station that provides the dual connectivity for the user equipment along with the secondary base station instead of the first master base station due to a handover, 
 the user equipment maintains a connection with the secondary base station during the handover from the first master base station to the second master base station and starts transmitting uplink data to the secondary base station before completion of a connection between the user equipment and the second master base station, 
 the secondary base station is connected to the second master base station in the handover and starts transmitting the uplink data to the second master base station before completion of the connection between the user equipment and the second master base station, the uplink data being received from the user equipment before completion of the connection between the user equipment and the second master base station, and 
 the second master base station starts transmitting the uplink data to a higher node before completion of the connection between the user equipment and the second master base station, the uplink data being received from the user equipment via the secondary base station before completion of the connection between the user equipment and the second master base station. 
   
     
     
         3 . The communication system according to  claim 2 ,
 wherein the second master base station transmits, to the user equipment via the secondary base station, a notification of transmission of the uplink data to the higher node, and   the user equipment discards the uplink data in a buffer upon reception of the notification.