Communication system and communication terminal device

Abstract

Provided is a communication system with low latency and high reliability, etc. Even after transitioning from RRC_CONNECTED to RRC_INACTIVE, a communication terminal device maintains secondary base station configuration information on configuring a secondary base station Even when at least one of a master base station and a secondary base station is changed during the RRC_INACTIVE, the communication terminal device maintains the secondary base station configuration information. The communication terminal device again transitions to the RRC_CONNECTED using the maintained secondary base station configuration information.

1 . A communication system, comprising:
 a communication terminal device; and   a plurality of base stations configured to perform radio communication with the communication terminal device,   wherein the plurality of base stations include a master base station and a secondary base station that provide the communication terminal device with dual connectivity,   the communication terminal device maintains secondary base station configuration information on configuring the secondary base station even after transitioning from RRC_CONNECTED to RRC_INACTIVE,   the communication terminal device maintains the secondary base station configuration information even when at least one of the master base station and the secondary base station is changed during the RRC_INACTIVE, and   the communication terminal device again transitions to the RRC_CONNECTED using the maintained secondary base station configuration information.   
     
     
         2 . The communication system according to  claim 1 ,
 wherein the maintained secondary base station configuration information includes configuration information of Service Data Adaptation Protocol (SDAP), and   the communication terminal device again transitions to the RRC_CONNECTED using the maintained configuration information of the SDAP.   
     
     
         3 . A communication terminal device configured to perform radio communication with a plurality of base stations,
 wherein the plurality of base stations include a master base station and a secondary base station that provide the communication terminal device with dual connectivity,   the communication terminal device maintains secondary base station configuration information on configuring the secondary base station even after transitioning from RRC_CONNECTED to RRC_INACTIVE,   the communication terminal device maintains the secondary base station configuration information even when at least one of the master base station and the secondary base station is changed during the RRC_INACTIVE, and   the communication terminal device again transitions to the RRC_CONNECTED using the maintained secondary base station configuration information.