Communication system, communication terminal, and network

Abstract

Provided is a technology that can increase the robustness of a communication system. A communication system includes: a communication terminal; a first network configured to perform radio communication with the communication terminal; and at least one second network configured to perform communication with the first network. When the first network determines to release connection between the first network and the communication terminal with the communication terminal being connected to the first network and to the at least one second network through the first network, the communication terminal or the first network instructs the at least one second network to release the connection with the communication terminal.

1 . A communication system, comprising:
 a communication terminal;   a first network configured to perform radio communication with the communication terminal; and   at least one second network configured to perform communication with the first network,   wherein when the first network determines to release connection between the first network and the communication terminal with the communication terminal being connected to the first network and to the at least one second network through the first network, the communication terminal or the first network instructs the at least one second network to release the connection with the communication terminal.   
     
     
         2 . The communication system according to  claim 1 ,
 wherein before the connection between the first network and the communication terminal is released, the communication terminal instructs the at least one second network to release the connection with the communication terminal through the first network.   
     
     
         3 . The communication system according to  claim 2 ,
 wherein after instructing the at least one second network to release the connection with the communication terminal, the communication terminal notifies the first network of acceptance of releasing the connection between the first network and the communication terminal.   
     
     
         4 . A communication terminal configured to perform radio communication with a first network,
 wherein when the first network notifies the communication terminal to release connection between the first network and the communication terminal with the communication terminal being connected to the first network and to at least one second network through the first network, the communication terminal instructs the at least one second network to release the connection with the communication terminal.   
     
     
         5 . A network configured to perform radio communication with a communication terminal and perform communication with at least another network,
 wherein when the network determines to release connection between the network and the communication terminal with the communication terminal being connected to the network and to the at least another network through the network, the network instructs the at least another network to release the connection with the communication terminal.