Radio terminal, radio terminal controlling apparatus and location registration auxiliary apparatus

A radio terminal controlling apparatus, comprising:

• receiving means for receiving, via an Internet protocol network, a first location registration request for registering a radio terminal of a first cellular network with a second cellular network existing in an area different from the area in which the radio terminal exists;
• selecting means for selecting a location registration auxiliary apparatus for aiding the location registration with said second cellular network based on said first location registration request;
• and
• transferring means for transferring said first location registration request to said selected location registration auxiliary apparatus.

A radio terminal, comprising:

• a first communication interface for connecting to a cellular network;
• a second communication interface for connecting to an Internet protocol network;
• first message generating means for generating a first location registration message for registering with said cellular network;
• second message generating means for generating a second location registration message based on said first location registration message;
• and
• sending controlling means for, controlling said first communication interface to have said first location registration message sent when registering with said cellular network via said first communication interface, and controlling said second communication interface to have said second location registration message sent when registering with said cellular network via said second communication interface and said Internet protocol network.

A radio terminal controlling method comprising the steps of:

• from a radio terminal having a first communication interface for connecting to a cellular network and a second communication interface for connecting to an Internet protocol network, receiving a location registration request sent via said second communication interface;
• storing a correspondence between identification information on said radio terminal and an address based on said received location registration request;
• in the case where said location registration request is not a location registration message in compliance with a standard of said cellular network, converting the location registration request into a location registration message in compliance therewith;
• and
• sending to the cellular network the location registration message in compliance with the standard of said cellular network.

A radio terminal controlling method, comprising the steps of:

• receiving, via an Internet protocol network, a first location registration request for registering a radio terminal of a first cellular network with a second cellular network existing in an area different from the area in which the radio terminal exists;
• selecting a location registration auxiliary apparatus for aiding the location registration with said second cellular network based on said first location registration request;
• and
• transferring said first location registration request to said selected location registration auxiliary apparatus.

A location registration method in a radio terminal having a first communication interface for connecting to a cellular network and a second communication interface for connecting to an Internet protocol network, comprising the steps of:

• generating a first location registration message for registering with said cellular network;
• converting said first location registration message into a second location registration message;
• and
• controlling said first communication interface to have said first location registration message sent when registering with said cellular network via said first communication interface, and controlling said second communication interface to have said second location registration message sent when registering with said cellular network via said second communication interface and said Internet protocol network.

A radio terminal emulation method, comprising the steps of:

• receiving a activation request for activating a virtual terminal unit emulating a radio terminal in compliance with a standard of a cellular network from any user terminal connected to an Internet protocol network;
• activating the virtual terminal unit in said Internet protocol network based on said activation request;
• storing a correspondence between said activated virtual terminal unit and said user terminal;
• and
• having a location registration request to said cellular network sent by said activated virtual terminal unit.