Method for changing voice coding mode, communication system, communication network and communication terminal

A communication system capable of voice communication between terminals included in different networks, comprising:

• a first network connected by a radio link to at least one first terminal having a first voice codec allowing any coding mode to be selected from a plurality of coding modes, monitoring the communication situation including quality of the radio link during voice communication of said first terminal to determine an appropriate coding mode based on the communication situation, and requesting said first terminal to make a change to said appropriate coding mode;
• and
• a second network connected to at least one second terminal capable of communicating with said first terminal, having at least one second voice codec allowing any coding mode to be selected from a plurality of coding modes, giving said second voice codec to said second terminal when said first terminal starts communicating with said second terminal, and changing the coding mode of said second voice codec given to said second terminal communicating with said first terminal upon reception of a request for change of the coding mode from the first terminal requested to change the coding mode by said first network.

A communication network connected to by a radio link to at least one first terminal having a voice codec allowing any coding mode to be selected from a plurality of coding modes, and also connected to another network having at least one voice codec allowing any coding mode to be selected from a plurality of coding modes to make it possible to establish communications between a second terminal given the voice codec of said another network and said first terminal, comprising:

• a monitoring apparatus monitoring the communication situation including quality of the radio link during voice communication of said first terminal;
• and
• a control apparatus determining an appropriate coding mode based on said communication situation, requesting said first terminal to make a change to said appropriate coding mode, and receiving from said first terminal a response indicating the fact that the coding modes of the voice codec of the first terminal and the voice codec given to the second terminal communicating with the first terminal are changed to confirm that the coding modes are changed.

A communication apparatus in a communication system connected by a radio link to at least one first terminal having a voice codec allowing any coding mode to be selected from a plurality of coding modes, and also connected to another network having at least one voice codec allowing any coding mode to be selected from a plurality of coding modes to make it possible to establish communications between a second terminal given the voice codec of said another network and said first terminal, comprising:

• a monitoring unit monitoring the communication situation including quality of the radio link during voice communication of said first terminal;
• and
• a control unit determining an appropriate coding mode based on said communication situation, requesting said first terminal to make a change to said appropriate coding mode, and receiving from said first terminal a response indicating the fact that the coding modes of the voice codec of the first terminal and the voice codec given to the second terminal engaged in voice communication with the first terminal are changed to confirm that the coding modes are changed.

A communication terminal having a voice codec allowing any coding mode to be selected from a plurality of coding modes, which is connected by a radio link to a first network monitoring the communication situation including quality of the radio link to determine a coding mode according to the communication situation, and is capable of communicating with another terminal given a voice codec allowing any coding mode to be selected from a plurality of coding modes by a second network interconnected with said first network,

• wherein upon request for change of the coding mode from said first network, the communication terminal requests said second network to change the coding mode and upon reception of a response indicating the fact that the coding mode of the voice codec of said second network is changed from said second network, the communication terminal changes the coding mode of the voice codec of the communication terminal and sends back the response to said first network.

A communication terminal having a voice codec allowing any coding mode to be selected from a plurality of coding modes, which is connected by a radio link to a network monitoring the communication situation including quality of the radio link to determine a coding mode according to the communication situation, and is capable of communicating with another terminal given a voice codec allowing any coding mode to be selected from a plurality of coding modes,

• wherein upon request for change of the coding mode from said network, the communication terminal requests said another terminal as a communication partner to change the coding mode and upon reception of a response indicating the fact that the coding mode is changed, the communication terminal changes the coding mode of the voice codec of the communication terminal and sends back the response to said network.