SIP server, terminal device, subscriber information management device and communication control method

摘要

Radio resources for maintaining a communication channel can be used efficiently by synchronously controlling a communication channel establishment process and a Registration process by SIP. If a SIP server 1A obtains a request message by SIP from a calling terminal device in a state in which a communication channel has not been established and a state in which a SIP transaction has not been established (step SO), a short message for prompting communication channel establishment and a Registration process is sent to a called terminal device 2B (steps S8 to S11). Then, a process for establishing a communication channel is performed (steps S17 and S18), and a process for establishing a SIP transaction is performed after the communication channel establishment process is performed (steps S19 and S20). By performing processes in this manner, when there is a request from the calling terminal, a control signal can be sent to prompt establishment of the communication channel and the Registration process and the transaction can be established.