| 摘要 |
As a result of a power saving technique for a portable dual terminal equipped with both WLAN unit and PHS unit, a call is usually relayed from an S-P gateway to a call receiver terminal via the PSTN, thereby incurring a call charge to the caller. According to the present invention, the call from the S-P gateway to the call receiver terminal (dual terminal) is terminated before a call charge is incurred, and the call receiver terminal calls back the S-P gateway via the IP network or the PSTN. The SIP server, instead of the call receiver terminal, identifies the caller terminal to call back, thereby connecting the call from the call receiver terminal to the caller terminal. In addition to this "callback method", the present invention further provides "reconnection method", "reconnection plus call-again method", and "call-again method", thus offering four types of methods. |
