The Mobile Internet Access Forum (MITF), which has standardized the PIAFS (PHS Internet Access Forum Standard) for high-speed Internet access using PHS, approved the specifications for MITF Dial-up Dormant Protocol at the third MITF General Assembly held on June 25, 2001 in Tokyo.

At the same General Assembly, it was agreed to dissolve the MITF and the Association of Radio Industries and Businesses (ARIB) inherited the maintenance and revision works for PIAFS and MITF Dial-up Dormant Protocol Specifications from it, and accordingly the specifications for those standards were posted on and became down-loadable from the ARIB website (http://www.arib.or.jp/).

MITF Dial-up Dormant Protocol Specifications, located between PPP (Point-to-Point Protocol) and PIAFS, provide higher (than PPP) layers with interrupt/resume functions of lower (than PIAFS) layers, as shown in Fig. 1. Through the interrupt/resume functions, sessions of higher (than PPP) layers can release lower layers (circuit switching system) while maintaining an active status.

The following two cases show examples of the usage of those functions:

• Case 1: When data communications is intermittent such as Internet access.


   In case where data stream does not flow in active communications as the Internet, users or access servers intermit and release communication channels. As shown in Fig. 2, the released communications channels are assigned to other usersO data communications. Thus, the limited frequency resources can be used efficiently to save usersO communications costs. When resuming the intermitted communications with higher sessions remaining intact, this can be done swiftly without authentication procedures.



• Case 2: When communications is interrupted for a short time such as in a tunnel


   For example, as shown in Fig. 3, when the terminal is entering a tunnel while the communications are in progress, if the terminal fails to maintain synchronization due to the signal loss, it automatically starts trying to reconnect and resume communications by requesting PIAFS features after passing through the tunnel. Accordingly, the terminal becomes robust to disconnection and as a result mobility can be improved significantly.

Fig1. Protocol stac


Fig2. Case1


Fig3. Case2