The following is a summary of an article contributed by Shoji Hara of DDI Tokyo Pocket Telephone Inc. (DDI-P) to volume 4 of Mobile Computing Guide magazine, translated by the PHS MoU Group.

Since DDI-P launched PHS “Moji-Denwa (character telephone)” service, user demand for non-voice communications has been growing. We believe that character communication is a key to further expansion of the mobile computing market.
“P-Mail Moji-Denwa” service has been very popular, accounting for about 45% of our total outgoing calls. Among the reasons for this popularity are:

1.   Two-way (sending/receiving) messaging;
2.   Reasonable pricing at 10 yen per message; and,
3.   User-friendliness.

This success has proven that the time is now ripe for us to strive for an increased market presence, focusing on non-voice communications services rather than on voice services.
Mobile computing should provide users with easy access to the information they want at anytime, from anywhere. Yet, charges should be kept at a reasonable level and billing systems should be made simpler for users. Meanwhile, content providers would be better off outsourcing the charge collection to concentrate on their content business. DDI-P developed a system satisfying these needs.
In December 1998, DDI-P opened a service center to enable exchanging e-mail and P-Mail messages (see Figs. 1 and 2). The functions of the center include:
1.   To support SMTP and HTTP protocols, which P-Mail terminals themselves do not, to enable e-mail and P-Mail message exchanges and access to content from the terminals.
2.   To serve content providers as a clearinghouse for charge collection, while helping them formulate rate systems and build their content systems with minimized facilities, for example, through one dedicated line connected to the center.
Because the center supports both P-Mail and general e-mail systems, content providers can continue using their HTTP-based servers and expertise in providing content for P-Mail service. The center has facilitated new entry into P-Mail content service, by making it easier for content providers to begin the service as long as they have entry-level communications facilities and prepared their own toll collection system.

Though terminals are generally equipped with advanced functions, users expect terminals to be priced reasonably. To meet this expectation, we paid consideration to the following:
1.   P-Mail DX is based on PIAFS, a completely open protocol.
2.   The terminals are equipped with minimized functions to keep their prices at a reasonable level, by shifting other major functions to the center, such as the support for SMTP and HTTP protocols that enable e-mail service and content access from the terminals.
3.   P-Mail DX terminals support texts of up to about 1,000 characters as well as bit-map files. They were designed for accommodating user convenience and for ensuring compatibility to enable direct communications. Another reason was to make content providers’ jobs easier.