PHS operators ASTEL Group (ASTEL), DDI Pocket Telephone Group (DDI-P), and *NTT DoCoMo Group (NTT DoCoMo), have developed and are going to implement the Short Message Service (SMS) in order to differentiate PHS services from the cellular services. ASTEL, DDI-P, and NTT DoCoMo respectively call their SMS services, 'A-Mail Plus', 'P-Mail', and '*Chara-Talk.' As of December 1, NTT DoCoMo took the operation of NTT Personal's PHS business.
The cellular operators recently launched similar SMS services, following the lead of the success of that service for PHS. The PHS operators have been continuously improving their SMS features and applications.
SMS messages were initially transmittable only among users that were subscribed to the same PHS operator. However, the users were expressing the need to expand sending capabilities to users that subscribed to other PHS operators. So, in response to these requests, DDI-P disclosed their SMS, P-Mail specification, which enables message of up to 20 characters to be communicated among fellow P-Mail users, to the industry. Based on this standardization, SMS messages are transmittable among the P-Mail, A- Mail Plus and Chara-Talk users.

ASTEL first launched their '**MOZIO DIRECT' service on October 15, 1998, which enables message transmission of maximum 512 letters. DDI-P launched P-Mail DX (Deluxe) service in December 1998, which has increased the capacity from 20 letters to a maximum 1,000 letters per message (**MOJI means character in Japanese).
As an add-on feature, ASTEL's MOZIO DIRECT service can transmit melody and illustrated pictures to another user. With DDI-P's P-Mail DX , the 'Chat-Tsushin' (communication for a while) function enables two-way message communication by holding the line open, while the regular SMS service cuts the line automatically when a message is transmitted. NTT DoCoMo's Chara-Talk can transmit melody as well as a message of up to 210 characters.
The PHS operators have installed Center Servers to provide more value- added MSM services. There are two types of services supported by the server; the storage service and the real-time service.

1. Storage Service:
This enables a PHS handset or PHS terminal to communicate a short e- mail message through the internet. Each subscriber has his own mail-box in the Center Server, and can communicate through the internet without an extra adapter and without subscribing to an internet provider. He can send a short message by dialing a PHS telephone number or by directing the message to a particular an e-mail address.
Furthermore, he can also access the server from a fixed telephone or at another e-mail terminal. This is one example of a media conversion service. Refer to Fig.-1.
Each PHS operator has added unique features respectively.

1. ASTEL's MOZIO Server Mail: communicate maximum 512 characters, simultaneously send a single message to a maximum of 10 addresses, send a melody, and store all of the received messages for 7 days.
   
2. DDI-P's P-Mail DX: communicate maximum of approx. 1,000 characters, simultaneously, send a single message to multiple addresses send a message at a pre-programmed time, transfer a received message to another number, and store about 500 received messages (maximum 1MB) for 1 month.
   
3. NTT DoCoMo provides three different types of services: Chara-Mail can store a maximum 20 messages which have 210 characters per message for 3 days. 'PALDIO E-Mail' enables e-mail communication from the specified PHS terminal or by connecting a personal computer. 'PALDIO I-Mail' enables transmission of handwritten letters and illustrations additionally, as well as to send a message to a fax machine. In the latter two services, the messages are stored for 7 days.

2. Real-time Service:
PHS handsets and PHS terminals can obtain a variety of information by accessing various sites through the center server. There are two access methods; manual access and automatic access, which is done by pre- registering your number, thereby automatically distributing pre-registered information. Currently available are news, weather forecast, stock market prices, telephone directory, etc. This service is currently available through ASTEL and DDI-P. Refer to Fig.-2 for system configuration.
With ASTEL's service, information can be searched using their location information capabilities, as well as automatically dialing any telephone number that may be included in the information pulled up by the terminal. With DDI-P, as much as a maximum of 1,000 characters worth of information can be accessed.
The actual traffic and demand for the SMS services have been increasing steadily, and will play a key role in PHS's leap forward into another growth phase.