PCS messaging is a digital SMS feature that allows a wireless phone to receive numeric pages and short text messages. This lets one device do the work of both pager and phone. Users can receive messages on their phone's display screens from a variety of sources: computers, telephones, e-mail, voice mail, and text dispatch (live operators take caller messages and send text messages to the PCS phone).

PCS uses the DCCH and DTCs to deliver the alphanumeric messages to and from the wireless phone. The messages are sent and received via a message center, which is a node on the wireless intelligent network. The messages contain a variety of attributes controlling their delivery, storage, and display behavior.

Message Architecture

Each network-originated PCS message consists of the following three basic elements:

• addressing information—tells the system to which phone the message is to be delivered
• alphanumeric text—the characters that make up the actual text message
• message attributes—tell the phone how to handle and display the message when it is received

Message Types

PCS messaging can deliver numeric-callback messages from a phone and alphanumeric messages sent via modem and computer. Examples of PCS messaging include paging and notification of new voice messages and e-mail messages. Messages of up to 239 characters can be sent over the air interface.

Operating Principle

The PCS messaging feature uses a dedicated paging terminal. When the network receives a PCS message, it locates the target phone and delivers the message. The phone notifies the user with a message icon, a beep, or both. The message can then be displayed and read. If users leave a PCS messaging area, the network stores any messages until they return. The network will repeatedly try to deliver a message until the phone is able to receive it.

Message Generation

The following entities can be used for PCS message generation:

• networking from existing paging terminals
• voice-response unit
• live operator text-dispatch service
• dial-up modem
• e-mail gateway
• data information source
• voice-mail system

Figure 7 shows a PCS teleservice messaging scheme in which a message is formulated in a personal computer (PC) and sent to the phone of the message recipient. Phone-screen displays differ depending on model and manufacturer, but they all show the number of new messages.

Figure 7. PCS Teleservice Messaging Scheme

Message Delivery

PCS messaging is designed to operate in practical, everyday situations.

• power on—If the phone is powered on, the message is available immediately just like a pager.

• phone engaged—If the phone is engaged in a voice conversation, the network delivers the message to the phone using the same DTC being used for the conversation.

• power off—If the phone is powered off, or the phone is out of a service area, the network message center stores the message for later delivery. As soon as the phone is powered on, the messages are delivered. This way messages are not missed if a phone is off, out of a service area, or in an area with poor reception.

• voice mail—When a caller reaches a user's voice mail, the system provides the option to send a callback-number message to the phone or to send an alphanumeric message using special Message Flash software.

• roaming—If the user is roaming in an area not supporting PCS messaging, the message center will store the message and deliver it when the phone reenters a PCS–supported area.