Project 25 digital radio systems support a conventional mode of operation. This document provides details of the procedures required such that, where systems are configured in the conventional mode, voice services SHOULD operate in accordance with the goals of Project 25:

a. Support any Project 25 conventional radio.

b. They interoperate across any Project 25 digital radio conventional system.

c. They are independent of the particular Project 25 equipment manufacturer.

This document describes the procedures necessary to support the Project 25 Conventional services, and provides the necessary guidelines for infrastructure requirements to support interoperability of these conventional services. This document is consistent with other pertinent Project 25 documents, namely:

a. Project 25 Common Air Interface (TIA-102.BAAA-A); and

b. Project 25 Conventional Control Messages (TIA-102.AABG).

This document does not explicitly address any procedures required in support of any nonconventional (e.g., trunking) modes of operation.

This document defines procedures for basic conventional radio systems. A conventional radio system is one that does not assign radio channels to SUs through the use of a control channel and over-the-air signaling. It is different from a trunking system which includes some means of assigning radios to channels.

A basic conventional radio system is one which meets the minimum requirements for this document. Additional functions or features MAY be added to a basic system as they are required. The operation of these additional functions is not discussed in this standard, but it is expected that they will be compatible with the basic operation as described here. Basic procedures covered in this standard are further restricted to the lower 2 OSI layers of the radio system. Operation of the encryption function, vocoder function, or user data applications is not explicitly defined here. Operation of trunking control is also not included.

There are several different types of conventional radio systems, depending on whether or not a repeater is used. These are diagrammed in Figure 1-1.

For the purposes of this document, basic conventional systems can be classified as either repeater systems or direct systems. Repeater systems make use of a full duplex base station that is configured so that all of the signals that are received are re-transmitted. Direct systems simply transmit directly from one unit to another without the assistance of any intervening repeater. Radio units in a system consist of mobile or portable units, and base stations. The mobile or portable units are represented as SU elements. The base station is represented as a BR (Base Repeater) element in Figure 1-1. The communication paths are represented as arrows. They are intended to show a simplex (i.e. one direction only) path. Generally, the radios MAY be capable of operating half duplex, which is to say that they can transmit or receive, but not both at the same time. The repeater is always full duplex. Full duplex operation for portables or mobiles is not discussed for a basic conventional system.