IEEE 1278 requires that all radios have a unique radio identifier. The figure below illustrates the relationship of the DIS identifying fields in PDU headers that are used in radio communications.
IEEE 1278.1 200x Draft 13 defines Entity Identifier as the Site Number, Application Number, and Entity Number. Simulation Address is defined as Site Number and Application Number, and Radio Identifier as Entity Identifier combined with Radio Number. The specification intends that radios are to be “attached” to (contained within) these entities. Usually entities have multiple radios. A given radio within an exercise is identified with an Entity Identifier and a Radio Number. Therefore, a given radio is identified by four fields. Each field can contain a value from 1 to 65,534. DIS requires that no radio be allowed on the network with a zero ID or an ID of 65,535.
Each radio is normally associated with an entity on the network and is “attached” to that entity. However, it is common for a radio to be stand-alone with its own Radio Identifier. When a transmitter is a stand-alone entity, there is no entity state PDU generated for it. This is a de-facto standard.
Each radio must have a unique ID for a given exercise. If more than one radio has the same ID, the radio may behave unpredictably and the incoming audio may be broken and indecipherable.