The simulated radio environment consists of transmitters, receivers and radios (which contains both a transmitter and receiver).
Radio transmitters publish information in the form of a transmitter pdu. The format of the transmitter pdu is in accordance with the DIS protocol versions 2.04 and 2.05. In short this pdu permits the radio to say who they are, where they are, what they are (AM, FM, etc) and their current state. This information is published periodically, determined by the DIS timeout rate used, when the transmitter is changing positions and when the transmitter changes between the On and Active Transmit states.
The DIS receiver objects in the simulated environment examine these transmitter pdus and determine possible in-tune and in-range radios. Factors such as range, modulation type, crypto state and frequency matching are considered.
When the transmitting radio sends audio in the form of signal pdus the receiver compares the DIS ID embedded in the signal pdu with the DIS ID of known in-tune and in-range transmitters and if they match permits the audio to be heard by the processed by the radio object.