ASTi has taken advantage of the flexibility provided by HLA to customize radio transmitter and receiver object classes to maximize efficiency. The big differences are listed below.

• The ASTi SOM does not include the "EntityIdentifier" or "RadioIndex" attributes. These attributes are throwbacks to the DIS ID structure. "EntityIdentifier" contains the Site/Application/Entity ID of the object while the "RadioIndex" contains the Radio ID. HLA uses object instance names (e.g. F16.UHF.tx) as opposed to ID strings to track objects. Because the DIS ID carries no meaning in HLA, the "EntityIdentifier" and "RadioIndex" attributes are unnecessary.
  
  
• The ASTi SOM combines cryptographic information into a single attribute to ensure that this information is updated at the same time. The RPR FOM includes the attributes CryptographicMode, CryptoSystem, and EncryptionKeyIndentifier for the RadioTransmitter object class. Having both CryptoGraphicMode and EncryptionKeyIndentifier is redundant as the Crypto Mode is derived from the high-order bit of the Key (per the DIS standards). Also, having these parameters as separate attributes allows for the possiblity that network conditions may cause one parameter to be updated without the others. The ASTi SOM includes crypto information as one attribute, Encryption, which is a complex datatype with fields Crypto System and Encryption Key. This organization eliminates redundancy and ensures that any update to crypto parameters are passed together.
  
  
• Likewise, the ASTi SOM combines Frequency and Frequency bandwidth as a single attribute while the RPR FOM has them as separate attributes. Again, the ASTi SOM representation of frequency groups related data together by using a complex datatype.
  
  
• ASTi SOM v3.2 includes a new interaction, EntityAttach which is not in the RPR FOM. This interaction basically maintains the ability to attach a radio to a particular entity dynamically that was available in DIS. This interaction uses object instance names as its parameters since object IDs are not used in HLA.