What is the difference between the Radio Tranceiver Pipeline Stage 0: Receiver Group and Stage 2: Closure?

What is the difference between the Radio Tranceiver Pipeline Stage 0: Receiver Group and Stage 2: Closure?

Stage 0:This stage is static, and is run only once at the beginning of the simulation. Its purpose is to eliminate tranceiver/receiver combinations that would NEVER work (for example, they are on a different frequency). This stage also eliminates receivers that are out of range physically. Even if a receiver eventually comes into range, it will not be added to the receiver group. This stage is used for efficiency. This way, the kernel doesn't waste events sending packets that would always be dropped.You can modify the pipeline stage code to make this process dynamic. For example, if a receiver is out of range at the beginning of the simulation but later comes into range, it would be added to the receiver group. For more information, reference Chapter 13 (Radio Package) of the Modeler Documentation.Stage 2 is line-of-sight. As two nodes move together/apart, they may be unable to communicate if an object (such as the Earth, a building, or a mountain) is between them. (Note that modeling landscape effects requires the OPNET Terrain Modeling Module). This stage is dynamic, meaning it is constantly updating whether or not a receiver is capable of getting transmissions.A common way to get around the line of sight issue is to increase a site's altitude. Or you can use the dra_closure_all pipeline stage, which always returns closure, no matter where two nodes are located. This stage allows for faster simulation runtimes, but is less realistic.

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