Before revision: This is an augmentation to aircraft URL which report aircraft position and velocity in such a way as to minimize interference with any other avionics system, maximize the possible number of participating aircraft, while not relying on any equipment on the ground, and protecting aircraft from potential attack.
After revision: This is an augmentation to aircraft transponders, which report aircraft position and velocity in such a way as to minimize interference with any other avionics system, maximize the possible number of participating aircraft, while not relying on any equipment on the ground, and protecting aircraft from potential attack.