A universal model for question-answering systems with special consideration of modern spread spectrum identification systems

The author considers question-answering (QA) systems with a number of platforms operating in a common space. The platforms are equipped with interrogators and/or with transponders. The goal of such QA systems is to obtain information about the characteristics of the platforms with transponders at the platforms with interrogators. A general model for QA systems is introduced. Based on this model, it is shown that the probability of identification, the information-theoretical efficiency, and the average cost are quantities suitable for evaluating QA systems. The theory is especially applicable to identification systems for friend or foe. For such a system the advantage offered by spread-spectrum techniques is determined