Evaluation of the covertness of time-hopping impulse radio using a multi-radiometer detection

Covert operation is an important requirement for military communications systems. Impulse radio is a promising ultra-wideband technique for tactical military communications. Using a simple, sub-optimal radiometer detection system, impulse radio has been shown previously to exhibit low probability of detection (LPD) compared to alternative systems. In this paper we quantitatively evaluate the covertness of impulse radio using a more complex radiometer detection scheme ideally suited for detection of time-hopping impulse radio signals. The more complex detection system that we consider utilizes multiple, wideband radiometers with outputs that are ORed and compared to a threshold. This "multi-radiometer" detection system is used to quantify covertness for single and multiple user configurations. We also evaluate covertness for cases where the detector incorporates varying amounts of prior knowledge about the impulse radio signals. The "average covertness" of impulse radio for a specified number of users is determined and then compared to DS-CDMA schemes with equivalent number of users.