The terrestrial-trunked radio (TETRA) specification is produced by the European Telecommunication Standards Institute for private mobile radio systems. We investigated the resilience of TETRA against intelligent intentional electromagnetic interference (IEMI) with low amplitude. Low power signals interfering with the higher layers of the system have the advantage of staying covert. The analysis shows that if the access assignment channel is corrupted, the mobile stations cannot start conversations with the base station. TETRA's modulation scheme is also investigated. π/4 differential quadrature phase shift keying (QPSK) is interfered with a continuous wave and a QPSK signal. The results show that a continuous wave created the largest error vector magnitude, but creates a peak in the received spectrum. The power of the QPSK signal, however, is distributed over a bandwidth and is more difficult to detect than the continuous wave in the received spectrum. From this, we conclude that the QPSK signal functions is more effective as an intelligent interference signal compared to a continuous wave. In this paper, it is shown that it is possible to create an IEMI that combines the vulnerability in the TETRA protocol with the QPSK signal to disrupt the service to the communication system, while staying covert.Index Terms-Communication system protocol, intelligent jammer, intentional electromagnetic interference, terrestrial-trunked radio.

We discuss the use of a metric based on the amplitude variation of a channel in the signal bandwidth to predict whether or not a digital wireless communication test system receiver will be able to demodulate a test signal. This metric is compared to another method consisting of the correlation calculated across the channel. A logistic regression analysis is used to provide a normalized assessment of the effectiveness of each metric as a predictive tool. We show that both metrics provide similar predictive capabilities, with the peak-to-minimum being significantly easier to calculate.