Power control in an LPI adaptive frequency-hopping system for HF communications

Frequency-hopping is considered to be an effective method for combating active jamming in military radio systems. To further improve the performance, so-called adaptive frequency-hopping (AFH), which uses an adaptively selected pool of the “best” hopping-frequencies for the communication, has been proposed. In this paper, we extend the adaptivity of the AFH scheme by adjusting the transmitted power on each channel individually. We investigate two novel power control algorithms; one that minimizes the initial bit error probability for every data frame, and one that aims at good LPI (low probability of intercept) properties by distributing the power so that all channels obtain the same signal-to-interference ratio (SSIR) at the receiver. Our analysis shows that the two power control algorithms give approximately equivalent communication performance. The resulting bit errors are mostly due to fast changes of the interfering signals which we cannot counteract with our relatively slow power control. Furthermore, the simulation results demonstrate the very good LPI capability of the SSIR algorithm