LPD properties of adaptive frequency hopping systems for HF communications

Adaptive frequency hopping (AFH) has been proposed as a technique to combat slow multipath fading and the severe interference problems in HF-links. In such a system, link quality measurements are fed back to the transmitter such that “bad” frequencies may be avoided. Results show a dramatic increase in bit error performance compared to conventional system, in particular in highly congested channels. In this paper, the ability of this scheme to “hide” its signals in the surrounding interference in order to avoid hostile detection is investigated. The notion of adaptive power control, selecting the proper power level on each frequency is introduced. Results show that an AFH-system exhibits excellent LPI/LPD properties since both average and peak transmitter power requirements can be dropped by several orders of magnitude