Antijamming Improvement for Frequency Hopping Using Noise-Jammer Power Estimator

Abstract

In frequency-hopping spread-spectrum (FHSS) systems, jammer detection and mitigation are important but difficult. Each slot of the FHSS experiences frequency-selective fading and unequal transceiver-frequency gains that hinder the detection of jammed slots and result in a poor bit-error rate (BER). To increase BER performance, we first propose a noise-jammer power estimator (NJPE) that estimates noise and jammer powers regardless of different channel gains, and derived its normalized Cramér–Rao bound (NCRB). Second, we developed a jammer detector based on gamma distribution, and designed a restoration method combining all nonjammed slots. Computer simulations verified the derived NCRB of the proposed NJPE by normalized mean squared error (NMSE), and showed that the jammer-detection probability of the proposed jammer detector was better than that of conventional detectors. The BER performance of the proposed method was also shown to be better than that of conventional methods.

Analysis of Low Probability of Detection Capability for Chaotic Standard Map-Based FH-OFDMA System

“…The FH-OFDMA system can be combined with channel coding resulting in frequency diversity when the channel response varies over the hopping distance, and such frequency diversity has been verified in many prior studies [4][5][6]. In the military domain, the authors of Reference [7] consider the condition that an adversary intentionally jams parts of frequency hopping slots and select non-jammed hopping sequences to obtain low bit error performance. However, in this study, we have fundamentally different focus on the advantage of the FH-OFDMA system that supports LPD against detection of adversaries, such as eavesdroppers or radiometers.…”