Joint Mainlobe and Sidelobe Jamming Mitigation via Randomized Intra-Group Subcarrier Selection in MDFH Systems

Conventional message-driven frequency-hopping (MDFH) systems are vulnerable to partial-band jamming, particularly when the jamming simultaneously affects both active and idle subcarriers, which disrupts energy-based detection. To address this limitation, this paper proposes a novel randomized intra-group subcarrier selection with joint suppression (RIJS-MDFH) scheme. In this framework, subcarriers are dynamically organized into configurable groups, and active carriers are randomized within each group. This structure decouples the jamming signal into distinct mainlobe and sidelobe components. The mainlobe is mitigated via rate-adaptive channel coding, whose rate is matched to the jamming bandwidth and the subcarrier mapping configuration. The sidelobe is suppressed using a filter-bank-based technique, effectively accelerating its roll-off. Simulation results demonstrate that the proposed scheme significantly outperforms existing MDFH systems in anti-jamming robustness under identical partial-band jamming conditions. At the same time, it preserves high spectral efficiency through flexible parameter adjustment. The work confirms that jointly addressing both jamming components enables reliable communication under low signal-to-jamming ratios, overcoming a key weakness of conventional MDFH designs.