Abstract
This paper presents a complete study and characterization of a real-time frequency-hopped, frequency shift-keyed testbed capable of transmitting data at 160 kb/s, with hopping rates of up to 80 Khops/s operating in the 906 MHz band. The system provides the highest hopping rate reported to date and sets a new trend for FHSS communications with superior low probability of interception/detection and anti-jamming (LPI/LPD/AJ) capabilities. The architecture features a direct digital frequency synthesizer to enable high-rate hopping, and a frequency correlator-based demodulator, plus all digital timing and frequency recovery algorithms to minimize complexity. Furthermore, single sideband modulation was used to achieve spectral efficiency. The testbed is software configured and provides the user with full control over the diversity combining techniques, symbol interleaving, packet structure, and acquisition protocols. A total of 5850 independent experiments were carried out under various receiver configurations and wireless environments. The results underscore the dramatic potential for a system that optimally combines high-rate hopping, interleaving, and equal gain combining to combat severe propagation conditions, including multipath fading and intentional jamming.