FSCM constellation mapping fusion for HF fading channels

To resolve the problems of unreliable transmission and low communication capacity caused by the time-frequency domain dual-selective fading of High Frequency (HF) channels, a constellation mapping fusion technology for HF Frequency Shift Chirp Modulation (FSCM) is proposed. On one hand, the FSCM technology is employed to compensate for the fast fading introduced by frequency domain expansion, and the spreading factor is used to adjust the transmission rate. On the other hand, based on the FSCM matching, by constructing a two-dimensional constellation mapping, the soft information and symbol weights of multipaths are extracted, thereby realizing single-channel RAKE fusion and multi-channel diversity fusion with symbol-by-symbol weighting. This effectively improves transmission reliability in HF dual-selective channels where the main and secondary paths switch. In typical HF scenarios defined by ITU-R F.1487, simulation results demonstrate that, compared with the traditional hard demodulation algorithms, the proposed soft information fusion algorithm can still ensure reliable transmission under low signal-to-noise ratio conditions, even with high multipath separation degrees. Moreover, through 24-hour field tests, the practical applicability of the proposed algorithm is further verified.