A new coded communication modulation scheme in very low frequency communication

Very low frequency (VLF) radio waves have very effective long-distance propagation characteristics. Therefore, they have a wide application prospect in underwater and underground communication. To effectively suppress the interference of channel noise and improve the performance of the VLF communication system, a low-density parity check (LDPC) coded orthogonal frequency division multiplexing-minimum frequency shift keying (OFDM-MSK) communication scheme is designed according to the characteristics of the VLF channel. Considering that the harmonic interference in the VLF channel can be regarded as frequency selective fading, the OFDM technology is applied to the VLF channel. In addition, the performance of VLF communication system is mainly affected by strong impulse atmospheric noise, which can be successfully simulated by symmetrical alpha stable (SαS) distribution. To reduce the impact of SαS noise on the OFDM system and data loss in frequency selective fading channel, LDPC channel coding technology is proposed. Finally, the robustness of the LDPC coded OFDM-MSK scheme is tested and evaluated from the perspective of the bit error rate (BER). The results show that the LDPC coded OFDM-MSK communication scheme has better performance than the independent OFDM-MSK communication scheme.