Enhancing Cross-Domain Magnetic Induction Communication via DF Relay with DPSK-DSSS Modulation

Cross-domain wireless communication is vital for underwater information acquisition, where Magnetic Induction (MI) communication excels due to its penetration and stability. However, near-field MI signals rapidly with distance and frequency, limiting single-hop transmission. Integrating cooperative relaying with MI communication addresses reliability and distance challenges. While Amplify-and-Forward (AF) and Decode-and-Forward (DF) strategies are studied, DF mode faces instability and error propagation in multi-relay systems. This paper proposes a DF -based DPSK-DSSS architecture: DPSK eliminates absolute phase dependence at relays to mitigate perturbation-induced misalignment, DSSS suppresses interference via code spreading, and distributed diversity enhances anti-fading. Simulations using an MI propagation model show the scheme achieves lower Bit Error Rate (BER) and higher Signal-to-Noise Ratio (SNR) than traditional DF and non-relay approaches, improving air-sea cross-domain MI communication reliability and range.