Coded Frequency Hopping for Direct-to-Satellite IoT Systems: Design and Analysis

Long range-frequency hopping spread spectrum (LR-FHSS) framework is a promising technology to enable the direct-to-satellite (DtS) Internet of Things systems with extensive coverage and high resistance to interference while maintaining cost-effectiveness. However, this system currently implements primitive channel coding in frequency-hopping spread-spectrum (FH-SS) without considering the characteristics of the interference signal. In this work, we propose an innovative coded frequency-hopping (FH) design that incorporates segment-level coding (SLC) in high order Galois field (GF) with erasure detection to enhance immunity against the clustered errors commonly encountered in FH-SS, thereby improving the reliability of DtS communication. Additionally, our design inherits the packet structure from LR-FHSS, enabling specific applicability in real-world scenarios. We have also established an analytical model to validate our proposed design in terms of packet loss rate (PLR) and energy consumption. The mathematical analyses and simulation of the proposed scheme quantify the effectiveness of this enhancement. The numerical results show that the proposed system can accommodate 20 times more users compared to LR-FHSS at a packet loss rate of 0.001, and it costs only approximately 50% of the energy consumption when achieving equivalent performance.