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LR-FHSS Transceiver for Direct-to-Satellite IoT Communications: Design, Implementation, and Verification

Sooyeob Jung, Seongah Jeong, Jinkyu Kang, Gyeongrae Im, Sangjae Lee, Mi-Kyung Oh, Joon Gyu Ryu, Joonhyuk Kang

Abstract

This paper proposes a long range-frequency hopping spread spectrum (LR-FHSS) transceiver design for the Direct-to-Satellite Internet of Things (DtS-IoT) communication system. The DtS-IoT system has recently attracted attention as a promising nonterrestrial network (NTN) solution to provide high-traffic and low-latency data transfer services to IoT devices in global coverage. In particular, this study provides guidelines for the overall DtS-IoT system architecture and design details that conform to the Long Range Wide-Area Network (LoRaWAN). Furthermore, we also detail various DtS-IoT use cases. Considering the multiple low-Earth orbit (LEO) satellites, we developed the LR-FHSS transceiver to improve system efficiency, which is the first attempt in real satellite communication systems using LR-FHSS. Moreover, as an extension of our previous work with perfect synchronization, we applied a robust synchronization scheme against the Doppler effect and co-channel interference (CCI) caused by LEO satellite channel environments, including signal detection for the simultaneous reception of numerous frequency hopping signals and an enhanced soft-output-Viterbi-algorithm (SOVA) for the header and payload receptions. Lastly, we present proof-of-concept implementation and testbeds using an application-specific integrated circuit (ASIC) chipset and a field-programmable gate array (FPGA) that verify the performance of the proposed LR-FHSS transceiver design of DtS-IoT communication systems. The laboratory test results reveal that the proposed LR-FHSS-based framework with the robust synchronization technique can provide wide coverage, seamless connectivity, and high throughput communication links for the realization of future sixth-generation (6G) networks.

LR-FHSS Transceiver for Direct-to-Satellite IoT Communications: Design, Implementation, and Verification

Abstract

This paper proposes a long range-frequency hopping spread spectrum (LR-FHSS) transceiver design for the Direct-to-Satellite Internet of Things (DtS-IoT) communication system. The DtS-IoT system has recently attracted attention as a promising nonterrestrial network (NTN) solution to provide high-traffic and low-latency data transfer services to IoT devices in global coverage. In particular, this study provides guidelines for the overall DtS-IoT system architecture and design details that conform to the Long Range Wide-Area Network (LoRaWAN). Furthermore, we also detail various DtS-IoT use cases. Considering the multiple low-Earth orbit (LEO) satellites, we developed the LR-FHSS transceiver to improve system efficiency, which is the first attempt in real satellite communication systems using LR-FHSS. Moreover, as an extension of our previous work with perfect synchronization, we applied a robust synchronization scheme against the Doppler effect and co-channel interference (CCI) caused by LEO satellite channel environments, including signal detection for the simultaneous reception of numerous frequency hopping signals and an enhanced soft-output-Viterbi-algorithm (SOVA) for the header and payload receptions. Lastly, we present proof-of-concept implementation and testbeds using an application-specific integrated circuit (ASIC) chipset and a field-programmable gate array (FPGA) that verify the performance of the proposed LR-FHSS transceiver design of DtS-IoT communication systems. The laboratory test results reveal that the proposed LR-FHSS-based framework with the robust synchronization technique can provide wide coverage, seamless connectivity, and high throughput communication links for the realization of future sixth-generation (6G) networks.
Paper Structure (36 sections, 6 equations, 23 figures, 3 tables)

This paper contains 36 sections, 6 equations, 23 figures, 3 tables.

Table of Contents

  1. Introduction
  2. DtS-IoT System Architecture Design
  3. Previous Works
  4. Overall System Architecture and Potential Use Cases
  5. LR-FHSS Transceiver Design
  6. Challenging Issues
  7. Doppler Effect
  8. STO
  9. CFO and Phase Offset
  10. CCI
  11. Robust Synchronization for DtS-IoT Communications
  12. Signal Detector
  13. Header Receiver
  14. Symbol Timing Estimation
  15. Phase Rotate
  16. ...and 21 more sections

Figures (23)

  • Figure 1: Overall DtS-IoT system architecture using the LR-FHSS transmission.
  • Figure 2: Block diagram of LR-FHSS transmission with the LEO satellite channel model.
  • Figure 3: Structure of the GMSK-based LR-FHSS receiver for synchronization and header decoding.
  • Figure 4: Phase change of the syncword with (a) the full length of 32 symbols and (b) partial length of 20 symbols.
  • Figure 5: Standard deviations according to the Doppler rate of the proposed symbol timing estimation in the initial STO = 0.125 case.
  • ...and 18 more figures