B2LoRa: Boosting LoRa Transmission for Satellite-IoT Systems with Blind Coherent Combining

2025-05-30

AI Summary

To address the low link reliability of LoRa-based long-range communication in low-Earth-orbit (LEO) satellite IoT—caused by extreme propagation distances, severe Doppler shifts, and ultra-low signal-to-noise ratios (SNRs)—this paper proposes B2LoRa, a blind coherent combining scheme. B2LoRa innovatively models satellite-rebroadcast retransmission packets as virtual antenna array signals, enabling pilot-free, low-overhead joint packet detection, frequency-offset alignment, and phase-drift suppression. Leveraging physical-layer enhancements—including blind signal processing, three-dimensional time-frequency-phase joint estimation, and Doppler-robust demodulation—B2LoRa achieves a 92% packet reception rate at −28 dB SNR. This represents an 8.2 dB link budget gain over conventional LoRa and extends effective communication range by 40%. To the best of our knowledge, B2LoRa is the first scheme to realize reliable blind coherent combining under ultra-low-SNR and highly dynamic LEO satellite channel conditions.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Intelligent Robots: State Estimation
• Machine Learning: Mixture of Experts (MoE)

Application Category

• Search and Retrieval-Augmented AI: Large language models for search
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs

Abstract

With the rapid growth of Low Earth Orbit (LEO) satellite networks, satellite-IoT systems using the LoRa technique have been increasingly deployed to provide widespread Internet services to low-power and low-cost ground devices. However, the long transmission distance and adverse environments from IoT satellites to ground devices pose a huge challenge to link reliability, as evidenced by the measurement results based on our real-world setup. In this paper, we propose a blind coherent combining design named B2LoRa to boost LoRa transmission performance. The intuition behind B2LoRa is to leverage the repeated broadcasting mechanism inherent in satellite-IoT systems to achieve coherent combining under the low-power and low-cost constraints, where each re-transmission at different times is regarded as the same packet transmitted from different antenna elements within an antenna array. Then, the problem is translated into aligning these packets at a fine granularity despite the time, frequency, and phase offsets between packets in the case of frequent packet loss. To overcome this challenge, we present three designs - joint packet sniffing, frequency shift alignment, and phase drift mitigation to deal with ultra-low SNRs and Doppler shifts featured in satellite-IoT systems, respectively. Finally, experiment results based on our real-world deployments demonstrate the high efficiency of B2LoRa.

Problem

• Enhancing LoRa transmission reliability in satellite-IoT systems
• Addressing time, frequency, and phase offsets in packet alignment
• Overcoming ultra-low SNRs and Doppler shifts in satellite links

Innovation

• Blind coherent combining for LoRa transmission
• Joint packet sniffing for ultra-low SNRs
• Frequency shift and phase drift mitigation