Doppler Estimation and Compensation Techniques in LoRa Direct-to-Satellite Communications

TL;DR

This paper introduces four frameworks for estimating and compensating Doppler effects in LoRa satellite communications, enhancing the reliability of IoT connectivity in remote areas.

Contribution

It proposes novel Doppler estimation and compensation frameworks specifically tailored for LoRa direct-to-satellite links, with comprehensive performance analysis.

Findings

Doppler effects significantly degrade LoRa DtS performance.

The proposed frameworks improve robustness against Doppler shifts.

Trade-offs between spreading factor and Doppler compensation are identified.

Abstract

Within the LPWAN framework, the LoRa modulation adopted by LoRaWAN technology has garnered significant interest as a connectivity solution for IoT applications due to its ability to offer low-cost, low-power, and long-range communications. One emerging use case of LoRa is DtS connectivity, which extends coverage to remote areas for supporting IoT operations. The satellite IoT industry mainly prefers LEO because it has lower launch costs and less path loss compared to Geostationary orbit. However, a major drawback of LEO satellites is the impact of the Doppler effect caused by their mobility. Earlier studies have confirmed that the Doppler effect significantly degrades the LoRa DtS performance. In this paper, we propose four frameworks for Doppler estimation and compensation in LoRa DtS connectivity and numerically compare the performance against the ideal scenario without the Doppler effect. Furthermore, we investigate the trade-offs among these frameworks by analyzing the interplay between spreading factor, and other key parameters related to the Doppler effect. The results provide insights into how to achieve robust LoRa configurations for DtS connectivity.