Exploring LR-FHSS Modulation for Enhanced IoT Connectivity: A Measurement Campaign

TL;DR

This study tackles the challenge of reliable IoT connectivity in urban LoRaWAN deployments under FCC US915 rules by conducting the first large-scale real-world comparison between LR-FHSS and LoRa modulation. Using a dual-modem testbed in Halifax, the authors quantify PRR, path loss, and RSSI across data rates DR0, DR5, and DR6, revealing that LR-FHSS with DR5 can improve PRR by up to ~20% in dense urban areas, while DR6 does not consistently outperform LoRa DR0. The work demonstrates the limitations of traditional propagation models in urban environments and provides a public dataset to support further research. The findings suggest that LR-FHSS can enhance network robustness and potentially reduce gateway deployments, with ongoing considerations for device availability, cost, and future satellite integration opportunities.

Abstract

This paper presents the first comprehensive real-world measurement campaign comparing LR-FHSS and LoRa modulations within LoRaWAN networks in urban environments. Conducted in Halifax, Canada, the campaign used a LoRaWAN platform capable of operating both modulations in the FCC-regulated US915 band. Real-world measurements are crucial for capturing the effects of urban topology and signal propagation challenges, which are difficult to fully replicate in simulations. Results show that LR-FHSS can achieve up to a 20% improvement in Packet Reception Rate (PRR) over traditional LoRa in dense urban areas. Additionally, the study investigated path loss and Received Signal Strength Indicator (RSSI), finding that LR-FHSS achieved a minimum RSSI of -138 dBm compared to LoRa's -120 dBm. The findings demonstrate that the introduction of LR-FHSS enhances communication robustness and reliability under regulatory limitations and suggest promising applications in LoRaWAN networks.

Figures (8)

• Figure 1: Waterfall plot of LoRa transmission using DR0 (SF10, $125~\mathrm{kHz}$ bandwidth)
• Figure 2: Waterfall plot of LR-FHSS transmission using DR5 (CR 1/3, $1.523~\mathrm{MHz}$ bandwidth)
• Figure 3: Schematic Overview of the LR-FHSS Testbed Setup
• Figure 4: Map of Halifax illustrating the extensive coverage of the measurement campaign, with blue trails representing the paths taken, covering more than 30% of the city's streets
• Figure 5: Comparison of packet reception rate as a function of distance between the transceiver and the gateway for DR0 (LoRa), DR5 (LR-FHSS), and DR6 (LR-FHSS), with 95% confidence intervals computed using the bootstrap technique.