A Survey on LR-FHSS: State of the Art and Future Directions

Long Range–Frequency Hopping Spread Spectrum (LR-FHSS) is a physical layer (PHY) scheme intended to enhance LoRaWAN capabilities in terms of scalability and robustness. Such features qualify LR-FHSS as a promising enabler in direct-to-satellite (DtS) and terrestrial Internet of Things (IoT) environments. Since its publication as part of the LoRaWAN specification, LR-FHSS has attracted increasing attention from the research community. The existing literature has focused on evaluating LR-FHSS performance, often in comparison with former LoRaWAN PHY alternatives (such as LoRa), by means of mathematical analysis, simulation, and real-world experimentation. LR-FHSS performance parameters of interest comprise delivery rate, energy consumption, network capacity, throughput, and latency. The research community has also designed LR-FHSS improvement techniques, either through receiver-side approaches or requiring modifications at both the transmitter and receiver. For the first time, the present paper offers a consolidated view of the state of the art, identifies current challenges, and proposes future directions in the field of LR-FHSS research.