4 - Radio channel access challenges in LoRa low-power wide-area networks

Abstract

Recently, Low-Power Wide Area Networks (LPWAN) play a key role in the Internet-of-Things (IoT) maturation process. Under the LPWAN broad term are a variety of technologies enabling power efficient wireless communication over very long distances. For instance, technologies based on ultra-narrow band modulation (UNB)–for example SigFox–or Chirp Spread Spectrum modulation (CSS)–for example LoRa–have become de facto standards in the IoT ecosystem. Given the incredible worldwide uptake of LPWAN networks for a large variety of innovative IoT applications, including multimedia sensors, it is important to understand the challenges behind large scale and dense LPWAN deployment, especially because both Sigfox and LoRa networks are currently deployed in unlicensed bands. This situation is most likely not going to change, at least in the next few years, as working in the unlicensed band allows for a much quicker uptake of the technology. This chapter has a particular focus on LoRa technology as it can be deployed in a private and ad-hoc manner, making experimental deployments much easier. Existing studies on LoRa scalability and radio channel access mechanisms for LoRa LPWAN will be reviewed and promising approaches will be presented in more details. The chapter will also provide to the readers useful information on the LoRa physical layer, as well as on promising interference mitigation techniques that can be applied such as capture effect and successive interference cancellation. The chapter will also give a large part on experimental results based on real-world deployments of both IoT test-beds and IoT production networks in the context of 3 R&D projects (2 EU H2020 projects–WAZIUP & WAZIHUB–and 1 national ANR project–PERSEPTEUR).