Carrier and Symbol Synchronisation for LoRa Receivers

Alexandre Marquet (1, 2, 3) , Nicolas Montavont (4)

1 IMT Atlantique - SRCD - Département Systèmes Réseaux, Cybersécurité et Droit du numérique
2 IRISA-D2 - RÉSEAUX, TÉLÉCOMMUNICATION ET SERVICES
3 OCIF - Objets communicants pour l'Internet du futur
4 OCIF - Objets communicants pour l'Internet du futur

LoRa is one of the most popular transmission scheme for the Internet of Things (IoT). It is used in many applications such as home automation, smart cities and smart agriculture. It provides low bitrate transmissions over long ranges, using unlicensed Industrial, Scientific and Medical (ISM) bands. Being a relatively new, and proprietary modulation, there are still challenges and improvements to be addressed and discovered. In this article, we cover estimation, tracking, and correction of slow varying timing and frequency offsets. Both timing and frequency offsets can arise, in particular , when oscillators, found in radios, are either of poor quality, or aged. The latter scenario is a serious concern for IoT, where devices are envisioned to stay in operation during decades without maintenance. The proposed estimators are based on symbol-by-symbol processing of the output of the demodulator. Tracking and correction are then performed by including these estimators in a tracking loop. Simulations show that the proposed closed-loop system can efficiently and jointly track timing and frequency offsets, even at low SNR.

Domaines: Réseaux et télécommunications [cs.NI]; Traitement du signal et de l'image [eess.SP]

Alexandre Marquet, Nicolas Montavont. Carrier and Symbol Synchronisation for LoRa Receivers. International Conference on Embedded Wireless Systems and Networks, Feb 2020, Lyon, France. pp.277-282. ⟨hal-02860476⟩