Ben Temim Mohamed Amine, Ferré Guillaume, Tajan Romain
IMS, University of Bordeaux, Bordeaux INP, CNRS UMR 5218, F-33400 Talence, France.
Sensors (Basel). 2022 Feb 25;22(5):1830. doi: 10.3390/s22051830.
LoRa is based on the chirp spread spectrum (CSS) modulation, which has been developed for low power and long-range wireless Internet of Things (IoT) communications. The structure of LoRa signals makes their decoding performance extremely sensitive to synchronization errors. To alleviate this constraint, we propose a modification of the LoRa physical layer, which we refer to as differential CSS (DCSS), associated with an original synchronization algorithm. Based on this modification, we are able to demodulate the received signals without performing a complete frequency synchronization and by tolerating some timing synchronization errors. Hence, our receiver can handle ultra narrow band LoRa-like signals since it has no limitation on the maximum carrier frequency offset, as is actually the case in the deployed LoRa receivers. In addition, in the presence of the Doppler shift varying along the packet duration, DCSS shows better performance than CSS, which makes our proposed receiver a good candidate for communication with a low-Earth orbit (LEO) satellite.
LoRa基于线性调频扩频（CSS）调制，该调制是为低功耗和远距离无线物联网（IoT）通信而开发的。LoRa信号的结构使其解码性能对同步误差极为敏感。为缓解这一限制，我们提出了对LoRa物理层的一种改进，我们将其称为差分CSS（DCSS），并关联了一种原始同步算法。基于此改进，我们能够在不进行完全频率同步且容忍一些定时同步误差的情况下对接收到的信号进行解调。因此，我们的接收器能够处理超窄带类LoRa信号，因为它对最大载波频率偏移没有限制，而实际部署的LoRa接收器就是这种情况。此外，在沿数据包持续时间存在多普勒频移变化的情况下，DCSS比CSS表现出更好的性能，这使得我们提出的接收器成为与低地球轨道（LEO）卫星通信的理想选择。
