Optimization of Discrete Phase Shifts for LoRa Wireless Communication Assisted by Reconfigurable Intelligent Surfaces

A Reconfigurable Intelligent Surface (RIS) system offers a cost-effective means to achieve high spectral and energy efficiency in future wireless networks by lever-aging numerous low-cost passive elements that redirect incident signals through adjustable phase shifts. Such benefits are especially relevant to Long Range (LoRa) systems employed in internet of things (IoT) applications. In this work, we investigate a RIS-assisted LoRa communication system, where a LoRa device transmits information to a LoRa gateway through the RIS in both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. This paper aims to enhance the performance in terms of bit error rate (BER) at the LoRa gateway by optimizing the discrete RIS phase shifts. First, we introduce our new system design. We then propose a training algorithm to determine the optimal RIS phase shifts by maximizing the received signal power. Finally, we evaluate the BER performance of the proposed communication system at the output of a coherent receiver. Simulation results demonstrate that the proposed method enhances BER performance over the conventional LoRa system in an additive white Gaussian noise (AWGN) channel for both scenarios.