  It has been proved that a long-range (LoRa) system can achieve long-distance
and low-power. However, the performance of LoRa systems can be severely
degraded by fading. In addition, LoRa technology typically adopts an
ALOHA-based access mechanism, which inevitably produces interfering signals for
the target user. To overcome the effects of fading and interference, we
introduce a reconfigurable intelligent surface (RIS) to LoRa systems. In this
context, both non-coherent and coherent detections are considered and their bit
error rate (BER) performance analyses are conducted. Moreover, we derive the
closed-form BER expressions for the proposed system over Nakagami-m fading
channels. Simulation results are used to verify the accuracy of our proposed
analytical results. It is shown that the proposed system outperforms the
RIS-free LoRa system, and the RIS-aided LoRa system adopting blind
transmission. Furthermore, the impacts of the spreading factor (SF), the number
of reflecting elements, and the Nakagami-m fading parameters are investigated.
It is shown that increasing the number of reflecting elements can remarkably
enhance the BER performance, which is an affective measure for the proposed
system to balance the trade-off between data rate and coverage range. We
further observe that the BER performance of the proposed system is more
sensitive to the fading parameter m at high signal-to-noise ratios.
