Enhancing LoRa Uplink Transmissions through RIS Beamforming and Index Modulation

Document Type

Article

Publication Date

1-1-2026

Abstract

Chirp spread spectrum (CSS) modulation-based long-range (LoRa) communication has attracted widespread attention owing to its long-range coverage and low-power consumption. However, the inherent trade-off between communication range and data rate in CSS modulation creates a throughput bottleneck, significantly limiting LoRa’s applicability in practical scenarios. To enhance the uplink data rate and reliability in LoRa communications, this paper proposes novel schemes that integrate reconfigurable intelligent surfaces (RIS) and index modulation (IM). Specifically, we develop comprehensive transmission and detection mechanisms for both single-node and multi-node scenarios. To improve the performance of single-node transmission, we introduce an IM scheme based on receiving antenna selection combined with RIS-assisted beamforming, and design a low-complexity sequential detector that exploits unique signal characteristics. To address the multi-node scenario with the co-spreading-factor (co-SF) interference, we propose a power control scheme at transmitters inspired by non-orthogonal access principles, and develop an asymptotically optimal RIS beamforming strategy. We further design an efficient demodulation scheme that leverages statistical features of the received signals across selected antennas. Extensive simulation results demonstrate that our proposed schemes effectively improve both bit error rate and data rate performance compared to conventional LoRa systems and related prior art.

Publication Source (Journal or Book title)

IEEE Internet of Things Journal

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