RIS-Aided LoRa Uplink Transmission With Differential Index Modulation

With the advantages of low power consumption, wide range coverage, low cost, and non-coherent detection capabilities, long-range (LoRa) technology exhibits signifblackicant potential for application across a wide range of fields, and has thus attracted considerable attention in recent years. Nevertheless, its real-world performance remains hampered by the low data transmission rate. In this paper, we leverage reconfigurable intelligent surface (RIS) and differential index modulation (DIM) in LoRa uplink systems, and develop a RIS-aided LoRa uplink transmission scheme with DIM to enhance the transmission data rate of the system. In the transmission design, additional information is conveyed by constructing RIS-aided space-time coding blocks and utilizing the activation sequence of receiving antenna array elements, followed by demodulation through a differential encoding-based IM strategy that does not require channel state information (CSI). In the detection design, the orthogonal characteristics of LoRa are leveraged to decouple the detections of LoRa symbols and RIS-aided space-time coding blocks, employing sphere decoding algorithms to reduce the complexity of differential detection. Simulation results demonstrate that the proposed transmission and detection design inherits the non-coherent detection characteristics of traditional LoRa and significantly enhances both the data rate and bit error rate performances of the system.