LoRaAid: Underground Joint Communication and Localization System Based on LoRa Technology

Much exploration has been conducted to ensure the successful implementation of underground applications based on wireless underground sensor networks (WUSNs). However, most of them only focus on the communication aspect while neglecting location information. As a matter of fact, for scenarios such as earthquake and mine emergency rescue, it is necessary to achieve communication and positioning simultaneously. Nevertheless, accomplishing this goal is challenging, as the underground environment not only causes tremendous attenuation but also has limited hardware resources. Long range (LoRa) technology has high reception sensitivity and a simple structure, making it well suited for underground emergency rescue. Therefore, we propose a LoRa-based joint communication and localization system called LoRaAid. When a disaster occurs, the wearable LoRa device transmits sensing information to surrounding buried nodes. Through collaboration between nodes, diversity reception of signals and location acquisition of the target can be achieved simultaneously. Two different schemes are proposed to achieve correct demodulation, and the closed-form expression for bit error rate (BER) is also derived. While implementing communication, LoRaAid uses the mapping relationship between noise-reduced received signal strength indicator (RSSI) and distance to achieve trilateral localization. Numerous experimental results demonstrate that LoRaAid can enable long-range communication while achieving decimeter-level positioning accuracy.