# Delay-Sensitive Multi-Sensor Routing Scheduling Method for Underground IoT in Mines
## 1 Introduction  
Underground mining is an industry with a high accident rate that presents significant risks to both workers and operations. The persistent challenges of preventing mining accidents, detecting them in real time, and mitigating their consequences has received increasing attention from both researchers and industry professionals [1]. Recently, advances in mining safety have focused on the integration of technology, particularly in predicting and preventing accidents before they occur. The early detection of hazards and minimizing the impact of incidents remain critical and complex areas of study [2]. A key aspect of these advances is the timely and accurate transmission of information within mines, making the Internet of Things (IoT) an essential tool in enhancing operational safety. In the context of mining, IoT sensor networks are indispensable for monitoring and managing critical data, including the status of equipment, personnel locations, and environmental conditions. These networks not only improve the efficiency of mine operations, but also significantly improve safety by detecting potential hazards before they escalate. IoT devices provide real-time data that enable predictive maintenance and early anomaly detection, thus preventing accidents. In addition, in the event of an accident, these sensor networks accelerate the transmission of key information, aiding in a faster emergencyresponse and improving the overall effectiveness of rescue operations. By relaying detailed event data, the impact on post-incident construction and recovery efforts is minimized. However, despite the potential of IoT in mining, wireless communication in such environments faces two primary challenges. First, data transmission delays occur because data packets often pass through multiple network nodes, reducing the timeliness of critical information. Second, data collisions caused by simultaneous transmissions from multiple sensors lead to packet loss, which compromises the reliability of the communication system. These challenges highlight the need for robust and efficient wireless transmission methods tailored to the demanding conditions of underground mines. To address these issues, various researchers have investigated routing and scheduling algorithms designed for use in underground mining environments. [PERSON] [3] and [PERSON] [4] have explored ways to optimize power consumption and extend the network lifetime of Wireless Sensor Networks (WSNs) by strategically placing sensors and applying quality-of-service strategies. Their research has focused on improving the reliability and scalability of the networks through load-balancing techniques. In particular, [PERSON] et al. [3] accounted for sensor mobility and channel characteristics, offering a comprehensive analysis of real-world applications. In addition, [PERSON] et al. [5] proposed a hierarchical communication structure, which organizes the network into separate layers of the protocol stack for communication and information transmission. This approach improves scalability and improves network robustness by optimizing resource utilization between routing nodes. [PERSON] et al. [6], on the other hand, introduced a delay-sensitive routing and scheduling method based on Ant Colony Optimization (ACO). Through simulations and performance comparisons, [PERSON]'s method demonstrated superior performance in minimizing delay and jitter under specific mining conditions. Despite the progress made, several challenges remain unresolved in current research. One major limitation is the insufficient consideration of transmission delay, as most studies emphasize energy efficiency and packet loss without addressing the varying transmission deadlines of different sensors. The lack of comprehensive delay analysis presents a gap in existing solutions, especially in time-sensitive applications.