## 2 Background and Related Work
### Related Work  
Only some works propose the deployment of sensor nodes for long-term planning in underground mining. However, articles that propose general frameworks and strategies to deploy sensors in mining were found in the literature review. In [42], the authors focus on enhancing the communication approach of relay nodes in WSN--IoT for underground coal mines. They propose a framework design for relay node deployment patterns with load balancing to maximize the network's lifetime. The proposed model improves the network coverage lifetime parameter compared to existing linear relay node deployment approaches. This paper does not provide any specific results as a proposal but suggests the need for experimental validation with various network analysis parameters to validate the proposed model. On the other hand, [PERSON] and [PERSON] [43] proposed a multilevel sensor deployment approach in an IIoT-based environmental monitoring system in underground coal mines to enhance the network's lifetime and minimize the tunneling effect (a quantum phenomenon where a particle can cross a barrier, even if in classical physics it would not have enough energy to do so) at each level in the network. A simulation was performed in Matlab(r), considering the parameters of transceivers such as frequency and packet size. The authors assumed parallel roadway mine structures in the 250-2000 m range. Also, they assumed a communication range of 40 m but did not consider the sensing range. The proposed technique extends the network lifetime by limiting the tunneling effect near the sink. Compared to previous algorithms [44; 45], it consumes more than 80% of the average power of the network system. Ref. [45] presents a deployment scheme for environmental monitoring in longwall coal mines. The proposed scheme is based on probabilistic event detection and applies the virtual force method to minimize overlapping regions, preserving network connectivity. The authors simulated the algorithm using a mine of 250 m in length. The sensing and communication ranges were assumed and set as 10 m and 20 m, but these values were not obtained through simulations or experimentation. The results show that the node deployment scheme improved connectivity and 2-3 hop communication to the nearest relay node compared to other schemes. Additionally, it optimized the coverage area using a minimal number of sensor nodes and was found to be cost-effective. [PERSON] et al. [46] propose a 3D node deployment method for underground coal mine tunnels. These authors applied an algorithm to solve the problem of k-coverage from three points inside the mine: sidewalls, roof, and the combination of walls and ceiling. It was considered a typical mine tunnel with a 100 m length for simulations. Furthermore, there was a sensing radius of 7 m. The deployment was optimized using the Annealing algorithm. The algorithm was evaluated according to the sensing efficiency (sensing radius), and redundancy was evaluated according to the coverage degree. The results suggested that the sensing efficiency is determined by the characteristics of the sensors and by the terrain of the monitored area. The redundancy of nodes affects the coverage's ability. A study about the deployment strategies based on surface mines (open-pit) was conducted in [47]. The authors investigate how topographical changes from continuous mining over a decade affect the propagation conditions and the performance of different wireless network deployment strategies (small-cells, macro-cells, and heterogeneous). This article compares deployment strategies and network capabilities to existing technologies to see if they can achieve specific performance goals, path loss, and signal-to-noise ratios (SINR) to guarantee coverage. The results show that heterogeneous deployments can be exploited to ensure continuous coverage in this ever-changing topography.