###### Abstract  
The environment of underground coal mines has challenging properties that makes this zone inadaptable for a stable communication system. Additionally, various deteriorating physical parameters strongly affect the performance of wireless networks, which leads to limited network coverage and poor quality of data communication. This study investigates the communication capability in underground coal mines by optimizing the wireless link to develop a stable network for an underground hazardous environment. A hybrid channel-modeling scheme is proposed to characterize the environment of underground mines for wireless communication by classifying the area of a mine into the main gallery and sub-galleries. The complex segments of mine are evaluated by categorizing the wireless links for the line-of-sight (LOS) zones and hybrid modeling is employed to examine the characteristics of electromagnetic signal propagation. For hybrid channel modeling, the multimode waveguide model and geometrical optic (GO) model are used for developing an optimal framework that improves the accessibility of the network in the critical time-varying environment of mines. Moreover, the influence of various deteriorating factors is analyzed using 2.4 GHz to 5 GHz frequency band to study its relationship with the vital constraints of an underground mine. The critical factors such as path loss, roughness loss, delay spread, and shadow fading are examined under detailed analysis with variation in link structure for the mine. underground wireless communication; EM wave propagation; hybrid channel modeling; mine waveguide model; path loss +
Footnote †: journal: Sensors  
0000-0001-5000-0000-0000-0000-0000-0000-0000-0000-00000-0000-0000-00000-00000-0000-00000-00000-00000-00000-00000-00000-00000-00000-00000-000000-00000-00000-00  
materials and high-power signals can cause disaster [4]. Predominantly, damages to network infrastructure from accidents in underground mines lead to link deterioration and communication failure. Consequently, the safety of workers is at stake. Therefore, an efficient and reliable communication system is required to ensure their safety. A system is required that can bear disasters and provide a robust tracking methodology. A stable communication framework does not only help to save work process time of machinery, but it also helps to transfer information quickly between a monitoring point and other underground units. As a result, it speeds up the rescue work in the case of accidents and natural disaster [5]. As well as the underground communication assistance and location estimation, a stable wireless system is useful for the control of mining equipment, remote monitoring, real-time access for operating information, and data gathering from a variety of sensors for underground mines. Therefore, a stable communication system is required to ensure smooth operations in underground mines and better safety. Concerning the significance of underground communication, although a large body of research exists for safe communication, several problems require immediate attention. One of the primary concerns is a safe and efficient wireless communication system to realize fast-track flexible sensor access, and larger coverage to underground monitoring areas [1; 6]. Physical structure and a sensitive medium of underground mines plays an important role in signifying the characteristics of signal propagation. Therefore, this research evaluates the influence of multiple deteriorating factors on wireless links by employing the optimized channel-modeling approach. A hybrid channel model scheme is used by classifying the different zones of a mine to examine the characteristics of electromagnetic signals. The main entrance of a mine is considered to be the mine gallery and the multiple branches are represented as sub-galleries.