Development of underground communication system for data transmission using Wi-Fi direct and power line communication

Safety and productivity are of utmost concern to companies in the underground mining industry. To improve safety and productivity, it is important to understand the underground environment using sensing methods. Such sensors obtain important measurement factors such as temperature, humidity, and gas concentration that assist with accurate decision making. However, it still remains challenging to develop a communication system that can transmit data obtained by the sensors from the underground to the surface. In addition to that, the cost of maintaining a wireline communication system in an ever-expanding underground mine is high and there is a high risk of wire breakage. Hence, the introduction and use of wireless communication networks (WSNs) in underground communication systems. This study proposes a data transmission system for an underground communication system in which Wi-Fi Direct and power line communications (PLC) are selected as part of the system. The purpose is to conduct a demonstration experiment and analyze the performance of the system based on the conditions of the mine. In this study, it was developed a data transfer system with minimum cost by using PLC and Wi-Fi Direct as a means of communication as well as Wi-Fi Ad hoc. The result of the Wi-Fi Direct system was that the distance from a data logger to a smartphone was 140 m in a straight line. At this time, the communication speed was 9.1MB/s, which means that the miner could recover 230MB of data before the data loggers pass the data to the miner's smartphone. The distance between smartphones was 130 m in a straight line, and they were able to communicate at 5.7MB/s. By the time the data is shared from one smartphone to another, 72MB of data can be shared. The necessary monitoring data in the underground mine can be transmitted reliably as text and image files. Moreover, based on the results of performance analysis, a design of a data transfer system for the underground mine is demonstrated. The costs of the proposed system are estimated and compared with the most common communication system (leaky feeder). The proposed system can achieve communication for only 3% of its cost and 2% of the maintenance cost. The proposed data transfer system can be installed in a complex underground mine including a dwarf space with low cost and can be easily expanded. This data transfer system can be diverted to other mines with the installation of equipment, making it the data transfer system that underground mining companies are looking for.