Search

Mine communication is an indispensable part of the intelligent development of coal mines. This paper analyzes the advantages and disadvantages of different communication systems and technologies in different development stages of wireless communication in underground coal mines. It is concluded that 5G and WiFi6 currently have significant technological advantages and good applicability in terms of transmission rate, delay, reliability, and user capacity. They are the mainstream solutions for mine wireless communication technology in recent years. This paper discusses the problems in underground wireless communication system construction and the corresponding development directions. ① Technological convergence issues. Different scenarios have different requirements for bandwidth, delay, power consumption and reliability. A single communication technology can not meet the requirements of all application scenarios in coal mines. It is necessary to select appropriate communication technology according to the actual application situation to meet the application requirements. Different technologies are integrated through protocol converters, gateways and other devices to form an integrated communication network platform for technological convergence above the ground and underground. ② System integration issues. Since each system is provided by different manufacturers, and the communication protocol and hardware interface are inconsistent, it is difficult to truly realize the data sharing of each system in the mine. It is necessary to provide standard interfaces, open network architecture, and unified user data to provide interconnection and inter-working functions for monitoring, emergency, production, and other systems. It is further required to provide unified data messages to enable data transmission with low delay, high concurrency, real-time, and synchronization within each system. ③ Device power consumption issues. The existing mine 5G base station and other equipment can only be made into a single flameproof product due to their high power consumption. The equipment is bulky, large, and difficult to install and maintain, which restricts the popularization of 5G technology in coal mine. Low-power design can be started from the main chip, RF module, and power amplifier module.

The mine 5G is the foundation of intelligent mine construction. In order to meet the diversified application requirements of intelligent mine, it is necessary to promote the realization of mine 5G-advanced communication evolution system through 5G-advanced communication evolution technology. The current status of mine 5G technology research and system deployment is reviewed. The mine 5G has preliminarily realized audio and video call, HD video analysis, equipment remote control and other applications. However, there are some problems such as single terminal form, heavy uplink load, separate construction of 5G-advanced communication system and positioning system, etc. This paper analyzes the applicability of 5G-advanced communication evolution technology of 3GPP Release 17 in mine 5G-advanced communication. It is pointed out that RedCap lightweight terminal technology, NR direct connection communication technology and NR positioning technology will become the key technologies of mine 5G communication evolution. The key technologies of mine 5G-advanced communication evolution are studied. RedCap lightweight terminal technology can meet the research and development requirements of low-power consumption and low-cost multimode terminals of mine wireless sensors, single-channel wireless transmission mine video monitoring equipment, intelligent miner lamps and intelligent wearable devices. NR direct connection communication technology is applied to mine automatic driving vehicle-mounted terminal, roadway side equipment and emergency communication relay equipment. It can meet the requirements of low delay and high reliable transmission of mine automatic driving and emergency communication. NR positioning technology is applied to mine communication and positioning integration to meet the technical requirements of mine communication and positioning system fusion. This paper puts forward the architecture of mine 5G-advanced communication evolution system. The study provides the direction for building 5G fully connected mine, supporting multi-link wireless access and realizing the integration of communication and perception.

Based on the basic concepts and connotations of digital twin, this paper analyzes the application advantages of digital twin technology in coal mine power grid. The operation management of the coal mine power grid is assisted by two means of synchronous entity operation status and digital simulation operation. The technology has the characteristics of data-driven, real-time update and synchronous feedback. The basic framework of the digital twin system of the coal mine power grid is proposed. The framework is composed of physical entity layer, digital twin model layer, user service management layer and data exchange layer. The operation mode of the digital twin system of the coal mine power grid is explored from two aspects of the physical entity and the digital twin model. This paper introduces the key technologies for establishing the digital twin system of the coal mine power grid. The technologies include digital twin model construction of coal mine power grid, intelligent data acquisition, intelligent communication based on 5G, digital twin intelligent database, and digital twin equipment intelligent management platform. The application scenarios of digital twin technology in the coal mine power grid are proposed. The scenarios include the condition evaluation of underground electrical equipment, fault location and protection of the coal mine power grid, intelligent monitoring of the coal mine power grid and intelligent inspection of underground lines. The digital twin technology is applied to the coal mine power grid to carry out dynamic simulation modeling on the state and operation of the coal mine power grid. On the one hand, the higher operation requirement of the current large-scale coal mine power grid relative to the ground power grid can be met. The safety of coal mine production can be guaranteed. On the other hand, the intelligent process of the coal mine power grid can be promoted. The efficient and reasonable utilization of data resources can be realized.

This paper analyses the development status and technical characteristics of intelligent and networked technologies for conventional ground automatic driving. This paper also analyses the coal mine environmental characteristics, such as no GNSS (global navigation satellite system) signal coverage, low roadway illumination, lots of obstructions and obstacles and ubiquitous coal dust. In the context of the above technical and environmental characteristics, this study puts forward the key technologies of automatic driving research in underground coal mine. The technologies include mobile high-precision positioning technology without GNSS, laser radar technology, underground obstacle detection technology based on millimeter wave radar, underground low illumination video real-time enhancement and characteristic matching technology, underground environment high-precision map technology, underground autonomous vehicle decision planning technology, underground autonomous vehicle control execution technology, underground 5G communication technology and C-V2X direct connection communication technology. It is pointed out that the application of automatic driving in underground coal mine has the advantages of significant demand for fewer people or no people, clear operation management subject, closed scene, fixed route, slow speed, controllable permeability, good 5G construction foundation, easy open interface, etc. The reference architecture of 'human-vehicle-roadway-cloud' coal mine underground network connected automatic driving system is constructed. The system includes underground automatic driving vehicle, roadway infrastructure, personnel, coal mine cloud/edge computing platform and coal mine automatic driving application service platform. This paper designs the coal mine automatic driving vehicle architecture, which includes perception positioning system, network connected collaborative system, vehicle-mounted operating system and vehicle basic components. This paper puts forward three stages of the evolution of the network connected automatic driving in underground coal mines. The first stage is remote control and automatic driving, which realizes the transfer of vehicle drivers from underground to ground. The second stage is the automatic driving of vehicles with emergency takeover boundary. The vehicles are mainly driven by automatic driving, and remote emergency takeover is used as a safety guarantee method. The third stage is 'human-vehicle-roadway-cloud' collaborative control, the underground autonomous vehicles operate safely, efficiently and autonomously to realize highly unmanned intelligent transportation.

At present, there are more researches on the concept and development plan of intelligent mines, and less researches on the intelligent construction results and key technologies. Based on the 5-layer technical structure of intelligent mine construction, taking the intelligent construction of Daliuta Coal Mine as an example, the paper discusses the intelligent construction and effectiveness in terms of fully mechanized mining, excavation, transportation, power supply, water supply and drainage systems. A total of about 100 fixed mine positions are canceled, and more than 200 operators are reduced. The construction helps to reduce the labor costs by 40 million yuan/a, save the industrial water and electricity consumption by 30%, improve the equipment utilization by 5%, and increase the total workforce efficiency by 10%. It is pointed out that the key points of intelligent mine construction are broadening the network channel, unifying the interfaces of various subsystems, ensuring the associated equipment safe and reliable, and hiring professional personnel teams. This paper summarizes the current difficulties in the intelligent mine construction and discusses the key technologies to be tackled. The technologies include automatic coal cutting, personnel detection of mobile equipment, wireless sensing, centralized refueling, intelligent security inspection at the mine entrance and unmanned driving.

Mining 5G provides a high-speed information transmission channel for the construction of intelligent mines. The remote control application of mining equipment based on 5G is a key means to achieve less human and unmanned mine production. The paper analyzes the shortcomings of using 4G and WiFi6 in remote control of mining equipment, and points out that 5G technology is a necessary support method for achieving remote control of mining equipment. A reference architecture for remote control application system of mining equipment based on 5G is constructed using the research method of information physics system architecture. Taking 5G+coal mining machine remote control as an example, the key technologies of 5G transmission link are studied. The information flow between monitoring data and remote control data is sorted out. The current 5G network adopts a layer three communication method, and point-to-point layer two communication is required between the control system of remote control of mining equipment and the controlled equipment. In order to solve this problem, a layer two tunnel construction method and 5G LAN technology have been studied, and a stable channel for remote control information transmission has been established. In order to address the high bandwidth transmission requirements of on-site monitoring data and the low latency transmission requirements of remote control data, a flexible and adaptable over the air bandwidth allocation mechanism for resource pre-scheduling and request scheduling is proposed. The on-site test results show that a total of 13 328 data packets are transmitted through the layer two tunnel, without any packet loss or unsuccessful reception. The end-to-end delay is 11.5-23.8 ms, which can meet the transmission requirements of remote control of mining equipment. The RSRP(reference signal receiving power) distribution is between −93 dB·m and −53 dB·m, and the SINR(signal to interference plus noise ratio) distribution is between 10 dB and 38 dB, indicating good wireless coverage. The reliability, end-to-end delay, and wireless coverage of the mining 5G wireless communication system can meet the transmission requirements of remote control of shearers.

Integrated localization and wireless communication(ILWC) is a new information technology based on hardware resources and software information sharing to realize the coordination of location and communication functions. This paper briefly introduces the research progress of wireless communication technology and localization technology, and reveals that ILWC technology is the inevitable result of the bearer services expansion of wireless communication system. This study summarizes the definition and connotation of ILWC technology in different research. The core idea of ILWC is defined as 'hardware integration and software sharing'. The research progress of ILWC technology is summarized according to the two stages of equipment reuse and deep fusion. Combined with the particularity of the scene of the coal mine, the concept of ILWC in the coal mine is put forward. Based on the sharing of time, space, spectrum, computing and other resources, the technology is the fusion technology of communication function and localization function with an automatic scene perception and dynamic and adaptive resource allocation mechanism. The adaptability of underground ILWC in roadway, central substation, underground parking lot, coal working face and other scenes is discussed. It is pointed out that the challenges faced by underground ILWC are the complexity of underground wireless channel, unbalanced deployment of base stations and precise recognition of complex underground scene.

The mine wireless communication system has the advantages of wide communication coverage, convenient connection, good mobility, easy to establish, simple setup and maintenance, etc. It plays an irreplaceable role in in the construction of mine intelligence. The whole mine wireless communication system mainly include WiFi(IEEE 802.11b/g/n/ac), 3G, 4G, 5G and WiFi6(IEEE 802.11ax) system. 3G system is gradually replaced. 4G and WiFi system are gradually reduced. 5G and WiFi6 system are at the initial stage, and will gradually become the mainstream. The 4G, 5G and WiFi/WiFi6 systems are analyzed from the aspects of technical points, main functions and applications. And the advantages and disadvantages of each system are pointed out in this paper. ① The main disadvantage of the mine 4G wireless communication system is that the bandwidth and real-time indicators cannot meet the needs of application scenarios such as high-definition intelligent video and remote control. ② The problems of 5G in practical use are listed as following points. In the case of multiple systems and multiple antennas, there is a security problem of wireless transmission signals. 5G base stations are mainly explosion-proof and intrinsically safe types, which are large in quality and volume. There are problems of inconvenient to use and limited in use. 5G terminal ecology is lacked. The communication modules are expensive and power consumption is high. It does not have the conditions for large-scale industrial applications. There are few practical application cases, and the application scenarios need to be further explored. ③ WiFi6 wireless communication system has high latency, relatively low mobility and reliability. The mobile phone terminal is not mature enough, which affects the quality of voice calls. Based on the above analysis, it is pointed out that the demand of intelligent mine for wireless communication system is the demand of large bandwidth, low latency, high reliability, multi-access, multi-system, multi-interface, and position information. Finally, this study points out the development trend of mine wireless communication system. The trend includes system fusion (wireless communication and wired communication fusion, wireless communication internal fusion, wireless communication system and other system fusion). It also includes communication and positioning integration, equipment intrinsic safety, terminal module low power consumption and protocol interface standardization.

In the transportation system communication network of the heading face, there are problems such as insufficient access capacity, low transmission reliability and insufficient transmission bandwidth. In order to solve the above problems, the necessity and feasibility of the application of 5G technology in the transportation system of the coal mine heading face are discussed. The performance index of the optimized 5G system in coal mine has reached the expectation. The performance can fully meet the requirements of the current intelligent construction of coal mine for wireless communication system. 5G communication module and 5G customer premise equipment (CPE) in coal mine can provide equipment support for various equipment and sensors of heading face to access 5G network. This paper introduces the key problems to be solved in the mining transformation of 5G equipment. The 5G network architecture for mining is established to meet the demand of underground 5G signal coverage. In order to solve the problem of high power consumption of 5G equipment, the structure of 5G equipment is optimized and the heat dissipation device is designed. The problem that the RF power exceeds the standard after the superposition of multiple RF outputs and antenna gain of 5G base station is solved. The 5G network architecture and function of the heading face transportation system are proposed. With the characteristics of large bandwidth, low delay, high reliability and wide connection of 5G network, the unified access of various sensing equipment, HD video monitoring and remote centralized control of each link of the heading face transportation system can be realized.

In order to solve the problems of various types, complex system and low resource sharing rate of software and hardware equipment, difficult network upgrading and transformation, and the incapability to meet the requirements of vertical services due to limited uplink and downlink transmission bandwidth and long total service delay, this paper proposes to introduce multi-access edge computing(MEC) technology into mine network to provide support for the realization of intelligent mine. For the intelligent mine service types of video monitoring, delay sensitive and connection, the application mode of MEC is discussed, and the characteristics of MEC supporting multiple protocols and equipment access are analyzed. It is pointed out that MEC is the only choice to provide integrated management and control based on the existing underground multiple protocols and equipment, and is the best solution to provide undifferentiated high-quality end-to-end service for users. The intelligent mine network computing tree model based on business requirements is established, and its evolution is divided into three stages, namely Pre-5G, 5G and Beyond-5G(6G). The main characteristics and symbolic technologies of each stage are analyzed, as well as the business characteristics such as load balance, business mobility, data security, scalability and integration characteristics. It is pointed out that each characteristic is the worst in the first stage and the best in the third stage. However, there is still a gap to achieve the goal of truly universal hardware devices and fully standardized interfaces. Combined with the computing tree model, the intelligent mine network MEC deployment model is proposed. It is pointed out that the model is based on a three-level flat structure with depth of 2, which can give full play to the edge computing capability of nodes at all levels, and dynamically select task unloading strategy while taking into account the load balance of nodes, so as to complete efficient task coordination. Moreover, the functions of nodes can be selected and flexibly deployed according to the actual situation on the ground or underground, which is suitable for all stages of intelligent mine construction.

The 5G application scenarios such as remote control, high-definition video, unmanned mine car and unmanned aerial vehicle in intelligent mine put forward new requirements for the uplink rate of wireless network. However, the current 5G network uplink rate is insufficient, which leads to the limitation of intelligent mine business. And the existing 5G network uplink rate enhancement algorithm has limited range to improve the uplink rate. In order to solve the above problems, this paper proposes an uplink rate enhancement algorithm for 5G network in intelligent mine. By using supplementary upload technology, the spectrum resource aggregation is realized by overlaying Sub-3 GHz low band on the high band of C-Band, and the uplink rate of the network is improved by frequency domain resource allocation and time domain resource scheduling. In the middle-near point area, when the base station performs uplink data scheduling, the user equipment uses the 3.5 GHz frequency band to send uplink data in the uplink time slot of the C-Band frequency band, and uses the 1.8/2.1 GHz frequency band to send uplink data in the downlink time slot of the C-Band frequency band. In the far point area, the 3.5 GHz frequency band uplink is limited, and the user equipment only uses the 1.8/2.1 GHz frequency band to send uplink data. The test results show that the algorithm improves the mine near-point area, middle-point area and far-point area uplink rate by 17%, 41% and 213% respectively, and the average network uplink rate is significantly improved.

The basic architecture of 5G wireless communication system in coal mine is proposed: 5G core network, base band unit (BBU), remote radio unit hub (RHUB) and 5G base station are connected by 5G bearer network to realize signaling transmission among network elements. Underground 5G base stations and antenna are used to realize underground wireless signal coverage. After the base stations are converged through a RHUB, they are connected to BBU and connected to the 5G core network. The advantages and disadvantages of two kinds of 5G core network construction schemes are compared, namely user plane function/mobile edge computing (UPF/MEC) sinking and independent private network. This paper studies the bearer networks between 5G core network and BBU, between BBU and RHUB, between RHUB and 5G base station. This study focuses on the characteristics and application scenes of the three bearing methods commonly used in the bearer network between the 5G core network and the BBU, namely the optical fiber direct connection, the slicing packet network (SPN) and the 5th generation fixed network (F5G). The design schemes of coal mine 5G base stations, 5G terminals and 5G communication modules are proposed. Combining the characteristics of 5G communication technology and the requirements of coal mine intelligence development, the typical applications of 5G wireless communication systems in coal mines are discussed, such as integrated communication, high-bandwidth service applications, intelligent working face service application, remote control of mining vehicles or unmanned driving, etc. It is pointed out the further optimization directions of the coal mine 5G wireless communication system, including the design of miniaturization industry 5G core network, the low-power and intrinsically safe design of coal mine 5G base stations and other equipment, the underground application of 5G equipment in the 700 MHz frequency band to improve the coverage of 5G base stations, the customization of coal mine 5G mobile terminals and the development of industry APPs, the development of low-power 5G communication modules, industry application scenes in combination with on-site needs, etc.

The existing research results of intelligent mining in coal mines have not been combined with the production practice to specify the application of key technologies of intelligent mining in coal mines. Taking the Madiliang Coal Mine as the engineering background, the key technologies and application effects of the construction achievements of intelligent mining in the coal mine named ten intelligent systems are described. The systems include intelligent dispatching remote centralized control system, equipment intelligent early warning and remote consultation system, intelligent coal mining system, intelligent heading system, intelligent belt transportation system, unattended integrated coal transportation and sale control system, intelligent traffic safety control system, Internet + remote office system, Internet of things + intelligent storage express service system and intelligent ventilation system. The key problems in intelligent mining in coal mines at this stage are pointed out in this paper, which include the urgent need to change the ideology and concept, large initial investment, unbalanced input-output ratio, poor adaptability of mining mode, unsound personnel training system and insufficient key technology innovation. In order to solve the above problems, it is proposed that the mutual collaboration between intelligent subsystems should be further enhanced, the research of intelligent robots should be promoted, the independent perception, analysis and decision-making capabilities of equipment should be improved, and the top-level architecture of intelligent coal mines and big data application centers should be built so as to realize intelligent coal mining, transportation and sales, improve mine production efficiency, ensure the safety of personnel, and achieve the goal of unmanned (fewer people) underground mining.

In recent years, WiFi and 4G communication technology are preferred in coal mine wireless communication system in China. With development of intelligent construction of coal mine, the performance of coal mine wireless communication system cannot meet needs of intelligent development of coal mine. The paper described key technologies and performance advantages of the fifth generation mobile communication technology (5G) by comparing with previous generation mobile communication technologies. It also discussed composition and networking mode of mine-used 5G wireless communication system. Combined with characteristics of 5G communication technology and needs of coal mine intelligentization development, it put forward application scenarios of 5G communication technology in coal mine, such as underground unmanned driving and intelligent transportation, whole mine location service, equipment remote control, fault remote diagnosis, large broadband service data transmission, coal mine robot cloud control, whole mine safety monitoring information collection, virtual reality/augmented reality mine. It is pointed out that 5G technology application scenarios for coal industry still need to be continuously explored and improved, and since 5G network has high requirements for carrying network, coal mine should estimate deployment cost, and build mine 5G communication network based on its own development status and needs.