Underground Communication System Research Articles

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.

Exploring the Complex underground social networks between Plants and Mycorrhizal Fungi known as the Wood Wide Web

Mycorrhizal fungi form symbiotic relationships with plant roots, connecting multiple plants through underground networks. This biologically based “wood wide web” facilitates resource transfers between plants and is hypothesized to act as an underground communication system. We explored mycorrhizal network dynamics in sub-tropical forests of northern Pakistan. Using isotopic tracing, DNA sequencing, and root imaging, we found mycorrhizal fungal networks transferred carbon, nitrogen, and phosphorus between trees and provided growth benefits to connected seedlings. Unexpectedly, we discovered single fungal genotypes linking trees across 2 km, demonstrating extensive network reach. Our results provide comprehensive field evidence that the World Wide Web functions as a cooperative conduit enabling plants to share resources, signaling chemicals, and defense compounds. Mycorrhizal networks appear critical for seedling establishment, kin recognition, and forest resilience. Further elucidating these complex dynamics will transform our understanding of belowground ecology and enable the application of nature’s symbiotic innovations

Bio-inspired vibrational wireless underground communication system

The internet of the underground things (IoUT) is an emerging field that concerns connected underground sensing nodes and can find applications in various fields such as geotechnical engineering, precision agriculture, and search and rescue operations. The complex underground environment and multiphase nature of the soil pose challenges to wireless underground communication. Most existing studies on wireless underground communication focus on the use of electromagnetic waves. However, as a highly lossy material for electromagnetic waves, soil can limit the range and reliability of data transmission. Inspired by subterranean animals that rely on vibrations or seismic waves for underground communication, the prototype system developed in this study is based on vibration. This system includes a bio-inspired vibrating source, a micro-electromechanical system (MEMS) accelerometer, a micro-controller, and a set of algorithms for encoding and decoding information. Specifically, the mole rats-inspired source is small in size, low in cost, and energy-efficient. An on-off-keying decoding algorithm enhanced with an error-correction algorithm is found to be robust in transmitting textual and imaginary information. With the current design, a maximum transmission bit rate of 16–17 bits per second and a transmission distance of 80 cm can be achieved. The bit error ratio is as low as 0.1%, demonstrating the robustness of the algorithms. The performance of the developed system shows that seismic waves produced by vibration can be used as an information carrier and can potentially be implemented in the IoUT.

Research on Ultra-Low-Frequency Communication Based on the Rotating Shutter Antenna

This paper proposes a rotating shutter antenna that can directly generate 2FSK signals in the ULF band and it is expected to be used as the transmitter for magnetic induction (MI) underground communication systems. The antenna was modeled using ANSYS Maxwell and the magnetic field distribution was simulated. The results show that the interaction between the high-permeability shutter and the mutual cancellation of magnets decreased the transmitting magnetic moment of the antenna. A prototype antenna was manufactured and the time and frequency properties of the measured Bz field were the same as the simulated results, while the magnitude of the measured signal was larger. The propagation characteristics of the antenna in air–soil–rock were simulated using FEKO and the results show that the signal strength was greater than 1 fT at a depth of 450 m from the antenna whose magnetic moment as 1 Am2. The relationship between different magnetic components and azimuth could be used to enhance the signal strength. The formula of the Bz field was derived using the measured magnitude versus distance and the path loss was also analyzed. Finally, the 2FSK modulation property of the antenna was verified by indoor communication experiments with a code rate of 12.5 bps in the ULF band.

Effective Visible Light Communication System for Underground Mining Industry

Adequate lightening and efficient communication technology have prime importance for safe underground mining communication system operations. Existing conventional light and communication systems used in underground mines are not very efficient solutions due to heavy power and maintenance requirements. Also, efficient communication technology is required for instantaneous reporting of any potential disaster event under hazardous underground environment. In this paper, we propose light fidelity (Li-Fi) as an efficient way of incident reporting as well as source of illumination for mines. Visible light communication (VLC) system is being used in mines operations, to support communication-blind areas. It exhibits superior performance over traditional radio frequency (RF) communication systems, in terms of low energy consumption, higher data rates achieved, and wide frequency band (430 − 790) T Hz. In this paper, we present VLC system for safe and reliable mining operations and analyze and discuss corresponding channel impulse response (CIR). We consider effect of shadowing and dust on our optical channel model. We compare the performance of our system with available methods in terms of bit error rate (BER), CIR, and prove the superiority of our proposed system.

On-Site and External Energy Harvesting in Underground Wireless

Energy efficiency is vital for uninterrupted long-term operation of wireless underground communication nodes in the field of decision agriculture. In this paper, energy harvesting and wireless power transfer techniques are discussed with applications in underground wireless communications (UWC). Various external wireless power transfer techniques are explored. Moreover, key energy harvesting technologies are presented that utilize available energy sources in the field such as vibration, solar, and wind. In this regard, the Electromagnetic (EM)- and Magnetic Induction (MI)-based approaches are explained. Furthermore, the vibration-based energy harvesting models are reviewed as well. These energy harvesting approaches lead to design of an efficient wireless underground communication system to power underground nodes for prolonged field operation in decision agriculture.

Wireless Underground Communications in Sewer and Stormwater Overflow Monitoring: Radio Waves through Soil and Asphalt Medium

Storm drains and sanitary sewers are prone to backups and overflows due to extra amount wastewater entering the pipes. To prevent that, it is imperative to efficiently monitor the urban underground infrastructure. The combination of sensors system and wireless underground communication system can be used to realize urban underground IoT applications, e.g., storm water and wastewater overflow monitoring systems. The aim of this article is to establish a feasibility of the use of wireless underground communications techniques, and wave propagation through the subsurface soil and asphalt layers, in an underground pavement system for storm water and sewer overflow monitoring application. In this paper, the path loss analysis of wireless underground communications in urban underground IoT for wastewater monitoring has been presented. The dielectric properties of asphalt, sub-grade aggregates, and soil are considered in the path loss analysis for the path loss prediction in an underground sewer overflow and wastewater monitoring system design. It has been shown that underground transmitter was able to communicate through thick asphalt (10 cm) and soil layers (20 cm) for a long range of up to 4 km.

Design and Implementation of Magnetic Induction based Wireless Underground Communication System Supporting Distance Measurement

Design and Implementation of Magnetic Induction based Wireless Underground Communication System Supporting Distance Measurement

Survey on Advances in Magnetic Induction-Based Wireless Underground Sensor Networks

Underground communication systems present a variety of new research challenges. Here, the goal is to establish an efficient wireless connection between the transceivers in the challenging underground medium. Typical applications for this type of communication systems include soil condition monitoring, earthquake prediction, communication in mines/tunnels, etc. These applications require a gathering of relevant information from multiple locations, which suggests the use of multiple sensor nodes that would be organized in wireless underground sensor networks (WUSNs). Due to the harsh propagation conditions in the soil medium (including rock, sand, and water sheds), traditional wireless signal propagation techniques using electromagnetic waves can only be applied for very short transmission ranges. In recent years, magnetic induction (MI)-based transmission has been proposed to overcome these issues. In this approach, induction coils are utilized as antennas in the transceivers in order to reduce the vulnerability of signal propagation to the soil properties, in particular the soil conductivity. Correspondingly, the design rules for optimum MI-WUSNs have been shown to substantially differ from the design rules for the traditional wireless communication systems due to unique properties of the transmission channel. In this survey paper, the recent advances in the area of MI-WUSNs are discussed, which range from signal transmission techniques and network design to wireless power transfer and localization. Also, new research challenges in this area are provided.

Development of wireless sensor networks for underground communication and monitoring systems (the cases of underground mine environments)

The challenges of maintaining safe workplaces and improving operations and services in underground mines are unique. These have largely been mitigated by implementing new technology of wireless sensor networks (WSNs) in the last few years. Establishment and development of a reliable monitoring and communication network through such hostile environments are still major concerns. In this study, a more comprehensive monitoring and communication system for underground mine environments using ZigBee network are developed. To this regard, experiments with real systems and prototypes are applied. The controllable and uncontrollable parameters of both underground environment and network for the establishment of ZigBee network are also assessed. Then, a practical method to design a model of an underground mine monitoring and communication system is proposed. This model was verified by testing system functions and applications for example, temperature, humidity and illumination readings, text messaging, and controlling ventilation fans throughout an underground mine in Western Australia. The monitoring and communication systems operated successfully and it demonstrated the reliable outcomes of their function and application for underground mines.

Interference effect of impulse noise on noise immunity of communication and control channels in underground structures

The interference effect of impulse noise on the noise immunity of underground communication systems is investigated. A comparative analysis of the noise immunity of an optimal demodulator of the discrete FM signals and of the system “wide band – limiter – narrow band”, in the presence of impulse noise, has been carried out.

On the Performance Enhancement When Combining STBC and Channel Estimation Techniques in Underground MIMO Channels

One way to enhance the channel data rate in enclosed environments is by incorporating multiple-input-multiple-output (MIMO) systems. Very often, this comes at the cost of data reliability. Motivated by the proven efficiency of space-time block coding (STBC) technique in conventional MIMO systems in improving the communication quality, we propose to incorporate it in wireless underground MIMO communication system and investigate data reliability at the reception in terms of bit error rate (BER). For this purpose, an intensive channel measurement campaign was performed in a mine-laboratory in northern Canada to obtain the perfect channel state. As a second step, the underground MIMO channel is estimated by sending a pilot sequence and using minimum mean square error (MMSE) principle on the received pilots. The resulting MIMO channel estimate is used to evaluate the data part in the STBC block and perform a decision using the maximum likelihood (ML) detector. Moreover, both the channel and transmitted data estimates are given analytically, and the degradation of the BER performance of the system due to MMSE estimation errors is studied using Monte Carlo simulations.

Delay Analysis of Underground Communication Using Network Coding

Underground communication system can be organized as a delay tolerant network (DTN), where delay analysis is of importance. In this paper, we derive the analysis method of block delivery delay in underground DTN using network coding. Unlike existing works that only use the contact-based model, we adopt the random walk on 2-D grid model as our mobility model. We define the innovativeness of a node as the number of new packet it can bring to the destination and derive the network state dynamics based on this definition. The simulations show that our analytic approach has better prediction to the delay performance.

On Matlab’s Simulations in Underground Mobile Multipath Channel

In underground channel environment, features of wireless mobile channel and channel modeling are discussed, and methods of calculating wireless channel model parameters by adopting even-interval tapped delay wire model are proposed. On this basis, Matlab simulation are carred out, whose results serve as theoretical foundation and criterion for further study of underground wireless communication system.

EXPERIMENTAL CHARACTERIZATION OF WIRELESS MIMO CHANNEL AT 5.8 GHZ IN UNDERGROUND GOLD MINE

This paper presents analysis results relative to an underground MIMO channel. Measurement campaigns were conducted in a former gold mine at a center frequency of 5.8GHz under Line- Of-Sight (LOS) scenario. Extracted data have been processed to obtain the relevant statistical parameters of the channel. The resulting propagation behavior difiers from frequently encountered in more typical indoor environments, such as o-ces and corridors. Indeed, the path loss exponent is less than 2 in MIMO conflguration due to the large number of scatters that increase the received power when compared to the free-space case. Moreover, there has been a signiflcant increase in spectral e-ciency, when using MIMO technique. Hence, according to calculated statistical parameters, wireless link performance is improved through the use of the MIMO scheme. All in all, multi antenna systems present an ideal alternative for future underground communication systems.

Design of High Gain and Broadband Antennas at 60 GHz for Underground Communications Systems

A new broadband and high gain dielectric resonator antenna for millimeter wave is presented. The investigated antenna configuration consists of a periodic square ring frequency selective surfaces on a superstrate, an aperture-coupled scheme feed, an intermediate substrate, and a cylindrical dielectric resonator. This antenna is designed to cover the ISM frequency band at 60 GHz (57 GHz–64 GHz). It was numerically designed using CST microwave Studio simulation software package. Another prototype with a plain dielectric superstrate is also studied for comparison purposes. A bandwidth of 13.56% at the centered frequency of 61.34 GHz and a gain of 11 dB over the entire ISM band have been achieved. A maximum gain of 14.26 dB is obtained at 60 GHz. This is an enhancement of 9 dB compared to a single DRA. HFSS is used to validate our antenna designs. Good agreement between the results of the two softwares is obtained. With these performances, these antennas promise to be useful in the design of future wireless underground communication systems operating in the unlicensed 60 GHz frequency band.

System Model of Underground UWB Based on MB-OFDM

To overcome the frequency-selective fading of ultra wide band (UWB) caused by the multi-path propagation in complicated environment of coal mines, an underground wireless communication system of UWB based on multi-band orthogonal frequency division multiplexing (MB-OFDM) for coal mine is presented. Inde-pendent angle impulse response is used to build up revised channel model for underground tunnels based on the traditional S-V model. With the revised channel model, we construct the underground UWB system based on MB-OFDM and give the band division scheme and the correction approach for channel. The model of the system was simulated in the complex environment of coal mine. Simulation results and analysis show that the underground wireless communication system of UWB based on MB-OFDM can effectively with-stand multipath fading and has the advantages of high anti-noise ability, low bit-error rate, and wide cover-age.

The readership for banned literature and its underground networks in apartheid South Africa

Based primarily on a series of oral interviews with readers, this article examines the circulation of banned literature in apartheid South Africa, exploring how banned books were exchanged, stored, read and discussed in a multitude of unusual ways. This article argues that such modes of circulation can be understood as an alternative literary culture or underground communication system, generating a parallel network with its own references and conventions. After considering the various ways and means through which people acquired, circulated and read banned material, the article concludes by asking what light this data may throw on broader book history debates. Innovation Vol. 35 2007 pp. 81-90

石炭資源の開発・利用に係わる環境技術と安全のアジアネットワーク 坑内リスク管理情報システム

Communication in underground is essential for mine safety and the importance is increasing rapidly. JCOAL and CSIRO in Australia are cooperating a research project about underground communication and risk management information system. The aim of the research is to make a revolutionary new mine safety monitoring system that involves a total risk management information system called Nexsys in the center. The new monitoring system intends to include a real time risk profile that indicates safety conditions in underground and decision support system that offer appropriate counter measures to mine operators in case of an accident. To realize these functions a knowledge base about various accidents is very important. Historical various accidents data on gas explosions and spontaneous combustions in Japan have been reviewed and a new accident knowledge base has been developed which includes newly-made three dimensional views of mine structure where the accidents occurred.Ventilation is a key factor for underground mine safety. An abnormal condition in a ventilation network such as a mine fire or roadway collapse is reflected on ventilation airflow rates rapidly. A computer program to locate the abnormal condition in the network using the airflow data from underground through the mine monitoring system was also developed and tested to add a useful tool to the new monitoring system. The details about the method for locating of abnormal condition in the network are described in the paper.

石油掘削における電磁波地中双方向通信システムの開発

石油掘削における電磁波地中双方向通信システムの開発