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Narrowband and Wideband Radio Channel Characteristics in Underground Mining Environments at 2.4 GHZ
Abstract
This paper presents comprehensive experimental results obtained from narrowband and wideband radio channel measurements in an underground mine with narrow veins at 2.4 GHz. From CW measurement data, large-scale distance-power curves and path-loss exponents of the environment are determined. Other relevant parameters such as mean excess delay, maximum excess delay and rms delay spread are extracted from wideband measurement data. Results show a propagation behavior that is specific for these underground environments with rough surfaces.
... In particular, a good communication system in underground mines can largely increase safety and production output. To date, however, there are few studies available in the literature which consider this special environment [1][2][3][4][5][6]. ...
... For the underground gallery considered and in the two frequency bands, random reflections have the effect of flattening the relationship between the rms delay spread and distance. In contrast, we have not seen the same phenomenon at the 40 m level of the mine [6], where the gallery is 5 meters large. In both cases, the profiles observed differ from those commonly found in indoor building environments [7] [8]. ...
This paper presents the experimental set-up and results of channel impulse response measurements conducted in an underground mining environment at center frequencies of 2.4 GHz and 5.8 GHz. The rms delay spread and the coherence bandwidth are estimated and compared for the two bands. The measurements showed that in the underground gallery considered and in the two frequency bands, random reflections have the effect of flattening the relationship between the rms delay spread and distance. In the 2.4 GHz band, the rms delay spread is less than or equal to 9.92 nanoseconds for 90% of all measurement locations. The corresponding value for the 5.8 GHz is 8.55 nanoseconds. It has been shown that the coherence bandwidth is highly variable as a function of the location of the receiver. No clear relationship is observed between the rms delay spread and the coherence bandwidth but a concentration of the coherence bandwidth values occurs when the delay spread is below 10 ns at both frequency bands. In general, it has been observed that underground radio channel characteristics are influenced by the configuration of this peculiar environment.
... The rms delay spread of each impulse response, for all the 420 measurements along the gallery and for both frequencies, tends to be flat, as can be seen in Figure 3. However, we have not observed exactly the same phenomenon at the 40 m depth of the mine [4], where the gallery is wider (5 meters). Both galleries (40 m depth and 70 m depth), have a different rms delay spread behavior as a function of distance and even differ significantly from what is commonly found in indoor building environments with smooth surfaces [4] [5]. ...
... However, we have not observed exactly the same phenomenon at the 40 m depth of the mine [4], where the gallery is wider (5 meters). Both galleries (40 m depth and 70 m depth), have a different rms delay spread behavior as a function of distance and even differ significantly from what is commonly found in indoor building environments with smooth surfaces [4] [5]. ...
Underground tunnels, such as caverns and mine galleries, are indoor environments far more hostile, in terms of wireless communication, than conventional ones like road tunnels, offices or factories. Wireless propagation behavior in these areas is found to be fairly peculiar, mainly due to the extreme roughness of wall surfaces. This paper presents comprehensive broadband measurement and modeling results of electromagnetic wave propagation in real underground mine tunnels at 2.4 and 5.8 GHz. Broadband radio propagation in these environments is observed to exhibit behavior that is quite different from conventional indoor environments with smooth surfaces. Notably, signal variation can be highly locally specific and site-specific, rms delay spread varies randomly with transmitter-receiver distance and no path arrival clustering effect is observed. These path time arrivals tend to follow a Modified Poisson distribution and amplitude tends to follow Rice and Rayleigh distributions for line-of-sight and non-line-of-sight cases, respectively. Extensive simulations have shown the models to be very close to reality.
... The LMMSE estimate has about 0-5dB gain in SNR over LS estimate for the same MSE values [2]. The major drawback of the LMMSE estimate is its high complexity, which grows exponentially with observation samples [10]. In a low rank approximation is applied to a linear minimum mean squared error estimator (LMMSE estimator) that uses the frequency correlations of the channel. ...
... The RF-based geolocation system [2], [3] employed in an underground mine uses the channel's impulse response (CIR) data, i.e. seven impulse response characteristics obtained from wideband measurements [7], [8], as the fingerprint information or 'signature', gathered at one receiver to locate the user's coordinates and to track the mobile station (figure 1). ...
In a harsh indoor environment, fingerprinting geolocation techniques perform better than the traditional ones, based on triangulation, because multipath is used as constructive information. However, this is generally true in static environments as fingerprinting techniques suffer degradations in location accuracy in dynamic environments where the properties of the channel change in time. This is due to the fact that the technique needs a new database collection when a change of the channel's state occurs. In this paper, a novel solution based on a hierarchy of artificial neural networks (ANNs) is proposed to enhance such a geolocation system. It is shown that the enhanced system detects the change in the channel's properties via geolocation reference points, identifies the new channel state and activates a new database that best represents the current radio environment
... Some channel propagation measurements in underground mines have been published. Nerguizian et al [5] made measurements and analysis for narrowband and wideband channels in an underground mine; other narrowband channel measurements are reported in [6]. UHF radio wave propagation in underground environments was analyzed in [7]. ...
This paper reports on experimental results of UWB channel propagation in underground mines. Because the mine architecture and topology is often irregular and composed of interconnected corridors, two cases were treated, namely LOS and NLOS. The goal of this work is not to formulate a channel model for UWB systems or to provide a universal model for all environments in which UWB devices will be operating, but rather to provide a set of tools that can be used to fairly evaluate the performance of different UWB physical layer proposals in real channels such as underground mines. This work was carried out by the Underground Communications Research Laboratory, LRCS, in the MMSL-CANMET experimental mine (Mining and Mineral Sciences Laboratories-Canadian Center for Minerals and Energy Technology) in Val-d'Or, Canada
... For the underground gallery considered and in the two frequency bands, random reflections have the effect of flattening the relationship between the rms delay spread and distance. In contrast, we have not seen the same phenomenon at the 40 m level of the mine [5], where the gallery is 5 meters large. In both cases, the profiles observed differ from those commonly found in indoor building environments [6] [7]. ...
This paper analyzes the results of wideband radio channel measurements conducted in an underground mining environment at center frequencies of 2.4 GHz and 5.8 GHz using a vector network analyzer. Relevant impulse response parameters such as the rms delay spread and the relative multipath total power are presented and compared for the two bands. The measurements suggest that in such an underground gallery and in the two frequency bands, random reflections have the effect of flattening the relationship between the rms delay spread and distance. In the 2.4 GHz band, the rms delay spread is less than or equal to 6.34 nanoseconds for 50% of all measurement locations. The corresponding value for the 5.8 GHz band is 4.98 nanoseconds. In general, it has been observed that underground radio channel characteristics are influenced by the configuration of this peculiar environment.
Benefits of low power multihop wireless mesh networking include a) low costs for configuration, installation and maintenance of both communication and power networks b) monitoring of sensors and control of actuators in dynamic or hazardous environments where wires are not an option c) reduction of system downtimes caused by faulty wire connectors or connections. The first standard in this emerging technology sector is Zigbee/802.15.4. Limitations of this standard include short range, suboptimal interference protection and vulnerability to multipath inter-symbol interference. A new communication standard is needed for applications that require low power wireless mesh networking with long range and robust RF links. Based on field measurements in two sample harsh environments, the authors conclude that the best foundation would be PHY and MAC layers based on low data rate, narrowband FHSS with short packets. Also, the multihop mesh network layer must be tailored to and tightly integrated with the underlying FHSS protocol for power-efficient control messaging and to ensure a stable network despite a node or link failure.
After a recent series of unfortunate underground mining disasters, the vital importance of communications for underground mining is underlined one more time. Establishing reliable communication is a very difficult task for underground mining due to the extreme environmental conditions. Until now, no single communication system exists which can solve all of the problems and difficulties encountered in underground mine communications. However, combining research with previous experiences might help existing systems improve, if not completely solve all of the problems. In this survey, underground mine communication is investigated. Major issues which underground mine communication systems must take into account are discussed. Communication types, methods, and their significance are presented.
In an underground mine, wireless systems based on ultra wideband (UWB) signals have the potential to improve the response time to mine emergencies by providing fast, reliable communications as well as precision position location. Much of the UWB research to date has focused on the in-building and (to a lesser degree) outdoor propagation environments. As a result, little information is available on the nature of UWB propagation in an underground mining environment. This paper presents preliminary path loss and power delay profile measurement results for a typical room-and-pillar underground mine located in southwest Virginia. Transmitters and receivers were separated by distances ranging from 20 m to over 300 m in both line-of-sight and non-line-of-sight configurations. These results indicate that for long corridor environments, similar to indoor hallways, a waveguide effect results in better than free space propagation. Additionally, UWB signals were found to experience less fading over a local area than CW signals. UWB signals also provide the opportunity to aid in position location by achieving very accurate time-of-arrival measurements, or via RF fingerprinting techniques. We show that initial attempts to determine position based on such an approach were also very promising. The results presented here are insufficient in number to make some definitive statements about UWB propagation in underground mines but are only a first step towards characterizing that propagation. Additionally, the initial results are similar to the trends seen in indoor environments thus providing optimism that UWB may be a viable physical layer for wireless systems in underground mines.
Wireless local area networks under the 802.11 standard offer a practical and interesting connectivity solution that features mobility, flexibility and reduction in deployment and usage costs. These networks have been tested in both indoor and outdoor environments, but little is known about their performance in confined environments such as underground mines. Measurements in the 2.4 and 5 GHz bands have been performed at the CANMET laboratory mine located in Val-d'Or, Quebec. The analysis of these measurements led to the conclusion that it is possible to adapt the 802.11 standard to underground communications. In this paper, we propose a wireless network based on the 802.11 standard combined with the DOCSIS data over cable standard as a backbone. We have also developed a methodology for wireless network deployment in underground mines.
Previous UWBchannel characterizations have been reported for various frequency bands predominantly for office environments. We present residential characterizations from 2 to 8 GHz, covering the spectrum under consideration by the FCC for UWBoverlay systems. A high degree of multipath fragmentation was found in the NLOS paths (about five times that of LOS). A mean of 7 paths for LOS and 35 paths for NLOS within 10 dBof the peak return path, with a standard deviation of 5 and 30 paths respectively. The percentage of total energy found within the 10 dBthreshold was 64% for NLOS, and 69% for LOS. This indicates that UWBreceivers must be very effective at gathering up multipath energy, especially for NLOS channels. Other channel characteristics examined include path loss exponent, shadow fading, mean excess delay and RMS delay spread. We present results for both complex baseband analysis as well as real passband (pulse based) analysis. Finally, measurements from dual receive antennas are analyzed to give spatial correlation of scattering for the UWBchannel.
This paper presents a model of the propagation of millimetric
waves along lossy dielectric side walls of random roughness found in a
mining environment. Two dimensional (2D) and three (3D) representations
are obtained with a new analytical method, the segmental statistical
method (SSM). It employs mathematical and geometric approaches linked to
a magnetic vectors projection representation, with the use of the ray
technique and the segmentation of the mining tunnel. Results are shown
to be in accordance with those obtained using the classical Rayleigh
roughness indicator. This new approach makes it possible to predict
propagation performance in extreme conditions in a long mining corridor
The paper presents a propagation characterization based on
wideband radio channel measurements made in a mine at a center frequency
of 1 GHz. The main attention is focused on the path loss and the delay
profile analysis. The path loss has been found to be 40 dB/dec in a
straight cave and 80 dB/dec in a curved cave. the delay spread was less
than 0.5 μs. The radio channel in the mine proved to be
non-reciprocal
Results from propagation measurements, conducted in an indoor
office environment at 2.4, 4.75, and 11.5 GHz, are presented. The data
were obtained in small clusters of six measurements, using a coherent
wideband measurement system. The channel characteristics for the three
frequencies are compared by evaluating path loss, rms delay spread, and
coherence bandwidth. An analytical model for evaluation of the bit-error
rate (BER) of the stationary frequency selective indoor channel is
developed for a coherent binary phase shift keying (BPSK) receiver,
based on the complex impulse response of the channel. Computational BER
results are obtained for data rates up to 50 Mb/s, using the measured
multipath channel impulse responses. The BER results for a number of
clusters are presented and compared for the maximum reliable data rate
as inferred by the measured rms delay spread of the channel
The paper reports the results of extensive measurements and
analysis of an indoor radio propagation channel's temporal variations.
The empirical data base consists of 192 one-min recordings of CW
envelope fading waveforms with both antennas stationary. Measurements
were carried out in an office environment at 1100 MHz with four
transmitter-receiver antenna separations of 5, 10, 20, and 30 m. Effects
of controlled degrees of motion with 0, 1, 2, 3, or 4 individuals
walking around the high antenna only, around the low antenna only, and
around both antennas were investigated. The reported results include
amplitude fading distributions, correlation properties, level crossing
rates, duration of fades statistics, and spectrum widths of the
frequency domain data, The results can be used in fixed wireless
computer communication applications, and in supplementing the available
spatial variation models of the indoor radio propagation channel
Towards location aware mobile ad hoc sensors A Systems Engineering Approach to Wireless Information Networks The Second Edition of this internationally respected textbook brings readers fully up to date with the myriad of developments in wireless communications. When first published in 1995, wireless communications was synonymous with cellular telephones. Now wireless information networks are the most important technology in all branches of telecommunications. Readers can learn about the latest applications in such areas as ad hoc sensor networks, home networking, and wireless positioning. Wireless Information Networks takes a systems engineering approach: technical topics are presented in the context of how they fit into the ongoing development of new systems and services, as well as the recent developments in national and international spectrum allocations and standards. The authors have organized the myriad of current and emerging wireless technologies into logical categories: * Introduction to Wireless Networks presents an up-to-the-moment discussion of the evolution of the cellular industry from analog cellular technology to 2G, 3G, and 4G, as well as the emergence of WLAN and WPAN as broadband ad hoc networks * Characteristics of Radio Propagation includes new coverage of channel modeling for space-time, MIMO, and UWB communications and wireless geolocation networks * Modem Design offers new descriptions of space-time coding, MIMO antenna systems, UWB communications, and multi-user detection and interference cancellation techniques used in CDMA networks * Network Access and System Aspects incorporates new chapters on UWB systems and RF geolocations, with a thorough revision of wireless access techniques and wireless systems and standards Exercises that focus on real-world problems are provided at the end of each chapter. The mix of assignments, which includes computer projects and questionnaires in addition to traditional problem sets, helps readers focus on key issues and develop the skills they need to solve actual engineering problems. Extensive references are provided for those readers who would like to explore particular topics in greater depth. With its emphasis on knowledge-building to solve problems, this is an excellent graduate-level textbook. Like the previous edition, this latest edition will also be a standard reference for the telecommunications industry.
We present the propagation characteristics at 2.45 and 18 GHz resulting from the statistical analysis of a narrowband measurement campaign in an underground mining environment. Parameters, such as the amplitude distribution of the envelope, level crossing rate, average fade duration and coherence time of the channel, have been examined. An analysis by linear regression has also been used to study the variations of the received power according to the transmitter-receiver distance.
RF channel measurements in mines have important applications in the field of mobile communications for improving operational efficiency and worker safety. This paper presents channel path loss measurements taken in a potash mine using a low cost RF channel measurement system. These measurements, taken at 915 MHz, are compared with a theoretical model. The measurements confirm that the mine tunnels can be modeled as oversized waveguides.
For pt.I see ibid., p.B13/1 to B13/8. In this paper the time domain (impulse response) of the indoor radio channel at 10 GHz is investigated. A discrete mathematical model is used to compute the rms delay spread and the maximum delay spread of the channel for different thresholds defined with respect to the peak line-of-sight component. Results concerning the number of received multipath components and the probability of occupancy of a certain delay time are given
This paper describes the experimental results dealing with the
radio coverage in mines. First the narrow band response of the channel
has been measured both in galleries and room with pillars in a frequency
range extending from 150 MHz to 900 MHz. Wide band measurements are then
described in order to optimize the telecommunication system
A method for measuring the transfer function of the indoor channel
using an HP network analyzer is presented. The theory of system
operation is discussed and data confirming the validity of this
technique are given. The complex impulse response is obtained from an
inverse discrete Fourier transform (IDFT) of the frequency response and
the resulting implications are examined. Results from autoregressive
moving average (ARMA) modeling using the transient error reconstruction
analysis (TERA) method to avoid resolution loss associated with data
windows is briefly presented. It is shown that an impulse response with
60 dB dynamic range and 5 ns resolution is realizable
This paper reports on experimental results and their
interpretations for an indoor extremely high frequency (EHF) multipath
channel. It is intended to help in establishing design guidelines for
indoor wireless communications systems using millimeter waves. It deals
with measurements obtained for the narrow and wideband indoor radio
channels at 37.2 GHz within a typical concrete building at Laval
University. Two kinds of transmission antennas, omnidirectional and
directional, are used to investigate the propagation characteristics for
the indoor channel. Under line-of-sight (LOS) conditions, the
distance-power law exponent is found to be lower than the free space
condition with walls playing a major role on the sustaining of high
level signals. Large- and smallscale variations extracted from the
original data are shown to follow log-normal and Rice distributions,
respectively. The observed wideband impulse response has delay spread
extending over a range up to 40 ns and a maximum root mean square (rms)
value of about 16 ns. Both amplitude and phase behaviors of the signals
are available for a better understanding of the various effects
The authors report experimental and modeling studies that
investigate the dependence of indoor radio channel multipath
characteristics on a transmit/receive range. Specifically, a simple
model for estimation of the complex baseband equivalent impulse response
for indoor channels is explained. Using this model, the relationship
between RMS delay spread and range on static indoor channels is
estimated. Results show that this relationship is nonmonotonic and has a
maximum at a range that depends on the building dimensions and the
electrical properties of reflecting surfaces. The model is used in
infinite, as well as finite, resolution modes to supplement the
measurements of impulse response characteristics in different buildings
using a limited resolution channel sounder. Experimental and modeling
results are combined to derive conclusions that confirm the anticipated
nonmonotonic relationship exists in empty buildings. Measurement results
demonstrate that furniture has the effect of destroying this
relationship, making RMS delay spread almost independent of range
A detailed analysis of time delay spread and signal level measurements at 850 MHz was performed within a large office building. The results were compared with studies of a much smaller and dissimilar office building. The results were found to be substantially the same, despite the physical differences of the buildings themselves. This may be due to external geographical features. Overall worst-case root mean square (rms) time delay spreads in the buildings were 250 ns and 218 ns in the larger and smaller building, respectively. However, these values improved to under 100 ns when there was a good direct path between the antennas. Time delay spread was also shown to be independent of relative antenna polarizations of the transmitter and receiver, even on line-of-sight paths. Received signal levels were below -90 dB with reference to the level at 0.3 m separation, in the worst cases.
This paper reports on experimental results of radio propagation in
two underground coal mines. Measurements were performed at 900 MHz on
horizontal and vertical polarization in typical coal mine operational
zones. Values of propagation loss in dB/100 m are derived. Additional
losses due to coal mine curvatures and common coal mining equipment
obstructions are also presented. A hybrid tunnel propagation model
consisting of the free space propagation model and the modified
waveguide propagation model is used to explain some measurement results.
Based on these results, we believe that microcellular radio
communications systems are feasible in coal mines
Theoretical and experimental aspects of the natural propagation of
high-frequency waves in mines are presented. A narrow-band and a
wide-band analysis have been carried out to determine the most important
characteristics of the channel such as the longitudinal attenuation, the
coherence bandwidth, and the delay spread of the impulse response in the
various areas of an underground mine. The basic principle of a
localization of a mobile has also been checked by determining the
direction of arrival of the waves
Wideband multipath measurements at 1300 MHz were made in five
factory buildings in Indiana. Root-mean-square delay spread (σ)
values were found to range between 30 and 300 ns. Median σ values
were 96 ns for line-of-sight paths along aisleways and 105 ns for
obstructed paths across aisles. Worst-case σ or 300 ns was
measured in a modern open-plan metal-working factory. Delay spreads were
not correlated with transmitter-receiver separation or factory
topography but were affected by factory inventory, building construction
materials, and wall locations. Wideband path loss measurements
consistently agreed with continuous-wave measurements made at identical
locations. It is shown that such empirical data suggest independent and
identical uniform distributions on the phases of resolvable multipath
signal components. Average factory path loss was found to be a function
of distance to the 2.2 power
In this tutorial survey the principles of radio propagation in
indoor environments are reviewed. The channel is modeled as a linear
time-varying filter at each location in the three-dimensional space, and
the properties of the filter's impulse response are described.
Theoretical distributions of the sequences of arrival times, amplitudes
and phases are presented. Other relevant concepts such as spatial and
temporal variations of the channel, large-scale path losses, mean excess
delay and RMS delay spread are explored. Propagation characteristics of
the indoor and outdoor channels are compared and their major differences
are outlined. Previous measurement and modeling efforts are surveyed,
and areas for future research are suggested
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