Nadir Hakem

Experimental Characterization of Ultra-Wideband Channel Parameter Measurements in an Underground Mine

Experimental results for an ultra-wideband (UWB) channel parameters in an underground mining environment over a frequency range of 3 GHz to 10 GHz are reported. The measurements were taken both in LOS and NLOS cases in two different size mine galleries. In the NLOS case, results were acquired for different corridor obstruction angles. The results were obtained during an extensive measurement campaign in the UWB frequency, and the measurement procedure allows both the large- and small-scale parameters such as the path loss exponent, coherence bandwidth, and so forth, to be quantified. The capacity of the UWB channel as a function of the physical depth of the mine gallery has also been recorded for comparison purposes.

Experimental evaluation of the ultra-wideband propagation channel in an underground mine

This paper presents a characterization of the ultra-wideband (UWB) propagation channel in an underground mining environment over a frequency range of 3 GHz to 10 GHz‥ Both LOS and NLOS measurements are considered at two corridor depth levels of 40m and 70m The results are based on experimental data obtained during an extensive measurement campaign in the UWB frequency range where the path loss exponent and the coherence bandwidth are used for comparison purposes as a function of the physical depth of the channel. This lead to a simple model sufficiently accurate to characterize the statistics of the received signal in an underground mine.

Wi-Fi-based positioning in underground mine tunnels

The Owl Positioning System (OwlPS) was originally designed as a general-purpose Wi-Fi-based indoor positioning system. It is also a tool to compare several positioning techniques from the same input data, and was used for this purpose in previous work. In this work, OwlPS is adapted to a very specific “indoor” environment, namely underground mine tunnels, which brings its own problematics in terms of radio signal propagation and therefore impacts positioning system design. Experiment were conducted at a formerly exploited gold mine, at 70 metres under ground level, across about 400 metres of drifts. Several scenarios were defined to mimic typical use cases.

Large-scale characterization of an underground mining environment for the 60 GHz frequency band

In order to improve the mining communication applications such as video with high data rates, a characterization of the underground mining channel was done. The use of the IEEE.802.15.3c standard with an OFDM modulation scheme for the 60 GHz can allowobtaining a data rate range from 31.5 Mbps to 5.67 Gbps. This paper provides the propagation characteristics of the mine, which is a complex electromagnetic environment, necessary to the deployment of networks in the IEEE.802.15.3c or the IEEE.802.11ad standard. The experimental results were obtained during an extensive measurement campaign over a frequency range of 61 GHz to 63 GHz in an underground mining environment. These results allow the extracting of the large scale parameters such as the path loss exponent which help to design wireless communication systems. The line of sight (LOS) measurements were performed in the middle of the gallery. Finally, a comparison of the results obtained in a mining environment and in a laboratory is done. The path loss exponents are less than 2 in both scenarios as the environments have dense concentration of scatterers.

A New Approach to Design Autonomous Wireless Sensor Node Based on RF Energy Harvesting System

Energy Harvesting techniques are increasingly seen as the solution for freeing the wireless sensor nodes from their battery dependency. However, it remains evident that network performance features, such as network size, packet length, and duty cycle, are influenced by the sum of recovered energy. This paper proposes a new approach to defining the specifications of a stand-alone wireless node based on a Radio-frequency Energy Harvesting System (REHS). To achieve adequate performance regarding the range of the Wireless Sensor Network (WSN), techniques for minimizing the energy consumed by the sensor node are combined with methods for optimizing the performance of the REHS. For more rigor in the design of the autonomous node, a comprehensive energy model of the node in a wireless network is established. For an equitable distribution of network charges between the different nodes that compose it, the Low-Energy Adaptive Clustering Hierarchy (LEACH) protocol is used for this purpose. The model considers five energy-consumption sources, most of which are ignored in recently used models. By using the hardware parameters of commercial off-the-shelf components (Mica2 Motes and CC2520 of Texas Instruments), the energy requirement of a sensor node is quantified. A miniature REHS based on a judicious choice of rectifying diodes is then designed and developed to achieve optimal performance in the Industrial Scientific and Medical (ISM) band centralized at 2.45 GHz. Due to the mismatch between the REHS and the antenna, a band pass filter is designed to reduce reflection losses. A gradient method search is used to optimize the output characteristics of the adapted REHS. At 1 mW of input RF power, the REHS provides an output DC power of 0.57 mW and a comparison with the energy requirement of the node allows the Base Station (BS) to be located at 310 m from the wireless nodes when the Wireless Sensor Network (WSN) has 100 nodes evenly spread over an area of 300 × 300 m2 and when each round lasts 10 min. The result shows that the range of the autonomous WSN increases when the controlled physical phenomenon varies very slowly. Having taken into account all the dissipation sources coexisting in a sensor node and using actual measurements of an REHS, this work provides the guidelines for the design of autonomous nodes based on REHS.

A novel piezoelectric micro-generator to power Wireless Sensors Networks in vehicles

This paper proposes an autonomous power supply to feed the nodes of a Wireless Sensor Network (WSN) used in vehicles. The vibration levels detected in a moving vehicle in an urban or semi urban area are used as the primary form of autonomous energy. Measurements show that a maximum power density of -16.9 dB/Hz is observed around 15 Hz for cruising speed up to. Our design is based on a cantilever piezoelectric transducer 90 km/h mechanically adjustable in frequency designed and manufactured to resonate very close to 15 Hz. Experimental results clearly demonstrate a level of energy sufficient to adequately supply power to a wireless sensor node. Specifically, for an optimum load resistance of 73.13 kΩ, a power of 3 μW is achieved by our autonomous supply.

Characterization of the 60 GHz channel in underground mining environment

This paper presents the first results at 60GHz of the path loss characterization in underground mining environment. The results are based on experimental data obtained during a measurement campaign using a frequency range from 60 to 62 GHz and a simple path loss model is used to characterize the large-scale fading of this type of environment.

Global Optimization of Multi Radio Mesh Access Point Location in Underground Area

This paper shows that with a proper placement of Mesh multi radio devices in a confined area, it is possible to reduce the congestion in the WMN (Wireless Mesh Network) by 50 to 60 percent according to the loaded traffic. The best portal deployment is obtained by minimizing the maximum traffic aggregation based on several constraints such as collision domain; routing and physical layer constraints. The different steps that must be fulfilled to reach this adequate deployment are clearly detailed. The effect of uneven resources utilization due to a non uniform spatial density of the workers in the confined area is also addressed. A well designed traffic distribution and a deployment algorithm for underground confined area are proposed and its effects on the WMN’s performance are evaluated by a Monte Carlo simulation.

Energy harvesting design for autonomous Wireless Sensors Network applied to trains

Wireless Sensor Networks (WSNs) technology is considered an excellent compromise for supporting monitoring applications on old trains operated by railway systems around the world. Although WSNs are optimized for energy management with regards to sensor nodes and communication protocols, their lifetimes remain limited by battery capacity. Deployment of new sensors or replacement of empty batteries is often required to extend the life of the WSN. These solutions are often expensive and challenging, particularly when the sensors are in unreachable places. Energy harvesting is a promising approach that addresses these issues: it powers WSNs by scavenging energy from the ambient train environment. This paper proposes a system that gathers energy generated by the trains vibration. The objective of this work is designing a harvester according to real measured vibration sources from a train and the energy requirement of a temperature/humidity sensor. Then we propose in this paper a guideline for configuring an autonomous wireless sensor node powered by a piezoelectric vibration energy harvester.

High gain cross DRA antenna array for underground communications

This paper presents the design of a high gain cross DRA array antenna (AXDRA) with a novel feeding method based on microstrip transmission line for millimeter-wave operation. Simulation results shows that the AXDRA achieves an impedance bandwidth from 57.5 GHz to 63 GHz covering ISM band, and gives an appreciable gain of 15.5 dBi, found to be stable within the passband. The size of the whole antenna structure is about 25mm×25mm and is therefore small enough to be used in underground communications systems. The simulation process was done using Computer Simulation Technology (CST) Microwave Studio.