Search and rescue in a forest environment

Progress In Electromagnetics Research B, 2013

The wireless communications in a tree canopy is essential for pre-harvesting control of fruit productions. To efficiently communicate between a sensor node and a sink node, channel characteristics in a tree canopy must be well-established. In this paper, propagation channel characteristics at the frequencies of 2.45 and 5.2 GHz have been estimated for designing a wireless communication system in a tree canopy. The proposed solution is based on measured path loss, time-varying signal strength and Angle of Arrival (AoA) for various paths in a tree canopy to estimate the channel. Since the waves reflect, refract, diffract and scatter from the foliage, it is complicated to find the true travelling path between a transmitter and a receiver at the nodes. The AoA estimator is used for physical interpretation of the channel. The experimental results demonstrate the channels in a tree canopy are mostly matched with the General Extreme Value model. The measured path gains illustrate that the appropriate antenna patterns must be selected to enhance the reliability of the system.

The increasing demand of clear communication in any situation and in any environment leads people to find a better way to communicate. Since the presence of tree canopies can affect the ability of a GSM signals through its way, one of the hardest environment is forested areas. In order to find a better way to communicate, the propagation features of the environment should be known.This study investigates the attenuation characteristics of GSM (2G, 3G and 4G) frequencies in the forest. Some theoretical models from literature were studied and simulated. The electrical field of the transmitted signal was measured in Sakarya. Due to weather and seasonal conditions, experiment was re-modeled with the trees with small, thin trunk and high amount of leaves. Finally, the literature data and experimental data were compared and discussed.

1982

A model for UHF radiowave propagation through a forest of tree trunks, branches, and leaves is developed using the discrete scattering theory of Foldy and Lax. The forest is represented as a time-invariant ensemble of tree trunks, branches, and leaves all having prescribed location and orientation statistics. Tree trunks are modelled as infinitely-long, circular, lossy-dielectric cylinders; branches as finitely-long, circular, lossy-dielectric cylinders; and leaves as flat, circular, lossy-dielectric discs. Mathematical expressions are found for the effective dyadic susceptibilities of the equivalent continuous medium and for the specific attenuation associated with the (coherent) fields. Using biophysical parameters typical of a deciduous, hardwood forest, these expressions are found to be in reasonable agreement with experimental results. An anisotropic half-space model of the forest is reflected-, and lateral wave components of the mean field presented for a pulse of a few nanose...

2014

The use of robotics in Search and Rescue operations is a topic that is gaining momentum in the scientific community. One aspect of such operations that has yet to be explored is that of wireless communication between the various robotic elements operating in the disaster area. This paper presents a model consisting of 15 Unmanned Ground Vehicles (UGVs), two Unmanned Aerial Vehicles (UAVs) and one Cell On Wheels (COW). This configuration explores the nature of such communication in the form of a network with payloads of sensor data, video data and telemetry bursts being sent from the UGVs via the UAV to the COW, and with telecommands being sent via the downlink. Another issue explored is that of horizontal handover that occurs when one UGV moves out of its home UAV’s coverage and moves into another UAV’s coverage. The results of the paper show that the network is fully functional with benchmark compliant video latency and jitter. Moreover, it is shown that the handover that occurs be...

2005 IEEE Antennas and Propagation Society International Symposium, 2005

To demonstrate a real-time, mobile, peer to peer, ad-hoc networked MIMO system in a realistic tactical environment, the Defense Advanced Research Projects Agency has instituted a program called Mobile Network MIMO. The first stage of this program is to demonstrate such a system in a rural foliated environment using MIMO equipped nodes using an ad hoc network. For any particular link both nodes are naturally at ground level. Such node placement necessitates a channel measurement and modeling effort to determine quantities such as spatial correlations, delay spread as well as propagation loss.

There is a deficit of propagation studies at wireless frequency bands in a peer to peer configuration at rural environments, which could be really interesting when designing wireless sensor networks. This paper tries to improve the knowledge of the propagation in these ambiances, in order to optimize the distances between devices in an actual network deployment. A large amount of received power samples were gathered in scrublands and grasslands, in order to obtain the general propagation equations for these scenarios.

Communication systems allow us to transmit messages through space at a certain time in order to communicate a transmitter and a receiver is needed. The messages transmitted can be represented as a sequence of symbols, light intensity, colors in a televised image, the sound pressure of the voice, etc. In this context communication systems can be decisive in emergency and rescue areas, which is why we will discuss the different communication systems occupying the radio spectrum in the city of Loja. The parameters to be considered will, transportable equipment, simplicity for a radio link , power requirements and ease of communication. The city of Loja in the south of Ecuador, affected by landslides, settlements, earthquakes , floods; areas that are in danger due to the location of the population on slopes, houses that are near rivers. That is why the most vulnerable areas to examine these events, the less affected areas and possible shelter centers. Alternatively communication earth station will be designed, as it meets the above parameters, allowing users to transport the most affected places, such as shelters or centers providing relief services (ECU911, hospitals). Besides the Transmit voice, data and video, will allow the link to anywhere on the planet. This system is not affected by technical problems when making a radio link, such as food, line of sight, communication (both can transmit voice, video and data) and can communicate anywhere in the world (dependent on satellite). To investigate this type of satellite companies that provide service, parts range, compatible equipment, frequency, antenna gain, calculations to establish a link with the satellite.

InComTech : Jurnal Telekomunikasi dan Komputer

A Wireless Sensor Network (WSN) system that uses wireless communication technologies occasionally experiences data loss when undertaking wireless data communication. This problem happens because of the WSN system being placed on top of the ground and surrounded by vegetation that adds more loss to the transmission. In order to avoid this problem, the wireless system design must meet its best performance. To build the best performing WSN system, electromagnetic wave behavior in the forest environment needs to be studied well. This paper investigates the electromagnetic wave behavior transmitted and propagated by a WSN node at less than 30 cm from the ground using a 920 MHz frequency. We have analyzed that low height (30 cm) and vegetation environments can also add more loss at about 30.96 dB to the free space pathloss model. The new 920 MHz (that adds 30.96 dB loss) model shows identical behavior to 2.4 GHz with an average difference of 12.24 dB. However, the 920 MHz model performs b...

Sensors

In this paper we consider the D2D (Device-to-Device) communication taking place between Wireless Sensor Networks (WSN) elements operating in vegetation environments in order to achieve the radio channel characterization at 2.4 GHz, focusing on the radio links blocked by oak and pine trees modelled from specimens found in a real recreation area located within forest environments. In order to fit and validate a radio channel model for this type of scenarios, both measurements and simulations by means of an in-house developed 3D Ray Launching algorithm have been performed, offering as outcomes the path loss and multipath information of the scenarios under study for forest immersed isolated trees and non-isolated trees. The specific forests, composed of thick in-leaf trees, are called Orgi Forest and Chandebrito, located respectively in Navarre and Galicia, Spain. A geometrical and dielectric model of the trees were created and introduced in the simulation software. We concluded that th...

2012

This work addresses the effects of vegetation coupling to HF/VHF wire antennas used in dense woods. A preliminary theoretical evaluation was carried out for wire dipoles, in which the electrical parameters of a thick forest were considered in the antenna resistance and reactance equations, instead of the vacuum properties. Then, impedance measurements of a few wire antennas for tactical radio links were performed in a vegetated site of Manaus, in the Brazilian Amazon. Comparing the open area to the forest results, moderate frequency shifts to the left were observed in the latter, as expected from the predictions.

Progress In Electromagnetics Research, 2010

A complete study for the deployment of a wireless sensor network in a forest based on ZigBee is presented in this paper. First, due to the lack of propagation models for peer to peer networks in forests, propagation experiments were carried out to determine the propagation model. This model was then used for planning and deploying an actual wireless sensor network. The performance of the network was compared with the expected theoretical behavior to extract some conclusions that are presented in the paper. Finally, some general conclusions, as an estimation of the minimum number of routers necessary to cover a given area, are extracted from the experiments and presented in the paper.

International journal of GEOMATE, 2024

Radio waves are significant for operating in an underground tunnel or a cave, such as two-way radio systems or emergency communication during rescue operations. Most applications used in the tunnels require wired connections because of the high attenuation of the wireless propagation. In particular, the attenuation in caves is higher than in tunnels because of the non-uniform nature of the walls. Therefore, this paper presents a study of the radio wave propagation within a cave. The experiment covers the low-frequency (LF) to ultra-high frequency (UHF) bands that aim to analyze the attenuation and behavior of waves in caves. Study results show that the low frequency and medium frequency (MF) bands can penetrate cave walls due to the deeper skin depth. At the same time, higher frequencies perform well in line-of-sight (LOS) propagation over short distances, albeit encountering significant attenuation in non-uniform cave environments. The skin depth condition obtained in the propagation result led to the Through-the-Earth (TTE) experiment by making two hand-made transceivers in the beginning band of MF at 350 kHz for transmitting and receiving waves between the mountain surface and the cave passage directly through the rock layer. The results of the TTE experiment show that the transceivers can transmit to 571 meters with a received power of -85.0 dBm before encountering an obstacle that makes it impossible to continue. Finally, the results are significant for developing the application of radio frequency within caves or tunnels and improving the application of the TTE technique with more versatility and efficiency.

IEEE Communications Magazine, 1985

Procedia Computer Science, 2019

During the movement of various types of transport (auto, rail) in forest, radio communications in the VHF / UHF bands are sharply disturbed, which is associated with attenuation and a change in the polarization plane (cross polarization effect) of radio waves in the forest. Therefore, this paper reviews the problem of the appearance of the cross-polarization effect appearance in the through propagation of VHF/UHF radio waves in forests. The parameters of cross-polarization are analyzed and the functional dependences XPD {f, ζF, rF}, XPR {f, ζF, rF} are evaluated on the operating frequency, forest vegetation properties and the distance traveled within the forest from the transmitting antenna to the receiving antenna. Rerouted by forward and backward vegetation elements, radio signals contain many cross-polarization components that can have levels comparable to the main (useful) component. An increase in cross-polarization components can be observed in the "forward" region, which can be formed by successively decreasing the useful component, ultimately causing a significant decrease in the XPD value. As a result, the relatively high cross-polarization component can consecutively reduce the level of the useful component, while the crosspolarization effect is random, and the XPD value with fluctuating distance between the transmitting and receiving stations begins to fluctuate relative to XPD = 0. Thus, the influence of forest vegetation on the propagation conditions in VHF/UHF ranges is not only manifested in a random variation of the attenuation coefficient, but also leads to a cross-polarization effect, which ultimately causes deep fading of the radio signal at the receiving point. This work can be used in assessing the fluctuations of received signals due to the occurrence of cross-polarization during transport traffic in the forest.

gazi university journal of science, 2021

Vegetation is a significant factor that affects the Quality of Service of radio waves. Several measurement campaigns have been conducted to predict the effect of trees on a radio wave at the micro and millimetre wavelengths. The experiments show that depth of vegetation is a major factor that contribute to signal attenuation. Furthermore, different components of the vegetation cause different behaviours of the radio wave. The empirical models did not put into to consideration the characteristics of the trees in the vegetation. The analytical approaches using wave theory have considered the vegetation characteristics, density and the geometry. This paper focuses on using existing models to characterise a vegetation based on measured parameters of a tree stand with a view to estimating the density of the foliage within a vegetation accurately. The foliage density will be used as the vegetation parameter in the wave theory model. Simulation of the signal attenuation will be conducted based on the density of the vegetation that will be estimated. The tree species selected for simulation are Pinus, Ash and Silver Birch tree species.