Ground Reflection Model Research Articles

Development and Field Testing of a Wireless Data Relay System for Amphibious Drones

Amphibious (air and water) drones, capable of both aerial and aquatic operations, have the potential to provide valuable drone applications in aquatic environments. However, the limited range of wireless data transmission caused by the low antenna height on water and reflection from the water surface (e.g., 45 m for vertical half-wave dipole antennas with the XBee S2CTM, estimated using the two-ray ground reflection model) persists as a formidable challenge for amphibious systems. To overcome this difficulty, we developed a wireless data relay system for amphibious drones using the mesh-type networking functions of the XBeeTM. We then conducted field tests of the developed system in a large marsh pond to provide experimental evidence of the efficiency of the multiple-drone network in amphibious settings. In these tests, hovering relaying over water was attempted for extension and bypassing obstacles using the XBee S2CTM (6.3 mW, 2.4 GHz). During testing, the hovering drone (<10 m height from the drone controller) successfully relayed water quality data from the transmitter to the receiver located approximately 757 m away, but shoreline vegetation decreased the reachable distance. A bypassing relay test for vegetation indicated the need to confirm a connected path formed by pair(s) of mutually observable drones.

BLE-Based Outdoor Localization With Two-Ray Ground-Reflection Model Using Optimization Algorithms

BLE-Based Outdoor Localization With Two-Ray Ground-Reflection Model Using Optimization Algorithms

Assessing the impact of ground reflection on measurement of the overall sound power level and acoustic radiation efficiency of rocket launches

Determining the sound power levels of a rocket is the first step in characterizing its radiation efficiency. Because the sound radiation from a launch vehicle is anisotropic, well-calibrated ground measurement stations are used, along with trajectory data, to obtain sound power. Historically, the effect of ground reflections appears to largely have been neglected in the literature, despite the potential to inflate OAPWLs and therefore radiation efficiency. This study investigates the likely effect of a finite-impedance ground on spectra, overall sound pressure levels, and power levels. The single-parameter ground reflection model by Embleton et al. [J. Acoust. Soc. Am. 74, 1239–1244 (1983)] is used to obtain an estimate for change in OASPL for a model spectrum based on space vehicle launches. When the correction is applied to the OAPWL it produces in a nearly 3dB reduction in level and reducing the efficiency by a factor of 2. This indicates the possibility that the 0.5% radiation power efficiency assumed for rockets in the past is too high.

3-D Simulation of MANET with UAV in Mountainous Areas

In recent years, there has been a worldwide boom in mountain climbing because the activity has become easier due to the higher functionality and lighter weight of mountaineering equipment. Along with this boom, mountain distress accidents have also increased. In the event of a disaster, effective communication with search and rescue victims is important. Mobile communication in the mountains, however, is limited because radio waves from the base station may be blocked due to topographic features, vegetation in the surrounding environment, etc. Therefore, a mobile ad hoc network (MANET) could be a useful means of communication. Recently, unmanned aerial vehicles (UAVs, e.g., drones and balloons) have become smaller and more sophisticated, with the result that UAVs could now be available as relay devices for MANETs. However, the effectiveness of MANETs in combination with UAVs in mountainous areas has not yet been clarified and no construction method has yet been established. Furthermore, in the case of mountain communication simulations, elevation differences of several thousand meters on mountain trails and radio wave propagation losses peculiar to mountains must be considered, as these conditions differ from those of common MANET simulations. Therefore, in this study, we simulated 3-dimensional MANET with UAVs using the Hotaka mountain range as an example case. Our radio wave propagation model includes the 2-ray ground reflection model, the double knife-edge diffraction loss model, and the standard model of vegetation attenuation. We simulated communication between a climber and a basecamp or hut on the mountain by MANET relayed by drones and a balloon in four scenarios, finding that the UAV expands the communicable area substantially in the mountains. We also examined the influence of rainfall and snow on mountain MANET communication.

Fundamental Study of Quantitative Evaluation of Radio Wave Output of Wireless Medical Telemetry Transmitters Operable in Medical Field

Wireless medical telemetry systems (WMTSs) are important medical equipment for monitoring of biological information such as the electrocardiogram of a patient in a remote location in real time. However, because WMTSs have characteristically used channels that are unique to the radio wave spectrum, many institutions have not previously managed WMTSs. Therefore, we examined a method for quantitative evaluation of the radio wave output of a wireless medical telemetry transmitter (WMTT) that can even be implemented in the medical field. In the experiments, we demonstrated the possibility of use of the method for quantitative evaluation of WMTT radio wave output in the medical field using two types of radio wave propagation model: a free-space propagation model and a two-ray ground reflection model. To determine the reference threshold value for use of each model, a breakpoint was found to be important to grasp the change point between short distance and long distance. It was indicated that the measured value was lower than the theoretical value below the breakpoint, while the measured value was slightly higher than the theoretical value beyond the breakpoint.

A Study of LoRa Performance in Monitoring of Patient’s SPO2 and Heart Rate based IoT

In this research, a sensor that will be equipped with blood oxygen saturation function (SPO2) blood and Heart Rate is MH-ET Live max30102 Sensor with Library Max30105. The advantage of this sensor is compatible with ATmega 328P, which is the Arduino board, the first experiment using Arduino Uno. Therefore, MH-ET Sensor data is integrated with Wireless Sensor Network (WSN) devices, e.g, LoRa (Long Range) 915 MHz and calculate WSN path loss when sending sensor data in mountainous areas, the model used to represent signal analysis and measurements in this study is the Ground Reflection (2-ray) model. therefore, the conditions that can be explained are patients who will send their data over hilly areas and hospitals or medical treatments called receiving nodes or coordinator nodes in much lower areas, in the same situation adding routers is expected to be a comparison of whether the data sent faster or even no impact. Furthermore, in this study, it is expected to provide clear results on the function of the router as the sender of pulse sensor data. The point is patients who are in a higher area with the level of impossibility in bringing the patient due to the condition of the patient so that the SPO2 data transmission and heart rate of the patient are expected to be known quickly by the medical authorities through the sensor node device attached to the patient's body. The use of the Adaptive Data Rate (ADR) Algorithm is used to optimize data rate, time on air (ToA) or airtime and energy consumption in the network. Therefore, the End Device (ED) in the ADR algorithm must be static (non-mobile). In the process of measuring the ADR algorithm in the position of sending data (uplink) n-bits to n-gateway. Next, the application server used is ThingsSpeak or The Things Network (TTN).

Role of earth bulge on the prediction of radio propagation path loss over irregular terrain

In this paper, we propose a new approach for the prediction of path loss for mobile radio waves over irregular terrain scenario based on the impact of earth bulge under different weather conditions. Earth bulge represents the circular segment or the curvature of the earth. As the weather changes, the value of earth bulge also varies. Different values of earth bulge are used according to the weather conditions from normal to worst. These values of earth bulge are used to compute actual distance in terms of geometric distance to the radio horizon between the transmitting and receiving points. The path loss is computed for this actual distance using two-ray ground reflection model. The results obtained for the path loss over actual distance for different weather conditions is compared with the corresponding path loss measurement data available for the existing terrain scenarios. The comparative results show the better agreement of the path loss measurement for the given scenarios with the path loss obtained under normal condition than the path loss obtained under other conditions. Also, data analysis from the comparative results shows that the mean error for normal weather condition is smaller than the mean error for other conditions.

Adaptive Control of IoT Wireless Networks in Shadowed Fading Channels

In this paper, a distributed transmission power control (TPC) scheme that jointly addresses the hidden and exposed terminal problem to enhance the spatial reuse and fairness performance of multi-hop wireless networks is proposed. Unlike other previous transmission power control schemes where the two-ray ground reflection (TRG) model is adopted, the proposed scheme is designed based on a log-normal shadowing (LNS) channel model. In addition, transmission power selection strategies to further compensate the influences of shadowing are presented. Results demonstrate that the proposed scheme outperforms the other TPC schemes in terms of spatial reuse and power consumption, resulting in an improved throughput and energy efficiency.

An indoor path loss model for wireless sensor networks

In this paper, path loss measurements were conducted and a path loss model was proposed for wireless sensor networks (WSNs) operating in indoor environment. This is done with a view to study transmit power requirements in indoor application of WSNs. The proposed model is a hybrid of the two-ray ground reflection model and the log-normal model and considers frequency and three-dimensional link trajectory as key parameters in evaluating path loss. The study highlights the effect of height on path loss exponent by means of various measurements taken in indoor environment. Comparison with the empirical data and other models in the literature was conducted and had very favourable results for the proposed model.

WAVE Communication-based V2I Channel Modeling

Wireless access in vehicle environment (WAVE) communication is currently being researched as core wireless communication technologies for cooperative intelligent transport systems (C-ITS). WAVE consists of both vehicle to vehicle (V2V) communication, which refers to communication between vehicles, and vehicle to infrastructure (V2I) communication, which refers to the communication between vehicles and road-side stations. V2I has a longer communication range than V2V, and its communication range and reception rate are heavily influenced by various factors such as structures on the road, the density of vehicles, and topography. Therefore, domestic environments in which there are many non-lines of sight (NLOS), such as mountains and urban areas, require optimized communication channel modeling based on research of V2I propagation characteristics. In the present study, the received signal strength indicator (RSSI) was measured on both an experience road and a test road, and the large-scale characteristics of the WAVE communication were analyzed using the data collected to assess the propagation environment of the WAVE-based V2I that is actually implemented on highways. Based on the results of this analysis, this paper proposes a WAVE communication channel model for domestic public roads by deriving the parameters of a dual-slope logarithmic distance implementing a two-ray ground-reflection model.

External Parasitic Elements on Clothing for Improved Performance of Wearable Antennas

A small (30 mm × 50 mm × 8 mm), waterproof 2.45 GHz wireless sensor with a standard meander line printed monopole has poor radiation characteristics when placed against the human body. A suitably optimized H-shape (step impedance resonator) parasitic element was added next to the antenna of the sensor on outer surface of clothing fabric. The parasitic element was placed on the outside of a fabric armband and was found to increase the total efficiency of the antenna by 13% in simulation results and enhanced the measured gain by 3 dB. The technique ensures that the armband is comfortable, washable, flexible, and operates successfully without wired connectors. The technique was optimized using simulation and experimental measurements with an adhesive aluminum strip. As the wireless sensor is waterproof and there is no access to the port of the antenna in the sensor, a two ray ground reflection model was used to match the received power in the spectrum analyzer using least rms curve fitting.

Phase Errors Simulation Analysis for GNSS Antenna in Multipath Environment

High-precision GNSS application requires the exact phase center calibration of antenna. Various methods are published to determine the locations of the phase center. In the outfield, when the phase errors that arose by multipath exceed the phase center variations (PCV) tolerance, the calibration values may be not useful. The objective of this paper is thus to evaluate the phase errors that arose by multipath signals. An improved model of antenna receiving signal is presented. The model consists of three main components: (1) an antenna model created by combination of right hand circular polarization (RHCP) and left hand circular polarization (LHCP), (2) a multipath signals model including amplitude, phase, and polarization, and (3) a ground reflection model applying to circular polarization signals. Based on the model, two kinds of novel up-to-down(U/D)ratios are presented. The performance of the model is assessed against the impact of up-to-down ratio of antenna on phase errors.

Inclusion of source extent and coherence in a finite-impedance ground reflection model with atmospheric turbulence

Acoustic data collected in static rocket tests are typically influenced by ground reflections. Furthermore, the partial coherence of the ground interaction due to atmospheric turbulence can play a significant role for larger propagation distances. Because the rocket plume is an extended radiator whose directionality is the result of significant source correlation, assessment of the impact of ground reflections in the data must include these effects. In this paper, a finite impedance-ground, single-source interference approach [G. A. Daigle, J. Acoust. Soc. Am. 65, 45–49 (1979)] that incorporates both amplitude and phase variations due to turbulence is extended to distributions of correlated monopoles. The theory for obtaining the mean-square pressure from multiple correlated sources in the presence of atmospheric turbulence is described. The effects of source correlation and extent, ground effective flow resistivity, and turbulence parameters are examined in terms differences in relative sound pressure level across a realistic parameter space. Finally, the model prediction is compared favorably against data from horizontal firings of large solid rocket motors. [Work supported by NASA MSFC and Blue Ridge Research and Consulting, LLC.]

The Wireless Network Routing Protocols and Data Communication Methods for Multiple Sensor Information Used in Mining Mechanical

In view of the development of wireless sensor system data transmission model in mine mechanical, we construct a ground reflection model of double path combined with the actual background demand based on the analysis of the wireless network routing protocol. Firstly, we put forward the selection strategy on wireless communication transmission power of multiple information sensor nodes. To build a data communication mode, we proposed the selection and evaluation method of network parameters based on graph theory. In consideration of the wireless channel model, combined with the initial random layout problem of network node, we explore whether to be neighbors between any two nodes arranged at random and the constraint relationship of wireless communication distance between nodes. Finally, we make up a dynamic routing selection algorithm with a view to dynamic nodes, and conduct the simulation analysis and experiment design. The research results show that with the increase of the random movement speed about network nodes, the process of depleting the energy of the nodes in the wireless sensor network speeds up, which explain the protocol given in the paper requires more energy to cope with the problem that the network topology changes frequently because of the random motion of nodes in network. The research results provide a reference to the wireless network node research and design in the electromechanical integration design.

Two‐Ray Modeling of Recombination Effects in The Presence of a Phase Conjugation Array

ABSTRACTThis article describes by means of a simple model how signal recombination effects behave under the influence of phase conjugating retrodirective array (RDA) technology. A two‐ray ground reflection model is used to predict the operational advantages of RDA technology in multipath rich environments. The simulation results show that advantageous signal recombination occurs due to automatic self‐phasing. As the number of elements in the RDA increases, the fading effect normally observed due to out of phase multipath signal is mitigated to the extent that the system approaches that of one operating in a free space environment. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1987–1989, 2013

A Transmission Power/Rate Control Scheme in CSMA/CA-Based Wireless Ad Hoc Networks

In this paper, a new power/rate control scheme is proposed to increase the network throughputs of carrier-sense-multiple-access-with-collision-avoidance (CSMA/CA)-based wireless ad hoc networks with multiple transmission rates. The design principle of the scheme is to utilize the space-time resource efficiently. For this purpose, a new measure that evaluates the space-time resource consumption per bit transmission is introduced. Simulation results show that the proposed scheme is effective in improving network throughputs under the two-ray ground reflection model and the Ricean model.

SHADOWING EFFECTS ON ROUTING PROTOCOL OF MULTIHOP AD HOC NETWORKS

Two-ray ground reflection model has been widely used as the propagation model to investigate the performance of an ad hoc network. But two-ray model is too simple to represent a real world network. A more realistic model namely shadowing propagation model has been used in this investigation. Under shadowing propagation model, a mobile node may receive a packet at a signal level that is below a required threshold level. This low signal level affects the routing protocol as well as the medium access control protocol of a network. An analytical model has been presented in this paper to investigate the shadowing effects on the network performance. The analytical model has been verified via simulation results. Simulation results show that the performance of a network becomes very poor if shadowing propagation model is used in compare to the simple two-ray model. Two solutions have also been proposed in this paper to overcome the effects of shadowing. One solution is a physical layer solution and the other one is a Medium Access Control (MAC) layer solution. Simulation results show that these two solutions reduce the shadowing effect and improve network performance.

A NOVEL ADAPTIVE WI-FI SYSTEM WITH RFID TECHNOLOGY

A novel adaptive Wireless-Fidelity (Wi-Fi) system is the combination of radio frequency identification (RFID) technology, programmable intelligent microcontroller development board (PIDB) and reconfigurable antenna with beam shape characteristics. The system is capable to sustain a Wi-Fi signal adaptively above its threshold level (-81dBm) within a range up to 100m across three different buildings with variety indoor environments and floors. It is found that the modified ground reflection model has successfully predicted the total path loss of the test-bay buildings which consist of corridors, several floors and windows. The modified propagation model is extremely crucial in determining the projection and height reconfigurable antenna to efficiently cover the scattered measurement points across the three buildings. The need of comparable signal strength is compulsory since the signal strength between 2.4GHz of reconfigurable beam shape antenna and 0.433GHz of RFID tag is different within the same distance. When reconfigurable beam shape antenna radiates with a minimum gain of 4.85dBi, the measured signal strength shows that most of the measurement points are below WiFi's threshold level which is from -69.001dBm to -115.4530dBm. However, the proposed system is able to boost all the signal strength above the threshold level with three different gain of reconfigurable beam shape antenna, 7.2dBi, 9.9dBi and 14.64dBi through the activation of mobile RFID tag at different measurement points at one time. The boosted signal strengths are within the range of -69dBm to -73.056dBm. The capability of the mobile RFID tag in producing certain level of signal strength has been successfully exploited as a wireless stimulator for the system to adaptively activate certain PIN diode switches of reconfigurable beam shape antenna in this finding. The proposed system also has a great potential in realizing a new smart antenna system replacing the conventional switching beam array (SBA) antenna.

Effect of Wireless Channels on the Performance of Ad Hoc Networks

Mobile ad hoc (MANET) network is a collection of wireless mobile nodes dynamically form-ing a temporary network without the use of any existing network infrastructure or centralized administration. To accomplish forwarding a packet to its destination, a routing protocol is used to discover routes between these nodes. This article presents a variety of results for packet-level simulations for the popular protocol—dynamic source routing (DSR)—when different channel models are used. Different radio propagation models representing the wireless channel have been proposed over the years, each one being suitable for a certain situation. The simplest model that represents wireless propagation is the freespace model. Other propagation models are the tworay ground reflection model and the shadowing model. Simulation results show that the performance metrics are highly affected by the channel model used, even the energy left or the number of nodes left alive are also different.

Ground detection of trans‐ionospheric pulse pairs by stations in the National Lightning Detection Network

Trans‐Ionospheric Pulse Pairs (TIPPs), as detected by the Blackbeard instrument on board the ALEXIS satellite, correlate with signals that the National Lightning Detection Network (NLDN) classifies as “cloud” lightning with a positive signal polarity (+IC). Correlation is only found for +IC pulses occurring in the 10 ms interval prior to TIPP occurrence. Apart from this single peak, there is no general change in lightning rates around TIPP time. Correlation between TIPPs and +IC strokes is statistically significant with 99.94% confidence. The amplitudes of +IC pulses that are associated with TTPPs are indistinguishable from the amplitudes of pulses that are not. The rise time of +IC pulses correlating with TIPPs, however, does appear to be longer than the noncorrelating +IC pulses, the median value being about 3 times greater than all other +IC pulses. By assuming TIPPs to be generated close to the detecting ground station, we can use the pulse separation time to calculate the source heights for the ground reflection model. The calculated height of TIPPs is consistent with a cloud source.