Two-ray Model Research Articles

Two-ray channel models with doppler effects for LEO satellite communications

In this paper we present some two-ray models with Doppler effects for Low Earth Orbit (LEO) satellite links. We show that satellite motion-caused Doppler shifts are different along the two rays, resulting in a time-varying phase shift. This is quantified with a few Doppler models and approximations. The combined interference effects, along with the path length difference caused phase shift, are calculated using a generic LEO pass-over. Channel gains are computed and compared using various antenna patterns and system parameters. The models show good agreements except for very low elevation angles. They demonstrate that a tracking antenna is effective in reducing fading for moderate to high elevation angles. Fixed patch antennas perform well. Omnidirectional and dipole antennas perform poorly. Higher carrier frequency and higher antenna height lead to faster fades. The fading becomes deeper at low elevation angles. Very fast fading is observed near the ends of a pass-over.

Measurement-based V2V propagation modeling in highway, suburban, and urban environments

Vehicle-to-vehicle (V2V) communication is one of the promising communication applications designed to optimize traffic conditions and has played a crucial role in the improvement of intelligent transportation technologies. Since there is still some uncertainty regarding generalized models that provide a more accurate representation of propagation environments, the existing literature emphasizes the need for additional experimental studies in various countries and propagation environments. This study aims to investigate the low-density and high-density characteristics of V2V channels for highway, suburban, and urban propagation environments in Türkiye. Thus, first, channel measurements were conducted for all propagation scenarios. Then, after the estimation of path loss parameters, the best-fitted path loss model was determined for each propagation scenario by comparing log-distance, two-ray, and log-ray models. It was observed that the log-ray model offered remarkably better performance than the two-ray model, especially in the majority of scenarios with two-ray characteristics. In addition, small-scale modeling and shadowing were also examined, and the outcomes were compared to relevant literature. Last, generalized path loss models were developed for six propagation scenarios and compared with previous studies. Providing additional experimental data on the impact of traffic and road environments that vary across countries on the V2V channel, this study not only validated and compared existing propagation models but also improved the representing accuracy and generalizability of the newly proposed propagation models. Here, all findings were presented in detail to support the motivation of the research.

The Multi-Cluster Fluctuating Two-Ray Fading Model

The Multi-Cluster Fluctuating Two-Ray Fading Model

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

Relay-assisted communication over a fluctuating two-ray fading channel

ABSTRACT The intricacies of relay-aided device-to-device (D2D) communication within the novel fluctuating two-ray (FTR) model is inspected in this study. Two cases with respect to co-channel interference are considered here, in case A, co-channel interferences due to unmanned aerial vehicles affect the relay while at the D2D receiver, the co-channel interferences follow the FTR model. In case B, interferences due to unmanned aerial vehicles affect the D2D receiver and the relay now experiences interferences over the FTR channels. The channel of a co-channel interference due to unmanned aerial vehicle is assumed to be a recently proposed single-shadowing based composite fading model. Further enhancing operational efficiency, the D2D receiver incorporates a power splitting mechanism for power harvesting. In this analysis a characteristic function-based approach is applied, which serves as the foundational cornerstone for deriving expressions that govern the outage and success probabilities. These intricate expressions are connected with critical factors, such as the dynamics of path-loss phenomena, the spatial separation between the interferers and the relay, the varying distances between the interferers and the D2D receiver, and the physical gap bridging the relay and the D2D receiver. Building upon the derived expressions, an extensive numerical analysis unfurls them for both interference cases.

Investigation of the Attenuation Rate of a Ultrawideband Wave Outdoors in a Two-Ray Model

Investigation of the Attenuation Rate of a Ultrawideband Wave Outdoors in a Two-Ray Model

Pathloss and Airframe Shadowing Loss of Air-to-Ground UAV Channel in the Airport Area at UHF- and L-Band

In air-to-ground unmanned aerial vehicle (UAV) communications, an accurate channel propagation model is very important for the evaluation and design of communication systems. For this purpose, we have conducted several channel measurement campaigns in the airport area at UHF- and L-band (around 433 MHz and 1.518 GHz). In the line-of-sight (LoS) case, we give the distance-dependent pathloss models for both frequenciy bands. Meanwhile, it is found that the measured pathloss in the LoS scenario has a good agreement with the two-ray propagation model at short link distances. This is because of the strong ground reflection path. In the non-LoS (NLoS) case, we propose the elevation-dependent pathloss model at UHF-band based on the field measurement results. On the other hand, considering that the airframe of the UAV can block the wave propagation during the 3-D rotation in the air and the taking off and landing procedures, we specifically analyze the statistical characteristics of the airframe shadowing loss for the two cases and provide the loss distribution models for the fixed-wing, small-sized UAVs made of wood structure and carbon fiber skins.

The Fluctuating Two-Ray Fading Model With Independent Specular Components

We introduce and characterize the independent fluctuating two-ray (IFTR) fading model, a class of fading models consisting of two specular components which fluctuate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">independently</i> , plus a diffuse component modeled as a complex Gaussian random variable. The IFTR model complements the popular fluctuating two-ray (FTR) model, on which the specular components are fully correlated and fluctuate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">jointly</i> . The chief probability functions of the received SNR in IFTR fading, including the PDF, CDF and MGF, are expressed in closed-form, having a functional form similar to other state-of-the-art fading models. Then, the IFTR model is empirically validated using multiple channels measured in rather diverse scenarios, including line of sight (LOS) millimeter-wave, land mobile satellite (LMS) and underwater acoustic communication (UAC), showing a better fit than the original FTR model and other models previously used in these environments. Additionally, the performance of wireless communication systems operating under IFTR fading is evaluated in closed-form in two scenarios: ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> ) exact and asymptotic bit error rate for a family of coherent modulations; and ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ii</i> ) exact and asymptotic outage probability.

Modeling LoRa Communications in Estuaries for IoT Environmental Monitoring Systems

Low-power wide-area networks (LPWANs) are extending beyond the conventional terrestrial domain. Coastal zones, rivers, and wetlands, among others, are nowadays common deployment settings for Internet-of-Things nodes where communication technologies such as Long Range (LoRa) are becoming popular. In this article, we investigate large-scale fading dynamics of LoRa line-of-sight (LoS) links deployed over an estuary with characteristic intertidal zones, considering both shore-to-shore (S2S) and shore-to-vessel (S2V) communications. We propose a novel methodology for path-loss prediction which captures: 1) spatial; 2) temporal; and 3) physical features of the RF signal interaction with the environmental dynamics, integrating those features into the two-ray propagation model. To this purpose, we resort to precise hydrodynamic modeling of the estuary, including the specific terrain profile (bathymetry) at the reflection point. These aspects are key to accounting for a reflecting surface of varying altitude and permittivity as a function of the tide. Experimental measurements using LoRa devices operating in the 868-MHz band show major trends in the received signal power in agreement with the methodology’s predictions.

Intelligent network planning tool for location optimization of unmanned aerial vehicle base stations using geographical images

Nowadays, automated and intelligent solutions are required by different services and applications to satisfy current industrial necessities. Internet of things/robotic devices have been found useful in the collection and processing of data for pattern recognition, analyzing and anticipating incident information, optimization, and provision of better and timely decision-making to enable network providers to measure the quality of services, thereby ensuring efficiency. Telecommunication systems need reliable and fast internet networks for connected devices and other business activities; thus, technologies are being explored to determine efficient ways of planning and installing base stations. Recently, possibilities of deploying unmanned aerial vehicles (UAVs) as base stations had been investigated. Although successes have been recorded, not much work has been done on network planning tools for location optimization of UAV base stations (UAV-BS) in 5G and beyond networks to the best of our knowledge. In this paper, an intelligent network planning tool (iNPT) for location optimization of UAV-BS has been developed with different channel models and network planning parameters. The developed tool has resources to suggest a better positioning of the UAV-BS using the simulated annealing meta-heuristic to optimize their locations. The tool also includes a battery management interface that can calculate the battery dissipation with reference to the received and transmitted power of the UAV-BS and display the estimated time of flight for the UAV-BS. Geographical information, such as the height of a specific region, obtained from a map is considered in the simulations. The results obtained using the COST231-Hata, Hata path loss, log distance, and two-ray ground reflection models have been presented in this paper. Based on the experimental results, the developed simulator can be useful in network planning tasks to improve coverage areas using UAV-BSs. In addition, the proposed tool has a friendly interface that provides geographical images, and the BSs and UAVs optimized locations.

Site-Specific Radio Propagation Model for Macrocell Coverage at Sub-6 GHz Frequencies

This article presents a radio propagation model for macrocell coverage predictions in built-up areas for sub-6-GHz frequency band. The proposed two-ray model is a combination of various individual propagation models available in the literature, namely the discrete mixed Fourier transform split-step parabolic-equation (DMFT-SSPE) to characterize reflection and diffraction phenomena due to the presence of buildings and terrain irregularities, the building-transmission model (BTM) to account for the signal attenuation through the nearby buildings and the International Telecommunication Union of Radio-communications (ITU-R) model for attenuation in vegetation to weight the excess attenuation caused by the surrounding vegetation. The performance of the proposed modeling approach was assessed against measurement results obtained from an extensive measurement campaign conducted in Rio de Janeiro, Brazil. The receiver (RX) antenna was assembled on an automotive van, and it was made to travel around the city recording the received signal level. Several drive tests were conducted, including different transmitter (TX) locations and scenarios, and at various frequencies foreseen for 5G systems, namely 750 MHz, 2.5 GHz, and 3.5 GHz.

A Roadside Unit Deployment Optimization Algorithm for Vehicles Serving as Obstacles

As an important direction of topology management and infrastructure construction in Internet of Vehicles (IoV), the problem of roadside unit deployment has been discussed a lot. Considering the problem of communication occlusion caused by mobile vehicles, a novel multi-objective optimization problem of roadside unit deployment under the constraints of target road coverage and communication reliability is proposed in this paper. Firstly, the traffic flow model of the vehicle is introduced, and the channel model considering the occlusion of a mobile vehicle is proposed by a practical two-ray model and knife-edge diffraction model. Then, on the basis of analyzing the difficulty of the problem, an Improved Artificial Bee Colony algorithm based on Neighborhood Ranking (NR-IABC) and a Greedy Heuristic (GH) algorithm are proposed to approximately solve the problem. The NR-IABC algorithm applies the “Neighborhood Ranking” method to reduce the search domain, and then to further reduce the solution time. In order to avoid a local optimum, the sensitivity and pheromone are used as the selection strategy to replace the traditional roulette selection method in the NR-IABC algorithm. In addition, the mutual attraction between bees is involved in the neighborhood search of the following bees, and a new nectar source is generated according to the reverse learning strategy to replace the worst nectar source at the end of each iteration. Finally, results of comparative simulations based on real-life datasets show that the NR-IABC-based solution can always deploy fewer RSUs, and thus is more cost-effective compared with the GH-based solution.

A Performance Analysis of VANETs Propagation Models and Routing Protocols

Vehicular Ad hoc Networks (VANETs) thrive on providing a communication channel between vehicles and infrastructures that facilitate efficient and safe Vehicle-to-Vehicle (V2V) as well as Vehicle-to-Infrastructure (V2I) communications. Reliable and efficient transmission amongst vehicles and Road Side Units (RSUs) is a prime concern of Intelligent Transportation System (ITS). One of the primary challenges involved in vehicular communication is designing an efficient routing mechanism for data dissemination from node to node via a reliable route. The harsh vehicular environment with varied road conditions and obstacles in the signal propagation path induces another challenge. Therefore, this paper presents a comparative analysis of existing routing protocols with propagation models to assist researchers in gaining insight into the existing propagation model and routing protocols. The study also optimizes routing and propagation models for reliable packet dissemination. This work uses a realistic scenario from Open Street Map (OSM), and simulations are performed using SUMO. The trace files generated from SUMO are used for further simulation in NS-3. The simulation results are presented and studied in detail. The results show that the Two-Ray Ground and FRIIS propagation model outperforms the compared models, and the routing protocol OLSR outperforms AODV and DSDV.

Random waypoint mobility and two-ray path loss model to analyse multiple routing protocols in mobile ad hoc networks

Mobile ad hoc networks face many challenges due to the wireless transmissions and mobility. The topology of the network changes rapidly due to the mobility of the nodes, and the wireless transmissions endure many effects like path loss, fading, interference, etc. The routing protocols in the mobile ad hoc networks are designed to provide the route under the dynamic topology and constraints environment. The purpose of this study is to analyse multiple routing protocols using random waypoint mobility of the nodes and by considering the effect of the two-ray path loss model for channel propagation. The simulation-based approach has been utilised to study the behaviour of the routing protocols in a dynamic environment. The flow of control messages and routing overheads has been analysed. The comparative performance of a set of six routing protocols has been analysed that assist in choosing the appropriate protocols for real deployments.

Channel Measurements and Characterizations for Long Range Air-to-Ground Communication Systems in the UHF Band

In this paper, we consider long range air-to-ground (AG) communication systems which support aeronautical platforms including unmanned aerial vehicles (UAVs) in the ultra high frequency (UHF) band. For such a system, we present the measurement based path loss analysis and multipath characteristic results at the distance of hundreds of kilometers. To this end, the experimental AG channel measurement system is implemented at the aircraft with various ground station (GS) environments. Through realistic flight tests, we observe the path loss behaviors for long range UHF channels with sea and ground earth surface reflections. By comparing the measurement results with the empirical path loss model and the spherical earth two-ray model, we demonstrate that our measurement results match well with the model. Moreover, for the multipath channel characterization, we provide field test results on the occurrence probability, delay, and power of multipath components in hilly and mountainous environments with various altitudes of the aircraft.

A Novel Approach for Securing Nodes Using Two-Ray Model and Shadow Effects in Flying Ad-Hoc Network

In the last decades, flying ad-hoc networks (FANET) have provided unique features in the field of unmanned aerial vehicles (UAVs). This work intends to propose an efficient algorithm for secure load balancing in FANET. It is performed with the combination of the firefly algorithm and radio propagation model. To provide the optimal path and to improve the data communication of different nodes, two-ray and shadow fading models are used, which secured the multiple UAVs in some high-level applications. The performance analysis of the proposed efficient optimization technique is compared in terms of packet loss, throughput, end-to-end delay, and routing overhead. Simulation results showed that the secure firefly algorithm and radio propagation models demonstrated the least packet loss, maximum throughput, least delay, and least overhead compared with other existing techniques and models.

Joint Optimization of Trajectory and Communication Resource Allocation for Unmanned Surface Vehicle Enabled Maritime Wireless Networks

In maritime wireless communications, unmanned surface vehicles (USVs) can improve coverage and transmission performance due to their agile maneuverability and flexible deployment. This paper considers a USV-enabled maritime wireless network, where a USV is employed to assist the communication between the terrestrial base station and ships. Considering the maritime environment characteristics and earth curvature, we establish the systematic USV kinetics and information transmission models. To guarantee fairness, we aim to maximize the minimum expected throughput overall ships by jointly optimizing the trajectory and communication resource allocation, subject to the constraints of the USV kinetics, safe sailing, breakpoint distances, line-of-sight links, resource allocation, and information-causality. Due to the complexity of the maritime two-ray signal propagation model, we propose a channel approximation method to find an upper bound of the throughput for the original problem. By the problem decomposition, two sub-problems are derived and solved iteratively using successive convex approximation and interior-point methods. Simulation results confirm the effectiveness of the proposed method and show that USV can significantly improve transmission performance in maritime wireless networks.

Unmanned Vehicles' Placement Optimisation for Internet of Things and Internet of Unmanned Vehicles.

Currently, the use of unmanned vehicles, such as drones, boats and ships, in monitoring tasks where human presence is difficult or even impossible raises several issues. Continuous efforts to improve the autonomy of such vehicles have not solved all aspects of this issue. In an Internet of Unmanned Vehicles (IoUV) environment, the idea of replacing the static wireless infrastructure and reusing the mobile monitoring nodes in different conditions would converge to a dynamic solution to assure data collection in areas where there is no infrastructure that ensures Internet access. The current paper fills a significant gap, proposing an algorithm that optimises the positions of unmanned vehicles such that an ad hoc network is deployed to serve specific wireless sensor networks that have no other Internet connectivity (hilly/mountainous areas, Danube Delta) and must be connected to an Internet of Things (IoT) ecosystem. The algorithm determines the optimum positions of UV nodes that decrease the path losses below the link budget threshold with minimum UV node displacement compared to their initial coordinates. The algorithm was tested in a rural scenario and 3rd Generation Partnership Project (3GPP), free space and two-ray propagation models. The paper proposes another type of network, a Flying and Surface Ad Hoc Network (FSANET), a concept which implies collaboration and coexistence between unmanned aerial vehicles (UAVs) and unmanned surface vehicles (USVs) and several use cases that motivate the need for such a network.

Elevation-angle based two-ray path loss model for Air-to-Ground wireless channels

Air-to-Ground (A2G) communication is considered as a significant enabler technology in next-generation networks. To make this a reality, a comprehensive understanding of the A2G channels is vital. This paper presents an Elevation Angle (EA) based two-ray mean path loss model for the A2G channels. In particular, we present closed-form expressions for the path loss with respect to the elevation angle and compare the results with ray-tracing simulation results. Our results show that mean path loss for the A2G channels can be accurately characterized by the proposed EA based two-ray model. Our study investigates different altitudes of the aerial terminal, different types of terrains, and two polarizations, wherein the proposed EA-based two-ray model matches well with the ray-tracing simulation results. Furthermore, a comparison of the proposed model with the other known path loss models in the literature is conducted. Finally, this work reveals an interesting relationship between the elevation angle and the signal down-fades, that these signal down-fades appear at approximately the same elevation angles regardless of the platform altitude.