Performance Investigation of High-Speed Train OFDM Systems under the Geometry-Based Channel Model

The high-speed of train (HST) in combination with the high carrier frequency of HST systems leads to the severe inter carrier interference (ICI) in the HST orthogonal frequency division multiplexing (HST-OFDM) systems. To avoid the complexity in OFDM receiver design for ICI eliminations, the OFDM system parameters such as symbol duration, signal bandwidth, and the number of subcarriers should be chosen appropriately. This paper aims to propose a process of HST-OFDM system performance investigation to determine these parameters in order to enhance spectral efficiency and meet a given quality-of-service (QoS) level. The signal-to-­interference-­plus-­noise ratio (SINR) has been used as a figure of merit to analyze the system performance instead of signal-to-noise ratio (SNR) as most of recent research studies. Firstly, using the non-stationary geometry-based stochastic HST channel model, the SINR of each subcarrier has been derived for different speeds of the train, signal bandwidths, and number of subcarriers. Consequently, the system capacity has been formulated as the sum of all the single channel capacity from each sub-carrier. The constraints on designing HST-OFDM system parameters have been thoughtfully analyzed using the obtained expressions of SINR and capacity. Finally, by analyzing the numerical results, the system parameters can be found for the design of HST-OFDM systems under different speeds of train. The proposed process can be used to provide hints to predict performance of HST communication systems before doing further high cost implementations as hardware designs

A Realistic 3D Non-Stationary Channel Model for UAV-to-Vehicle Communications Incorporating Fuselage Posture

Considering the unmanned aerial vehicle (UAV) three-dimensional (3D) posture, a novel 3D non-stationary geometry-based stochastic model (GBSM) is proposed for multiple-input multiple-output (MIMO) UAV-to-vehicle (U2V) channels. It consists of a line-of-sight (LoS) and non-line-of-sight (NLoS) components. The factor of fuselage posture is considered by introducing a time-variant 3D posture matrix. Some important statistical properties, i.e. the temporal autocorrelation function (ACF) and spatial cross correlation function (CCF), are derived and investigated. Simulation results show that the fuselage posture has significant impact on the U2V channel characteristic and aggravate the non-stationarity. The agreements between analytical, simulated, and measured results verify the correctness of proposed model and derivations. Moreover, it is demonstrated that the proposed model is also compatible to the existing GBSM without considering fuselage posture.Comment: 12 pages, 8 figures, CNCO

Channel Model and Performance Analysis of Millimetre-wave UAV Air-to-Ground Link under UAV Wobbling

Fifth-generation (5G) and beyond mobile communication networks are expected to meet an explosion of data traffic usage and a fast-varying environment. The millimetre-wave communications and unmanned aerial vehicles (UAVs) communications are two important methods to tackle these challenges. To thoroughly investigate millimetre-wave UAV communications, it is essential to have a good understanding of electromagnetic wave propagation in the millimetre-wave band between the UAV-carried aerial base station or the mobile relay node and ground nodes, which is known as the UAV air-to-ground (A2G) channel model. To support the millimetre-wave UAV A2G network design, it is vital to have a deep cognition of the network performance evaluation parameters of the UAV A2G link, e.g., throughput and energy efficiency. This thesis discusses three problems related to millimetre-wave UAV A2G communications. In this study, the effect of the inevitable UAV wobbling on the millimetre-wave UAV A2G channel is first investigated. The wobbling process of a hovering UAV, which is affected by wind gusts and the high vibration frequency of its propellers and rotors, is modelled. The analytical temporal autocorrelation function (ACF) for the millimetre-wave UAV A2G link is derived. With the derived temporal ACF equation, the Doppler power spectrum density for the millimetre-wave UAV A2G link is investigated. The numerical results show that the temporal ACF decreases quickly with time and the impact of the Doppler effect caused by UAV wobbling is significant on bit error probability (BEP) for the millimetre-wave A2G link. Then, the problem of throughput for the millimetre-wave UAV A2G link under UAV wobbling is investigated. Two types of detectors at the receiver to demodulate the received signal and get the instantaneous BEP of a millimetre-wave UAV A2G link under UAV wobbling are introduced. Based on the designed detectors, an adaptive modulation scheme maximising the average transmission rate under UAV wobbling by optimizing the data transmission time subject to the maximum tolerable BEP is proposed. The numerical results show that the proposed adaptive modulation maximises the temporally averaged transmission rate of the millimetre-wave UAV A2G link compared with other transmission policies under UAV wobbling. After proposing the adaptive modulation, the power control to minimise the power consumption is investigated considering the limited on-board energy of a UAV. A power control policy that minimises the transmission power while maintaining both the BEP under the threshold and the maximised average transmission rate is proposed for the millimetre-wave UAV A2G link under UAV wobbling. The energy efficiency of the UAV A2G link is evaluated to show how effective this power control policy is. The numerical results show that the power control policy reduces the power consumption by up to 50% for wobbling millimetre-wave UAV A2G links and the energy efficiency of the system under power control is higher than that of the adaptive modulation scheme without the power control policy. In summary, the thesis studies the channel characteristics and evaluates the performance of the millimetre-wave UAV A2G link under wobbling to support the future millimetre-wave UAV communication network deployment. A key observation is that even for weak UAV wobbling, the temporal ACF of the UAV A2G link deteriorates quickly, making the link difficult to establish a reliable communication link. To keep the reliable A2G link and achieve high throughput, the adaptive modulation scheme of the millimetre-wave UAV A2G link under wobbling is proposed. The power control policy for the adaptive modulation of the millimetre-wave UAV A2G link could save power by over 50% and support the green UAV A2G link

A 3D GBSM for high-speed train communication systems under deep cutting scenarios

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This paper proposes a novel three-dimensional (3D) cylinder geometry-based stochastic model (GBSM) for non-isotropic multiple-input multiple-output (MIMO) Rice fading channels in high-speed train (HST) wireless communications under deep cutting scenarios. Using a validated approximation, the closed-form expression of the space-time correlation function (ST CF) of the proposed GBSM is obtained. Different from two-dimensional (2D) channel models, in the 3D GBSM the elevation angles and the height of the base station (BS) antenna relative to the mobile station (MS) one are introduced. The numerical results show the rationality of the approximation and how the arrangements of antennas affect the ST CF

A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles

In recent years, there has been a dramatic increase in the use of unmanned aerial vehicles (UAVs), particularly for small UAVs, due to their affordable prices, ease of availability, and ease of operability. Existing and future applications of UAVs include remote surveillance and monitoring, relief operations, package delivery, and communication backhaul infrastructure. Additionally, UAVs are envisioned as an important component of 5G wireless technology and beyond. The unique application scenarios for UAVs necessitate accurate air-to-ground (AG) propagation channel models for designing and evaluating UAV communication links for control/non-payload as well as payload data transmissions. These AG propagation models have not been investigated in detail when compared to terrestrial propagation models. In this paper, a comprehensive survey is provided on available AG channel measurement campaigns, large and small scale fading channel models, their limitations, and future research directions for UAV communication scenarios

A three dimensional MIMO channel model for unmanned Aerial vehicle in urban environments

Increasing the availability of Unmanned Aerial Vehicles (UAV's) platforms leads to a variety of applications for aerial exploration, surveillance, and transport. Many of these applications rely on the communication between the UAV and the ground receiver which is subjected to high mobility that may lead to restrictions on link connectivity and throughput. In order to design high throughput and efficient communication schemes for these scenarios, a deep understanding of the communication channel behavior is required, especially taking into account measurement data from flight experiments. Channel propagation in urban environments involves diffraction effects which modify the Line-of-Sight (LoS) contribution of the total received signal, especially when the receiver is located on the ground. This process leads to scenarios where Multiple-Input Multiple-Output (MIMO) signal processing can take advantage from this situation. In this context, the goal of this paper is to study the diffraction effects of the LoS component through spatial correlation metrics of the signal. To accomplish this, we propose the use of a geometric stochastic technique to model the channel behavior which lies between High Altitude Platforms (HAP) and terrestrial link communications.Fil: Mendoza, Horacio Aurelio. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Corral Briones, Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; Argentin

A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future

A High Altitude Platform Station (HAPS) is a network node that operates in the stratosphere at an of altitude around 20 km and is instrumental for providing communication services. Precipitated by technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels, and battery energy densities, and fueled by flourishing industry ecosystems, the HAPS has emerged as an indispensable component of next-generations of wireless networks. In this article, we provide a vision and framework for the HAPS networks of the future supported by a comprehensive and state-of-the-art literature review. We highlight the unrealized potential of HAPS systems and elaborate on their unique ability to serve metropolitan areas. The latest advancements and promising technologies in the HAPS energy and payload systems are discussed. The integration of the emerging Reconfigurable Smart Surface (RSS) technology in the communications payload of HAPS systems for providing a cost-effective deployment is proposed. A detailed overview of the radio resource management in HAPS systems is presented along with synergistic physical layer techniques, including Faster-Than-Nyquist (FTN) signaling. Numerous aspects of handoff management in HAPS systems are described. The notable contributions of Artificial Intelligence (AI) in HAPS, including machine learning in the design, topology management, handoff, and resource allocation aspects are emphasized. The extensive overview of the literature we provide is crucial for substantiating our vision that depicts the expected deployment opportunities and challenges in the next 10 years (next-generation networks), as well as in the subsequent 10 years (next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial

6G Enabled Advanced Transportation Systems

The 6th generation (6G) wireless communication network is envisaged to be able to change our lives drastically, including transportation. In this paper, two ways of interactions between 6G communication networks and transportation are introduced. With the new usage scenarios and capabilities 6G is going to support, passengers on all sorts of transportation systems will be able to get data more easily, even in the most remote areas on the planet. The quality of communication will also be improved significantly, thanks to the advanced capabilities of 6G. On top of providing seamless and ubiquitous connectivity to all forms of transportation, 6G will also transform the transportation systems to make them more intelligent, more efficient, and safer. Based on the latest research and standardization progresses, technical analysis on how 6G can empower advanced transportation systems are provided, as well as challenges and insights for a possible road ahead.Comment: Submitted to an open access journa