971 research outputs found
Propagation channel characterisation and modelling for high-speed train communication systems
High-mobility scenarios, e.g., High-Speed Train (HST) scenarios, are expected to be
typical scenarios for the Fifth Generation (5G) communication systems. With the
rapid development of HSTs, an increasing volume of wireless communication data
is required to be transferred to train passengers. HST users demand high network
capacity and reliable communication services regardless of their locations or speeds,
which are beyond the capability of current HST communication systems. The features
of HST channels are significantly different from those of low-mobility cellular
communication systems. For a proper design and evaluation of future HST wireless
communication systems, we need accurate channel models that can mimic the
underlying channel characteristics, especially the non-stationarity for different HST
scenarios. Inspired by the lack of such accurate HST channel models in the literature,
this PhD project is devoted to the modelling and simulation of non-stationary
Multiple-Input Multiple-Output (MIMO) channels for HST communication systems.
In this thesis, we first give a comprehensive review of the measurement campaigns
conducted in different HST scenarios and address the recent advances in HST channel
models. We also highlight the key challenges of HST channel measurements and
models. Then, we study the characterisation of non-stationary channels and propose
a theoretical framework for deriving the statistical properties of these channels.
HST wireless communication systems encounter different channel conditions due to the
difference of surrounding geographical environments or scenarios. HST channel models
in the literature have either considered large-scale parameters only and/or neglected
the non-stationarity of HST channels and/or only consider one of the HST scenarios.
Therefore, we propose a novel generic non-stationary Geometry-Based Stochastic
Model (GBSM) for wideband MIMO HST channels in different HST scenarios, i.e.,
open space, viaduct, and cutting. The corresponding simulation model is then developed
with angular parameters calculated by the Modified Method of Equal Area
(MMEA). The system functions and statistical properties of the proposed channel
models are thoroughly studied. The proposed generic non-stationary HST channel
models are verified by measurements in terms of stationary time for the open space
scenario and the Autocorrelation Function (ACF), Level Crossing Rate (LCR), and
stationary distance for the viaduct and cutting scenarios. Transmission techniques which are capable of utilising Three-Dimensional (3D) spatial
dimensions are significant for the development of future communication systems.
Consequently, 3D MIMO channel models are critical for the development and evaluation
of these techniques. Therefore, we propose a novel 3D generic non-stationary
GBSM for wideband MIMO HST channels in the most common HST scenarios. The
corresponding simulation model is then developed with angular parameters calculated
by the Method of Equal Volume (MEV). The proposed models considers several timevarying
channel parameters, such as the angular parameters, the number of taps, the
Ricean K-factor, and the actual distance between the Transmitter (Tx) and Receiver
(Rx). Based on the proposed generic models, we investigate the impact of the elevation
angle on some of the channel statistical properties. The proposed 3D generic
models are verified using relevant measurement data.
Most standard channel models in the literature, like Universal Mobile Telecommunications
System (UMTS), COST 2100, and IMT-2000 failed to introduce any of the HST
scenarios. Even for the standard channel models which introduced a HST scenario,
like IMT-Advanced (IMT-A) and WINNER II channel models, they offer stationary
intervals that are noticeably longer than those in measured HST channels. This has
inspired us to propose a non-stationary IMT-A channel model with time-varying parameters
including the number of clusters, powers, delays of the clusters, and angular
parameters. Based on the proposed non-stationary IMT-A channel model, important
statistical properties, i.e., the time-variant spatial Cross-correlation Function (CCF)
and time-variant ACF, are derived and analysed. Simulation results demonstrate
that the stationary interval of the developed non-stationary IMT-A channel model
can match that of relevant HST measurement data.
In summary, the proposed theoretical and simulation models are indispensable for the
design, testing, and performance evaluation of 5G high-mobility wireless communication
systems in general and HST ones in specific
Propagation and Wireless Channel Modeling Development on Wide-Sense Vehicle-to-X Communications
The need for improving the safety and the efficiency of transportation systems has become of extreme importance. In this regard, the concept of vehicle-to-X (V2X) communication has been introduced with the purpose of providing wireless communication technology in vehicular networks. Not like the traditional views, the wide-sense V2X (WSV2X) communications in this paper are defined by including not only vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications but also train-to-X (T2X) communications constituted of train-to-train (T2T) and train-to-infrastructure (T2I) communications. All the information related to the wide-sense V2X channels, such as the standardization, scenarios, characters, and modeling philosophies, is organized and summarized to form the comprehensive understanding of the development of the WSV2X channels
A Simplified Multipath Component Modeling Approach for High-Speed Train Channel Based on Ray Tracing
Channel Modeling and Characteristics for 6G Wireless Communications
[EN] Channel models are vital for theoretical analysis, performance evaluation, and system deployment of the communication systems between the transmitter and receivers. For sixth-generation (6G) wireless networks, channel modeling and characteristics analysis should combine different technologies and disciplines, such as high-mobil-ity, multiple mobilities, the uncertainty of motion trajectory, and the non-stationary nature of time/frequency/space domains. In this article, we begin with an overview of the salient characteristics in the modeling of 6G wireless channels. Then, we discuss the advancement of channel modeling and characteristics analysis for next-generation communication systems. Finally, we outline the research challenges of channel models and characteristics in 6G wireless communications.This research was supported by the National Key R&D Program of China under grant 2018YFB1801101; the National Nature Science Foundation of China (No. 61771248 and 61971167); the Jiangsu Province Research Scheme of Nature Science for Higher Education Institution (No. 14KJA510001); and the Open Research Fund of the National Mobile Communications Research Laboratory, Southeast University (No. 2020D14).Jiang, H.; Mukherjee, M.; Zhou, J.; Lloret, J. (2021). Channel Modeling and Characteristics for 6G Wireless Communications. IEEE Network. 35(1):296-303. https://doi.org/10.1109/MNET.011.200034829630335
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
Terahertz Wireless Channels: A Holistic Survey on Measurement, Modeling, and Analysis
Terahertz (0.1-10 THz) communications are envisioned as a key technology for
sixth generation (6G) wireless systems. The study of underlying THz wireless
propagation channels provides the foundations for the development of reliable
THz communication systems and their applications. This article provides a
comprehensive overview of the study of THz wireless channels. First, the three
most popular THz channel measurement methodologies, namely, frequency-domain
channel measurement based on a vector network analyzer (VNA), time-domain
channel measurement based on sliding correlation, and time-domain channel
measurement based on THz pulses from time-domain spectroscopy (THz-TDS), are
introduced and compared. Current channel measurement systems and measurement
campaigns are reviewed. Then, existing channel modeling methodologies are
categorized into deterministic, stochastic, and hybrid approaches.
State-of-the-art THz channel models are analyzed, and the channel simulators
that are based on them are introduced. Next, an in-depth review of channel
characteristics in the THz band is presented. Finally, open problems and future
research directions for research studies on THz wireless channels for 6G are
elaborated.Comment: to appear in IEEE Communications Surveys and Tutorial
Accuracy-Complexity Tradeoff Analysis and Complexity Reduction Methods for Non-Stationary IMT-A MIMO Channel Models
open access journalHigh-mobility wireless communication systems have attracted growing interests in recent years. For the deployment of these systems, one fundamental work is to build accurate and efficient
channel models. In high-mobility scenarios, it has been shown that the standardized channel models, e.g., IMT-Advanced (IMT-A) multiple-input multiple-output (MIMO) channel model, provide noticeable longer
stationary intervals than measured results and the wide-sense stationary (WSS) assumption may be violated.
Thus, the non-stationarity should be introduced to the IMT-A MIMO channel model to mimic the channel characteristics more accurately without losing too much efficiency. In this paper, we analyze and compare
the computational complexity of the original WSS and non-stationary IMT-A MIMO channel models. Both the number of real operations and simulation time are used as complexity metrics. Since introducing the nonstationarity to the IMT-A MIMO channel model causes extra computational complexity, some computation reduction methods are proposed to simplify the non-stationary IMT-A MIMO channel model while retaining an acceptable accuracy. Statistical properties including the temporal autocorrelation function, spatial cross-correlation function, and stationary interval are chosen as the accuracy metrics for verifications. It is shown that the tradeoff between the computational complexity and modeling accuracy can be achieved by using these proposed complexity reduction methods
A Non-Stationary IMT-Advanced MIMO Channel Model for High-Mobility Wireless Communication Systems
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.With the recent developments of high-mobility wireless communication systems, e.g., high-speed train (HST) and vehicle-to-vehicle (V2V) communication systems, the ability of conventional stationary channel models to mimic the underlying channel characteristics has widely been challenged. Measurements have demonstrated that the current standardized channel models, like IMT-Advanced (IMT-A) and WINNER II channel models, offer stationary intervals that are noticeably longer than those in measured HST channels. In this paper, we propose a non-stationary channel model with time-varying parameters including the number of clusters, the powers and the delays of the clusters, the angles of departure (AoDs), and the angles of arrival (AoAs). Based on the proposed non-stationary IMT-A channel model, important statistical properties, i.e., the local spatial cross-correlation function (CCF) and local temporal autocorrelation function (ACF) are derived and analyzed. Simulation results demonstrate that the statistical properties vary with time due to the non-stationarity of the proposed channel model. An excellent agreement is achieved between the stationary interval of the developed non-stationary IMT-A channel model and that of relevant HST measurement data, demonstrating the utility of the proposed channel model
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