Wireless Channel Simulation Research Articles

An effective method for modelling wireless communication systems

Statement of the problem. To describe the multipath propagation of radio signals using two models: the ray tracing method and the method of stochastic simulation. Let us consider the stochastic model as the most general one that allows to describe various scenarios and factors influencing signal propagation such as multipath, arrival time variance, distance loss, atmospheric conditions, etc. Under real-world conditions, channel variation does not follow a Gaussian distribution. Coloured non-Gaussian noise has to be taken into account in the design and modelling of the wireless communication system. The complexity of the stochastic channel modelling method is that the variation of PSD power spectral density function and PDF probability density function of a random variable are strongly related to each other. To remove the limitations of existing methods, the Gaussian random variable filtering method is used. But in contrast to the applied simulation techniques, we will use Global Search Optimization (GSE) algorithm. Objective. To investigate a possibility of generation of colored non-Gaussian noise which satisfies the specified requirements by the filtering method based on the global search optimization algorithm. Results. The method based on the global search optimization algorithm for generating colored non-Gaussian noise, which satisfies specified requirements of the Spectral Power Density function and the Probability Density function, is proposed. Numerical simulation results confirm its effectiveness. The advantage of the new method is that the complexity of calculating the required pre-distortion for the filter is replaced by a simple search method. Once the required coefficients are found, non-Gaussian noise generation can be accomplished by secondary filtering and inverse transform. Practical Significance. Compared to methods based on block structures or other analytical methods, the proposed method is more suitable for real-time wireless channel simulation.

Physics‐based wave propagation model assisted vehicle localisation in tunnels

AbstractConnected and autonomous vehicles systems can provide a safe and convenient transportation solution through wireless communication between vehicles and roadside communication infrastructure. The vehicle's ability to establish its location plays an important role in such systems. This article presents an efficient localisation framework by combining physics‐based wireless propagation models and fingerprint localisation algorithms. To that end, a parabolic wave equation (PWE)‐based wireless channel simulator is utilised to obtain the direction of arrival (DOA) values that construct the fingerprint dataset. A detailed procedure on how to obtain the DOA information using PWE, as well as analysis and guidelines on the selection of the key parameters of the localisation framework are provided. Numerical results are compared with theoretical data in terms of accuracy, and the selection of parameters during the localisation process is investigated in actual road tunnel cases. Besides, various numbers of wireless access points and schemes of fingerprinting algorithms have been studied, showing the capability of the proposed approach to be employed for the pre‐design of wireless communication systems.

Optimizing the Focusing Performance of Non-Ideal Cell-Free mMIMO Using Genetic Algorithm for Indoor Scenario

This paper proposes a genetic algorithm (GA) combined with ray tracer to generate a cell-free topology of massive MIMO (mMIMO) for the optimal focusing performance serving multiple users. The realistic hardware impairment, for instance the non-ideal power amplifier, is taken into account of the system modeling and topology optimization. To the best of our knowledge, this is the first attempt to apply GA in optimizing the hardware-impaired multi-user cell-free mMIMO. Although the demonstrated numerical analysis is for indoor scenario, the proposed approach is transferable for generic scenarios. In GA, the base station (BS) antennas’ placement is encoded with an adjusted binary matrix representation, which is straightforward for the subsequent genetic operations. The explored candidates by GA can evolve beyond the parents, where the fitness of individuals is evaluated dynamically via a ray tracer radio channel simulator. Compared to the traditional GA, our proposed GA can find better solutions with a faster convergence speed. The algorithm provides near-optimal results in experiments, applicable to generic environment with multiple mobile users and different signal-to-interference-plus-noise ratios.

A top–down approach for building realistic reference scenarios and simulation framework for LTE C-V2X communications

Many vehicle-to-everything (V2X) applications and use cases require their feasibility to be simulated, tested, and validated in realistic traffic scenarios and under various network conditions before real-time testbed implementation. As cellular-V2X (C-V2X) becomes a superior technology for future connected and autonomous vehicles, the need for a simulation framework, which integrates traffic and network simulators with a realistic channel model, becomes more evident. The challenge is to overcome existing simulation platforms’ weaknesses and improve simulation results’ accuracy while preserving flexibility with manageable implementation complexity. This paper proposed a top–down approach for building reference scenarios with macroscopic and microscopic layers, which interweaves traffic, network, and channel simulators. The basis for the proposed simulation framework is realistic scenario data, which provides the input to the road traffic simulator and the radio channel simulator. The core of the whole simulator is the network simulator interacting with the two other simulators via dedicated interfaces. The road traffic simulator generates the vehicles’ positions and is forwarded to the network simulator, which requests the radio channel simulator for the path loss values on the transmitter–receiver (TX-RX) link. As a proof of concept, the simulation results focused on the load and interference analysis in the absence and presence of V2X traffic.

Semi-Deterministic Dynamic Millimeter-Wave Channel Modeling Based on an Optimal Neural Network Approach

Billions of mobile terminals will be deployed in various Internet of Things (IoT), in which millimeter-wave (mmWave) technology will be gradually applied. Accurate modeling and simulation of wireless channel is the base for efficient design and performance evaluation. This becomes more important for industrial scenarios, which might be highly dynamic and potentially different from well-investigated cellular deployment scenarios. In this work, a novel semi-deterministic mmWave dynamic channel modeling approach based on optimal neural network (ONN) principle is proposed. The ONNs are radial basis function (RBF) neural networks (NNs) trained with optimal variance parameters and are applied to predict large-scale channel parameters (LSCPs) [e.g., path loss (PL), delay spread (DS), and angle spread (AS)]. Based on the ONNs’ predicted large-scale parameters and simplified propagation environment including the layout of transmitter (TX), receiver (RX), and major scatterers, the proposed channel modeling approach can generate accurate dynamic channel parameters. The proposed approach is validated by the channel data measured at a high-voltage substation. Large-scale parameters, multipath component (MPC) distributions, and power delay profiles (PDPs) are validated. The proposed approach is demonstrated to be an accurate, fast, and robust channel modeling method, which can be used for both link-level and system-level channel simulation for future design and optimization of industrial IoT.

Site-specific millimeter-wave compressive channel estimation algorithms with hybrid MIMO architectures

In this paper, we present and compare three novel model-cum-data-driven channel estimation procedures in a millimeter-wave Multi-Input Multi-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. The transceivers employ a hybrid analog-digital architecture. We adapt techniques from a wide range of signal processing methods, such as detection and estimation theories, compressed sensing, and Bayesian inference, to learn the unknown virtual beamspace domain dictionary, as well as the delay-and-beamspace sparse channel. We train the model-based algorithms with a site-specific training dataset generated using a realistic ray tracing-based wireless channel simulation tool. We assess the performance of the proposed channel estimation algorithms with the same site's test data. We benchmark the performance of our novel procedures in terms of normalized mean squared error against an existing fast greedy method and empirically show that model-based approaches combined with data-driven customization unanimously outperform the state-of-the-art techniques by a large margin. The proposed algorithms were selected as the top three solutions in the "ML5G-PHY Channel Estimation Global Challenge 2020" organized by the International Telecommunication Union.

Optical Wireless Channel Simulation for Communications Inside Aircraft Cockpits

Communications inside an aircraft cockpit are currently based on wired connections especially for the audio headsets used by the pilots. A wireless headset would be an advantage in terms of comfort and flexibility but the use of classical radio frequencies is limited by interference and security issues. Optical wireless communication technology is an option for headset connectivity. Indeed, as optical beams are confined, this technology provides robustness against the risk of hacking, thus increasing security. In addition, the use of optical waves ensures the absence of radio-frequency disturbances. Using simulation, this article presents a thorough study of the optical wireless channel behavior inside the cockpit of an aircraft by considering a headset worn by a pilot possibly in motion and an access point at the ceiling. The impact of the characteristics of the environment model, such as the level of geometric description, the reflectivity of materials and for the first time, the ambient noise induced by the sun, is highlighted. System performance is evaluated in terms of optimal half-power angles and the necessary optical power of the light sources.

Electromagnetic coupling effect in the complex integrated channel of hypersonic vehicles and experimental verification

The communication link of hypersonic vehicles suffers in a complex electromagnetic channel environment with the multipath effect, large Doppler effect caused by the high speed of the hypersonic vehicles, and parasitic modulation caused by vortex turbulence of dynamic plasma sheath. The inherent coupling relationship between these effects exists even though they are with different physical generation mechanisms, which will seriously affect the reception effect of the communication signal from the perspective of the wireless channel. This study investigates the electromagnetic coupling relation between the hypersonic spatial channel and the dynamic plasma sheath channel. The coupling relation is derived in the frequency domain, and the integrated channel simulation model is established as well. Theoretical simulation results demonstrate that the harmonic spectral lines of the plasma sheath power spectrum are moved to the right with the line-of-sight Doppler frequency shift. The spectral spread of the hypersonic spatial channel is coupled to the channel power spectrum of the plasma sheath that forms multiple spectrum extension areas. The new spectral extensions caused by coupling effect will make the traditional narrowband matching receive mode face enormous challenges. The electromagnetic coupling effect in the integrated channel is also verified through channel sounding experiments on ground integrated channel emulation environment composed of plasma simulation device and wireless channel simulator. The deep understanding of this coupling effect is essential to wireless channel modeling and design of adaptive reception methods for hypersonic vehicles.

Multiuser wireless channel simulation for communication systems with nonparametric reception

When combined with error-correction codes reception techniques based on nonparametric hypothesis testing and order statistics provide strong immunity to different types of interference including multiuser interference. That makes communication systems using such reception techniques most appealing candidates for various applications such as Machine-to-Machine (M2M) communications and Internet Of Things (IOT). Unfortunately analytical treatment of communication systems with nonparametric reception remains a cumbersome task. Therefore simulation remains the main tool for the development of such systems. For multiuser systems supporting hundreds of active users and operating in fading channels (e.g. IOT) time spending grows drastically hampering the design process. Thus the development of simplified multiuser channel models is of great interest. In this paper two simplified mathematical models of multiuser interference for the case of a single user nonparametric reception are proposed. The effectiveness of the proposed models is compared by means of modulation. Special attention is paid to the problem of software implementation of the models proposed.

Wireless Channel Modeling Simulation and Hardware Implementation

Channel simulator is an important part of the accurate evaluation of the fading characteristics of wireless channel. Efficient design and implementation of wireless channel simulator is very important for the design and verification of wireless systems. The greatest impact on the wireless communication system is a small-scale fading variation. According to the transmission characteristics, this paper analyzed the small scale fading model, the mathematical modeling simulation and hardware implementation. The measured results show that the statistical characteristics of hardware simulators output decline signal in conformity with the theoretical value, can simulate the attenuation, decline of wireless communication system, and doppler frequency shift and other transmission characteristics.

A Novel 3D Non-Stationary Wireless MIMO Channel Simulator and Hardware Emulator

In this paper, a new WINNER+-based 3-D non-stationary geometry-based stochastic model (GBSM) for multiple-input multiple-output channels is proposed, as well as extended evolving algorithms of time-variant channel parameters. Meanwhile, important statistical properties of the channel model, i.e., time-variant autocorrelation function, time-variant cross-correlation function, and time-variant Doppler power spectrum density are derived and analyzed. Moreover, we propose an efficient hardware implementation method, namely, sum-of-frequency-modulation (SoFM) method, to generate non-stationary channel coefficients. By utilizing compact hardware architecture with SoFM modules, the proposed 3-D non-stationary GBSM is realized on a field-programmable gate array hardware platform. Simulations and hardware measurement results demonstrate that our proposed channel simulator and emulator can get more accurate and realistic Doppler frequency than those of the existing models. In addition, hardware measurements of statistical properties are also well consistent with the corresponding theoretical ones, which verify the correctness of both the hardware emulation scheme and theoretical derivations.

Design and Implementation of Wireless Channel Simulator Based on Shaping Filter

Currently, the reliability of wireless channel simulation is poor, and it cannot provide the interface for the actual physical equipment. Rayleigh fading channel model is used as the theoretical model in this paper, proposed a model based on shaping filter method and easy to implement for FPGA hardware. The model uses a computer to realize the shaping filter to reduce the consumption of the FPGA chip resources; linear interpolation method to achieve the Doppler frequency shift, Rayleigh fading. Test results show that the output of the hardware simulator fading characteristics consistent with the theoretical value, it can be used for wireless communication system simulation test.

Geometry-Based Stochastic Channel Model for Two-Story Lobby Environment at 10 GHz

This paper presents a complete parametrization for a three-dimensional (3-D) geometry-based stochastic radio channel model (GSCM) at 10.1 GHz based on a measurement campaign. The radio channel measurements were carried out with a vector network analyzer over a 500 MHz bandwidth in a two-story lobby environment. The measurements were conducted with $9 \times 324$ dual polarized virtual antenna arrays in line-of-sight (LOS) and non-LOS propagation conditions. The recorded data was postprocessed using the estimation of signal parameters via rotation invariance algorithm. The statistical analysis was carried out to provide full 3-D parametrization for the GSCM. The parametrization was verified by radio channel simulations. Multiple-input multiple-output (MIMO) channel is reconstructed from the estimated propagation paths and equivalently the channel simulations are performed by quasi-deterministic radio channel generator using our measurements-based parameters. The channel capacity, Demmel condition number, and relative condition numbers are used as the verification metrics. The results show that the reconstructed MIMO channel matches well the simulated MIMO channel.

Study of Linear and Decision Feedback Equalizers on Fading Channels

For evaluating the performance of wireless digital communication system the most important part is the simulation of wireless channel, as whole performance of the system is depends upon it. The Band limited communication channel, due to its dispersive time response, may restrict the high data rate, due to Inter symbol Interference (ISI). If the ISI is not taken care off and compensated may cause high Bit Error Rate (BER). Equalizers are used for this purpose. In this paper the performance of Linear and Decision Feedback Equalizers (DFE) are evaluated on three wireless channels i.e. two ray path, Rayleigh and Rician. A model of communication system having Quadrature Amplitude Modulation (QAM) with fading channels is implemented using MATLAB. The performance of Linear and DFE is evaluated on the basis of Bit Error Rate (BER) with varying Signal to Noise Ratio (SNR). The simulation results showed the performance of two equalizers on different channels. The Rayleigh channel model is the most suitable model for urban areas as it is the model which simulates a channel with no Line of Sight (LOS) path and is the most difficult environment. General Terms ISI (Inter-symbol Interference), BER (Bit Error Rate), SNR (Signal to Noise Ratio)

Inter-Floor Wide Band Radio Channel Measurements and Simulation Applying Saleh-Valenzuela Model

This paper explores the accuracy of Saleh-Valenzuela (SV) statistical simulation model in time of arrival domain (ToA) applied on inter-floor wide band indoor radio channels. In order to extract the model parameters, an extensive measurement campaign was performed inside a modern building by applying vector network analyzer method at frequency of 1.8 GHz. The measurement results are presented in form of path loss exponent and delay spread statistics for each number-of-floors (NOF) distance between the antennas (up to 4). Path loss exponent was found to be around 3 for antennas on a same floor and around 5.5 for any other case when antennas were on separated floors. CDFs of rms delay spread may be divided into two groups: the first group is made of single-floor (SF) case and distanced-floors (DF) cases (three or more floors separated antennas) which showed similarities performing median value at 20 ns. For neighboring-floors (NF) cases (one and two floors separation) this value was increased to 35 ns. SV simulation, run with the extracted parameters, assessed delay spread statistics sufficiently good for the first group of CDFs. In order to assess the second group results, it was necessary to introduce simple corrections in SV model application.

Development of a MATLAB Toolbox for Mobile Radio Channel Simulators

A profound knowledge of mobile radio channels is required for the development, evaluation, and also assessment at practical conditions of present and future mobile radio communication systems. The modelling, analysis, and simulation of mobile radio channels are important key area in current context. In addition to that, knowledge of channel behaviour in mobile radio communication is extensively recommended for the study of transmitter/receiver performances under different propagation scenarios. Our intention in this research work was to develop various kinds of mobile fading channel simulators using MATLAB and embed them into MATLAB software as a toolbox. Implemented channel simulators were combined MATLAB as a toolbox which users can easily select well-known channel models to test and to study the performance of mobile communication systems. It gives better support for the new users to work on the developed channel simulators, run the test procedures as well as parameter computation. The toolbox contains channel simulators for simulating non-stationary land mobile satellite channel, spatial shadowing processes, MIMO channels, multiple uncorrelated Rayleigh fading channels, mobile to mobile channel, frequency hopping channels etc. Set of test procedures were developed such as the autocorrelation function ACF, average duration of fades ADF, the probability density function PDF, and the level-crossing rate LCR etc., in order to test and to confirm the correctness of the implemented channel simulators. Proposed new algorithms to compute the model parameters of the channel simulators were also implemented in the toolbox to enable the parameterization of the channel simulators under specific propagation conditions. Some of the simulation models were implemented based on specification of GSM system by CEPT-COST 207. DOI: http://dx.doi.org/10.4038/jur.v2i1-2.7853 J. Univ. Ruhuna 2014 2:40-45

A Hardware Based Ricean Fading Radio Channel Simulator

The rise of the need of fading radio channel simulators is due to time and cost of field tests of wireless communications systems. There exist two approaches to design a hardware based fading simulators, namely the filter based and sum of sinusoids (SOS) methods. This paper introduces a hardware based Ricean fading simulator that is based on SOS and utilizes empirical formulas that were derived based on extensive measurements to estimate the Ricean distribution K factor. The simulator presented here can simulate the Ricean fading radio channel under different parameters including antenna height, antenna beam width, season and distance between the transmitter and the receiver.

Design and Simulation of Wireless Communication System Channel in Coal Mine Based on OFDM Technology

The OFDM technology is applied in the mobile communication system of underground coal mine, the wireless communication system channel of underground coal mine is researched. The underground channel model is established, and the simulation is taken for testing the performance of system. The simulation results show that the OFDM technology can be applied in the mobile communication system in underground coal mine, and the transmission rate of the system and the ability of anti-interference are improved.

The Development of FPGA-based Wireless Channel Simulator using LabVIEW

The development of channel model for wireless communication system is currently becoming important to fulfill the entire user’s requirements and increasing demand where to provide a good communication link between the users at everywhere and anytime. An accurate techniques or operator is needed to model a very flexible channel for wireless communication application. Previous channel model is developed based on the time-frequency operator which is limited to Narrowband signaling. This operator uses Doppler shift to account for mobility in propagation space. This paper proposes a Wideband channel model which is valid for all kind of signaling and conditions. Mathematical channel model is used to represent a generic channel simulator which is implemented as channel simulator. The development and measurement of channel simulator is using LabVIEW. The LabVIEW can be used as basic software and can be turned into hardware part by connecting to other devices for real-time channel simulation. The illustration and snapshot of the channel simulator modeling in term of LabVIEW code program are presented.

An Improved Iterative Nonlinear Least Square Approximation Method for the Design of SISO Wideband Mobile Radio Channel Simulators

In this paper, we present an improved version of the iterative nonlinear least square approximation (INLSA) method for designing measurement-based single-input single-output (SISO) wideband channel simulators. The proposed method aims to fit the time-frequency correlation function (TFCF) of the simulation model to that of a measured channel. The parameters of the simulation model are determined iteratively by minimizing the Frobenius norm, which serves as a measure for the fitting error. In contrast to the original INLSA method, the proposed approach provides a unique optimized set of model parameters, which guarantees a quasi-perfect fitting with respect to the TFCF. We analyze the performance of the proposed method in terms of the goodness of fit to the measured data. The investigations will be carried out with respect to the TFCF and the scattering function. We demonstrate that the proposed approach is a powerful tool for the design of measurement-based wideband channel simulators, which are important for the performance evaluation of mobile communication systems under real-world propagation conditions.