Papers by Cheng-Xiang Wang
Wireless Communications and Mobile Computing, 2009
For the practical simulation and performance evaluation of mobile‐to‐mobile (M2M) communication s... more For the practical simulation and performance evaluation of mobile‐to‐mobile (M2M) communication systems, it is desirable to develop accurate M2M channel simulation models for more realistic scenarios of non‐isotropic scattering. In this paper, by using a ‘double‐ring’ concept to describe M2M non‐isotropic scattering environments, we propose new deterministic and stochastic sum‐of‐sinusoids (SoS) based simulation models. The proposed simulation models extensively consider the distributions of the angle of arrival (AoA) and the angle of departure (AoD), and thus provide a good approximation to the desired statistical properties of the reference model. Copyright © 2009 John Wiley & Sons, Ltd.
Wireless Personal Communications, Dec 18, 2011
The cognitive radio multiple-input multiple-output Gaussian broadcast channels are studied where ... more The cognitive radio multiple-input multiple-output Gaussian broadcast channels are studied where multiple antennas are available for both primary users and secondary users in a spectrum sharing environment, and the sum-rate capacity is also obtained under both the SUs' transmit power constraint and interference power constraint at the primary receivers. The paper principally consists of two steps. First, a duality technique and dirty paper coding are adopted to simplify the channels. Second, we propose an iterative power allocation algorithm to obtain the maximum sum-rate capacity and examine the effects of the constraint parameters on the concerned quantities. Finally, numerical simulation results are presented to validate the proposed theoretical analysis.
IEEE Communications Surveys & Tutorials, 2018
Optical wireless communications (OWCs) refer to wireless communication technologies which utilize... more Optical wireless communications (OWCs) refer to wireless communication technologies which utilize optical carriers in infrared, visible light, or ultraviolet bands of electromagnetic spectrum. For the sake of an OWC link design and performance evaluation, a comprehensive understanding and an accurate prediction of link behavior are indispensable. Therefore, accurate and efficient channel models are crucial for the OWC link design. This paper first provides a brief history of OWCs. It also considers OWC channel scenarios and their utilization trade-off in terms of optical carrier, range, mobility, and power efficiency. Furthermore, the main optical channel characteristics that affect the OWC link performance are investigated. A comprehensive overview of the most important OWCs channel measurement campaigns and channel models, primarily for wireless infrared communications and visible light communications, are presented. OWCs channel models are further compared in terms of computation speed, complexity, and accuracy. The survey considers indoor, outdoor, underground, and underwater communication environments. Finally, future research directions in OWCs channel measurements and models are addressed. Index Terms-Wireless infrared communications, visible light communications, optical wireless channel characteristics, optical wireless channel measurements, optical wireless channel models. I. INTRODUCTION R ADIO frequency (RF) wireless systems designers have been facing the continuously increasing demand for
IEEE Journal on Selected Areas in Communications, 2017
Most millimeter wave (mmWave) channel measurements are conducted with different configurations, w... more Most millimeter wave (mmWave) channel measurements are conducted with different configurations, which may have large impacts on propagation channel characteristics. In addition, the comparison of different mmWave bands is scarce. Moreover, mmWave massive multiple-input multipleoutput (MIMO) channel measurements are absent, and new propagation properties caused by large antenna arrays have rarely been studied yet. In this paper, we carry out mmWave massive MIMO channel measurements at 11-, 16-, 28-, and 38-GHz bands in indoor environments. The space-alternating generalized expectation-maximization algorithm is applied to process the measurement data. Important statistical properties, such as average power delay profile, power azimuth profile, power elevation profile, root mean square delay spread, azimuth angular spread, elevation angular spread, and their cumulative distribution functions and correlation properties, are obtained and compared for different bands. New massive MIMO propagation properties, such as spherical wavefront, cluster birth-death, and non-stationarity over the antenna array, are validated for the four mmWave bands by investigating the variations of channel parameters. Two channel models are used to verify the measurements. The results indicate that massive MIMO effects should be fully characterized for mmWave massive MIMO systems.
Science China Information Sciences, 2016
The coexistence of wireless body sensor networks (WBSNs) is a very challenging problem, due to st... more The coexistence of wireless body sensor networks (WBSNs) is a very challenging problem, due to strong interference, which seriously affects energy consumption and spectral reuse. The energy efficiency and spectral efficiency are two key performance evaluation metrics for wireless communication networks. In this paper, the fundamental tradeoff between energy efficiency and area spectral efficiency of WBSNs is first investigated under the Poisson point process (PPP) model and Matern hard-core point process (HCPP) model using stochastic geometry. The circuit power consumption is taken into consideration in energy efficiency calculation. The tradeoff judgement coefficient is developed and is shown to serve as a promising complementary measure. In addition, this paper proposes a new nearest neighbour distance power control strategy to improve energy efficiency. We show that there exists an optimal transmit power highly dependant on the density of WBSNs and the nearest neighbour distance. Some important properties are also addressed in the analysis of coexisting WBSNs based on the IEEE 802.15.4 standard, such as the impact of intensity nodes distribution, optimal guard zone, and outage probability. Simulation results show that the proposed power control design can reduce the outage probability and enhance energy efficiency. Energy efficiency and area spectral efficiency of the HCPP model are better than those of the PPP model. In addition, the optimal density of WBSNs coexistence is obtained.
IEEE Transactions on Vehicular Technology, 2016
In cognitive radio (CR) systems, it is crucial for secondary users to reliably detect spectral op... more In cognitive radio (CR) systems, it is crucial for secondary users to reliably detect spectral opportunities across a wide frequency range. This paper studies a novel multi-rate sub-Nyquist spectrum sensing (MS 3 ) system capable of performing wideband spectrum sensing in a cooperative CR network over fading channels. The aliasing effects of sub-Nyquist sampling are modelled. To mitigate such effects, different sub-Nyquist sampling rates are applied such that the numbers of samples at different CRs are consecutive prime numbers. Moreover, the performance of MS 3 over fading channels (Rayleigh fading and log-normal fading) is analysed in the form of bounds on the probabilities of detection and false alarm. The key finding is that the wideband spectrum can be sensed using sub-Nyquist sampling rates in MS 3 over fading channels, without the need of spectral recovery. In addition, the aliasing effects can be mitigated by the use of different sub-Nyquist sampling rates in a multi-rate sub-Nyquist sampling system.
IEEE Transactions on Vehicular Technology, 2014
Two-tier femtocell networks is an efficient communication architecture that significantly improve... more Two-tier femtocell networks is an efficient communication architecture that significantly improves throughput in indoor environments with low power consumption. Traditionally, a femtocell network is usually configured to be either completely open or completely closed in that its channels are either made available to all users or used by its own users only. This may limit network flexibility and performance. It is desirable for owners of femtocell base stations if a femtocell can partially open its channels for external users access. In such scenarios, spectrum and energy efficiency becomes a critical issue in the design of femtocell network protocols and structure. In this paper, we conduct performance analysis for two-tier femtocell networks with partially open channels. In particular, we build a Markov chain to model the channel access in the femtocell network and then derive the performance metrics in terms of the blocking probabilities. Based on stationary state probabilities derived by Markov chain models, spectrum and energy efficiency are modeled and analyzed under different scenarios characterized by critical parameters, including number of femtocells in a macrocell, average number of users, and number of open channels in a femtocell. Numerical and Monte-Carlo (MC) simulation results indicate that the number of open channels in a femtocell has an adverse impact on the spectrum and energy efficiency of two-tier femtocell networks. Results in this paper provide guidelines for trading off spectrum and energy efficiency of two-tier femtocell networks by configuring different numbers
IEEE Communications Surveys & Tutorials, 2018
The fifth generation (5G) mobile communication systems will be in use around 2020. The aim of 5G ... more The fifth generation (5G) mobile communication systems will be in use around 2020. The aim of 5G systems is to provide anywhere and anytime connectivity for anyone and anything. Several new technologies are being researched for 5G systems, such as massive multiple-input multiple-output (MIMO) communications, vehicle-to-vehicle (V2V) communications, high-speed train (HST) communications, and millimeter wave (mmWave) communications. Each of these technologies introduces new propagation properties and sets specific requirements on 5G channel modeling. Considering the fact that channel models are indispensable for system design and performance evaluation, accurate and efficient channel models covering various 5G technologies and scenarios are urgently needed. This paper first summarizes the requirements of the 5G channel modeling, and then provides an extensive review of the recent channel measurements and models. Finally, future research directions for channel measurements and modeling are provided.
Two-Stage Hybrid-Field Beam Training for Ultra-Massive MIMO Systems
2022 IEEE/CIC International Conference on Communications in China (ICCC), Aug 11, 2022
Pre-clinical investigations of multi-path propagation in transcranial Doppler ultrasound flow phantom
There are various practical situations in medical applications when pre-clinical investigations m... more There are various practical situations in medical applications when pre-clinical investigations must be performed using a simulation environment or test bench prior to human studies. One example is the analysis of propagation channels in Transcanial Doppler (TCD) ultrasound (US), a signal processing challenge requiring the analysis of data from US waves scattered in three dimensions (3D). When examining the effects of scatterers in such channels, it is common to use a data acquisition test bench and a Doppler flow phantom. Such medical phantoms are frequently required to verify image and signal processing systems, and are often used to support algorithm development for a wide range of imaging and blood flow assessments. In this paper we describe a TCD simulation environment for the acquisition, investigation and pre-clinical data analysis of multi-path propagation in TCD US systems. This is demonstrated by comparing the anticipated theoretical and simulation channel statistics with the measured acoustic characteristics in terms of the probability distribution and autocorrelation functions.
Higher layer synchronization in an ECMA-368 Ultra Wideband network
ABSTRACT An algorithm for implementing higher layer synchronization in ECMA-368 networks is being... more ABSTRACT An algorithm for implementing higher layer synchronization in ECMA-368 networks is being developed within the framework of the EUWB research and development project. In this paper, we adapt three synchronization algorithms used in wireless sensor networks to suit an Ultra Wideband (UWB) network and evaluate their performance in order to determine the best algorithm for a video streaming application scenario. We also propose some extensions to the ECMA-368 standard that would facilitate the implementation of these algorithms. For these purposes, we have simulated a UWB beacon group in OPNET. We observe that the algorithms that correct for clock drift are better suited for implementation in a UWB network.
The spatial correlation properties of multiple in- put multiple output (MIMO) channels can greatl... more The spatial correlation properties of multiple in- put multiple output (MIMO) channels can greatly affect the performance of MIMO systems. It is therefore important to develop MIMO channel models which can provide accurate spatial correlation characteristics. This paper starts with the brief review of MIMO channel models and then concentrates on investigating the spatial correlation characteristics of the Spatial Channel Model (SCM) in the Third Generation Partnership Project (3GPP) and the Kronecker Based Stochastic Model (KBSM) at three levels, namely the cluster level, link level, and system level. The KBSM has the spatial separability at all the three levels. The SCM shows the spatial separability at the link and system levels, but not at the cluster level since its spatial correlation is related to the joint distribution of the angle of arrival (AoA) and angle of departure (AoD). The KBSM with the Gaussian shaped Power Azimuth Spectrum (PAS) is found to fit best the 3GPP SCM in terms of the spatial correlations. Despite of its simplicity and analytical tractability, the KBSM is restricted to model only the average spatial behavior of MIMO channels. The SCM provides more insights of the variations of different MIMO channel realizations but the implementation complexity is relatively high.
Optimization of LTE scheduling using multi-objective evolutionary algorithms
The performance of cellular mobile telephone (LTE) networks is impaired by the amount of interfer... more The performance of cellular mobile telephone (LTE) networks is impaired by the amount of interference experienced within the network. In particular, LTE networks are susceptible to inter-cell interference which is experienced when two neighboring cells transmit on the same portion of the frequency spectrum. We propose an adaptive scheduler that can be adopted by LTE networks to minimize inter-cell interference; the scheduler can itself be optimized for the prevailing network environment by using evolutionary algorithms. We describe this scheduler along with a number of experiments that explore its optimization in a number of network environments. In particular we find that either single-objective or multiobjective evolutionary algorithms find parameterisations for the adaptive scheduler that lead to mean throughput for users and sectors that is comparable to established schedulers, but with significantly improved performance for the users at the 5th percentile of throughput.
Non-stationary wideband MIMO channel models for high-speed train wireless communication systems
Summary form only given. In high-speed train wireless communication systems, the underlying chann... more Summary form only given. In high-speed train wireless communication systems, the underlying channels are essentially non-stationary due to fast-varying channel conditions. For the design, performance evaluation, and optimization of high-speed train wireless communication systems, it is a prerequisite to develop non-stationary channel models with time-varying small-scale fading parameters. In this talk, we propose novel non-stationary geometry-based stochastic models (GBSMs) with time-varying parameters for wideband high-speed train multiple-input multiple-output (MIMO) channels. The statistical properties of the proposed GBSMs are studied, such as time-variant spatial cross-correlation function and stationary interval. We also investigate the performance of spatial modulation systems employing the proposed GBSM. It has been demonstrated that the proposed channel models have the capability to characterize the non-stationarity of high-speed train channels and the stationary interval can well fit relevant channel measurements. The talk will end with discussing recent advances and future challenges in MIMO channel models.
Higher layer synchronization in an ECMA-368 Ultra Wideband network
2010 IEEE International Conference on Ultra-Wideband, 2010
ABSTRACT An algorithm for implementing higher layer synchronization in ECMA-368 networks is being... more ABSTRACT An algorithm for implementing higher layer synchronization in ECMA-368 networks is being developed within the framework of the EUWB research and development project. In this paper, we adapt three synchronization algorithms used in wireless sensor networks to suit an Ultra Wideband (UWB) network and evaluate their performance in order to determine the best algorithm for a video streaming application scenario. We also propose some extensions to the ECMA-368 standard that would facilitate the implementation of these algorithms. For these purposes, we have simulated a UWB beacon group in OPNET. We observe that the algorithms that correct for clock drift are better suited for implementation in a UWB network.
3-D Half-spheroid models for transcranial Doppler ultrasound propagation channels
IEEE-EMBS International Conference on Biomedical and Health Informatics (BHI), 2014
ABSTRACT In this paper, a method of characterization of a transcranial Doppler (TCD) ultrasound p... more ABSTRACT In this paper, a method of characterization of a transcranial Doppler (TCD) ultrasound propagation channel is proposed. A simplified 3-D isotropic half-spheroid scattering channel model is described. The temporal autocorrelation function (ACF) is investigated. Based on the theoretical model, a sum-of-sinusoids (SoS) simulation model is proposed and its spatial-temporal properties are investigated.
IEEE Communications Magazine, 2009
Vehicle-to-vehicle communications have recently received much attention due to some new applicati... more Vehicle-to-vehicle communications have recently received much attention due to some new applications, such as wireless mobile ad hoc networks, relay-based cellular networks, and intelligent transportation systems for dedicated short range communications. The underlying V2V channels, as a foundation for the understanding and design of V2V communication systems, have not yet been sufficiently investigated. This article aims to review the state-of-the-art in V2V channel measurements and modeling. Some important V2V channel measurement campaigns and models are briefly described and classified. Finally, some challenges of V2V channel measurements and modeling are addressed for future studies.
A Novel Channel Estimation Scheme for Frequency-Selective mmWave Massive MIMO Systems
In this paper, a two-stage channel estimation scheme is presented for frequency-selective millime... more In this paper, a two-stage channel estimation scheme is presented for frequency-selective millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems with hybrid precoding. Specifically, at the first stage, likelihood function with respective to the channel angle of departure (AoD) and angle of arrival (AoA) are maximized by the deterministic maximum likelihood (DML) estimator to obtain a coarse channel estimate. At the second stage, a space-alternating generalized expectation-maximization (SAGE) based algorithm is proposed to refine the channel parameters. In addition, an angle paring scheme is proposed to paired the AoA and AoD. Simulation results show the better performance of the proposed method.
A Novel 3D Non-Stationary Maritime Wireless Channel Model
IEEE Transactions on Communications, Mar 1, 2022
In this paper, a novel 3-dimensional (3D) non-stationary geometry-based stochastic model (GBSM) i... more In this paper, a novel 3-dimensional (3D) non-stationary geometry-based stochastic model (GBSM) is proposed to mimic the ship-to-ship multiple-input multiple-output (MIMO) communication channels. To reflect the realistic maritime propagation environment, the effects of rough sea surface scattering and evaporation duct propagation are investigated in the proposed channel model. The model considers the movements of transmitter (Tx), receiver (Rx), and scatterers, and is capable of capturing the channel characteristics, including non-stationary characteristics, spatial consistency, location-dependent property, etc. Through taking the array cluster evolution into account, the proposed channel model can describe massive MIMO channels and can easily switch to conventional MIMO channel model by adjusting corresponding parameters. Based on the proposed model, key statistical properties like delay/angular/Doppler power spectrum density (PSD), space-time correlation function (STCF), stationary interval, and root mean square (RMS) Doppler/delay spreads in multi-scenarios are derived. The usefulness and accuracy of the proposed model are demonstrated by comparing theoretical results, simulation results, and corresponding measurement results.
Uploads
Papers by Cheng-Xiang Wang