Dr Ammar Ghazal

Job: VC2020 Lecturer in Wireless Communications

Faculty: Technology

School/department: School of Engineering and Sustainable Development

Research group(s): Institute of Engineering Sciences (IoES)

Address: De Montfort University, The Gateway, Leicester, LE1 9BH UK

T: 00 44 (0)116 201 3947

E: ammar.ghazal@dmu.ac.uk

W: http://www.dmu.ac.uk/about-dmu/academic-staff/technology/ammar-ghazal/ammar-ghazal.aspx

 

Personal profile

Ammar Ghazal is a VC2020 Lecturer in Wireless Communications in the Faculty of Technology at De Montfort University, Leicester, UK. He received the BSc degree in Electronics and Telecommunication Engineering from Damascus University, Syria. He studied for his MSc by Research and PhD degrees at the Universities of Edinburgh and Heriot-Watt University, Edinburgh, UK.

Upon his BSc graduation, Ammar worked as a Lab Instructor at International University for Science & Technology (IUST). In the first instance he worked as a Radio Planning & Optimisation Engineer then as a Core Network Engineer. He has also worked as a Lab Instructor at Damascus University, where he was awarded a full scholarship to pursue a postgraduate degree in the UK. His PhD and MSc research have focused on propagation channel characterisation and modelling in 4G and 5G communication systems.

Ammar’s current research interests include (B)5G communication systems, wireless propagation channel characterisation and modelling, non-stationary channel models, high mobility wireless propagation, and advanced MIMO communication technologies.

Research group affiliations

 

Publications and outputs 

  • Accuracy-Complexity Tradeoff Analysis and Complexity Reduction Methods for Non-Stationary IMT-A MIMO Channel Models
    Accuracy-Complexity Tradeoff Analysis and Complexity Reduction Methods for Non-Stationary IMT-A MIMO Channel Models Zhang, Yan; Ghazal, Ammar; Wang, Cheng-Xiang; Zhou, Hongrui; Duan, Weiming; Aggoune, el-Hadi High-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. open access journal
  • Channel Measurements and Models for High-Speed Train Wireless Communication Systems in Tunnel Scenarios: A Survey
    Channel Measurements and Models for High-Speed Train Wireless Communication Systems in Tunnel Scenarios: A Survey Liu, Yu; Ghazal, Ammar; Wang, Cheng-Xiang; Ge, Xiaohu; Yang, Yang; Zhang, Yapei The rapid developments of high-speed trains (HSTs) introduce new challenges to HST wireless communication systems. Realistic HST channel models play a critical role in designing and evaluating HST communication systems. Due to the length limitation, bounding of tunnel itself, and waveguide effect, channel characteristics in tunnel scenarios are very different from those in other HST scenarios. Therefore, accurate tunnel channel models considering both large-scale and small-scale fading characteristics are essential for HST communication systems. Moreover, certain characteristics of tunnel channels have not been investigated sufficiently. This article provides a comprehensive review of the measurement campaigns in tunnels and presents some tunnel channel models using various modeling methods. Finally, future directions in HST tunnel channel measurements and modeling are discussed. 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.
  • A Non-Stationary IMT-Advanced MIMO Channel Model for High-Mobility Wireless Communication Systems
    A Non-Stationary IMT-Advanced MIMO Channel Model for High-Mobility Wireless Communication Systems Ghazal, Ammar; Yuan, Yi; Wang, Cheng-Xiang; Zhang, Yan; Yao, Qi; Zhou, Hongrui; Duan, Weiming 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. 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.
  • Performance Investigation of Spatial Modulation Systems Under Non-Stationary Wideband High-Speed Train Channel Models
    Performance Investigation of Spatial Modulation Systems Under Non-Stationary Wideband High-Speed Train Channel Models Fu, Yu; Wang, Cheng-Xiang; Ghazal, Ammar; Aggoune, el-Hadi M.; Alwakeel, Mohammed M. In this paper, the bit error rate (BER) performance of a new multiple-input-multiple-output technique, named spatial modulation (SM), is studied under a novel non-stationary wideband high-speed train (HST) channel model in different scenarios. Time-varying parameters obtained from measurement results are used to configure the channel model to make all results more realistic. A novel statistic property called the stationary interval in terms of the space-time correlation function is proposed to describe the channel model's time-varying behavior. The accurate theoretical BER expression of SM systems is derived under the time-varying wideband HST channel model with the non-ideal channel estimation assumption. The simulation results demonstrate that the BER performance of SM systems shows a time-varying behavior due to the non-stationary property of the employed HST channel model. The system performance can maintain a relative stationary status within the specified stationary interval. It can also be observed that the BER performance of SM systems under the HST channel model is mainly affected by the correlation between sub-channels, inter-symbol-interference, Doppler shift, and channel estimation errors. 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.
  • Statistical Properties of High-Speed Train Wireless Channels in Different Scenarios
    Statistical Properties of High-Speed Train Wireless Channels in Different Scenarios Liu, Yu; Zhang, Yapei; Ghazal, Ammar; Wang, Cheng-Xiang; Yang, Yang In this paper, we compare the statistical properties of high-speed train (HST) wireless channels in different scenarios using a generic non-stationary HST channel model that has been verified by channel measurements (Ghazal et al., 2015). We mainly focus our comparison and analysis on the three most common HST scenarios, i.e., the rural area, cutting, and viaduct scenarios. Several channel statistical properties such as the temporal autocorrelation function (ACF), space cross-correlation function (CCF), and space- Doppler (SD) power spectrum density (PSD) are investigated. The impacts of different scenario- specific parameters on the channel statistical properties are also studied via numerical analysis. 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.
  • A generic non-stationary MIMO channel model for different high-speed train scenarios
    A generic non-stationary MIMO channel model for different high-speed train scenarios Ghazal, Ammar; Wang, Cheng-Xiang; Liu, Yu; Fan, Pingzhi; Chahine, Mohamed Khaled This paper proposes a generic non-stationary wideband geometry-based stochastic model (GBSM) for multiple-input multiple-output (MIMO) high-speed train (HST) channels. The proposed generic model can be applied on the three most common HST scenarios, i.e., open space, viaduct, and cutting scenarios. A good agreement between the statistical properties of the proposed generic model and those of relevant measurement data from the aforementioned scenarios demonstrates the utility of the proposed channel model. 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.
  • Channel Measurements and Models for High-Speed Train Communication Systems: A Survey
    Channel Measurements and Models for High-Speed Train Communication Systems: A Survey Wang, Cheng-Xiang; Ghazal, Ammar; Ai, Bo; Liu, Yu; Fan, Pingzhi The recent development of high-speed trains (HSTs) as an emerging high mobility transportation system, and the growing demands of broadband services for HST users, introduce new challenges to wireless communication systems for HSTs. Accurate and efficient channel models considering both large-scale and non-stationary small-scale fading characteristics are crucial for the design, performance evaluation, and parameter optimization of HST wireless communication systems. However, the characteristics of the underlying HST channels have not yet been sufficiently investigated. This paper first provides a comprehensive review of the measurement campaigns conducted in different HST scenarios and then addresses the recent advances in HST channel models. Finally, key challenges of HST channel measurements and models are discussed and several research directions in this area are outlined.
  • A 3D GBSM for high-speed train communication systems under deep cutting scenarios
    A 3D GBSM for high-speed train communication systems under deep cutting scenarios Feng, Liu; Fan, Pingzhi; Wang, Cheng-Xiang; Ghazal, Ammar 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. 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.
  • A Multi-mode Waveguide Tunnel Channel Model for High-Speed Train Wireless Communication Systems
    A Multi-mode Waveguide Tunnel Channel Model for High-Speed Train Wireless Communication Systems Liu, Yu; Wang, Cheng-Xiang; Ghazal, Ammar; Wu, Shangbin; Zhang, Wensheng The recent development of high-speed trains (HSTs) introduces new challenges to wireless communication systems for HSTs. For demonstrating the feasibility of these systems, accurate channel models which can mimic key characteristics of HST wireless channels are essential. In this paper, we focus on HST channel models for the tunnel scenario, which is different from other HST channel environments, such as rural area and viaducts. Considering unique characteristics of tunnel channel environments, we extend the existing multi-mode waveguide tunnel channel model to be time dependent, obtain the channel impulse responses and then further investigate the certain key tunnel channel characteristics such as temporal autocorrelation function (ACF) and power spectrum density (PSD). The impact of time on ACFs and PSDs, and the impact of frequency on the received power are revealed via numerical results. 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.
  • A Nonstationary Wideband MIMO Channel Model for High-Mobility Intelligent Transportation Systems
    A Nonstationary Wideband MIMO Channel Model for High-Mobility Intelligent Transportation Systems Ghazal, Ammar; Wang, Cheng-Xiang; Ai, Bo; Yuan, Dongfeng; Haas, Harald The recent development of high-speed trains (HSTs), as a high-mobility intelligent transportation system, and the growing demands of broad-band services for HST users, introduce new challenges to wireless communication systems for HSTs. The deployment of mobile relay stations on top of the train carriages is one of the promising solutions for HST wireless systems. For a proper design and evaluation of HST wireless communication systems, we need accurate channel models that can mimic the underlying channel characteristics for different HST scenarios. In this paper, a novel nonstationary geometry-based stochastic model (GBSM) is proposed for wideband multiple-input multiple-output HST channels in rural macrocell scenarios. The corresponding simulation model is then developed with angle parameters calculated by the modified method of equal areas. Both channel models can also be used to model nonstationary vehicle-to-infrastructure channels in vehicular communication networks. The system functions and statistical properties of the proposed channel models are investigated based on a theoretical framework that describes nonstationary channels. Numerical and simulation results demonstrate that the proposed channel models have the capability to characterize the nonstationarity of HST channels. The statistical properties of the simulation model, verified by the simulation results, can match those of the proposed theoretical GBSM. An excellent agreement is achieved between the stationary intervals of the proposed simulation model and those of relevant measurement data, demonstrating the utility of the proposed channel models. 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.

Research interests/expertise

  • 5G communication systems
  • Wireless propagation channel characterisation and modelling
  • Visible light communication
  • Non-stationary channel models
  • High-mobility wireless propagation
  • Advanced MIMO communication technologies

Areas of teaching

  • Mobile communication
  • Communication networks
  • Electromagnetism

Qualifications

  • PhD in Electrical Engineering, University of Edinburgh and Heriot-Watt University
  • MSc by Research in Electrical Engineering, Heriot-Watt University and University of Edinburgh
  • BSc in Electronics and Communication Engineering, Damascus University

Courses taught

  • Principle of mobile communications
  • Communications and networks
  • Communication systems
  • Digital circuits
  • Electrical circuits
  • Control and instrumentation engineering

Honours and awards

  • First Class Prize (Bassel Prize), Damascus University, September 2006
  • Full-Scholarship for PhD study, Damascus University, August 2008

Membership of professional associations and societies

  • Graduate student member of IEEE
  • Fellow of the higher education association (FHEA)
  • Microsoft certified professional

Professional licences and certificates

  • Modern Digital RF Transceivers, Rohde & Schwarz
  • CST STUDIO SUITE 2018 Workshop, CST
  • CST STUDIO SUITE - Microwave and Antenna Training, CST
  • Review of Signal Systems and Digital Signal Processing, IEEE
  • Radar Systems Engineering, IEEE
  • 4G Broadband LTE, IEEE
  • Core Networks Signaling for 3G Networks Rel.4, Nokia Siemens
  • 3G Rel.4 Switching Core Network Operation & Maintenance, Nokia Siemens
  • GSM Cell Planning Workshop, Ericsson
  • Practical Communication Strategies, MAK / SYRIATEL
  • CCNP-BSCI Course, CISCO, New Horizons
  • MCP certificate, Microsoft
  • Windows Server 2003 Infrastructure, SBS
  • Windows Server 2003 Management, SBS
  • CompTIA Networks+, SBS
  • CCNA-ICDN Course, New Horizons

Current research students

  • Badar Al Maamari, International PhD, 1 stsupervisor 
  • Katharina Seitz, PhD, 2nd supervisor
  • Amruthavarshini Subburaya Bharathi, PhD, 2nd supervisor
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