Ali Ali

Dr Ali Ali

Postgraduate Research Student

Academic and research departments

Institute for Communication Systems.


My research project


A. Ali and M. O. Hasna (2019) Energy Harvesting Schemes for UAV based Communications
This paper presents two generic charging and transmission schemes to find the trade-off between the altitude of an Unmanned aerial vehicle (UAV) base station and the acquired harvested energy for maximum coverage area. The first scheme seeks the optimal balance between the coverage area and the harvested energy using simultaneous wireless charging and information transmission (SWCIT). The second scheme proposes time allocation to increase the UAV flying period where multiplexing information transmission and energy harvesting is optimized. Finally, the two schemes are implemented on a real UAV system to verify whether equipping it with energy harvesting technology is practical or not.
A. Ali, A. Massoud, M. O. Hasna, T. Khattab, T. Jabban and M. Aref Nema (2019) Modeling of CubeSat Orientation Scenario and Solar Cells for Internet of Space Provision
As a cost-effective alternative to traditional satellites, CubeSats have emerged to provide new space experimentation opportunities. The power budgeting of CubeSats is an essential part of the designing process due to the size, weight, and available surface constraints, and hence the total generated power is affected by these constraints. Consequently, there is a considerable need for accurate determination of the received solar irradiation and the required energy storage. This paper presents a study pertinent to CubeSat power budgeting as an Internet of Space provider depending on determining the incident solar irradiation on its sides for Nadir-Orientation Scenario. The electrical power system should guarantee power provision during the CubeSat mission, which typically depends on solar cells conditions such as temperature and irradiation, along with the energy storage system
A. J. Ali, M. Khalily, A. Araghi and R. Tafazolli (2021) Polarization-Insensitive Circular Reflectarray for Satellite Applications in Ka-band
A polarization-insensitive circular reflectarray antenna (RA) for long-distance wireless communications is investigated. By combining patches, dipoles, and rings, a polarization-insensitive unit cell is achieved. With a phase variation of around 314° between 30 GHz and 32 GHz, a circular reflectarray with a radius of 400 mm is built. Simulation results indicate a maximum realized gain of 27.6 dB at 30 GHz.
A. J. Ali et al. (2021) Power Budgeting of LEO Satellites: An Electrical Power System Design for 5G Missions
Although Geostationary-Equatorial-Orbit (GEO) satellites have achieved significant success in conducting space missions, they cannot meet the 5G latency requirements due to the far distance from the earth surface. Therefore, Low-Earth-Orbit (LEO) satellites arise as a potential solution for the latency problem. Nevertheless, integrating the 5G terrestrial networks with LEO satellites puts an increased burden on the satellites' limited budget, which stems from their miniature sizes, restricted weights, and the small available surface for solar harvesting in the presence of additional required equipment. This paper aims to design the Electrical Power System (EPS) for 5G LEO satellites and investigate altitudes that meet the latency and capacity requirements of 5G applications. In this regard, accurate solar irradiance determination for the nadir-orientation scenario, Multi-Junction (MJ) solar cells modeling, backup batteries type and number, and designing highly-efficient converters are addressed. Accordingly, the power budgeting of the 5G LEO satellite can be achieved based on defining the maximum generated power and determining the satellite's subsystem power requirements for 5G missions. In the sequel, the measured and simulated values of the electrical V-I characteristics of an MJ solar panel are compared to validate the model by using a Clyde Space solar panel that reaches a maximum power generation of approximately 1 W at ( I MPP =0.426 A, V MPP =2.35 V). Moreover, a synchronous boost converter circuit is designed based on commercial off-the-shelf elements.
Ali Jihad Ali, Mohsen Khalily, Ali Araghi, Seyed Ehsan Hosseininejad, Rahim Tafazolli (2021) A Circular Reflectarray for OAM Generation at Terahertz Regime for 6G Applications
A circular reflectarray antenna (RA) for generating Orbital Angular Momentum (OAM) modes in the Terahertz (THz) band is introduced. An interlaced unit cell is proposed to reach a phase variation of 328∘ at 185 GHz to 188 GHz. Combining RA, OAM, and THz technologies in one structure can be utilized to reach the future requirements of 6G networks. That is due to the additional degree of freedom that OAM beams can provide for data multiplexing in short-distance wireless communication.
Ali Ali, Mohsen Khalily, Tim Brown, and Rahim Tafazolli (2022) Metasurface-based THz reflectarray antenna with vortex multiplexing and beam-steering capabilities for future wireless communications
This article investigates the unexplored potentials of vortices or orbital angular momentum (OAM) beams using the low-cost and high-gain dielectric reflectarray antennas (RAs) at the terahertz (THz) band. It proposes a paradigm to enable 3D beam-steering or OAM multiplexing by a single structure via tilted OAM beams. That, in turn, requires reaching the maximal attainable angles either to send multiple beams to different receivers or to focus the OAM beams of different modes in a desired direction. For this reason, two concepts are addressed in this work: (i). generating a single 3D steered OAM beam and (ii) producing multiple off-centered OAM beams with different modes. A volumetric unit cell is adopted to be accurately tuned through the aperture to steer the generated beams towards the desired direction(s). The proposed paradigm can be utilized to produce RAs with beam-steering or OAM multiplexing capabilities as candidates for THz indoor communications.
Ali Jihad Ali, Mohsen Khalily, Ali Araghi, Seyed Ehsan Hosseininejad, Rahim Tafazolli (2021) OAM-based Reflectarray Antenna for THz Indoor Communications
The proposed paper presents a reflectarray antenna (RA) to generate different orbital angular momentum (OAM) beams in the terahertz (THz) band. A phase-variation of 341° at 116 GHz is achieved by the utilized unit cell, which is comprised of circular and square rings. The discussed antenna employs THz, RAs, and OAM technologies to enhance the antenna characteristics to be a potential candidate for the 6G indoor communications.
Ali Ali, Mohsen Khalily, Tim Brown, and Rahim Tafazolli (2022) Beam-steering capability for OAM-based reflectarray at 5G-mmWave frequencies
The ability of the reflectarray antenna (RA) to perform orbital angular momentum (OAM) beam-steering with low divergence angles at the fifth generation (5G) millimetre-wave (mmWave) bands is demonstrated. To provide steered OAM beams, it is necessary to regulate the scatterer's geometries smoothly throughout the focal area to follow the required twisted distribution. The traditional numerical method to compensate for the phase is modified to enable the 3D scanning property of OAM beams, so it is possible to avoid the feeder blockage and produce high-gain steered OAM beams. Likewise, reducing the inherent beam divergence of OAM beams can be obtained by examining the most satisfactory phase distribution of the scatterers by fitting the focal length. The simulated radiation pattern is validated by the measured radiation pattern of the fabricated RA in the frequency range between 28.5 and 31.5 GHz.
Ali Ali, Mohsen Khalily, and Rahim Tafazolli (2022) Ultra-Wideband Dielectric Reflectarray Antenna with OAM beams for mm-Wave Applications
The proposed structure is presented to improve the inherited limited bandwidth and reduce the production of grating lobes in reflectarray antennas (RAs). A dielectric RA with 200 mm × 200 mm is designed and simulated to produce an orbital angular momentum beam (OAM) of the second mode with averaged realized gain of around 20 dBi in the band of 25-40GHz, which covers most of 5G mm-wave bands (n257, n258, n260, and n261). To achieve the mentioned specifications, an inter-element spacing of 0.25λ is adopted.
Demos Serghiou, Mohsen Khalily, Ali Ali, Tim Brown, and Rahim Tafazolli (2022) Characterisation of Frequency Selective Reflections off Indoor Surfaces for 92–110 GHz
In this paper, we investigate the reflection properties of different interior surfaces in the 92–110 GHz sub-Terahertz (THz) band. The measurements were conducted in an indoor environment by placing the surface in a specular configuration between the Transmitter (Tx) and Receiver (Rx) and collecting a large set of data by offsetting the Tx and Rx in parallel to the surface. The measurements were performed using an Agilent N5230A Vector-Network-Analyzer (VNA). In particular, we present a statistical analysis in the frequency domain to show how frequency selective each surface reflection is and how constant this behaviour is across the whole data set. We introduce the Power-Delay-Profile (PDP) to characterize the multipath behaviour of the channel and calculate the Root-Mean-Square (RMS) delay spread. The measurement results provide a good insight for future propagation work to be done for the development of indoor communications systems at sub-THz frequencies.
Anton Tishchenko, Ali Ali, Paul Botham, Fraser Burton, Mohsen Khalily, and Rahim Tafazolli (2022) Reflective Metasurface for 5G mmWave Coverage Enhancement
The proposed intelligent reflective surface (IRS) is presented to compensate for the path loss and enhance the coverage of 5G networks at mm-wave band. A (π) shaped element with variable-sized dipoles, distributed in a certain way to maintain a phase length curve over 340° in the range of 23–27 GHz, is addressed in this work. The proposed structure can be an ideal candidate for 5G mm-wave band n258.