Mohammed Alresheedi - Profile on Academia.edu (original) (raw)

Papers by Mohammed Alresheedi

2019 21st International Conference on Transparent Optical Networks (ICTON)

Wavelength division multiplexing (WDM) and non-orthogonal multiple access (NOMA) are employed in ... more Wavelength division multiplexing (WDM) and non-orthogonal multiple access (NOMA) are employed in a visible light communication (VLC) system to increase the capacity of the system. The system is evaluated using two different scenarios focusing on power and data rate, where the first scenario is based on fair power allocation while the second scenario provides equal power allocation. Data rate variation is evaluated as a function of the users positioning and mobility. In both scenarios the proposed NOMA-WDM system achieved higher data rate NOMA system.

2019 21st International Conference on Transparent Optical Networks (ICTON)

The achievable data rate in indoor wireless systems that employ visible light communication (VLC)... more The achievable data rate in indoor wireless systems that employ visible light communication (VLC) can be limited by multipath propagation. Here, we use computer generated holograms (CGHs) in VLC system design to improve the achievable system data rate. The CGHs are utilized to produce a fixed broad beam from the light source, selecting the light source that offers the best performance. The CGHs direct this beam to a specific zone on the room's communication floor where the receiver is located. This reduces the effect of diffuse reflections. Consequently, decreasing the intersymbol interference (ISI) and enabling the VLC indoor channel to support higher data rates. We consider two settings to examine our propose VLC system and consider lighting constraints. We evaluate the performance in idealistic and realistic room setting in a diffuse environment with up to second order reflections and also under mobility. The results show that using the CGHs enhances the 3dB bandwidth of the VLC channel and improves the received optical power.

Room Temperature Operated Hydrogen Sensor Using Palladium Coated on Tapered Optical Fiber

SSRN Electronic Journal

Optical Fiber and Wireless Communications, 2017

Adaptive beam steering in optical wireless communication (OWC) system has been shown to offer per... more Adaptive beam steering in optical wireless communication (OWC) system has been shown to offer performance enhancements over traditional OWC systems. However, an increase in the computational cost is incurred. In this chapter, we introduce a fast hologram selection technique to speed up the adaptation process. We propose a fast delay, angle and power adaptive holograms (FDAPA-Holograms) approach based on a divide and conquer methodology and evaluate it with angle diversity receivers in a mobile optical wireless (OW) system. The fast and efficient fully adaptive FDAPA-Holograms system can improve the receiver signal to noise ratio (SNR) and reduce the required time to estimate the position of the receiver. The adaptation techniques (angle, power and delay) offer a degree of freedom in the system design. The proposed system FDAPA-Holograms is able to achieve high data rate of 5 Gb/s with full mobility. Simulation results show that the proposed 5 Gb/s FDAPA-Holograms achieves around 13 dB SNR under mobility and under eye safety regulations. Furthermore, a fast divide and conquer search algorithm is introduced to find the optimum hologram as well as to reduce the computation time. The proposed system (FDAPA-Holograms) reduces the computation time required to find the best hologram location from 64 ms using conventional adaptive system to around 14 ms.

Visible Light Communications, 2017

Dimming is an important feature of an indoor lighting system where the illumination level can be ... more Dimming is an important feature of an indoor lighting system where the illumination level can be controlled by the user. Therefore, integrating a visible light communication (VLC) system with an illumination system poses some challenges. One of the main issues is that the light unit should be "ON" all the time to ensure continuous communication. To ensure acceptance and adoption of VLC systems, an important issue should be addressed: how to communicate when the lights are "OFF" or partially dimmed. In this chapter, we propose five new infrared optical wireless (IROW) systems to support VLC systems when the light is totally turned off or significantly dimmed. To take advantage of both VLC and IROW, we introduce and implement the concept of a collaborative VLC/IROW system. In addition, we investigate the impact of partial dimming on the VLC system's performance, and we propose an adaptive rate technique (ART) to mitigate the impact of light dimming. Moreover, in the case of no dimming, the VLC and IROW systems can collaborate to increase the data rate so it is higher than that in the pure VLC system. We have achieved 10 Gbps in an indoor environment, which is a 2Â increase in the data rate compared with a pure VLC system.

Applied Sciences, 2022

This paper presents the generation and characterization of femtosecond pulses utilizing graphene-... more This paper presents the generation and characterization of femtosecond pulses utilizing graphene-polymethyl-methacrylate (PMMA) thin-film saturable absorber (SA), which is subjected to different lengths of single-mode fiber (SMF) in an erbium-doped fiber laser cavity. The graphene/PMMA-SA is prepared by using a simple transfer procedure of the thin-film on a fiber ferrule. By increasing the SMF length from 0 to 4 m, the corresponding group velocity dispersion of the entire cavity is estimated to change from −0.033 to −0.121 ps2. Analysis of the pulse performance shows that the pulse width behavior varies from 820 fs to 710 fs against different cavity lengths. Similarly, the pulse repetition rate and the spectral bandwidth can be adjusted from 12.5 to 10.0 MHz, and from 8.2 to 5.6 nm, respectively. A comprehensive discussion on the pulse performance is presented, which can contribute to widening the knowledge on the operation of graphene-based soliton mode-locked erbium-doped fiber l...

In the past few years, the demand for high data rate services has increased dramatically. The con... more In the past few years, the demand for high data rate services has increased dramatically. The congestion in the radio frequency (RF) spectrum (3 kHz ~ 300 GHz) is expected to limit the growth of future wireless systems unless new parts of the spectrum are opened. Even with the use of advanced engineering, such as signal processing and advanced modulation schemes, it will be very challenging to meet the demands of the users in the next decades using the existing carrier frequencies. On the other hand, there is a potential band of the spectrum available that can provide tens of Gbps to Tbps for users in the near future. Optical wireless communication (OWC) systems are among the promising solutions to the bandwidth limitation problem faced by radio systems. In this paper, we give a tutorial survey of the most significant issues in OWC systems that operate at short ranges such as indoor systems. We consider the challenging issues facing these systems such as (i) link design and system requirements, (ii) transmitter structures, (iii) receiver structures, (iv) challenges and possible techniques to mitigate the impairments in these systems, (v) the main applications and (vi) open research issues. In indoor OWC systems we describe channel modelling, mobility and dispersion mitigation techniques. Infrared communication (IRC) and visible light communication (VLC) are presented as potential implementation approaches for OWC systems and are comprehensively discussed. Moreover, open research issues in OWC systems are discussed.

2019 21st International Conference on Transparent Optical Networks (ICTON), 2019

In this paper, we address the optimization of wavelength resource allocation in multiuser WDM Vis... more In this paper, we address the optimization of wavelength resource allocation in multiuser WDM Visible Light Communication (VLC) systems. A Mixed Integer Linear Programming (MILP) model that maximizes the sum of Signal-to-Interference-plus-Noise-Ratio (SINR) for all users is utilized. The results show that optimizing the wavelength allocation in multiuser WDM VLC systems can reduce the impact of the interference and improve the system throughput in terms of the sum of data rates for up to 7 users.

Noise‐like pulse generation with tungsten trioxide/polydimethylsiloxane‐clad microfiber saturable absorber

Microwave and Optical Technology Letters, 2022

We report the formation of noise‐like pulse (NLP) with tungsten trioxide/polydimethylsiloxane‐cla... more We report the formation of noise‐like pulse (NLP) with tungsten trioxide/polydimethylsiloxane‐clad microfiber saturable absorber integrated in a ring‐cavity erbium‐doped fiber laser. The NLP operation was confirmed by the presence of a coherence spike on top of a broad pedestal in the autocorrelation trace, with the measured pulse width value of 410 fs and 3.56 ps respectively. By increasing the pump power from the mode‐locking threshold of 280–3300 mW, the spectral bandwidth was stretched from 22.3 to 22.8 nm, while the output power increased from to 1.9 to 24.3 mW. The maximum pulse energy of 3.5 nJ was generated at a repetition rate of 7 MHz. The signal‐to‐noise ratio was measured to be 53.8 dB, which indicated a good stability of pulse laser.

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

Optical wireless communication (OWC) systems have been the subject of a significant amount of int... more Optical wireless communication (OWC) systems have been the subject of a significant amount of interest as they can be used in sixth generation (6G) wireless communication to provide high data rates and support multiple users simultaneously. This paper investigates the impact of receiver orientation on resource allocation in optical wireless systems, using a wavelength division multiple access (WDMA) scheme. Three different systems that have different receiver orientations are examined in this work. Each of these systems considers 8 simultaneous users in two scenarios. WDMA is utilised to support multiple users and is based on four wavelengths offered by Red, Yellow, Green and Blue (RYGB) LDs for each AP. An angle diversity receiver (ADR) is used in each system with different orientations. The optimised resource allocations in terms of wavelengths and access point (AP) is obtained by using a mixed-integer linear programming (MILP) model. The channel bandwidth and SINR are determined in the two scenarios in all systems. The results show that a change in the orientation of the receiver can affect the level of channel bandwidth and SINR. However, SINRs in both scenarios for all users are above the threshold (15.6 dB). The SINR obtained can support t data rate of 5.7 Gbps in both scenarios in all systems.

2019 IEEE Conference on Standards for Communications and Networking (CSCN), 2019

Interference between cells or users can have a significant impact on the quality of optical wirel... more Interference between cells or users can have a significant impact on the quality of optical wireless communication (OWC) links. This paper studies the coexistence of infrared based Micro cells with Visible light communication based Pico and Atto Cells for downlink communication. The signal to noise ratio (SNR) of each cell and the signal to interference and noise ratio (SINR) between cells are evaluated when an angle diversity receiver and an imaging receiver are used. The results show that Atto cell systems provide higher SNR and data rates compared to the Pico cell systems which provide higher SNR and data rates compared to Micro cell systems. The Micro cell systems however provide mobility as they provide a larger coverage area, followed by the Pico cell systems.

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

Optical wireless communication (OWC) systems have been the subject of attention as a promising wi... more Optical wireless communication (OWC) systems have been the subject of attention as a promising wireless communication technology that can offer high data rates and support multiple users simultaneously. In this paper, the impact of room size is investigated when using wavelength division multiple access (WDMA) in conjunction with an angle diversity receiver (ADR). Four wavelengths (red, yellow, green and blue) can be provided in this work based on the RYGB LDs transmitter used. Three room sizes are considered with two 8-user scenarios. A mixed-integer linear programming (MILP) model is proposed for the purpose of optimising the resource allocation. The optical channel bandwidth, SINR and data rate have been calculated for each user in both scenarios in all rooms. Room A, which is the largest room, can provide a higher channel bandwidth and SINR compared to the other rooms. However, all rooms can provide a data rate above 5 Gbps in both scenarios.

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

High reliability and availability of communication services is a key requirement that needs to be... more High reliability and availability of communication services is a key requirement that needs to be ensured by service providers. Since the direct line-of-sight (LOS) beam is prone to blockage in indoor optical wireless communication systems, a backup link needs to be at hand in case of blockage, and hence channel allocation algorithms should be blockage-aware. In this paper, the impact of beam blockage due to a disc with varying size and distance from the receiver is studied where blockage is quantitatively evaluated using percentage blockage for 512 room locations at 25 cm separation. It was found that assigning two links with maximum separation between the serving access points can reduce or eliminate blockage compared to the case when resilience is not implemented. Increasing the number of allocated access points per user further increases resilience.

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

The design of a wireless communication system that can support multiple users at high data rates ... more The design of a wireless communication system that can support multiple users at high data rates inside an aircraft is a key requirement of aircraft manufacturers. This paper examines the design of an on-board visible light communication (VLC) system for transmitting data on board Boeing 747-400 aircraft. The reading light unit of each seat is utilised as an optical transmitter. A red, yellow, green, and blue (RYGB) laser diode (LD) is used in each reading light unit for transmitting data. An angle diversity receiver (ADR), which is an optical receiver that is composed of four branches (in this work), is evaluated. The signal-to-interference-plus-noise ratio (SINR) and data rate are determined. Three scenarios have been examined where, in the first scenario, one device is used, in the second scenario two devices are used and in the third scenario three devices are used by each passenger. The proposed system can offer high SINRs that support high data rates for each passenger by using simple on-offkeying (OOK).

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

In this paper, we investigate the impact of user distribution on resource allocation in visible l... more In this paper, we investigate the impact of user distribution on resource allocation in visible light communication (VLC) systems, using a wavelength division multiple access (WDMA) scheme. Two different room layouts are examined in this study. Three 10-user scenarios are considered, while an optical angle diversity receiver (ADR) with four faces is used. A mixed-integer linear programming (MILP) model is utilized to identify the optimum wavelengths and access point (AP) allocation in each scenario. The results show that a change in user distribution can affect the level of channel bandwidth and SINR. However, a uniform distribution of users in the room can provide a higher channel bandwidth as well as high SINR above the threshold (15.6 dB) for all users compared to clustered users, which is a scenario that has the lowest SINR with supported data rate above 3.2 Gbps.

2019 IEEE Conference on Standards for Communications and Networking (CSCN), 2019

Offering a high data rate to users inside the cabin is attractive for the aircraft building compa... more Offering a high data rate to users inside the cabin is attractive for the aircraft building companies. This paper presents an optical wireless system that uses visible light for transmitting data. The reading light for each seat is used as a transmitter in this work to offer high data rates. Red, yellow, green, and blue (RYGB) laser diode (LD) are utilised in each reading light to obtain a high modulation bandwidth. Two types of reading lights based on angle diversity transmitter (ADT) units are utilised in this paper for illumination and communication. Additionally, two kinds of optical receivers are used: four branches angle diversity receiver (ADR) and 25 pixels imaging receiver (ImR). The delay spread and the signal to interference and noise ratio (SINR) are evaluated. The proposed system can offer high data rates up to 22.8 Gbps for each user by using simple on-off-keying (OOK) modulation.

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

In this paper, we use the percentage blockage as a metric when an opaque disc obstructs the Line-... more In this paper, we use the percentage blockage as a metric when an opaque disc obstructs the Line-of-Sight link from the access point to the receiver in an optical wireless indoor communication system. The effect of the different parameters of the obstructing object are studied, these are the radius, the height, and the horizontal distance from the receiver in the positive y direction. The percentage of blocked room locations to the total number of room locations when varying the disc parameters is studied assuming a single serving link. It was found that depending on the dimensions of the obstructing object and the distance from the receiver in addition to which access point is serving the user, that blockage can vary between 0% up to 100%. Furthermore, the service received by a user, in terms of beam blockage depends on the access point they are connected to. The resulting fairness challenges will be addressed in resource allocation optimization in future work.

2018 International Conference on Optical Network Design and Modeling (ONDM), 2018

In this paper, the performance of visible light communication (VLC) systems, employing Space Time... more In this paper, the performance of visible light communication (VLC) systems, employing Space Time Block Coding (STBC) and Repetition Coding (RC) techniques for an indoor environment is investigated and analyzed. The indoor channel impulse response is taken into account assuming line-of-sight (LOS) and Non-LOS (NLOS) scenarios. The proposed systems employ multiple transmit light emitting diodes (LEDs) with one and two photodetectors (PDs). Various physical arrangements and placements of the LEDs and PD within the indoor scenario are considered. Simulation results show that, for a specific LEDs and PDs arrangement, RC techniques outperform the respective STBC techniques. Furthermore, a 2x2 multiple-input multipleoutput (MIMO) VLC system implementing Alamouti STBC is investigated and compared with the RC scheme using a single receiver. It is shown that adding another PD can achieve a signalto-noise ratio (SNR) improvement of about 5 dB and 2 dB over the Alamouti and RC schemes with a single PD, respectively.

2019 IEEE International Conference on Computational Science and Engineering (CSE) and IEEE International Conference on Embedded and Ubiquitous Computing (EUC), 2019

Providing uplink high data rate is one of the big concerns in visible light communication (VLC) s... more Providing uplink high data rate is one of the big concerns in visible light communication (VLC) systems. This paper introduces an uplink VLC system based on an infrared transmitter with beam steering to provide high data rates. In this work, a 4 branches angle diversity receiver (ADR) is used and the resultant delay spread and SNR are examined. The proposed system achieved data rates up to 3.57 Gb/s using simple on-off-keying (OOK).

2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020

In this paper, a non-orthogonal multiple access (NOMA) visible light communication (VLC) system i... more In this paper, a non-orthogonal multiple access (NOMA) visible light communication (VLC) system is investigated. The system uses angle diversity receivers (ADRs) to provide high data rates. The ADR has 4 branches, each directed to a different direction. An 8m × 4m sized room is modelled to study the resource allocation to users according to their channel conditions to maximize the data rate. The results show that using ADRs improves the data rate by an average of 35% compared to a system using wide FOV receivers.