The increased proliferation of connected devices requires a development of innovative technologie... more The increased proliferation of connected devices requires a development of innovative technologies for the next generation of wireless systems. One of the key challenges, however, is the spectrum scarcity, owing to the unprecedented broadband penetration rate in recent years. Based on this, visible light communication (VLC) has recently emerged as an effective potential solution for enabling high-speed short-range communications. Yet, despite their undoubted advantageous features, VLC systems suffer from several limitations which constraint their capabilities. As a result, several multiple access (MA) techniques, such as space-division multiple access (SDMA) and non-orthogonal multiple access (NOMA), have been considered in VLC networks as an effective approach, among others, to circumvent these limitations. However, despite their achievable multiplexing gain, their overall performance is still limited compared to the overall potential of this technology. Motivated by this, the presented article offers two contributions: firstly, we provide an overview of the key MA technologies used in VLC systems and then we introduce rate-splitting multiple access (RSMA), and discuss its capabilities and potentials in VLC systems. Secondly, through realistic system modeling and simulations of an RSMA-based two-user scenario, we illustrate the flexibility of RSMA as well as its superiority in terms of the achievable weighted sum rate over NOMA and SDMA in the context of VLC. Finally, we discuss technical challenges, open issues, and research directions, along with the offered results and insights that are expected to be useful towards the effective practical realization of RSMA in VLC configurations. INDEX TERMS Multiple-input multiple-output, non-orthogonal multiple access, rate-splitting multiple access, space-division multiple access, visible light communication.
5G networks are required to provide very fast and reliable communications while dealing with the ... more 5G networks are required to provide very fast and reliable communications while dealing with the increase of users traffic. In Heterogeneous Networks (HetNets) assisted with Device-to-Device (D2D) communication, traffic can be offloaded to Small Base Stations or to users to improve the network's successful data delivery rate. In this paper, we aim at maximizing the average number of files that are successfully delivered to users, by jointly optimizing caching placement and channel allocation in cache-enabled D2D-assisted HetNets. At first, an analytical upper-bound on the average content delivery delay is derived. Then, the joint optimization problem is formulated. The non-convexity of the problem is alleviated, and the optimal solution is determined. Due to the high time complexity of the obtained solution, a low-complex sub-optimal approach is proposed. Numerical results illustrate the efficacy of the proposed solutions and compare them to conventional approaches. Finally, by investigating the impact of key parameters, e.g. power, caching capacity, QoS requirements, etc., guidelines to design these networks are obtained.
The increased proliferation of connected devices and emergence of internet-of-everything represen... more The increased proliferation of connected devices and emergence of internet-of-everything represent a major challenge for broadband wireless networks. This requires a paradigm shift towards the development of innovative technologies for the next generation wireless systems. One of the key challenges towards realizing this vision, however, is the scarcity of spectrum, owing to the unprecedented broadband penetration rate in recent years. A promising solution to the current spectrum crunch is the proposal of visible light communications (VLC), which explores the unregulated visible light spectrum to enable high-speed short range communications, in addition to providing efficient lighting. This solution is envisioned to offer a considerably wider bandwidth, that can accommodate ubiquitous broadband connectivity to indoor users and further offload data traffic from overloaded cellular networks. Although VLC is inherently secure and able to overcome the shortcomings of current RF wireless systems, it suffers from several limitations, including the limited modulation bandwidth of light-emitting diodes. In this respect, several interesting solutions have been proposed in the recent literature to overcome this limitation. In particular, most common orthogonal and non-orthogonal multiple access techniques initially proposed for RF systems, e.g., space-division multiple access and NOMA, have been considered in the context of VLC. In spite of their promising multiplexing gains, the performance of these techniques is somewhat limited. Consequently, in this article a new and generalized multiple access technique, called rate-splitting multiple access (RSMA), is introduced and investigated for the first time in VLC networks. In this article, we first provide an overview of the key multiple access technologies used in VLC systems. Then, we propose the first comprehensive approach to the integration of RSMA with VLC systems. In our proposed RSMA-VLC framework, signal-to-interference and noise ratio expressions are derived and subsequently used to evaluate the weighted sum rate (WSR) performance of a twouser scenario. Our results illustrate the flexibility of RSMA in generalizing other multiple access techniques, namely NOMA and SDMA, as well as its superiority in terms of WSR in the context of VLC.
In this letter, we present a model for quadrotor unmanned aerial vehicles (UAVs), including contr... more In this letter, we present a model for quadrotor unmanned aerial vehicles (UAVs), including control, communication, and wireless charging. In so doing, we investigate associated energy and battery dynamics. Indeed, energy and battery expressions are derived by leveraging motors' and battery electrical models. Through an experiment, their performances are evaluated for different parameters. The objective is to provide a simple yet practical model of quadrotor UAV consumed/harvested energy and battery dynamics for researchers conducting work on energy-efficient aerial networks.
In this paper, we aim to sustain unmanned aerial vehicle (UAV) based missions for longer periods ... more In this paper, we aim to sustain unmanned aerial vehicle (UAV) based missions for longer periods of times through different techniques. First, we consider on-the-mission UAV recharging by a low-power laser source (below 1 kilowatt). In order to achieve the maximal energy gain from the low-power laser source, we propose an operational compromise, which consists of the UAV resting over buildings with cleared line-ofsight to the laser source. Second, to provide a precise energy consumption/harvesting estimation at the UAV, we investigate the latter's dynamics in a mission environment. Indeed, we study the UAV's battery dynamics by leveraging the electrical models for motors and battery. Subsequently, using these models, the path planning problem in a particular Internet-of-Things based usecase is revisited from the battery perspective. The objective is to extend the UAV's operation time using both laser-charging and accurate battery level estimation. Through a graph theory approach, the problem is solved optimally, and compared to benchmark trajectory approaches. Numerical results demonstrate the efficiency of this novel battery perspective for all path planning approaches. In contrast, we found that the energy perspective is very conservative and does not exploit optimally the available energy resources. Nevertheless, we propose a simple adjustment method to correct the energy perspective, by carefully evaluating the energy as a function of the UAV motion regimes. Finally, the impact of several parameters, such as turbulence and distance to charging source, is studied.
Unmanned aerial vehicle (UAV)-enabled edge federated learning (FL) has sparked a rise in research... more Unmanned aerial vehicle (UAV)-enabled edge federated learning (FL) has sparked a rise in research interest as a result of the massive and heterogeneous data collected by UAVs, as well as the privacy concerns related to UAV data transmissions to edge servers. However, due to the redundancy of UAV collected data, e.g., imaging data, and non-rigorous FL participant selection, the convergence time of the FL learning process and bias of the FL model may increase. Consequently, we investigate in this paper the problem of selecting UAV participants for edge FL, aiming to improve the FL model's accuracy, under UAV constraints of energy consumption, communication quality, and local datasets' heterogeneity. We propose a novel UAV participant selection scheme, called data-efficient energyaware participant selection strategy (DEEPS), which consists of selecting the best FL participant in each sub-region based on the structural similarity index measure (SSIM) average score of its local dataset and its power consumption profile. Through experiments, we demonstrate that the proposed selection scheme is superior to the benchmark random selection method, in terms of model accuracy, training time, and UAV energy consumption.
With the advent of rapid globalization and the interborder supply chain network, the reliability ... more With the advent of rapid globalization and the interborder supply chain network, the reliability and efficiency of transportation systems have become even more critical. Indeed, trans-continental highways need particular attention due to their important role in sustaining globalization. In this context, intelligent transportation systems (ITS) can actively enhance the safety, mobility, productivity, and comfort of trans-continental highways. However, ITS efficiency depends greatly on the roads where they are deployed, on the availability of power and connectivity, and on the integration of future connected and autonomous vehicles. To this end, high altitude platform station (HAPS) systems, due to their mobility, sustainability, payload capacity, and communication/caching/computing capabilities, are seen as a key enabler of future ITS services for trans-continental highways; this paradigm is referred to as HAPS-ITS. The latter is envisioned as an active component of ITS systems to support a plethora of transportation applications, such as traffic monitoring, accident reporting, and platooning. This paper discusses how HAPS systems can enable advanced ITS services for trans-continental highways, presenting the main requirements of HAPS-ITS and a detailed case study of the Trans-Sahara highway.
This paper develops a deep reinforcement learning solution to simultaneously optimize the multi-U... more This paper develops a deep reinforcement learning solution to simultaneously optimize the multi-UAV cellassociation decisions and their moving velocity decisions on a given 3D aerial highway. The objective is to improve both the transportation and communication performances, e.g., collisions, connectivity, and HOs. We cast this problem as a Markov decision process (MDP) where the UAVs' states are defined based on their velocities and communication data rates. We have a 2D transportation-communication action space with decisions like UAV acceleration/deceleration, lane-changes, and UAV-base station (BS) assignments for a given UAV's state. To deal with the multi-dimensional action space, we propose a neural architecture having a shared decision module with multiple network branches, one for each action dimension. A linear increase of the number of network outputs with the number of degrees of freedom can be achieved by allowing a level of independence for each individual action dimension. To illustrate the approach, we develop Branching Dueling Q-Network (BDQ) and Branching Dueling Double Deep Q-Network (Dueling DDQN). Simulation results demonstrate the efficacy of the proposed approach, i.e., 18.32% improvement compared to the existing benchmarks.
Fifth-generation and beyond (5G and xG) wireless networks are envisioned to meet the requirements... more Fifth-generation and beyond (5G and xG) wireless networks are envisioned to meet the requirements of vertical applications like high traffic throughput, ultra-massive connectivity, extremely low latency, and high quality of service. Disruptive technologies, such as massive multiple-input multiple-output, millimeter wave, and multiple access are being deployed to meet these requirements. However, their deployment poses several challenges, including a lack of network transparency, management decentralization, and reliability. Moreover, the heterogeneity of future networks raises security concerns, e.g., confidentiality, privacy, and trustworthiness. Indeed, due to the emergence of novel paradigms, e.g., quantum computing, traditional security approaches are no longer sufficient to protect over-the-air communications. Hence, 5G/xG networks must consider smart security techniques to operate seamlessly and efficiently. Within this context, physical layer security (PLS) and blockchain rep...
As the world we live in becomes smaller and more interconnected, with people and goods traveling ... more As the world we live in becomes smaller and more interconnected, with people and goods traveling for thousands of kilometers to reach their destinations, the reliability and efficiency of transportation systems have become critical. Indeed, trans-continental highways need particular attention due to their important role in sustaining globalization. In this context, intelligent transportation systems (ITS) can actively enhance the safety, mobility, productivity, and comfort of trans-continental highways. However, ITS efficiency depends greatly on the roads where they are deployed, on the availability of power and connectivity, and on the integration of future connected and autonomous vehicles. To this end, high altitude platform station (HAPS) systems, due to their mobility, sustainability, payload capacity, and communication/caching/computing capabilities, are seen as a key enabler of future ITS services for trans-continental highways; this paradigm is referred to as HAPS-ITS. The latter is envisioned as an active component of ITS systems to support a plethora of transportation applications, such as traffic monitoring, accident reporting, and platooning. This paper discusses how HAPS systems can enable advanced ITS services for trans-continental highways, presenting the main requirements of HAPS-ITS and a detailed case study of the Trans-Sahara highway.
2020 IEEE 17th Annual Consumer Communications & Networking Conference (CCNC)
In this work, we deal with the violation probability of data update interval for a wireless senso... more In this work, we deal with the violation probability of data update interval for a wireless sensor network with energy harvesting capabilities, in the context of monitoring applications requiring a continuous update of sensing information. Specifically, we consider a wireless sensor network consisting of independent energy harvesting sensor nodes providing status updates to a non energy harvesting sink. A sensor node generates a status update message when its battery becomes fully charged. The generated message is then transmitted without further energy management, i.e., using all the available harvested energy and according to a first-come-first-served access method. In this paper, we first derive the update interval distribution for a random energy arrival process. Then, the violation probability of the update interval is derived in closed-form for the onenode wireless sensor network. It is shown that it highly depends on the size of the battery. Furthermore, the update interval of a multi-node system is characterized. Obtained analytical and numerical results show that there exists an optimal battery size that minimizes the violation probability. Moreover, the design of the system introduces an interesting trade-off. On one hand, a small battery is charged quickly and thus updates are sent more frequently but with a high error rate. On the other hand, a larger battery increases the transmit power and boosts the successful data transmission probability but increases the time required before transmitting.
ICC 2021 - IEEE International Conference on Communications
On-board battery consumption, cellular disconnectivity, and frequent handoff are key challenges f... more On-board battery consumption, cellular disconnectivity, and frequent handoff are key challenges for unmanned aerial vehicle (UAV) based delivery missions, a.k.a., cargo-UAV. Indeed, with the introduction of UAV technology into cargo shipping and logistics, designing energy-efficient paths becomes a serious issue for the next retail industry transformation. Typically, the latter has to guarantee uninterrupted or slightly interrupted cellular connectivity for the UAV's command and control through a small number of handoffs. In this paper, we formulate the trajectory planning as a multi-objective problem aiming to minimize both the UAV's energy consumption and the handoff rate, constrained by the UAV battery size and disconnectivity rate. Due to the problem's complexity, we propose a dynamic programming based solution. Through simulations, we demonstrate the efficiency of our approach in providing optimized UAV trajectories. Also, the impact of several parameters, such as the cargo-UAV altitude, disconnectivity rate, and type of environment, are investigated. The obtained results allow to draw recommendations and guidelines for cargo-UAV operations.
In this paper, we aim to sustain unmanned aerial vehicle (UAV) based missions for longer periods ... more In this paper, we aim to sustain unmanned aerial vehicle (UAV) based missions for longer periods of times through different techniques. First, we consider on-the-mission UAV recharging by a low-power laser source (below 1 kilowatt). In order to achieve the maximal energy gain from the low-power laser source, we propose an operational compromise, which consists of the UAV resting over buildings with cleared line-ofsight to the laser source. Second, to provide a precise energy consumption/harvesting estimation at the UAV, we investigate the latter's dynamics in a mission environment. Indeed, we study the UAV's battery dynamics by leveraging the electrical models for motors and battery. Subsequently, using these models, the path planning problem in a particular Internet-of-Things based usecase is revisited from the battery perspective. The objective is to extend the UAV's operation time using both laser-charging and accurate battery level estimation. Through a graph theory approach, the problem is solved optimally, and compared to benchmark trajectory approaches. Numerical results demonstrate the efficiency of this novel battery perspective for all path planning approaches. In contrast, we found that the energy perspective is very conservative and does not exploit optimally the available energy resources. Nevertheless, we propose a simple adjustment method to correct the energy perspective, by carefully evaluating the energy as a function of the UAV motion regimes. Finally, the impact of several parameters, such as turbulence and distance to charging source, is studied.
UAVs can be used as aerial relays to provide communication services in remote uncovered areas or ... more UAVs can be used as aerial relays to provide communication services in remote uncovered areas or dense environments with occasional high capacity demands. However, due to the low power of Internet-of-Things (IoT) devices, UAV-based IoT applications, such as precision agriculture and environment monitoring, may experience high shadowing or equipment failure, which degrades the communications' quality between IoT devices and their gateways. To tackle this issue, we consider the long range (LoRa) communication technology. Specifically, we investigate the performance of LoRA-enabled aerial communications, where a LoRa gateway communicates with a distant IoT device through the assistance of an amplify-and-forward aerial relay. Under the assumption of shadowed Rician fading channels, we characterize at first the end-to-end LoRa communication link. Then, we derive an exact symbol error rate expression for the underlying system model. Finally, numerical results are presented to corrobor...
Inter-cell interference (ICI) and inter-user interference (IUI) constitute a major issue towards ... more Inter-cell interference (ICI) and inter-user interference (IUI) constitute a major issue towards achieving the optimum spectral efficiency (SE) and energy efficiency (EE) performance in multi-cell visible light communication (VLC) networks. Hence, advanced multiple access techniques need to be leveraged in order to improve the provided service to the users of such interfering networks. To this end, the present contribution proposes the integration of coordinated beamforming (CB) with rate-splitting multiple access (RSMA) in multi-cell VLC systems. Specifically, we consider the design of beamformers for the common and private streams in a coordinated manner between different attocells, which is shown to provide efficient mitigation of the incurred interference. Additionally, the formulated optimization problem aims to minimize the sum of the mean squared error across all attocells in order to jointly determine the optimum receive filters and coordinated transmit beamformers for RSMA streams. In this context, we illustrate through extensive computer simulations, which are carried out in a realistic setup that assumes noisy channel state information acquisition, the distinct flexibility and robustness of CB-based RSMA in mitigating the incurred interference. Finally, the offered results demonstrate the superiority of CB-based RSMA in terms of achievable SE and EE performance in multi-cell VLC Manuscript
Reconfigurable Smart Surface (RSS) is assumed to be a key enabler for future wireless communicati... more Reconfigurable Smart Surface (RSS) is assumed to be a key enabler for future wireless communication systems due to its ability to control the wireless propagation environment and, thus, enhance communications quality. Although optimal and continuous phase-shift configuration can be analytically obtained, practical RSS systems are prone to both channel estimation errors, discrete control, and curse of dimensionality. This leads to relaying on a finite number of phase-shift configurations that is expected to degrade the system's performances. In this paper, we tackle the problem of quantized RSS phase-shift configuration, aiming to maximize the data rate of an orthogonal frequency division multiplexing (OFDM) point-to-point RSSassisted communication. Due to the complexity of optimally solving the formulated problem, we propose here a sub-optimal greedy algorithm to solve it. Simulation results illustrate the performance superiority of the proposed algorithm compared to baseline approaches. Finally, the impact of several parameters, e.g., quantization resolution and RSS placement, is investigated.
The increased proliferation of connected devices requires a development of innovative technologie... more The increased proliferation of connected devices requires a development of innovative technologies for the next generation of wireless systems. One of the key challenges, however, is the spectrum scarcity, owing to the unprecedented broadband penetration rate in recent years. Based on this, visible light communication (VLC) has recently emerged as an effective potential solution for enabling high-speed short-range communications. Yet, despite their undoubted advantageous features, VLC systems suffer from several limitations which constraint their capabilities. As a result, several multiple access (MA) techniques, such as space-division multiple access (SDMA) and non-orthogonal multiple access (NOMA), have been considered in VLC networks as an effective approach, among others, to circumvent these limitations. However, despite their achievable multiplexing gain, their overall performance is still limited compared to the overall potential of this technology. Motivated by this, the presented article offers two contributions: firstly, we provide an overview of the key MA technologies used in VLC systems and then we introduce rate-splitting multiple access (RSMA), and discuss its capabilities and potentials in VLC systems. Secondly, through realistic system modeling and simulations of an RSMA-based two-user scenario, we illustrate the flexibility of RSMA as well as its superiority in terms of the achievable weighted sum rate over NOMA and SDMA in the context of VLC. Finally, we discuss technical challenges, open issues, and research directions, along with the offered results and insights that are expected to be useful towards the effective practical realization of RSMA in VLC configurations. INDEX TERMS Multiple-input multiple-output, non-orthogonal multiple access, rate-splitting multiple access, space-division multiple access, visible light communication.
The proliferation of connected devices and emergence of internet-of-everything represent a major ... more The proliferation of connected devices and emergence of internet-of-everything represent a major challenge for broadband wireless networks. This requires a paradigm shift towards the development of innovative technologies for next generation wireless systems. One of the key challenges is the scarcity of spectrum, owing to the unprecedented broadband penetration rate in recent years. A promising solution is the proposal of visible light communications (VLC), which explores the unregulated visible light spectrum to enable high-speed communications, in addition to efficient lighting. This solution offers a wider bandwidth that can accommodate ubiquitous broadband connectivity to indoor users and offload data traffic from cellular networks. Although VLC is secure and able to overcome the shortcomings of RF systems, it suffers from several limitations, e.g., limited modulation bandwidth. In this respect, solutions have been proposed recently to overcome this limitation. In particular, mo...
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Papers by Wael JAAFAR