54 research outputs found
Performance Enhancement Using NOMA-MIMO for 5G Networks
The integration of MIMO and NOMA technologies addresses key challenges in 5G and beyond, such as connectivity, latency, and dependability. However, resolving these issues, especially in MIMO-enabled 5G networks, required additional research. This involved optimizing parameters like bit error rate, downlink spectrum efficiency, average capacity rate, and uplink transmission outage probability. The model employed Quadrature Phase Shift Keying modulation on selected frequency channels, accommodating diverse user characteristics. Evaluation showed that MIMO-NOMA significantly improved bit error rate and transmitting power for the best user in download transmission. For uplink transmission, there was an increase in the average capacity rate and a decrease in outage probability for the best user. Closed-form formulas for various parameters in both downlink and uplink NOMA, with and without MIMO, were derived. Overall, adopting MIMO-NOMA led to a remarkable performance improvement for all users, even in challenging conditions like interference or fading channels
Design and performance analysis of optical attocell networks
The exponentially increasing demand for high-speed wireless communications will no longer
be satisfied by the traditional radio frequency (RF) in the near future due to its limited spectrum
and overutilization. To resolve this imminent issue, industrial and research communities have
been looking into alternative technologies for communication. Among them, visible light communication
(VLC) has attracted much attention because it utilizes the unlicensed, free and safe
spectrum, whose bandwidth is thousand times larger than the entire RF spectrum. Moreover,
VLC can be integrated into existing lighting systems to offer a dual-purpose, cost-effective and
energy-efficient solution for next-generation small-cell networks (SCNs), giving birth to the
concept of optical attocell networks.
Most relevant works in the literature rely on system simulations to quantify the performance
of attocell networks, which suffer from high computational complexity and provide limited
insights about the network. Mathematical tools, on the other hand, are more tractable and
scalable and are shown to closely approximate practical systems. The presented work utilizes
stochastic geometry for downlink evaluation of optical attocell networks, where the co-channel
interference (CCI) surpasses noise and becomes the limiting factor of the link throughput. By
studying the moment generating function (MGF) of the aggregate interference, a theoretical
framework for modeling the distribution of signal-to-interference-plus-noise ratio (SINR) is
presented, which allows important performance metrics such as the coverage probability and
link throughput to be derived. Depending on the source of interference, CCI can be classified
into two categories: inter-cell interference (ICI) and intra-cell interference. In this work,
both types of interference are characterized, based on which effective interference mitigation
techniques such as the coordinated multipoint (CoMP), power-domain multiplexing and successive
interference cancellation (SIC) are devised. The proposed mathematical framework is
applicable to attocell networks with and without such interference mitigation techniques.
Compared to RF networks, optical attocell networks are inherently more secure in the physical
layer because visible light does not penetrate through opaque walls. This work analytically
quantifies the physical-layer security of attocell networks from an information-theoretic point of
view. Secrecy enhancement techniques such as AP cooperation and eavesdropper-free protected
zones are also discussed. It is shown that compared to AP cooperation, implementing secrecy
protected zones is more effective and it can contribute significantly to the network security
Multi-user visible light communications: State-of-the-art and future directions
Visible light communications (VLC) builds upon the dual use of existing lighting infrastructure for wireless data transmission. VLC has recently gained interest as cost-effective, secure, and energy-efficient wireless access technology particularly for indoor user-dense environments. While initial studies in this area are mainly limited to single-user point-to-point links, more recent efforts have focused on multi-user VLC systems in an effort to transform VLC into a scalable and fully networked wireless technology. In this paper, we provide a comprehensive overview of multi-user VLC systems discussing the recent advances on multi-user precoding, multiple access, resource allocation, and mobility management. We further provide possible directions for future research in this emerging topic.King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia ; TÜBİTAKPublisher versio
Five Facets of 6G: Research Challenges and Opportunities
Whilst the fifth-generation (5G) systems are being rolled out across the
globe, researchers have turned their attention to the exploration of radical
next-generation solutions. At this early evolutionary stage we survey five main
research facets of this field, namely {\em Facet~1: next-generation
architectures, spectrum and services, Facet~2: next-generation networking,
Facet~3: Internet of Things (IoT), Facet~4: wireless positioning and sensing,
as well as Facet~5: applications of deep learning in 6G networks.} In this
paper, we have provided a critical appraisal of the literature of promising
techniques ranging from the associated architectures, networking, applications
as well as designs. We have portrayed a plethora of heterogeneous architectures
relying on cooperative hybrid networks supported by diverse access and
transmission mechanisms. The vulnerabilities of these techniques are also
addressed and carefully considered for highlighting the most of promising
future research directions. Additionally, we have listed a rich suite of
learning-driven optimization techniques. We conclude by observing the
evolutionary paradigm-shift that has taken place from pure single-component
bandwidth-efficiency, power-efficiency or delay-optimization towards
multi-component designs, as exemplified by the twin-component ultra-reliable
low-latency mode of the 5G system. We advocate a further evolutionary step
towards multi-component Pareto optimization, which requires the exploration of
the entire Pareto front of all optiomal solutions, where none of the components
of the objective function may be improved without degrading at least one of the
other components
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