265 research outputs found
Secrecy Design of Indoor Visible Light Communication Network under Downlink NOMA Transmission
In this work, we investigate the transmission sum rate as well as the secrecy
sum rate of indoor visible light communication (VLC) networks for mobile
devices with the power domain non-orthogonal multiple access (NOMA)
transmission, where multiple legitimate users are equipped with photodiodes
(PDs). We introduce a body blockage model of the legitimate users as well as
the eavesdropper to focus on the case where the communications from
transmitting light-emitting diodes (LEDs) to receiving devices are blocked by
the bodies of receiving users. Furthermore, in order to improve the secrecy
without any knowledge of the channel state information (CSI) of the
eavesdropper, a novel LED arrangement is introduced to reduce the overlapping
area covered by LED units supporting different users. We also propose two LED
operation strategies, called simple and smart LED linking, and evaluate their
performance against the conventional broadcasting in terms of transmission sum
rate and secrecy sum rate. Through computer simulations, the superiority of our
proposed strategies is demonstrated.Comment: 30 pages, 13 figures. This work has been submitted to the IEEE for
possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
Non-Orthogonal Multiple Access for Hybrid VLC-RF Networks with Imperfect Channel State Information
The present contribution proposes a general framework for the energy
efficiency analysis of a hybrid visible light communication (VLC) and Radio
Frequency (RF) wireless system, in which both VLC and RF subsystems utilize
nonorthogonal multiple access (NOMA) technology. The proposed framework is
based on realistic communication scenarios as it takes into account the
mobility of users, and assumes imperfect channel-state information (CSI). In
this context, tractable closed-form expressions are derived for the
corresponding average sum rate of NOMA-VLC and its orthogonal frequency
division multiple access (OFDMA)-VLC counterparts. It is shown extensively that
incurred CSI errors have a considerable impact on the average energy efficiency
of both NOMA-VLC and OFDMAVLC systems and hence, they should not be neglected
in practical designs and deployments. Interestingly, we further demonstrate
that the average energy efficiency of the hybrid NOMA-VLCRF system outperforms
NOMA-VLC system under imperfect CSI. Respective computer simulations
corroborate the derived analytic results and interesting theoretical and
practical insights are provided, which will be useful in the effective design
and deployment of conventional VLC and hybrid VLC-RF systems
Non-Orthogonal Multiple Access for FSO Backhauling
We consider a free space optical (FSO) backhauling system which consists of
two base stations (BSs) and one central unit (CU). We propose to employ
non-orthogonal multiple access (NOMA) for FSO backhauling where both BSs
transmit at the same time and in the same frequency band to the same
photodetector at the CU. We develop a dynamic NOMA scheme which determines the
optimal decoding order as a function of the channel state information at the CU
and the quality of service requirements of the BSs, such that the outage
probabilities of both BSs are jointly minimized. Moreover, we analyze the
performance of the proposed NOMA scheme in terms of the outage probability over
Gamma-Gamma FSO turbulence channels. We further derive closed-form expressions
for the outage probability for the high signal-to-noise ratio regime. Our
simulation results confirm the analytical derivations and reveal that the
proposed dynamic NOMA scheme significantly outperforms orthogonal transmission
and existing NOMA schemes.Comment: This paper has been submitted to IEEE WCNC 201
Energy-efficient non-orthogonal multiple access for wireless communication system
Non-orthogonal multiple access (NOMA) has been recognized as a potential solution for enhancing the throughput of next-generation wireless communications. NOMA is a potential option for 5G networks due to its superiority in providing better spectrum efficiency (SE) compared to orthogonal multiple access (OMA). From the perspective of green communication, energy efficiency (EE) has become a new performance indicator. A systematic literature review is conducted to investigate the available energy efficient approach researchers have employed in NOMA. We identified 19 subcategories related to EE in NOMA out of 108 publications where 92 publications are from the IEEE website. To help the reader comprehend, a summary for each category is explained and elaborated in detail. From the literature review, it had been observed that NOMA can enhance the EE of wireless communication systems. At the end of this survey, future research particularly in machine learning algorithms such as reinforcement learning (RL) and deep reinforcement learning (DRL) for NOMA are also discussed
Wearable Communications in 5G: Challenges and Enabling Technologies
As wearable devices become more ingrained in our daily lives, traditional
communication networks primarily designed for human being-oriented applications
are facing tremendous challenges. The upcoming 5G wireless system aims to
support unprecedented high capacity, low latency, and massive connectivity. In
this article, we evaluate key challenges in wearable communications. A
cloud/edge communication architecture that integrates the cloud radio access
network, software defined network, device to device communications, and
cloud/edge technologies is presented. Computation offloading enabled by this
multi-layer communications architecture can offload computation-excessive and
latency-stringent applications to nearby devices through device to device
communications or to nearby edge nodes through cellular or other wireless
technologies. Critical issues faced by wearable communications such as short
battery life, limited computing capability, and stringent latency can be
greatly alleviated by this cloud/edge architecture. Together with the presented
architecture, current transmission and networking technologies, including
non-orthogonal multiple access, mobile edge computing, and energy harvesting,
can greatly enhance the performance of wearable communication in terms of
spectral efficiency, energy efficiency, latency, and connectivity.Comment: This work has been accepted by IEEE Vehicular Technology Magazin
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