3,121 research outputs found
Optical Non-Orthogonal Multiple Access for Visible Light Communication
The proliferation of mobile Internet and connected devices, offering a
variety of services at different levels of performance, represents a major
challenge for the fifth generation wireless networks and beyond. This requires
a paradigm shift towards the development of key enabling techniques for the
next generation wireless networks. In this respect, visible light communication
(VLC) has recently emerged as a new communication paradigm that is capable of
providing ubiquitous connectivity by complementing radio frequency
communications. One of the main challenges of VLC systems, however, is the low
modulation bandwidth of the light-emitting-diodes, which is in the megahertz
range. This article presents a promising technology, referred to as "optical-
non-orthogonal multiple access (O-NOMA)", which is envisioned to address the
key challenges in the next generation of wireless networks. We provide a
detailed overview and analysis of the state-of-the-art integration of O-NOMA in
VLC networks. Furthermore, we provide insights on the potential opportunities
and challenges as well as some open research problems that are envisioned to
pave the way for the future design and implementation of O-NOMA in VLC systems
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
Precoded Chebyshev-NLMS based pre-distorter for nonlinear LED compensation in NOMA-VLC
Visible light communication (VLC) is one of the main technologies driving the
future 5G communication systems due to its ability to support high data rates
with low power consumption, thereby facilitating high speed green
communications. To further increase the capacity of VLC systems, a technique
called non-orthogonal multiple access (NOMA) has been suggested to cater to
increasing demand for bandwidth, whereby users' signals are superimposed prior
to transmission and detected at each user equipment using successive
interference cancellation (SIC). Some recent results on NOMA exist which
greatly enhance the achievable capacity as compared to orthogonal multiple
access techniques. However, one of the performance-limiting factors affecting
VLC systems is the nonlinear characteristics of a light emitting diode (LED).
This paper considers the nonlinear LED characteristics in the design of
pre-distorter for cognitive radio inspired NOMA in VLC, and proposes singular
value decomposition based Chebyshev precoding to improve performance of
nonlinear multiple-input multiple output NOMA-VLC. A novel and generalized
power allocation strategy is also derived in this work, which is valid even in
scenarios when users experience similar channels. Additionally, in this work,
analytical upper bounds for the bit error rate of the proposed detector are
derived for square -quadrature amplitude modulation.Comment: R. Mitra and V. Bhatia are with Indian Institute of Technology
Indore, Indore-453552, India, Email:[email protected],
[email protected]. This work was submitted to IEEE Transactions on
Communications on October 26, 2016, decisioned on March 3, 2017, and revised
on April 25, 2017, and is currently under review in IEEE Transactions on
Communication
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