199 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
A cross-layer heuristic algorithm for addressing shadowing problem in optical attocell networks
The performance of visible light communication (VLC)-based optical attocell networks degrades due to shadowing caused by opaque objects. In order to improve reliability, we propose a cross-layer algorithm to find the optimal routing and resource allocation schemes when shadowing occurs. Simulation results show that the optimal scheme found by the proposed algorithm significantly improves the performance of optical attocell networks with one randomly shadowed link
Optimization of non-orthogonal multiple access based visible light communication systems
In visible light communication (VLC), the data is transmitted by modulating the light emitting diode (LED). The data-rate is throttled by the narrow modulation bandwidth of LEDs, which becomes a barrier for attaining high transmission rates. Non-orthogonal multiple access (NOMA) is a new scheme envisioned to improve the system capacity. In addition to multiple access schemes, optimization techniques are applied to further improve the data rate. In this letter, convex optimization is applied to NOMA-based VLC system for downlink. The proposed optimization system is analyzed in terms of the bit error rate (BER) and the sum-rate
Multiple Access Techniques for VLC in Large Space Indoor Scenarios: A Comparative Study
The growing demand for high speed indoor wireless connectivity is among the driving forces for data transmission based on visible-light communications (VLC). For relatively large-space indoor scenarios, the development of appropriate spectrally-efficient multiple-access (MA) techniques enables efficient handling of multiple users, in particular, in dealing with the limited modulation bandwidth of the light-emitting diodes. In this paper, we present a comparative study between different MA techniques proposed in the recent literature for VLC networks. The most appropriate schemes for large-scale network deployments are further investigated in different scenarios to contrast their performance in terms of the achievable throughput
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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