1,062 research outputs found
Spectrum-Efficient Triple-Layer Hybrid Optical OFDM for IM/DD-Based Optical Wireless Communications
In this paper, a triple-layer hybrid optical orthogonal frequency division multiplexing
(THO-OFDM) for intensity modulation with direct detection (IM/DD) systems with a high spectral efficiency is proposed. We combine N-point asymmetrically clipped optical orthogonal frequency division
multiplexing (ACO-OFDM), N/2-point ACO-OFDM, and N/2-point pulse amplitude modulated discrete
multitoned (PAM-DMT) in a single frame for simultaneous transmission. The time- and frequency-domain
demodulation methods are introduced by fully exploiting the special structure of the proposed THO-OFDM.
Theoretical analysis show that, the proposed THO-OFDM can reach the spectral efficiency limit of the
conventional layered ACO-OFDM (LACO-OFDM). Simulation results demonstrate that, the time-domain
receiver offers improved bit error rate (BER) performance compared with the frequency-domain with ∼40%
reduced computation complexity when using 512 subcarriers. Furthermore, we show a 3 dB improvement
in the peak-to-average power ratio (PAPR) compared with LACO-OFDM for the same three layers
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
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