1,896 research outputs found
Coded Index Modulation for Non-DC-Biased OFDM in Multiple LED Visible Light Communication
Use of multiple light emitting diodes (LED) is an attractive way to increase
spectral efficiency in visible light communications (VLC). A non-DC-biased OFDM
(NDC OFDM) scheme that uses two LEDs has been proposed in the literature
recently. NDC OFDM has been shown to perform better than other OFDM schemes for
VLC like DC-biased OFDM (DCO OFDM) and asymmetrically clipped OFDM (ACO OFDM)
in multiple LEDs settings. In this paper, we propose an efficient multiple LED
OFDM scheme for VLC which uses {\em coded index modulation}. The proposed
scheme uses two transmitter blocks, each having a pair of LEDs. Within each
block, NDC OFDM signaling is done. The selection of which block is activated in
a signaling interval is decided by information bits (i.e., index bits). In
order to improve the reliability of the index bits at the receiver (which is
critical because of high channel correlation in multiple LEDs settings), we
propose to use coding on the index bits alone. We call the proposed scheme as
CI-NDC OFDM (coded index NDC OFDM) scheme. Simulation results show that, for
the same spectral efficiency, CI-NDC OFDM that uses LDPC coding on the index
bits performs better than NDC OFDM
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
On the Performance of Single- and Multi-carrier Modulation Schemes for Indoor Visible Light Communication Systems
In this paper, we investigate and compare the performance of single- and
multi-carrier modulation schemes for indoor visible light communication (VLC).
Particularly, the performances of single carrier frequency domain equalization
(SCFDE), orthogonal frequency division multiplexing (OFDM) and on-off keying
(OOK) with minimum mean square error equalization (MMSE) are analyzed in order
to mitigate the effect of multipath distortion of the indoor optical channel
where nonlinearity distortion of light emitting diode (LED) transfer function
is taken into account. Our results indicate that SCFDE system, in contrast to
OFDM system, does not suffer from high peak to average power ratio (PAPR) and
can outperform OFDM and OOK systems. We further investigate the impact of LED
bias point on the performance of OFDM systems and show that biasing LED with
the optimum value can significantly enhance the performance of the system.
Bit-interleaved coded modulation (BICM) is also considered for OFDM and SCFDE
systems to further compensate signal degradation due to inter-symbol
interference (ISI) and LED nonlinearity.Comment: 6 Pages, IEEE Globecom conference 201
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