Investigation into Using Compensation for the Nonlinear Effects of the Output of LEDs in Visible Light Communication Systems

This paper investigate the effects of the nonlinear output power to the input current transfer function of a light emitting diode (LED) used as the transmitter in visible light communication systems, and proposes a compensation technique to mitigate the non-linearity. Using an off the shelf red, amber, blue, green (RAGB) LED the nonlinear transfer function is measured and then compensated for. The results show that, for the green LED, which has the highest degree of nonlinearity, an improvement in the received error vector magnitude (EVM)of almost 7 dB can be achieved. We also show that, the improvement in EVM over the uncompensated scheme decreases with increased LED linearity

Experimental demonstration of multi-Gbps multi sub-bands FBMC transmission in mm-wave radio over a fiber system

The filter bank multicarrier (FBMC) modulation format is considered as a potential candidate for future wireless 5G due to its feature of high suppression for out-of-band emissions, which allows combining multiple sub-bands with very narrow band-gaps, and hence increases the overall wireless transmission capacity. In this paper, we experimentally demonstrate the generation of multi sub-bands FBMC signals at millimeter-wave (mm-wave) for radio-over-fiber (RoF) systems. The designed multi sub-bands FBMC system consists of 5 sub-bands of 800 MHz with inter sub-band gaps of 781.25 kHz. The composite 5 sub-bands FBMC signal is generated with no band-gap between dc to the first sub-band to preserve the bandwidth of the system. Each FBMC sub-band consists of 1024 sub-carriers and is modulated with uncorrelated data sequences. The aggregate FBMC signal is carried optically by externally modulating a free running laser and is converted to millimeter waves (mm-waves) by photomixing with another free running laser at a frequency offset of 53 GHz. At the receiver, the received electrical mm-wave signal is down-converted to an intermediate frequency (IF) and then post-processed using digital signal processing (DSP) techniques. With the use of the simple recursive least square (RLS) equalizer in the DSP receiver, the achieved aggregate data rate is 8 Gbps and 12 Gbps for 16 quadrature amplitude modulation (QAM), and 64 QAM, respectively with a total bandwidth of 4.2 GHz. The system performance is evaluated by measuring error vector magnitude (EVM) and bit error rate (BER) calculations

Non-Orthogonal Multi-band CAP for Highly Spectrally Efficient VLC Systems

In this work we propose and experimentally demonstrate a novel non-orthogonal multi-band carrier-less amplitude and phase (NM-CAP) scheme for bandlimited visible light communication systems in order to increase the spectral efficiency. We show that a bandwidth saving up to 30% can be achieved thus resulting in 44% improvement in the measured spectral efficiency with no further bit error rate performance degradation compared to the traditional m-CAP scheme. We also show that higher order systems can provide higher bandwidth compression than low order systems. Furthermore, with no additional functional blocks at the transmitter or the receiver the proposed scheme introduces no extra computational complexity.Comment: 6 pages, 5 figure

Non-Orthogonal Multi-band CAP for Highly Spectrally Efficient VLC Systems

In this work we propose and experimentally demonstrate a novel non-orthogonal multi-band carrier-less amplitude and phase (NM-CAP) scheme for bandlimited visible light communication systems in order to increase the spectral efficiency. We show that a bandwidth saving up to 30% can be achieved thus resulting in 44% improvement in the measured spectral efficiency with no further bit error rate performance degradation compared to the traditional m-CAP scheme. We also show that higher order systems can provide higher bandwidth compression than low order systems. Furthermore, with no additional functional blocks at the transmitter or the receiver the proposed scheme introduces no extra computational complexity

A Hybrid Variable m-CAP-Based Indoor Visible Light Communications and Fingerprint Positioning System

A variable multi-band carrier-less amplitude and phase (m-CAP)-based indoor hybrid visible light link for data communications and positioning is investigated in this paper. Here, we have adopted the fingerprinting algorithm for positioning. Both the link performance in terms of the bit error rate (BER) and the positioning error (PE) are evaluated for a range of Eb/N0 and step sizes for the data communications and localization, respectively. Results show that, the best PE value and the spectral efficiency of the proposed system are ~2 cm and 6.15 b/s/Hz with respect for a step size of 2 cm and a 7% forward error correction BER limit of 3.8 × 10-3, respectively

Multi-band Carrier-less Amplitude and Phase Modulation for VLC: An Overview

The rapid development of solid-state lighting technologies has been the stimulus for visible light communications (VLC) to be the focus of enormous interest over the last decade. The key feature of simultaneous data transmission and illumination using white light-emitting diodes (LEDs) makes VLC a potential candidate for future power efficient communication networks that aim to meet the ever-increasing demands for high-speed internet services. Researchers, motivated by the success of VLC technology, have developed a number of techniques and methods to support communication systems with both high transmission speeds and spectral efficiency. Here, we provide an overview of the multi-band carrier-less amplitude and phase (m-CAP) modulation technique enabling highly spectrally efficient VLC links in bandlimited environments

Visible light communications: multi-band super-Nyquist CAP modulation

In this paper, we experimentally demonstrate the performance of a non-orthogonal multi-band super-Nyquist carrier-less amplitude and phase (m-SCAP) modulation for visible light communications (VLC). We break the orthogonality between sub-bands in the frequency domain by compressing the spectrum, purposely overlapping them, and introducing inter-band interference (IBI). We demonstrate that our proposed system can tolerate IBI, and hence spectral efficiency can be increased without introducing additional complexity to the receiver. We show that m-SCAP can tolerate up to 30% and 20% compression for 4- and 16-level quadrature amplitude modulation, respectively, thus leading to an improvement in spectral efficiencies up to 40% and 25%, respectively, at the cost of bit error rate performance, which however remains below the 7% forward error correction limit. Moreover, the experimental results are supported by numerical simulations

A new concept of multi-band carrier-less amplitude and phase modulation for bandlimited visible light communications

Abstract: In this paper, we propose a novel method of multi-band carrier-less amplitude and phase (m-CAP) modulation for optical wireless communication (OWC) systems. In conventional m-CAP systems, the total signal bandwidth is divided into m equally distributed subcarriers. In this work, for the first time, we set the subcarrier bandwidths such that the first subcarrier is the same as the LED bandwidth, and subsequently distribute the remaining bandwidth equally between m - 1 subcarriers. We show that using m = 4, 6, 8 and 10 subcarriers and 16-QAM, the first subcarrier is able to achieve a bit error rate (BER) target of 10-4 (i.e., which is below the 7% forward error correction (FEC) BER limits of 3.8 × 10-3)at Eb/N0 = 15.5 dB. This is a power penalty of -1.5 dB to achieve the same average performance as the first five, four and three subcarriers of the conventional 10, 8 and 6-CAP and a power penalty of ~1 dB for new 4-CAP to achieve the average performance of the first two subcarriers of the conventional 4-CAP. Consequently, using the proposed m-CAP concept we show a reduction in the complexity by reducing the number of finite impulse response (FIR) filters by 80%, 75%, -67% and 50% in contrast to the conventional 10, 8, 6, and 4-CAP, respectively