A Novel Unipolar Transmission Scheme for Visible Light Communication

Abstract

This paper proposes a novel unipolar transceiver for visible light communication (VLC) by using orthogonal waveforms. The main advantage of our proposed scheme over most of the existing unipolar schemes in the literature is that the polarity of the real-valued orthogonal frequency division multiplexing (OFDM) sample determines the pulse shape of the continuous-time signal and thus, the unipolar conversion is performed directly in the analog instead of the digital domain. Therefore, our proposed scheme does not require any direct current (DC) biasing or clipping as it is the case with existing schemes in the literature. The bit error rate (BER) performance of our proposed scheme is analytically derived and its accuracy is verified by using Matlab simulations. Simulation results also substantiate the potential performance gains of our proposed scheme against the state-of-the-art OFDM-based systems in VLC; it indicates that the absence of DC shift and clipping in our scheme supports more reliable communication and outperforms the asymmetrically clipped optical-OFDM (ACO-OFDM), DC optical-OFDM (DCO-OFDM) and unipolar-OFDM (U-OFDM) schemes. For instance, our scheme outperforms ACO-OFDM by at least 3 dB (in terms of signal to noise ratio) at a target BER of 10 −4 , when considering the same spectral efficiency for both schemes.

Novel Unipolar Optical Modulation Techniques for Enhancing Visible Light Communication Systems Performance

“…OFDM systems achieve high spectral efficiency (SE) and high data rate transmission for multiple users by transmitting spectrally efficient OFDM signals with minimal inter symbol interference (ISI). However, employing OFDM and those high-order modulation techniques in the VLC systems needs some adaptations to be applied to achieve high data rates with real and unipolar data form [11]. One of these adaptations is applying the Hermitian symmetry on the transmitted data at the input of the IFFT [12,13], which results in converting the data into real form at the cost of reducing the data rate to half compared to the rate of the traditional OFDM (real and imaginary).…”

“…One of these adaptations is applying the Hermitian symmetry on the transmitted data at the input of the IFFT [12,13], which results in converting the data into real form at the cost of reducing the data rate to half compared to the rate of the traditional OFDM (real and imaginary). The issue of converting the bipolar signal into a unipolar one was the main motivation for many researchers [5,[8][9][10][11]. So, different modified OFDM systems were under investigation taking into consideration SE, power efficiency (PE), bit error rate (BER), and nonlinearity distortion.…”

“…Previous studies introduced different techniques like DC-biased optical-OFDM (DCO-OFDM) [14,15], which main merit is achieving the maximum data rate ratio (DRR) of (50%) in the VLC systems at the cost of adding a DC bias that leads to power inefficiency and degrading the system BER performance [16]. Asymmetrically clipped optical (ACO)-OFDM [17,18], FLIP-OFDM [19,20], and unipolar OFDM (U-OFDM) [11,21], schemes have a low DRR of (25%), but better BER system performance compared to DCO-OFDM system. Asymmetrically clipped DC biased optical (ADO)-OFDM [9], is considered as a hybrid technique of ACO-OFDM and DCO-OFDM.…”

Low-Complexity Optical Transmitter Design for Future Generations

“…LEDs offer twin capabilities in VLC: they emit lights akin to an electric lightbulb and act as a domestic transmitter for other appliances [9]. A VLC model employs the Intensity Modulation (IM) and Direct Detection (DD) principles to transmit data, which prevents the transmitted data from becoming unipolar [10]. LEDs have a myriad of benefits, including low-power, extended life, cooler operation, cost savings, and quick switching, as well as their compact size and short links.…”

Compressed image transmission in precoded OFDM VLC systems

“…On the other hand, visible light communication (VLC) has the advantages of being free of electromagnetic interference and having large spectrum resources; thus, it has been widely researched [11][12][13]. Integrating orthogonal frequency division multiplexing (OFDM) with VLC can improve the frequency efficiency of VLC systems.…”