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[IEEE 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Mon Tresor, Plaine Magnien, Mauritius (2018.12.6-2018.12.7)] 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Hybrid PLC-VLC based on ACO-OFDM
摘要： The recent successful development and standardization of the power line communication (PLC) (ITUT G.9960/61, CENELEC EN50065-1, IEEE 1901) and visible light communications (VLC) (IEEE 802.15.7), has resulted in lot of research interest in consideration to the integration of the PLC and VLC technologies. In addition, these technologies present the advantage related to cost effectiveness as a strong research motivation. In this paper, based on the positive aspect of VLC technology, we exploit the Hermitian symmetry to design a hybrid system combining PLC and VLC technologies using orthogonal frequency division multiplexing (OFDM). Asymmetrically clipped optical OFDM (ACO-OFDM) is employed in VLC and investigated when combined with PSK-OFDM (used in PLC). The proposed hybrid PLC-VLC system in this paper takes advantage of the inherent nulling feature of the ACO-OFDM to mitigate impulsive noise that is present in the PLC channel, where the optimal threshold, Tc to combat the impulse is investigated through simulations. While on the other hand taking advantage of the fact that both DCO-OFDM and PSK-OFDM employ the FFT, to achieve a simplified system.
关键词： OFDM,PLC-VLC integration,ACO-OFDM
更新于2025-09-23 15:22:29
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Spectral-Efficient Reconstructed LACO-OFDM Transmission for Dimming Compatible Visible Light Communications
摘要： Dimming control is critical in practical visible light communication (VLC) systems to satisfy illumination demand. Upon exploiting multiple layers of asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) signals for simultaneous transmission, layered ACO-OFDM (LACO-OFDM) constitutes a promising spectral-efficient modulation technique for VLC. However, dimming by integrating the industry-preferred pulse width modulation (PWM) to the LACO-OFDM scheme induces severe clipping noise due to the nonlinearity of LEDs. In this paper, we conceive a reconstructed LACO-OFDM (RLACO-OFDM) scheme incorporating the PWM technique for VLC to accommodate the dimming demands for indoor illumination, while maintaining a spectral-efficient communication link. Moreover, superior to its counterparts, the transmitted symbols in the RLACO-OFDM based VLC system can be readily recovered by a standard LACO-OFDM receiver while no additional detection of the PWM signal is required, which reduces the receiver complexity. Numerical results demonstrate that the proposed RLACO-OFDM is capable of realizing high spectral efficiency over a broad dimming range.
关键词： asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM),layered ACO-OFDM,pulse width modulation (PWM),Visible light communication (VLC),dimming control
更新于2025-09-19 17:15:36
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Investigation of LED Non-linearity on DCO-OFDM and ACO-OFDM in VLC Systems using Multichip RGB LEDs for Indoor Applications
摘要： The impact of the LED non-linearity on the Intensity Modulation Direct Detection (IM-DD) in the VLC using OFDM for white light generated using RGB LEDs for indoor applications is analyzed. This work extends the orders of harmonics for analysis and investigates the impact of this non-linearity issue on OFDM techniques. The wavelengths (Red, Green and Blue) are individually set at the LED and their induced photocurrent in a Si PD is calculated. The result shows that the wavelength corresponding to the 625nm induces 5dB and 3dB more power than 528nm and 458nm respectively. We choose 625nm as the OFDM signal carrier for transmission keeping the other two un-modulated. We compare the effects of the non-linearity of the LED on the two OFDM techniques- Asymmetrical clipped optical (ACO) and Direct current biased optical (DCO). Our simulation results show that the power of the 2nd and 3rd order intermodulation components for ACO-OFDM is 3dB lesser than DCO-OFDM. The required SNR for ACO-OFDM is found to be 3dB lesser as compared to DCO-OFDM. The clipping effect of the LED remains unchanged irrespective of the OFDM variation applied.
关键词： Visible Light Communication,White Light,ACO-OFDM,LED,DCO-OFDM,Non-Linear Distortion
更新于2025-09-12 10:27:22
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ACO–OFDM with Improved Bandwidth Efficiency over Long Haul and MIMO Optical Fiber Communication Systems
摘要： Authors propose an improved orthogonal frequency division multiplexing (OFDM) scheme in which the information samples are transmitted in otherwise discarded negative frame of asymmetrically clipped OFDM (ACO–OFDM). ACO–OFDM has two similar positive and negative OFDM envelopes so that clipping does not result in loss of signal information. The flipped polarity negative samples are inserted at the zeros of positive frame or back to back with positive frame, in time-compressed frame such that composite signal has the same frame duration as ACO–OFDM but improved transmission power, bandwidth efficiency. Simulation results for bit error rate with respect to number of subcarriers and optical launch power show that the proposed time-compressed OFDM frames perform better in high-dispersion condition over long distance, high data rate, and high transmission power over single-mode fiber. It has been demonstrated that the proposed time-compressed frame structure also performs well with the 2*2 MIMO setup for multimode fiber link.
关键词： ACO–OFDM,Efficiency,Dispersion,Nonlinearity,MIMO,Bandwidth
更新于2025-09-11 14:15:04
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Indoor visible light positioning combined with ellipse-based ACO-OFDM
摘要： Visible light communications have recently gained increasing attention as it is appealing for a wide range of applications such as indoor positioning. However, the light-emitting diode-based indoor positioning systems suffer from multipath distortion inside a room, leading to high positioning error. In order to mitigate the effect of multipath distortion of the optical channel, an indoor visible light positioning algorithm combined with ellipse-based asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) is proposed in this study, wherein the real-valued output of orthogonal frequency division multiplexing is modulated onto an ellipse, and only the imaginary value from the complex point on the ellipse is transmitted. Moreover, a received-signal-strength technique is used to determine the location of the receiver, and the Trust- region technique is employed to realise the 3D positioning. Simulation results demonstrate that this proposed algorithm can achieve high positioning accuracy, and the impact of different system parameters on the positioning accuracy is further investigated compared with the systems based on ACO-OFDM.
关键词： indoor positioning,ellipse-based modulation,Trust-region technique,ACO-OFDM,visible light communications,multipath distortion,RSS technique
更新于2025-09-10 09:29:36