- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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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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Efficient Blind Adaptive CSE to Reduce Cyclic Prefix Length in Direct Detection Optical OFDM Systems
摘要： Direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems for a long-reach of standard single mode fiber (SSMF) require a large length of cyclic prefix (CP) to avoid the inter-symbol interference (ISI) effect caused by group velocity dispersion (GVD). Unfortunately, this method is inefficient due to the energy wasted in CP samples. In order to reduce the CP length and to mitigate the residual ISI, a novel blind adaptive channel shortening equalizer (CSE) is proposed in this paper. Based on the orthogonality between subcarriers in the fast Fourier transform (FFT) property, the proposed algorithm attempts to minimize the sum-squared correlation (SSCM) between each sample located in a well-defined window to update the CSE coefficients. Thus, the combined channel-CSE response is shortened. Therefore, it can cancel the residual ISI effect due to the GVD and the short CP length. The performance of the system is evaluated on basis of bit error rate (BER) versus optical signal to noise ratio (OSNR) for different CP lengths. The simulation results validate the new algorithm SSCM and show that it can reduce the CP length with a much better system improvement than existing algorithms.
关键词： SSMF,DDO-OFDM,cyclic prefix,CSE,GVD
更新于2025-09-19 17:15:36
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New binary particle swarm optimization on dummy sequence insertion method for nonlinear reduction in optical direct-detection orthogonal frequency division multiplexing system
摘要： In the paper, a novel new binary particle swarm optimization method based on dummy sequence insertion is proposed and experimentally demonstrated in the IM-DD optical orthogonal frequency division multiplexing (OOFDM) system. This technique can mitigate nonlinearity of OOFDM system without any channel side information. Experimental results demonstrate that compared to the original scheme, the improvement in the receiver sensitivity by the proposed scheme is 1.9 dB and 3.2 dB with launch powers of 2 dBm and 8 dBm, respectively, at the BER of FEC 3.8 × 10^{-3} after transmission over 100-km standard single-mode fiber. At a complementary cumulative distribution function of 10^{-4}, the PAPR of OFDM signal can be reduced about 2.8 dB by using the proposed scheme, while the receiver-side hardware is the same as the origin.
关键词： Optical fiber communication,Particle swarm optimization (PSO),Dummy sequence insertion (DSI),Orthogonal frequency division multiplexing (OFDM)
更新于2025-09-19 17:15:36
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New Spectrum Efficient Reconfigurable Filtered-OFDM Based L-Band Digital Aeronautical Communication System
摘要： To meet an ever-increasing demand of the spectrum for aeronautical communication, we propose new L-band digital aeronautical communication system (LDACS) using reconfigurable filtered OFDM (Ref-OFDM). The proposed protocol enables transceivers to dynamically adapt the transmission bandwidth over a wide range to meet the desired quality of service, and high out-of-band attenuation leads to significant improvement in the vacant spectrum utilization. We support our claims via simulation and complexity comparison results for various realistic channel conditions.
关键词： Air to ground communication,air-traffic management (ATM),Spectrum efficiency,Reconfigurable Filtered OFDM,L-band Digital Aeronautical Communication System (LDACS)
更新于2025-09-19 17:15:36
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Bit-interleaved polar coded modulation scheme for high-order QAM encoded DDO-OFDM systems
摘要： In the paper, a simple generation scheme of the twin-SSB-OFDM signal based on one OFDM transmitter is proposed in the direct-detection optical orthogonal frequency-division multiplexing (DDO-OFDM) system. Compared with traditional generation scheme that requires two OFDM transmitters, it has lower implementation complexity and lower cost. In addition, to enhance the spectral efficiency (SE) for DDO-OFDM system, an efficient bit-interleaved polar coded modulation (BIPCM) scheme adopting 256 quadrature-amplitude modulation (256-QAM) is proposed. Moreover, a quadratic polynomial permutation (QPP) interleaver is adopted for polar coded modulation (PCM) to further improve the overall system performance. The simulation results exhibit that the proposed scheme can achieve more than 4 dB and 5 dB Q-factor improvement compared to the conventional schemes with PCM and without BIPCM, respectively. At the same time, aided by the efficient 256-QAM BIPCM scheme, the receiver sensitivity is improved and the laser linewidth requirement is less strict compared to the conventional schemes.
关键词： Bit-interleaved polar coded modulation (BIPCM),Direct-detection optical orthogonal frequency-division multiplexing (DDO-OFDM),Single-side-band (SSB) modulation
更新于2025-09-19 17:15:36
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The spectral efficiency augmented HACO-OFDM based visible light communications
摘要： The conventional hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (HACO-OFDM) has an obvious spectral efficiency loss due to the fact that the real part of the even subcarriers are not utilized. This paper proposes a scheme to augment the spectral efficiency of HACO-OFDM. In this scheme, more spectrum resources are exploited because the real part of selected even subcarrier group is utilized for data modulation at different depths. When the same modulation orders are used, the proposed scheme is able to achieve higher spectral efficiency than HACO-OFDM at the cost of acceptable increased computational complexity. When this scheme takes 5 depths, the joint modulation scheme uses 16QAM-4PAM and 64QAM-4PAM, the spectral efficiency of the proposed scheme can be increased by 31.33% and 23.48%, respectively. Moreover, compared with HACO-OFDM, the proposed scheme has advantages of lower PAPR and higher immunity to LED nonlinearity.
关键词： Visible light communications,HACO-OFDM,ASE-DMT
更新于2025-09-19 17:15:36
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Extended Spatial-Index LED Modulation for Optical MIMO-OFDM Wireless Communication
摘要： An efficient optical modulation technique for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) visible light communication system is proposed in this paper. The proposed modulation technique is termed as extended spatial-index light-emitting diode (LED) modulation. In the proposed technique, the indices (the spatial domain) of the LEDs are exploited in a dynamic style to not only get rid of the optical OFDM time-domain (OFDMtd) shaping problem but also to expand the LED indices spatial modulation domain. The indices of the active LEDs in the proposed technique are changed from the two LEDs active situation to the situation where all or several LEDs are active. Moreover, within the selected active LED indices, the power weight distribution and the positions of the OFDM components are varied to expand the resultant spatial domain. Therefore, the proposed technique offers a considerable spectral efficiency improvement over the up-to-date LED index OFDM modulation schemes even with a lower number of LEDs. The key idea of the proposed technique is to maximize the LEDs’ indices spatial position (spatial domain) utilization, where both the power weight allocation and the positions of the complex OFDM time domain components are varying several times over the same active LED indices combination, which improve the optical system spectral efficiency. The simulation results asserted the superiority of the proposed technique, as it improves both the average bit error rate (ABER) and the achievable data rate (R) compared with existing up-to-date OFDM-LED index modulations with even lower computational complexity.
关键词： optical MIMO-OFDM,generalized led index modulation,OFDM-LED index modulation,visible light communication (VLC)
更新于2025-09-19 17:13:59
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Optical polar based MIMO-OFDM with fully generalised index-spatial LED modulation
摘要： A novel efficient visible light communication (VLC) modulation technique teams as polar fully generalised index-spatial (PFGIS) modulation light emitting diode (LED) for the multi-input multi-output (MIMO) optical polar based OFDM (MIMO-POFDM) system is proposed here. The PFGIS is a spectrally efficient (SE) modulation scheme which introduces an elegant solution to tackle the OFDM signal shaping problem, moreover, the PFGIS improves the optical MIMO-OFDM system SE. In the PFGIS, the Cartesian complex OFDM signal is transformed to polar OFDM (POFDM). Then, the indices of the active LEDs are exploited to convey the POFDM signal components. While, the spatial position of the LEDs are exploited as a spatial modulation (SM). In the SM, the LEDs indices used for data transmission are changed from the case of two LEDs are selected to case where all/multiple LEDs are selected. Subsequently, the proposed system achievable data rate is linearly increased with the LEDs number. The PFGIS gives higher SE even with a lower LEDs number compared with the recently OFDM optical LED index modulation techniques. Simulation results confirm the efficiency of the proposed PFGIS in improving both the achievable data rate and the bit error rate compared with the up-to-date LED index modulation OFDM schemes.
关键词： multi-input multi-output (MIMO),spatial modulation (SM),visible light communication (VLC),polar fully generalised index-spatial (PFGIS) modulation,optical polar based OFDM (MIMO-POFDM),spectral efficiency (SE)
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Experimental Device-Independent Certification of a SIC-POVM
摘要： In this paper, we consider an orthogonal frequency division multiplexing communication system that adopts frame-by-frame transmission in high-speed railway (HSR) scenario. Due to the increase in demand for the QoS sensitive services, an efficient QoS-aware transmission strategy that improves the system performance is required urgently. Many efforts have been devoted to addressing this problem with the assumption of block fading channel in a frame duration. However, due to the frequent channel quality variation in a frame duration and serious inter channel interference in HSR scenario, the throughput of the QoS sensitive services degrades severely. Hence, a robust cross-layer transmission strategy that combines adaptive modulation (AM) scheme with truncated automatic repeat request protocol is proposed. In this cross-layer formulation, the normalized average throughput is optimized subject to the average power and the packet loss rate (PLR) requirements. First, we derive the closed form average bit error rate that represents the PLR requirement at the physical layer. Second, we obtain the solution of robust AM scheme and power allocation policy in the case of continuous rate. Third, we present the adaptive bits and power allocation scheme in the case of discrete rate, which can be implemented in practice. Finally, the performance of the proposed transmission strategy is evaluated by extensive simulations. Comparing with the constant transmit power AM scheme, the throughput increases by 20%, which demonstrates that the proposed robust cross-layer design is suitable for the HSR communication systems.
关键词： OFDM systems,Adaptive modulation,robust cross-layer design,QoS,fast time-varying fading channel,high-speed railway,packet loss rate
更新于2025-09-19 17:13:59
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Enhanced Optical Communications Through Joint Time-Frequency Multiplexing Strategies
摘要： We present a power-efficient and reduced-complexity all-optical approach to generate high-bit rate superchannels, based on joint time-frequency multiplexing. Both optical orthogonal frequency division multiplexing (OFDM) and Nyquist-optical time division multiplexing (N-OTDM) signals are generated and processed using a wavelength-selective switch (WSS). We use the fractional Fourier transform (FrFT) to introduce the largest degree of flexibility in optical networking, and we experimentally demonstrate that the transmitted signal can be received either in parallel, as OFDM subcarriers, or in series, as an N-OTDM signal. Compared to conventional optical OFDM, we achieve peak to average power ratio (PAPR) flexible reduction; compared to N-OTDM, we introduce chromatic dispersion (CD) management. We successfully demonstrate a field trial experiment of 4-channel 40 Gb/s hybrid OFDM/N-OTDM transmission over the 89.2-km Japan gigabit network-extreme (JGN X) test bed, with 1 bit/s/Hz spectral efficiency.
关键词： optical Fourier transform,optical signal processing,Nyquist OTDM,OFDM,fractional Fourier transform
更新于2025-09-19 17:13:59