- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Performance Enhancement of Probabilistically Shaped OFDM Enabled by Precoding Technique in an IM-DD System
摘要： Probabilistically shaped orthogonal frequency-division multiplexing (PS-OFDM) signal is proposed and experimentally demonstrated in a low-cost intensity-modulation and direct-detection (IM-DD) system for optical access networks. The concatenation of constant composition distribution matcher (CCDM) and low-density parity-check (LDPC) code sequentially implements probabilistic amplitude shaping (PAS) and channel coding. Thanks to the precoding scheme, all data subcarriers can be treated equally by one optimized probabilistic distribution. Experimental results demonstrate that constant amplitude zero autocorrelation sequence (CAZAC) precoding can offer optimal performance compared to orthogonal circulant transform (OCT) precoding and discrete Fourier transform spread (DFT-spread) in terms of increasing generalized mutual information (GMI) and reducing PAPR. Moreover, probabilistically-shaped 64-QAM OFDM signal can provide shaping gains of 1.04/0.94/0.64 dB at 4.0/3.6/3.0 bits/QAM symbol compared to traditional 64-QAM OFDM signal. Meanwhile, compared to traditional 16-QAM OFDM, it can offer shaping gains of 1.64/0.64 dB at 3.6/3.0 bits/QAM symbol. In addition, net data rate ranging from 32.66 to 43.55-Gb/s over 20-km single mode fiber (SMF) can be achieved by only adjusting the probabilistic distribution.
关键词： precoding technique,optical access networks,Probabilistically-shaped orthogonal frequency-division multiplexing (PS-OFDM),intensity-modulation and direct-detection (IM-DD)
更新于2025-09-16 10:30:52
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Microwave Photonic Based 1/n Frequency Divider
摘要： A new microwave photonic frequency divider is presented. It is capable of generating a microwave frequency component with a frequency of 1/n times the input microwave signal frequency. The 1/n frequency divider is implemented based on an optoelectronic oscillator consisting mainly of a dual-parallel Mach Zehnder modulator for microwave signal modulation and an optical filter for sideband suppression. Experimental results are presented which demonstrate 1/2 and 1/3 frequency component generation. The phase noise measurements show that the 1/2 and 1/3 frequency components have improved phase noise performance by 6 and 9 dB, respectively.
关键词： microwave photonics,optoelectronic oscillator,frequency division
更新于2025-09-12 10:27:22
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Disaster management using free space optical communication system
摘要： A novel method for disaster management using free space optical link is proposed in this paper. Free space optics recently gained great attention since it has advantages over RF communication such as high bandwidth, license free spectrum and highly secured transmission. Besides all these, FSO faces challenges during transmission due to atmospheric turbulence-induced fading. Diversity techniques are used in this paper to mitigate the fading effects. The capacity of multiple input multiple output (MIMO) free space optical (FSO) networks is increased using polarization division multiplexing (PDM). This paper proposed a novel method of MISO and MIMO-OFDM which uses both odd and even subcarriers to improve the transmission capacity. The separated OFDM subcarriers are combined using PDM, which supports two independent data channels on a single wavelength with orthogonal polarization states. The system performance is evaluated under various atmospheric turbulence conditions. This paper introduces a novel application of MIMO-FSO system during disaster scenario. The atmosphere is considered to be turbulent in nature, and Malaga model is used to characterize the channel. The closed-form expressions for MIMO-FSO are derived, and the graphs for the performance under different turbulent conditions are plotted.
关键词： Malaga channel model,Optical orthogonal frequency division multiplexing (OFDM),Ergodic capacity,Multiple input multiple output (MISO),Polarization division multiplexing (PDM),Free space optical networks (FSO)
更新于2025-09-11 14:15:04
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Symbol Error Probability Analysis of DFrFT-based OFDM Systems with CFO and STO in Frequency Selective Rayleigh Fading Channels
摘要： In this article we derive exact symbol error probability (SEP) expressions for orthogonal frequency-division multiplexing (OFDM) based on discrete fractional Fourier transform (DFrFT) when symbol timing offset (STO) and carrier frequency offset (CFO) are present together. Closed form expressions are derived for binary phase shift keying, quadrature phase shift keying, and 16-ary quadrature amplitude modulation in the case of transmission over a frequency selective Rayleigh fading channel. As is well known, in OFDM the presence of CFO destroys the orthogonality between the sub-carriers, generating inter-carrier interference (ICI), while the presence of STO introduces intersymbol interference, between successive symbols, and phase rotations in frequency domain, within the same symbol. It is well recognized that an OFDM system based on DFrFT is more robust to ICI introduced by CFO than that based on discrete Fourier transform (DFT). Motivated by this, the combined effect of CFO and STO on the SEP of a DFrFT-based OFDM system is analyzed. Our results show that the DFrFT-based OFDM system outperforms that based on the DFT for different values of the DFrFT ‘angle parameter’. Monte Carlo simulations are used to demonstrate the correctness of the derived analytical expressions.
关键词： sampling-type FrFT,frequency selective fading,carrier frequency offset.,orthogonal frequency-division multiplexing (OFDM),Error rate analysis,symbol timing offset
更新于2025-09-10 09:29:36
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[IEEE 2017 IEEE International Conference on Computational Intelligence and Computing Research (ICCIC) - Coimbatore, India (2017.12.14-2017.12.16)] 2017 IEEE International Conference on Computational Intelligence and Computing Research (ICCIC) - Multiuser Visible Light Communication System For Reliable Wireless Communication
摘要： Visible Light Communication (VLC) is evolving likewise a guaranteeing act on give pervasive remote association. In this paper, we study an indoor multiuser Visible Light Communication framework can substantially increase the achievable bit rate of Adaptively Modulated Optical Orthogonal Frequency-Division Multiplexing (AMO-OFDM) system and has the ability to maximise data throughput by adjusting the number of bits per subcarrier based on the set of subcarrier's channel Gain to Noise Ratio (GNR). For each subcarrier resolved alongside OFDM, those comparing precoding grids will be in the recurrence area to eradicate multiuser viewed as obstruction. VLC is one of the promising candidates because of its features of non-licensed channels, high bandwidth and low power consumption. As a visible light source can be used both for illumination and communication, therefore, it saves the extra power that is required in RF communication. The revolution in the field of solid state lighting leads to the replacement of florescent lamps by Light Emitting Diodes (LEDs) which further motivates the usage of VLC.The modulation bandwidth of white emanation is about ～2MHz.
关键词： VLC (Visible Light Communication),Multiple transmitter and receiver links,MIMO (Multiple Input Multiple Output),OFDM (Orthogonal Frequency Division Multiplexing),MMSE (Minimum Mean-Squared Error),Precoding
更新于2025-09-10 09:29:36
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Convolution neural network-based time-domain equalizer for DFT-Spread OFDM VLC system
摘要： This paper presents a novel time-domain equalizer for visible light communication (VLC) system using machine learning (ML) method. In this work, we employ discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) as modem scheme and convolution neural network (CNN) as kernel processing unit of equalizer. After estimating channel state information (CSI) from training sequence, the proposed equalizer recovers transmitted symbols according to the estimated CSI. Numerical simulations indicate that the equalizer can significantly enhance bit error rate (BER) performance. For example, when signal-to-noise ratio (SNR) is 20dB and 16/32/64-quadrature amplitude modulation (QAM) is exploited, original BER is about 0.5 while the BER after recovery achieves 10?5, which is much lower than forward error correction (FEC) limit 3.8×10?3. This work promotes the application of ML in VLC domain. To the best of our knowledge, this is the first time a CNN-based equalizer has been explored.
关键词： Machine learning (ML),Discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM),Visible light communication (VLC),Convolution neural network (CNN)
更新于2025-09-10 09:29:36
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Design and Assembly of SPT-3G Cold Readout Hardware
摘要： The third-generation upgrade to the receiver on the South Pole Telescope, SPT-3G, was installed at the South Pole during the 2016–2017 austral summer to measure the polarization of the cosmic microwave background. Increasing the number of detectors by a factor of 10 to ～ 16, 000 required the multiplexing factor to increase to 68 and the bandwidth of the frequency-division readout electronics to span 1.6–5.2 MHz. This increase necessitates low-thermal conductance, low-inductance cryogenic wiring. Our cold readout system consists of planar thin-film aluminum inductive–capacitive resonators, wired in series with the detectors, summed together, and connected to 4K SQUIDs by 10 ? μm-thick niobium–titanium (NbTi) broadside-coupled striplines. Here, we present an overview of the cold readout electronics for SPT-3G, including assembly details and characterization of electrical and thermal properties of the system. We report, for the NbTi striplines, values of R ≤ 10?4(cid:2), L = 21 ± 1 nH, and C = 1.47 ± .02 nF. Additionally, the striplines’ thermal conductivity is described by k A = 6.0 ± 0.3 T 0.92±0.04 μW mm K?1. Finally, we provide projections for cross talk induced by parasitic impedances from the stripline and find that the median value of percentage cross talk from leakage current is 0.22 and 0.09% from wiring impedance.
关键词： Frequency-division multiplexing,Cosmic microwave background,SPT-3G
更新于2025-09-10 09:29:36
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Beam-Time Block Coding With Joint User Grouping and Beamforming for FDD Massive MIMO Systems
摘要： A downlink (DL) precoding scheme that needs no DL training nor uplink (UL) feedback for massive MIMO systems operated under frequency-division duplex (FDD) is proposed, whereas most of the schemes in the literature were proposed to compress the overhead of training and feedback. Due to the above advantage, the proposed scheme is suitable for extremely low-latency applications. This scheme exploits angle reciprocity of FDD systems to enable the base station to acquire partial DL channel state information through a previous UL signaling. A joint user grouping and beamforming optimization method without DL training and UL feedback is proposed to enhance spectral efficiency and mitigate interference between multiple UEs during DL data transmission. Simulation results suggest that the proposed scheme possesses a comparable performance to a number of previous grouping-based schemes that require DL training and UL feedback.
关键词： angle reciprocity,no CSI feedback.,frequency-division duplex,Massive MIMO,beam-time block coding
更新于2025-09-10 09:29:36
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An Overview of OFDM-Based Visible Light Communication Systems From the Perspective of Energy Efficiency Versus Spectral Efficiency
摘要： In this paper, the energy ef?ciency and the spectral ef?ciency for orthogonal frequency division multiplexing (OFDM)-based visible light communication schemes are studied, which is crucial for practical application with limited energy resources. The conventional schemes, including asymmetrically clipped optical OFDM (ACO-OFDM), pulse-amplitude-modulated discrete multitone, and direct current biased optical OFDM, are compared in terms of energy ef?ciency and spectral ef?ciency relationship. The in?uence of power allocation for asymmetrically clipped dc biased optical OFDM and hybrid ACO-OFDM is also investigated. The energy ef?ciency and spectral ef?ciency of layered ACO-OFDM with a variable layer number are calculated and their relationship is also formulated. These conventional and hybrid modulation schemes are analyzed and compared through computer simulations, which should be considered in practice according to the requirements of illumination and transmission.
关键词： visible light communication (VLC),spectral ef?ciency,orthogonal frequency division multiplexing (OFDM),Energy ef?ciency
更新于2025-09-09 09:28:46
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Deployment Issues and Performance Study in a Relay-Assisted Indoor Visible Light Communication System
摘要： This paper investigates the deployment issues and analyzes the performance of a relay-assisted indoor visible light communications (VLC) system with dc-biased optical orthogonal frequency division modulation (DCO-OFDM). The study considers two light sources in an office environment. One light source works as the information source and is located at the ceiling while the other one works as the relay terminal, which usually is a desk light or a floor light. We analyze the general blockage in a room, discuss the path loss of the VLC channel, and compare received signal power from a line of sight (LOS) link and a non-LOS link. The constraints on the relay height in order to achieve LOS connection are investigated. Simplified optimal power allocation under illumination and blockage constraints is proposed. Bit error rate performance is analyzed and the required signal power is derived for the relay-assisted DCO-OFDM VLC system. The study shows that in a relay-assisted VLC system, the blockage of source to destination link has trivial influence on the overall system performance if relays are properly deployed.
关键词： indoor,visible light communications (VLC),dc-biased optical orthogonal frequency division modulation (DCO-OFDM),relay,Channel model,power allocation
更新于2025-09-09 09:28:46