- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - New Delhi, India (2019.3.9-2019.3.15)] 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - Design of a Synchronous Counter with Two-dimensional 10 x 10 LED array for Calibration of Timing Parameters of Video Cameras
摘要： Digital television signal is a promising signal of opportunity for wireless positioning. This paper studies the time of arrival (TOA) estimation on the European standard DVB-T signals in the context of positioning. Theoretical analysis on the autocorrelation of the pilot signal and multipath error envelop suggests that DVB-T has the appropriate characteristics for positioning. A software defined radio-based DVB-T receiver is developed for field testing, in which the radio frequency DVB-T signals are first sampled by universal software radio peripheral, and then algorithms of the coarse symbol synchronization, the pilot detection, the first path acquisition, and the delay tracking are sequentially performed to obtain the TOA estimation. To quantify the TOA tracking results on real DVB-T signals, field testing campaigns are carried out in five cities in Southern France. Test results showed that, in the high signal-noise ratio condition, the 2-σ error interval is within 1 m. By taking into account all the field tests, the interval of 95% accuracy is within 4 m and the corresponding C/N0 varies from 48 to 62 dB-Hz. In addition, with the developed TOA estimation method, the synchronization of the emitters with global positioning system time is evaluated and the distance difference of the multiple emitters within single frequency networks are also measured during the tests.
关键词： delay locked loop,software defined radio (SDR),wireless positioning,Digital TV,orthogonal frequency division multiplexing (OFDM),time of arrival
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Development and Characterization of III-V/Si Multijunction Photovoltaics for Space Application
摘要： Clipping is one of the simplest peak-to-average power ratio reduction schemes for orthogonal frequency division multiplexing (OFDM). Deliberately clipping the transmission signal degrades system performance, and clipping mitigation is required at the receiver for information restoration. In this paper, we acknowledge the sparse nature of the clipping signal and propose a low-complexity Bayesian clipping estimation scheme. The proposed scheme utilizes a priori information about the sparsity rate and noise variance for enhanced recovery. At the same time, the proposed scheme is robust against inaccurate estimates of the clipping signal statistics. The undistorted phase property of the clipped signal, as well as the clipping likelihood, is utilized for enhanced reconstruction. Furthermore, motivated by the nature of modern OFDM-based communication systems, we extend our clipping reconstruction approach to multiple antenna receivers and multi-user OFDM. We also address the problem of channel estimation from pilots contaminated by the clipping distortion. Numerical findings are presented that depict favorable results for the proposed scheme compared to the established sparse reconstruction schemes.
关键词： Clipping,Bayesian sparse signal estimation,OFDM,PAPR reduction,multi-user communication,channel estimation
更新于2025-09-16 10:30:52
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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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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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Optical Fiber and Wireless Communications || OFDM Systems for Optical Communication with Intensity Modulation and Direct Detection
摘要： Intensity modulation and direct detection (IM/DD) is a cost-effective optical communication strategy which finds wide applications in fiber communication, free-space optical communication, and indoor visible light communication. In IM/DD, orthogonal frequency division multiplexing (OFDM), originally employed in radio frequency communication, is considered as a strong candidate solution to combat with channel distortions. In this research, we investigate various potential OFDM forms that are suitable for IM/DD channel. We will elaborate the design principles of different OFDM transmitters and investigate different types of receivers including the proposed iterative receiver. In addition, we will analyze the spectral efficiency and decoding complexities of different OFDM systems to give a whole picture of their performance. Finally, simulation results are given to assess the detection performance of different receivers.
关键词： modulation,detection,OFDM,optical communication,IM/DD
更新于2025-09-12 10:27:22
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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) - Highly Flat Optical Frequency Comb Based on the Time Lens Principle
摘要： Broad bandwidth optical frequency combs (OFCs) have received much attention in recent years due to a dramatic growth of their applications, such as spectroscopy measurements, microwave photonics applications, and optical communications. There are several advanced optical superchannel systems, which have been practically implemented by OFCs, such as a Tbit/s coherent optical orthogonal frequency division multiplexing (OFDM) system [1] and Tbit/s single-channel coherent Nyquist pulse transmission systems with high spectral efficiency [2], etc. Those systems require the OFC with a high degree of flatness and broad bandwidth that are difficult to achieve with conventional methods based on sinusoidal phase modulation (SPM).
关键词： microwave photonics,optical frequency combs,Nyquist pulse transmission,OFDM,spectroscopy measurements,optical communications
更新于2025-09-12 10:27:22
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Adaptive Subspace Method for Phase Noise Estimation in CO-OFDM Systems
摘要： In this paper, a blind phase noise estimation method for a coherent optical orthogonal frequency-division multiplexing (CO-OFDM) system is considered. Based on the subspace approach, a simple and robust method is proposed to adaptively estimate and track phase noise in CO-OFDM systems. The idea behind this novel technique is to estimate the singular vectors that correspond to the smallest singular values of the noise subspace. A weighting parameter, which is derived based on the forward–backward linear prediction technique, is subsequently constructed using the obtained singular vectors of the noise subspace to adaptively estimate the phase noise in the system. Also, a variable step size is introduced to ensure an improved performance as well as stable convergence. Simulation results are shown to demonstrate the effectiveness as well as the efficiency of the proposed algorithm, which is implemented in a polarization multiplexed CO-OFDM system stressed by polarization mode dispersion, chromatic dispersion, and other polarization-dependent losses along the fiber link.
关键词： subspace method,adaptive algorithms,CO-OFDM,phase noise estimation,OFDM
更新于2025-09-11 14:15:04
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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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[IEEE 2019 16th International Multi-Conference on Systems, Signals & Devices (SSD) - Istanbul, Turkey (2019.3.21-2019.3.24)] 2019 16th International Multi-Conference on Systems, Signals & Devices (SSD) - Performance Evaluation of White LED-based OFDM-VLC Systems with Blue Filters: Experimental Study
摘要： This paper experimentally evaluates the performance of visible light communications (VLC) systems employing phosphor-coated white light emitting diodes (LEDs). Phosphor-coated white LEDs though widely used commercially, are known to limit the system’s maximum data rate. Such a limitation is conventionally treated by two methods: either adding a blue filter at the receiver or using orthogonal frequency multiplexing (OFDM) digital modulation technique. Adding a blue filter at the receiver is controversial in current literature and claimed to decrease the signal-to-noise-ratio (SNR) or to be inefficient if OFDM is employed. Hence, in this work, we experimentally evaluate the above OFDM based VLC system with and without a blue filter. Results are compared to prove that adding a blue filter at the receiver boosts SNR and bit-error-rate (BER) values. This, in turn, helps maximize the data rates supported by such systems. The addition of a blue filter is tested with different modulation techniques. Results in this work remove the controversy around employing a blue filter in OFDM based VLC systems with phosphor-coated white LEDs. Improved BERs and SNRs at high data rates are observed. Specifically, this experimental work demonstrates a BER enhancement of ～40% and ～15% for data rates up to 12 Mbps when a blue filter is added.
关键词： phosphor LEDs,OFDM,experimental study,VLC,blue filters
更新于2025-09-11 14:15:04
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Data Suppression in Wavelength-Reuse WDM-PON Using Semiconductor Optical Amplifier with Faraday Rotator Mirror and Fabry-Perot Etalon
摘要： We experimentally study data suppression characteristics of a semiconductor optical amplifier with a Faraday rotator mirror used for wavelength-reuse WDM-PON. Bidirectional transmission over 10 km assisted by spectral trimming using a Fabry-Perot etalon is demonstrated.
关键词： TWDM-PON,Access Network and Subsystem,OFDM-PON,Future high capacity and long-reach access networks including WDM-PON,Semiconductor optical amplifiers
更新于2025-09-11 14:15:04