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Now showing 1 - 10 of 13

Utilization of multi-band OFDM modulation to increase traffic rate of phosphor-LED wireless
(2015-01-26)
Yeh, Chien-Hung
;
Chen, Hsing-Yu
;
Chow, Chi-Wai
;
Liu, Yen-Liang
;
光電工程學系
To increase the traffic rate in phosphor-LED visible light communication (VLC), a multi-band orthogonal frequency division multiplexed (OFDM) modulation is first proposed and demonstrated. In the measurement, we do not utilize optical blue filter to increase modulation bandwidth of phosphor-LED in the VLC system. In this proposed scheme, different bands of OFDM signals are applied to different LED chips in a LED lamp, this can avoid the power fading and nonlinearity issue by applying the same OFDM signal to all the LED chips in a LED lamp. Here, the maximum increase percentages of traffic rates are 41.1%, 17.8% and 17.8% under received illuminations of 200, 500 and 1000 Lux, respectively, when the proposed three-band OFDM modulation is used in the VLC system. In addition, the analysis and verification by experiments are also performed. (C) 2015 Optical Society of America
High Speed Imaging 3 x 3 MIMO Phosphor White-Light LED Based Visible Light Communication System
(2016-12-01)
Hsu, Chin-Wei
;
Chow, Chi-Wai
;
Lu, I-Cheng
;
Liu, Yen-Liang
;
Yeh, Chien-Hung
The phosphor light-emitting diode (LED) has been widely used not only for indoor illumination but for the optical transmitter (Tx) as well in visible light communication (VLC). However, the transmission data rate is significantly limited by the modulation bandwidth of LED because of the low-speed response of phosphor. In order to enhance the data rate of the VLC system, we demonstrate a 3 x 3 imaging multiple-input multiple-output (MIMO) VLC system. Besides, the pre-equalizer circuit is used to extend the bandwidth of the LED Tx. Orthogonal frequency division multiplexing (OFDM) with bit-loading algorithm is used. By using the proposed scheme, the original 1 MHz bandwidth commercially available phosphor white light LED can achieve 1 Gbps data rate over 1-m free-space transmission distance.
Adaptive filtering for white-light LED visible light communication
(2017-01-01)
Hsu, Chin-Wei
;
Chen, Guan-Hong
;
Wei, Liang-Yu
;
Chow, Chi-Wai
;
Lu, I-Cheng
White-light phosphor-based light-emitting diode (LED) can be used to provide lighting and visible light communication (VLC) simultaneously. However, the long relaxation time of phosphor can reduce the modulation bandwidth and limit the VLC data rate. Recent VLC works focus on improving the LED modulation bandwidths. Here, we propose and demonstrate the use of adaptive Volterra filtering (AVF) to increase the data rate of a white-light LED VLC system. The detailed algorithm and implementation of the AVF for the VLC system have been discussed. Using our proposed electrical frontend circuit and the proposed AVF, a significant data rate enhancement to 700.68 Mbit/s is achieved after 1-m free-space transmission using a single white-light phosphor-based LED. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Demonstration of High Speed Imaging 3x3 MIMO-OFDM Visible Light Communication System
(2016-01-01)
Hsu, Chin-Wei
;
Lu, I-Cheng
;
Liu, Yen-Liang
;
Yeh, Chien-Hung
;
Chow, Chi-Wai
We experimentally demonstrate the 3x3 imaging multiple-input multiple-output (MIMO) visible light communication (VLC) system, using orthogonal frequency division multiplexing (OFDM) modulation and bit-loading, a total data rate > 800-Mbit/s over 1-m transmission is achieved without using blue-filter.
Investigation of phosphor-LED lamp for real-time half-duplex wireless VLC system
(2016-06)
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Chen, Hsing-Yu
;
Liu, Yen-Liang
;
Hsu, Dar-Zu
In this investigation, a 71.3 to 148.4 Mbit s(-1) white phosphor-LED visible light communication (VLC) system is proposed and demonstrated under the practical transmission length of 140 to 210 cm. Here, a commercial white-light LED lamp with five cascaded phosphor-LED chips is utilized for illumination and communication simultaneously. In the measurement, we utilize the optical orthogonal frequency division multiplexing quadrature amplitude modulation (OFDM-QAM) with bit-loading algorithm and propose an optimal bias-tee circuit design to improve the modulation bandwidth from 1 MHz to 27 MHz. Moreover, a blue optical filter is not used on the client side. Finally, to realize and demonstrate the real-time transmission performance in the proposed LED VLC system, a commercial OFDM-based digital signal processor (DSP) chip is utilized on the LED lighting side and client side, respectively. Hence, the proposed real-time half-duplex VLC transmission could achieve the 70 Mbit s(-1) downstream and upstream data throughputs, under a practical transmission length of 200 cm.
Adaptive filtering for white-light LED visible light communication
(2017-01)
Hsu, Chin-Wei
;
Chen, Guan-Hong
;
Wei, Liang-Yu
;
Chow, Chi-Wai
;
Lu, I-Cheng
White-light phosphor-based light-emitting diode (LED) can be used to provide lighting and visible light communication (VLC) simultaneously. However, the long relaxation time of phosphor can reduce the modulation bandwidth and limit the VLC data rate. Recent VLC works focus on improving the LED modulation bandwidths. Here, we propose and demonstrate the use of adaptive Volterra filtering (AVF) to increase the data rate of a white-light LED VLC system. The detailed algorithm and implementation of the AVF for the VLC system have been discussed. Using our proposed electrical frontend circuit and the proposed AVF, a significant data rate enhancement to 700.68 Mbit/s is achieved after 1-m free-space transmission using a single white-light phosphor-based LED. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
High-Speed 2x2 MIMO-OFDM Visible Light Communication Employing Phosphorescent LED
(2016)
Lu, I-Cheng
;
Liu, Yen-Liang
;
Lai, Chih-Han
;
光電工程學系
;
Department of Photonics
We experimentally demonstrated a 2x2 multiple-input multiple-output (MIMO) visible light communication (VLC) system using commercial phosphorescent white light emitting diodes (LEDs) and low-cost PIN photodiodes (PDs). Additionally, a pre-equalizer was used to extend the available modulation bandwidth up to 100 MHz. Using spectral-efficient orthogonal frequency division multiplexing (OFDM) modulation with bit-loading algorithm, we successfully achieved high-speed VLC transmission at > 1 Gbit/s over a free-space link of 0.6 m.
Theory and Technology for Standard WiMAX Over Fiber in High Speed Train Systems
(2010-08-15)
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Liu, Yen-Liang
;
Wen, Sz-Kai
;
Chen, Shi-Yang
In this investigation, we propose and investigate the standard WiMAX access in high speed railway (HSR) using radio over fiber (RoF) link. We also discuss the theory of mobile WiMAX at a target speed of 300 km/hr in simulation. We also analyze the effect of the Doppler frequency shift over HSR. The effective transmission fiber length in the WiMAX-RoF system was limited due to the time-division-duplex (TDD) protocol in the practical WiMAX. Thus, we also demonstrate the transmission limitation and performance of the standard WiMAX access in RoF link. The performances of throughput and packet loss at different fiber lengths are also investigated and discussed. Furthermore, a WiMAX-RoF field trial is also demonstrated based on a simple two RAUs RoF architecture. It was tested and measured in the SongShan tunnel of the Taiwan high speed railway (THSR).
Real-time white-light phosphor-LED visible light communication (VLC) with compact size
(2013-11-04)
Yeh, Chien-Hung
;
Liu, Yen-Liang
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
In this demonstration, we first demonstrate a real-time phosphor-LED visible light communication (VLC) system with 37 Mbit/s total throughput under a 1.5 m free space transmission length. The transmitter and receiver modules are compact size. Utilizing our proposed pre-equalization technology, the similar to 1 MHz bandwidth of phosphor LED could be extended to similar to 12 MHz without using blue filter. Thus, the increase in bandwidth would enhance the traffic data rate for VLC transmission. The maximum bit-rate achieved by the VLC system is 37 Mbit/s, and a video transmission at 28.419 Mbit/s is demonstrated using the proposed VLC system. In addition, the relationships of received power and signal performance are discussed and analyzed. (C) 2013 Optical Society of America
Investigation of Using Injection-Locked Fabry-Perot Laser Diode With 10% Front-Facet Reflectivity for Short-Reach to Long-Reach Upstream PON Access
(2013-06-01)
Chen, Hsing-Yu
;
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Sung, Jiun-Yu
;
Liu, Yen-Liang
In this paper, we propose and investigate an injection-locked Fabry-Perot laser diode (FP-LD) with 10% front-facet reflectivity by using orthogonal frequency-division multiplexing-quadrature amplitude modulation (OFDM-QAM) in each optical network unit (ONU) for colorless operation in the carrier-distributed passive optical network (PON). Here, the 10-Gb/s 16-QAM OFDM upstream traffic can be generated via a 2.5-GHz-bandwidth injection-locked FP-LD for the short-reach (SR)-to-long-reach (LR) transmission. In this measurement, the CW injection power of -12 dBm for an injection-locked FP-LD is required to achieve 100-km single-mode fiber (SMF) transmission. Hence, error-free transmissions of 20-, 50-, 75-, and 100-km fiber lengths are achieved with the power penalties of 0.33, 0.86, 1.20, and 1.76 dB at the bit error rate (BER) of 3: 8 x 10(-3), respectively, for upstream traffic. Moreover, the relationship of CW injection power and signal-to-noise ratio (SNR) of each OFDM subcarrier in the injection-locked FP-LD has also been analyzed.

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