Browsing by Author "Lin, Wan-Feng"

Now showing 1 - 3 of 3

Design of Visible Light Communication System for Maintaining Uniform Data Rate
(2014-01-01)
Sung, Jiun-Yu
;
Lin, Wan-Feng
;
Wu, Yu-Fu
;
Chow, Chi-Wai
;
Yeh, Chien-Hung
Light-emitting diode (LED) is gradually replacing the fluorescent lamp for lighting. Higher modulation bandwidth of LEDs makes the additional application of visible light communication (VLC) possible. Every location of a VLC system should be provided by equal data rate for smooth communication. However, locations away from the LED lamp have less power. These low-power locations have lower signal-to-noise ratio (SNR); and hence lower data rate can be achieved. For achieving high capacity VLC, strategies should be adequately provided to mitigate this problem. Moreover, for some real-time continuous applications, such as video and voice, latency reduction plan should also be considered. In this paper, an orthogonal frequency-division multiplexing access (OFDMA) based system was proposed to solve the above problem. Because we do not use time-division multiplexing access (TDMA) based system, the latency issue can be reduced. The OFDMA based system is also beneficial for large scale operation because the user bandwidth is not reduced by TDM mechanism. Signal-to-noise-plus-interference ratio (SNIR) distribution of the VLC system is designed to ensure uniform and optimal system capacity. Discrete multi-tone (DMT) is used for this VLC system. The DMT subcarriers are bit-loaded depending on the LED frequency response. More subcarriers are allocated for communication at low SNIR locations. Hence, nearly equal data rate can be provided everywhere. Demonstration of 17 Mb/s/LED data rate was provided.
Orthogonal frequency-division multiplexing access (OFDMA) based wireless visible light communication (VLC) system
(2015-11-15)
Sung, Jiun-Yu
;
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Lin, Wan-Feng
;
Liu, Yang
An orthogonal frequency-division multiplexing access (OFDMA) based visible light communication (VLC) system is proposed in this paper. The architecture of the proposed system is divided into several VLC cells, which is defined in this paper. The deployment and upgrade of the system involve only simple combination of the VLC cells. Hence it is economically advantageous. To guarantee smooth communication, nearly equal data rate is provided at every location within the system with no concern on the system scale. The user location monitor strategy is also discussed to solve the region division issues. The characteristics of the proposed system are analyzed in detail in this paper. A one-dimensional experiment was demonstrated with 13.6 Mb/s data rate. (C) 2015 Elsevier B.V. All rights reserved.
Using specific and adaptive arrangement of grid-type pilot in channel estimation for white-lightLED-based OFDM visible light communication system
(2015-03-01)
Lin, Wan-Feng
;
Chow, Chi-Wai
;
Yeh, Chien-Hung
;
光電工程學系
;
Department of Photonics
Orthogonal frequency division multiplexing (OFDM) is a promising candidate for light emitting diode (LED)-based optical wireless communication (OWC); however, precise channel estimation is required for synchronization and equalization. In this work, we study and discover that the channel response of the white-lightLED-based OWC was smooth and stable. Hence we propose and demonstrate using a specific and adaptive arrangement of grid-type pilot scheme to estimate the LED OWC channel response. Experimental results show that our scheme can achieve better transmission performance and with some transmission capacity enhancement when compared with the method using training-symbol scheme (also called block-type pilot scheme). (C) 2014 Elsevier B.V. All rights reserved.