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 ~1 MHz bandwidth of phosphor LED could be extended 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.
The light-emitting diode (LED) is among promising candidates of light sources in visible light communication (VLC); however, strong internal polarization fields in common c-plane LEDs, especially green LEDs, result in low frequency and limited transmission performance. This study aims to overcome the limited 3-dB bandwidth of long-wavelength InGaN/GaN LEDs. Thus, semipolar (20–21) micro-LEDs (μLEDs) were fabricated through several improved approaches on epitaxy and chip processes. The μLED exhibits a 525 nm peak wavelength and good polarization performance. The highest 3-dB bandwidth up to 756 MHz and 1.5 Gbit/s data rate was achieved under a current density of 2.0 kA/cm2. These results suggest a good transmission capacity of green semipolar (20–21) μLEDs in VLC applications.
For systems with slow and f a s t subsystems a near-optimum state r e g u l a t o r i s composed of two subsystem regulators. Conditions for complete s e p a r a t i o n o f slow and f a s t r e g u l a t o r d e s i g n s are formulated. A second order approximation of t h e optimal performance is achieved without the knowledge of t h e small s i n g u l a r p e r t u r b a t i o n parameter. 1. I n t r o d u c t i o n Linear time-invariant models of many physical systems contain slow and f a s t modes. Control problems for such models are often illconditioned and have motivated several modelsimplification approaches. Simplified models obtained via aggregation [I] and Bominant modes [2,3] approaches neglect fast modes and some of t h e p o o r l y c o n t r o l l a b l e and observable slow modes. I n t h e s i n g u l a r p e r t u r b a t i o n method [4,51 both slow and f a s t modes are r e t a i n e d , b u t a n a l y s i s and design problems are solved in two s t a g e s , f i r s t f o r t h e f a s t and then for the slow modes. However t h e s e p a r a t i o n i n 151 was not complete since the slow regulator design depended on the fast feedback gain matrix. This paper presents a new procedure for a complete separation o f slow and f a s t r e g u l a t o r designs. Furthermore the performance achieved by the composition of a slow and a f a s t r e g u l a t o r proposed here is a second order approximation of the optimal performance. It is s i g n i f i c a n t that, i n c o n t r a s t t o p r e v i o u s d e s i g n s , t h i s n e a r -o p t i m a l regulator does not require the knowledge of t h e singular perturbation parameter P. Hence t h i s r e g u l a t o r i s applicable to systems where I.L r e p r es e n t s small u n c e r t a i n p a r a m e t e r s . I n a d d i t i o n t o t h e p r e s e n t a t i o n o f t h e s e new r e s u l t s , a n o t h e r purpose of this paper is t o g i v e a s e l f -c o n t a i n e d development of the two-time-scale method based on s i n g u l a r p e r t u r b a t i o n s [ 8 , 9 , 1 0 1 . The paper assumes only the knowledge of standard facts of l i n e a r c o n t r o l t h e o r y . No f a m i l i a r i t y w i t h t h e s i n g u l a r p e r t u r b a t i o n l i t e r a t u r e i s r e q u i r e d . 2. Slow and Fast Subsystems W e consider a s i n g u l a r l y p e r t u r b e d l i n e a r time-invariant syatem k1 = Allxl +A12x2 +B1u, x l ( 0 ) = xl0 ( l a ) P52 $ 1~1 + $ 2~2 + B2ua x2 ( 0 ) -x 2 0 O b ) Y = C L X l +c2x2 (IC 1 where p is a small p o s i t i v e s c a l a r , t h e s t a t e x is formed by t h e nl-and ?-vectors xl, x2, the c o n t r o l u is an m-vector and the output y a kvector. As shown i n [ l l l , system (1) possesses a two-time-scale property, that is, it has n1 small eigenvalues of magnitude O ( 1 ) and "2 large eigenvalues of magnitude O$). 1 Preliminary to a separation of slow and fast designs, system (1) is approximately decomposed i n t o a slow subsystem w i t h n1 small eigenvalues and a fast subsystem w i t h 9 ...
Complementary Metal-Oxide-Semiconductor (CMOS) image sensors are widely used in mobile-phone and cameras. Hence, it is attractive if these image sensors can be used as the visible light communication (VLC) receivers (Rxs). However, using these CMOS image sensors are challenging. In this work, we propose and demonstrate a VLC link using mobile-phone camera with data rate higher than frame rate of the CMOS image sensor. We first discuss and analyze the features of using CMOS image sensor as VLC Rx, including the rolling shutter effect, overlapping of exposure time of each row of pixels, frame-to-frame processing time gap, and also the image sensor "blooming" effect. Then, we describe the procedure of synchronization and demodulation. This includes file format conversion, grayscale conversion, column matrix selection avoiding blooming, polynomial fitting for threshold location. Finally, the evaluation of bit-error-rate (BER) is performed satisfying the forward error correction (FEC) limit.
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