doc.: IEEE 15-13-0434-00-0led

1. July 2013 Synchronization scheme for LED-ID systems doc.: IEEE 15-13-0434-00-0led July. 2013. Jin Young Kim*, Yu Min Hwang*, Jae Sang Cha**, Kye San Lee***, Yeong Min Jang**** Kwangwoon University*, Seoul National University of Science and Technology**,Kyunghee University***, Kookmin University**** Seoul, Korea Jin Young Kim, Kwangwoon University

2. Contents • Motivation • Optical Wireless Channel Model • Proposed Frame Synchronization Scheme • Gold-sequence Generator • Simulation Results • Conclusions Jin Young Kim, Kwangwoon University

3. Motivation • Synchronization • To insert a fixed binary pattern of “sync word” periodically into the data stream to ensure that the receiver correctly reads the incoming bits. • Overhead of transmission. • Cost of out-of-synch state • Data streams are not always received with continuous complete errorless frames. • We may spend a lot of time to detect a frame or bits stream. • [Reference] J. Y. Kim, “Detection loss due to phase error in a code division multiple access system,” IEICE Transactions on Communications, Oct. 2001. Jin Young Kim, Kwangwoon University

4. Motivation • Frame synchronization for LED-ID Systems • Essential part of high-speed transmission • Still, it has not been fully investigated yet. • Correct synchronization • Optimization of transmission efficiency • Throughput improvement Jin Young Kim, Kwangwoon University

5. Frame Synchronization • For a receiver to demodulate a frame alignment signal, it must know where the beginning of a frame is. • To do this, transmitters embed a sync word called marker • Initially, several repetitions of the sync word precedes the data message • • • • • • sync word start of message Jin Young Kim, Kwangwoon University

6. What is the LED-ID System • Definition of LED-ID • - Light Emitting Diode Identification (LED-ID) is a technology that uses communication via light waves (especially visible light) to contactless exchange voice/video/data among one Tag(or Reader) to one or more identified Readers(or Tags). • Components of LED-ID • LEDs(maybe likened transmitter) • Photo Detector(maybe likened • receiver) • Each Reader and Tag of LED-ID • must have at least one LED and PD Jin Young Kim, Kwangwoon University

7. Characteristics of LED-ID • Long Brightness, Low Power Consumption • Frequency Band • - Visible light band (384 THz ~ 790 THz) • - No interference with RF • High speed Read and write capability • Security • No harmful to human • Green technology Jin Young Kim, Kwangwoon University

8. Reader Model • FOV: A receiver only detects light whose angle of incidence is less than FOV • R : distance between the source and receiver • : Receiving area • : Vector value from O to receiver O Jin Young Kim, Kwangwoon University

9. LOS Impulse Response Channel Modeling • Impulse response • : angle between and ) : solid angle subtended by receiver’s differential area O Jin Young Kim, Kwangwoon University

10. Multiple Bounce Impulse Response Channel Modeling • : response of the light undergoing exactly k reflections Jin Young Kim, Kwangwoon University

11. Block diagram of the proposed LED-ID system Proposed Frame Synchronization Scheme Jin Young Kim, Kwangwoon University

12. Procedure of inserting the ROGS in the ith OFDM frame. Proposed Frame Synchronization Scheme : Power of the orthogonal Gold-sequence : Orthogonal Gold-sequence of the user whose value is : Data frame : Guard interval : One orthogonal Gold-sequence length • ROGS : Repeated Orthogonal Gold Sequence Jin Young Kim, Kwangwoon University

13. Observation interval of • Find the start position of the OFDM frame of the user Proposed Frame Synchronization Scheme : LED-ID channel impulse response Jin Young Kim, Kwangwoon University

14. Gold-sequence is generated by two m-sequences Can generate N+2 codes of length N= 2n-1 Low cross-correlations= Example: n=5, cross correlation= {-1,-9,7} Gold-sequence Generator Jin Young Kim, Kwangwoon University

15. Codes Examples • m-sequence with n=5 • Gold sequence with n=5 Jin Young Kim, Kwangwoon University

16. Parameters Jin Young Kim, Kwangwoon University

17. Autocorrelation values over LED-ID channel Simulation Results (b) ROGSB schemes (a) MSB schemes • MSB : maximal length shift register sequence (m-sequence) based • ROGSB : repeated orthogonal Gold sequence based Jin Young Kim, Kwangwoon University

18. Cross-correlation values over LED-ID channel Simulation Results (b) MSB with two identical sequences (c) ROGSB schemes (a) MSB schemes Jin Young Kim, Kwangwoon University

19. Auto-correlation values over interfered by impulsive noise Simulation Results (b) MSB with two identical sequences (c) ROGSB schemes (a) MSB schemes Jin Young Kim, Kwangwoon University

20. Cross-correlation values over interfered by impulsive noise Simulation Results (b) MSB with two identical sequences (c) ROGSB schemes (a) MSB schemes Jin Young Kim, Kwangwoon University

21. Propose the efficient synchronization scheme based on m-sequence for LED-ID system • Gold-sequence has better cross-correlation property than other code • Proposed scheme can be applied to synchronization module of the LED-ID • Bit Error Probability and Outage Probability: under investigation. . Conclusions Jin Young Kim, Kwangwoon University