September 2009 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: VLC-CDM Scheme using Scalable Data Rate Code Date Submitted: September 2009 Source: *Kye San Lee [Kyunhee Univ] **.Jae Sang Cha[ Seoul National Univ. Of Technology], ***Yeong Min Jang[ Kookmin Univ.] Dong Ho Cha [Kyunhee Univ], Su Jin Bae[Kyunghee Univ.] Address Voice:82-10-4455-4370, 5624, E-Mail: * kyesan@khu.ac.kr, ** chajs@snut.ac.kr, **yjang@kookmin.ac.kr Re: Abstract: VLC-CDM Scheme using Scalable Data Rate Code Purpose: Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

Weakness of conventional VLC September 2009 Weakness of conventional VLC VLC system Issues : Interference from Lighting equipment. Interference.(MPI/MAI etc) Fixed Data rate. Proposed VLC system Issues : Eliminate the lighting interference. Interference reduction Scalable Data Rate Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

Proposal Scheme Presented VLC system Fixed Data Rate. September 2009 Proposal Scheme Presented VLC system Fixed Data Rate. Weakness of Lighting sourced interference. Performance degrade on Multipath Channel or Multiple access environments Proposed VLC system. Scalable Spread Spectrum techniques have been proposed to reduce the impact of interferences as MPI or MAI Proposed system by using SSC(Scalable Spread Code) can achieve the variable data rate according to the separate channel environments. Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

Spreading Codes Scalable spreading code September 2009 Spreading Codes Conventional spreading codes Walsh code Walsh code based on the Hadamard matrix, is usually used as channelization code in CDMA schemes because of its excellent orthogonality. PN(Pseudo-Noise)code M-sequence Because the correlation characteristics of m-sequence with the same code length is limited, the mobile communication systems use the m-sequence as a function is very small. Gold code Gold code have been developed by with better periodic cross correlation and autocorrelation properties. Gold code sequences are constructed by taking a pair of preferred m-sequences, generating by the modulo-2 sum of these two sequences for each of L cyclically shifted versions of one sequence relative to the other sequence. Scalable spreading code Unipolar or Bipolar type Characteristics: High orthogonality, Variable SF, Scalable data rate. Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

Table 1 Parameters For the Diffuse Channel exponential-decaying September 2009 Parameters Setting Table 1 Parameters For the Diffuse Channel Table 2 Parameters For TYPE Ⅳ LED [4] Light Physical Quality Modulation Scheme IM-DD Pulse Modulation OOK-NRZ Multiplexing Method WDM Data rate 400[Mbit/s] Noise Model AWGN is dominant Optical channel model exponential-decaying model Background light noise 0[dBm] Duty ratio r 100% red green blue Wavelength (nm) 610 565 450 Mixture ratio 1 11.17 7.19 O/E conv. efficiency (A/W) 0.52 0.48 0.4 Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

Simulation Result September 2009 Fig. 6. A BER performance of non spread spectrum VLC system versus various RMS delay spread Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

No interference environment( One LOS path) September 2009 No interference environment( One LOS path) Modulation Scheme IM-DD Pulse Modulation OOK-NRZ Multiplexing Method WDM Data rate 400[Mbit/s] Spread code Random code,walsh code, m-sequence, gold code Noise Model AWGN is dominant Optical channel model No multi-path Background light noise 0[dBm] Fig. 8. A BER performance of Directed LOS channel. Table 3 Parameters For the Directed LOS Channel Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

Interference (Delay spread) environments September 2009 Interference (Delay spread) environments Fig.9 BER performance for RMS delay spread=2ns Fig.10 BER performance for RMS delay spread=10ns Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

September 2009 Conclusion We considered that VLC-CDM scheme using various SF codes reduced interferences. By using Scalable SF codes, we can reduce the effect of VLC intereference Our work focused to an adaptive rate based VLC-CDM schemes using enhanced spreading codes. Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.