1. September 2009
Project: IEEE P 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: , 5624, * **
Re:
Abstract: VLC-CDM Scheme using Scalable Data Rate Code
Purpose:
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Kye San Lee.Jae Sang Cha,Yeong Min Jang et al.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.