1. Experimental Demonstration of High-Order
Modulation for Optical Camera Communication
University of Science and Technology of China, Hefei
Wei Huang, Peng Tian, Chen Gong, Zhengyuan Xu

2. Outline Background of this research Higher-order modulation for OCC
The CDF-based receiver
Experimental results and discussion
Conclusions

3. Outline Background of this research Higher-order modulation for OCC
The CDF-based receiver
Experimental results and discussion
Conclusions

4. Background of OCC
Fig 1. The system diagram of optical camera communication

5. Background of OCC ITS Hiding-Commun Positioning Nea-Commun How to
Satisfy it?
Hiding-Commun
Positioning

6. Outline Background of this research Higher-order modulation for OCC
Experimental results and discussion
Conclusions

7. High-order Modulation for OCC
Assume the signal constellation set includes 𝐿= 2 𝐾 signal levels, denoted as 𝑆
𝑆≜{ 𝑠 1 , 𝑠 2 ,⋯, 𝑠 𝐿 }
For 𝐿-level, 𝐾 information bits 𝑏 𝐾 𝑏 𝐾−1 ⋯ 𝑏 1 are modulated to one of the 𝐿 signal levels. Let 𝒀 denote grey signal in ROI (𝑀×𝑁) receiver
𝒀≜ 𝑦 11 ⋯ 𝑦 1𝑁 ⋮ ⋱ ⋮ 𝑦 𝑀1 ⋯ 𝑦 𝑀𝑁 𝑀×𝑁
0≤𝑦 𝑖𝑗 <256, 1≤𝑖≤𝑀,1≤𝑗≤𝑁
with

8. The CDF-based Receiver
Given a certain threshold 𝑐,0≤𝑐<256, define the fraction of pixels whose grey levels are larger than 𝑐, thus
𝐹 (𝑐,𝒀)≜ 𝑖=1 𝑀 𝑗=1 𝑁 𝟏( 𝑦 𝑖𝑗 >𝑐) 𝑀×𝑁
Let 𝐹 𝑐,𝒀 ≜1− 𝐹 (𝑐,𝒀), and denote the vector consisting of the CDF of the received signal
𝑣 𝒀 ≜ 𝐹 0,𝒀 ,𝐹 1,𝒀 ,⋯𝐹 255,𝒀 𝑇
The detected level for transmitted signal 𝑠 𝑖 0 based on CDF, is
𝑖 0 𝐶𝐷𝐹 =arg mi n 1≤𝑖≤𝐿 𝑣 𝒀 − 𝑣 𝑖
The training level

9. The Mean Grey-based Receiver
For the detection based on the mean grey level, the detection metric is given by
𝑦 ≜ 1 𝑀𝑁 𝑖=1 𝑀 𝑗=1 𝑁 𝑦 𝑖𝑗 = 𝑐= 𝐹 𝑐,𝒀
=256− 𝑒 𝑇 ⋅𝑣(𝒀)
Then signal 𝑠 𝑖 0 is detected if the following condition is satisfied
𝑖 0 𝑀𝑒𝑎𝑛 =arg mi n 1≤𝑖≤𝐿 𝑒 𝑇 ⋅𝑣 𝒀 − 𝑒 𝑇 ⋅ 𝑣 𝑖

10. Outline Background of this research Higher-order modulation for OCC
Experimental results and discussion
Conclusions

11. Experimental Platform for OCC
Programmable RGB-LED array
PC-Demodulator
OCC Receiver based on FPGA
Fig2：The actual experiment setting for high order modulation in OCC.

12. Experimental Setting for OCC
The image sensor key specifications
Manufacture process
CMOS
Output formats
10bits RAW
Pixel size
2um*2um
Frame Rate
330fps
Lens size
1/3 inch
Semi-angle at half power of LED
12.5o
Resolution
672*380
Communication distance
50cm~300cm (without lens)
The packet format in OCC

13. Nonideality in Actual OCC System
Fig3. The received flicker noise due to fluorescent lamp.

14. Flicker Noise
Fig4. The received flicker noise due to fluorescent lamp.

15. Nonlinear Between Tx-Rx
Fig5. The nonlinearity in OCC.

16. CDF for 4PAM Modulation Fig7. The CDF for 4-PAM modulation
(ROI size 120×120, TR distance 100cm)

17. BER vs Different Modulation Depths
Fig8. The BER performance for different modulation depths.

18. BER vs Different ROI Size
Fig9. The BER performance for different ROI sizes
(TR distance 100cm, modulation depth )

19. BER vs Different TR Distances
Fig10. The BER performance for different transmission distances
(block size 120×120, modulation depth )

20. Outline Background of this research Higher-order modulation for OCC
Experimental results and discussion
Conclusions

21. Conclusions Higher-order modulation is possible in OCC;
Optimal modulation level allocation is needed for actual OCC system;
More advanced signal demodulation algorithm is need for actual OCC system;
The BER performance and transmission distance can be improved by lens sequence and tracking systems.

22. Thank you
(Q&A)