Compensation schemes for uneven illumination and LED light-emitting instability in optical camera communication...

Area of Science:

• Optical Camera Communication (OCC)
• Wireless Optical Communication Systems
• Digital Signal Processing

Background:

• Optical Camera Communication (OCC) systems aim to increase data rates using advanced modulation techniques like 8-composite-amplitude-shift-keying (8CASK).
• Static demodulation thresholds in multi-level Amplitude Shift Keying (ASK) systems are susceptible to performance degradation caused by uneven LED illumination and light-emitting instability.
• These illumination variations lead to fluctuations in image gray levels, negatively impacting the bit-error-rate (BER).

Purpose of the Study:

• To propose and demonstrate a novel demodulation scheme for 8CASK OCC systems.
• To mitigate the adverse effects of uneven illumination and LED instability on BER performance.
• To enhance the overall data transmission reliability and rate of OCC systems.

Main Methods:

• Implementation of an 8-composite-amplitude-shift-keying (8CASK) modulation scheme for enhanced data rates.
• Development of an uneven illumination compensation algorithm to correct for light intensity variations.
• Integration of a pixel matrix threshold overall update algorithm for dynamic threshold adjustment.
• Application of a secondary decision algorithm to refine signal demodulation and error correction.

Main Results:

• The proposed demodulation scheme successfully compensates for illumination unevenness and LED instability.
• The system achieved a communication rate of 9 kbit/s at a distance of 250 cm under 135 lux illumination.
• A low bit-error-rate (BER) of 8.01 × 10^-5 was recorded, demonstrating significant performance improvement.

Conclusions:

• The developed demodulation scheme effectively addresses the challenges of illumination variations in OCC systems.
• The proposed methods significantly improve the BER performance of 8CASK OCC systems.
• This research contributes to the advancement of high-data-rate and reliable optical wireless communication.