The Performance Of QC-LDPC Codes In The Visible Light Communication

LED is widely used in our routine life and generally replacing incandescent and fluorescent lamps for illumination. Thus, visible light communication (VLC) has emerged as a novel hot point in recent years. VLC is a communication mode which employs LEDs as transmitters and photoelectric detectors or imaging sensors as receivers. And what is more, LED can be used for illumination and communication alike, which improves engergy ultilization ratio. Besides, VLC has several of competitive advantages over high transmission power, unlicensed spectrum, safe for human beings, and immune from interference with radio bands, etc.However, VLC would be deteriorated by ambient interference, including background solar radiation and artificial light sources, and photoelectric detectors noise. In order to improve the reliability, error-correction codes are employed in the VLC systems, as they are important ways for correcting errors. The paper proposed the VLC systems based QC-LPDC codes model, and investigated the performance of QC-LDPC codes in the VLC by simulation and experiments. According to the two occasion which might occur in the VLC, the paper simulate in the VLC systems without obstructions and with obstructions. In the VLC systems without obstructions model, there is no obstructions between the LED and the photoelectric detector. It is a line of sight. It is found that the BER using QC-LDPC codes can reach 10-6, when the SNR is 1.6dB, code length is 2304 and code rate is 1/2. In the VLC systems with obstructions model, an obstruction is placed before the photoelectric detector. When the received signal falls down from high level, due to something blocks the receiver, the adaptation amplifier automatically switches amplification factor to the high level, for example, from level "1" to level "10". And the signal in the switching time is uncertain. It is found that BER using QC-LDPC codes can reach 10-6, when code length is 2304, code rate is 1/2, and SNR is 3dB. The experiment results show that the BER is much lower when using QC-LDPC codes, and it can reach 10-5 when code length is 576, code rate is 1/2, and the illumination is 10lux. Therefore, the performance of QC-LDPC codes in the visible light communication is good.