Apparatus and method for transmitting and receiving visible light communication
View Patent ↗A visible light communication (VLC) transmitting apparatus modulates source data to an orthogonal frequency division multiplexing (OFDM) symbol according to an OFDM modulation method, inserts a diffusion code that is allocated to the VLC transmitting apparatus into a frequency axis of the OFDM symbol, converts the OFDM symbol in which the diffusion code is inserted to a visible light modulation signal, and transmits the converted visible light modulation signal. Thereby, a signal of the VLC transmitting apparatus in which a VLC receiving apparatus wants can be easily detected.
1. A receiving method of a VLC receiving apparatus, the receiving method comprising:
detecting a visible light wireless signal;
converting the visible light wireless signal to a digital signal;
detecting a signal of a VLC transmitting apparatus wanting to receive using a diffusion code that is inserted into the digital signal;
removing the diffusion code from the detected signal; and
restoring a signal in which the diffusion code is removed to original data by demodulating with an OFDM method,
wherein the detecting of a signal comprises:
calculating an auto-correlation value between a sequential sample signal of a signal into which the diffusion code is inserted among the digital signal and a diffusion code of the VLC transmitting apparatus wanting to receive; and
detecting a digital signal corresponding to a signal having a maximum value of the calculated auto-correlation value.
2. The receiving method of claim 1 , wherein the diffusion code comprises one of a PN code, a Walsi code, a Kasami code, and an M-sequence.
3. The receiving method of claim 1 , wherein the diffusion code comprises an M-sequence.
4. The receiving method of claim 1 , wherein the calculating of an auto-correlation value comprises:
calculating a log likelihood ratio of the sample signal; and
detecting a maximum value of an auto-correlation value between the log likelihood ratio of the sample signal and the diffusion code of the VLC transmitting apparatus wanting to receive.
5. A VLC receiving apparatus, comprising:
a photoelectric converter that detects a visible light modulation signal and that converts the visible light modulation signal to a digital signal; and
a demodulation unit that detects a signal of a VLC transmitting apparatus wanting to receive from the digital signal using a diffusion code of the VLC transmitting apparatus wanting to receive, and that restores the detected signal to original data by demodulating according to an OFDM method,
wherein the demodulation unit comprises a signal receiving unit that calculates an auto-correlation value between a sequential sample signal of a signal into which the diffusion code is inserted among the digital signals and the diffusion code of the VLC transmitting apparatus wanting to receive, and that detects a digital signal corresponding to a signal having a maximum value among the calculated auto-correlation values.
6. The VLC receiving apparatus of claim 5 , wherein the diffusion code comprises one of a PN code, a Walsi code, a Kasami code, and an M-sequence.
7. The VLC receiving apparatus of claim 5 , wherein the demodulation unit further comprises:
a diffusion code removing unit that removes the diffusion code from the digital signal corresponding to a signal having the maximum value;
a guard interval removing unit that removes a cyclic prefix from a signal in which the diffusion code is removed;
a fast Fourier transform (FFT) unit that transforms the signal in which the diffusion code is removed to a signal of a frequency domain by performing FFT; and
a symbol demapper that restores the signal of a frequency domain to original data by symbol demapping.