Time domain reshuffling for OFDM based indoor visible light communication systems

Area of Science:

• Optical Communications
• Signal Processing

Background:

• Indoor visible light communication (VLC) systems using orthogonal frequency division multiplexing (OFDM) suffer from inter-symbol crosstalk (ISC) due to non-ideal transmission.
• Insufficient guard intervals and dispersive channels exacerbate ISC in OFDM-VLC systems.

Purpose of the Study:

• To introduce a novel time domain reshuffling (TDR) technique to mitigate inter-symbol crosstalk (ISC) in both DC-biased optical (DCO-) and asymmetrically clipped optical (ACO-) OFDM VLC systems.
• To propose a unified TDR design for simplified implementation in DCO- and ACO-OFDM VLC systems.

Main Methods:

• Derivation of the time domain reshuffling (TDR) concept from the inverse Fourier transform.
• Application of simple frequency domain operations to relocate signal high peaks and alleviate ISC.
• Monte-Carlo simulations to analyze signal high peak values and peak-to-average power ratio (PAPR).

Main Results:

• TDR effectively alleviates inter-symbol crosstalk (ISC) in both DCO- and ACO-OFDM VLC systems.
• Improved bit error rate (BER) performance was demonstrated with TDR, showing significant signal-to-noise ratio (SNR) gains.
• For binary phase shift keying (BPSK) at a BER of 10^-3 with ISC of 1/64, TDR achieved SNR gains of approximately 1.6 dB for DCO-OFDM and 6.6 dB for ACO-OFDM.
• Reliable transmission was shown for rectangle 8-quadrature amplitude modulation (8-QAM) with ISC of less than 1/64 using TDR.

Conclusions:

• The proposed time domain reshuffling (TDR) technique is an effective method for mitigating inter-symbol crosstalk (ISC) in OFDM-based VLC systems.
• TDR offers significant performance improvements in terms of bit error rate (BER) and signal-to-noise ratio (SNR) for both DCO- and ACO-OFDM schemes.
• The unified TDR design simplifies implementation while maintaining reliable data transmission under challenging channel conditions.