Adaptive threshold decision for on-off keying transmission systems in atmospheric turbulence

This paper investigates an adaptive threshold decision (ATD) scheme without the knowledge of channel state information (CSI) for optical wireless communication (OWC). Based on the low-pass characteristic of atmospheric turbulence channels, a low-pass filter is designed for the received signals, and the filtered signal can be employed as decision threshold. Theoretical analyses show that performance of ATD is very close to that with perfect CSI. Monte Carlo simulations demonstrate that the proposed scheme shows only 0.0221dB signal-to-noise (SNR) loss at most with Rytov variance of 0.05 and SNR of 21dB. An indoor experiment results are presented, which match well with that of theoretical prediction. The scheme is simple and without CSI, hence the efficient scheme makes the real-time implementation of high-speed transmissions for OWC based on ATD feasible.