This paper considers secure communication over free-space optical (FSO) links suffering from turbulence-induced fading. In particular, we study the average secrecy capacity of applying physical layer security to achieve security in an FSO communication system with binary-level on-off keying intensity modulation and threshold detection, a widely used system in FSO communication. We first define the instantaneous secrecy capacity for our system and then provide a lower bound of it, which is achieved based on a simple design principle for practical applications and yields a simpler equation. We next derive a general expression of the average secrecy capacity and the corresponding lower bound based on bit error probabilities. Finally, numerical analysis is conducted for the special case of the correlated log-normal fading model to show the impacts of fading and channel correlation on the average secrecy capacity.
@article{arxiv.1601.06377,
title = {Average Secrecy Capacity of Free-Space Optical Communication Systems with On-Off Keying Modulation and Threshold Detection},
author = {Jinxiao Zhu and Yin Chen and Masahide Sasaki},
journal= {arXiv preprint arXiv:1601.06377},
year = {2016}
}