We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security.
@article{arxiv.1607.07799,
title = {Free-space optical channel estimation for physical layer security},
author = {Hiroyuki Endo and Mikio Fujiwara and Mitsuo Kitamura and Toshiyuki Ito and Morio Toyoshima and Yoshihisa Takayama and Hideki Takenaka and Ryosuke Shimizu and Nicola Laurenti and Giuseppe Vallone and Paolo Villoresi and Takao Aoki and Masahide Sasaki},
journal= {arXiv preprint arXiv:1607.07799},
year = {2016}
}