  Physical layer authentication (PLA) is the process of claiming identity of a
node based on its physical layer characteristics such as channel fading or
hardware imperfections. In this work, we propose a novel PLA method for the
inter-satellite communication links (ISLs) of the LEO satellites. In the
proposed PLA method, multiple receiving satellites validate the identity of the
transmitter by comparing the Doppler frequency measurements with the reference
mobility information of the legitimate transmitter and then fuse their decision
considering the selected decision rule. Analytical expressions are obtained for
the spoofing detection probability and false alarm probability of the fusion
methods. Numerically obtained high authentication performance results pave the
way to a novel and easily integrable authentication mechanism for the LEO
satellite networks.
