Physical- Layer Authentication based on Spreading Code Watermarking for IoT Networks

Physical-layer authentication (PLA) is capable of providing lightweight security solutions for the next-generation Internet of Things (IoT) networks. This paper adopts and modifies the spreading code authentication techniques originally designed for the Global Navigation Satellite System to apply PLA to narrowband IoT networks. In particular, two watermarking schemes including single- and multi-frame watermarking are developed to replace chip values in the spreading code segment for the PHY-layer preamble. In the single-frame scheme, a whole watermark sequence is embedded into one single frame in a preamble-bit-wise manner, with a randomly generated set of indices indicating the position of the watermarked segments, and the receiver makes a correlation test to make authentication decisions once receiving a message. In the multi-frame scheme, a watermark sequence is split and periodically embedded into several frames, and the receiver conducts joint authentication for these frames. Simulation results of single-frame watermarking along with the prototype validation of multi-frame watermarking based on the GNU Radio/USRP SDR platform corroborate the effectiveness of both schemes.