Radio frequency watermarking for OFDM wireless networks

In this work, we apply watermarking to the physical layer of the wireless baseband modulation waveform, with the motivation to improve flexibility and efficiency of authentication processes in a secure wireless network. We present two baseband watermarking methods, called constellation dithering (CD) and baud dithering (BD), applied to orthogonal frequency division multiplexing (OFDM). We provide the watermark detection and capacity performance attributes in an additive white Gaussian noise (AWGN) channel. Both watermarking techniques allow interoperability with uninformed systems (such as receivers in the 802.11 WLAN commercial standard). Results indicate that, while the BD method provides higher detection robustness and capacity, the CD method exhibits more performance flexibility and is easily modified to the desired user characteristics.