"Watermarking" for convolutionally/turbo coded systems and its applications

Watermarking is a process that embeds one signal into another signal to provide a hidden identity. It is widely used in multimedia signal processing for copyright protection purpose. Motivated by the observation that in some applications it is highly desirable for the physical layer itself to have some user identifying features instead of obtaining such information from the media access control (MAC) layer, we extend the watermarking idea and propose a method to give a convolutionally or turbo coded system a hidden identity. The proposed algorithm embeds a periodic watermark sequence into the convolutionally coded data sequence in the transmitter and detects the watermark using the channel error information supplied by the forward error control (FEC) module in the receiver. It does not consume any extra transmission bandwidth by properly designing the watermark sequence using the properties of convolutional codes. The algorithm has several potential applications in wireless and satellite communications. It is easy to implement and fits generic modems