Performance evaluation of OFDM based watermarking robust to multipath spatial shifts

A digital watermark is a visible or invisible pattern embedded in a digital image which can be used for copyright protection, authentication, broadcast monitoring, telemedicine and many more. This paper describes how an efficient CDMA based spread spectrum technique can be combined with the most prominent spectrum efficient OFDM technology to formulate a robust watermarking algorithm which is suitable for image distortions due to time delays and spatial shift that may occur during the transmission of watermarked images. A detailed simulation of embedding and decoding algorithm was performed and compared the performance with the existing DCT, DWT and FWHT based techniques. Simulation results reveal that the proposed algorithm is computationally efficient, robust and is well suited for wireless multipath fading channel. The algorithm was tested against a number of possible noises in the wireless channels and various geometric and signal processing operations. The proposed algorithm is proved to be robust enough to extract a good quality watermark compared to well-known techniques.