Performance improvement of spread spectrum based image watermarking schemes through M-ary modulation

Abstract

In spread spectrum communication the use of M-ary modulation is a popular extension to binary signaling usually resulting in a significant performance improvement. Furthermore it was shown that for increasing M and for certain schemes M-ary modulation works at the channel capacity. In this work we investigated on how to use M-ary modulation in the context of spatial spread spectrum based watermarking schemes. The performance of M-ary watermarking schemes is theoretically analyzed and the results verified through empirical test. We show that in general M-ary modulation based on the biorthogonal extension of the Hadamard matrix results in a significant performance improvement for values of M > 4. Furthermore we show that the performance improvement does not decrease under noise like distortion such as lossy JPEG compression.