Improved spread spectrum: a new modulation technique for robust watermarking

TLDR

The paper proposes improved spread spectrum (ISS), a new watermarking modulation technique. ISS modifies the watermarking modulation so that the signal no longer acts as a noise source. Compared to traditional spread spectrum, ISS delivers significant gains—up to 20 dB SNR improvement or orders‑of‑magnitude error‑probability reduction—matching the noise‑robustness of quantization index modulation without its amplitude‑scale sensitivity, and performs as robustly as traditional SS in practice.

Abstract

This paper introduces a new watermarking modulation technique, which we call improved spread spectrum (ISS). When compared with traditional spread spectrum (SS), the signal does not act as a noise source, leading to significant gains. In some examples, performance improvements over SS are 20 dB in signal-to-noise ratio (SNR) or ten or more orders of magnitude in the error probability. The proposed method achieves roughly the same noise robustness gain as quantization index modulation (QIM) but without the amplitude scale sensitivity of QIM. Our proposed ISS is as robust in practice as traditional SS.