Henrique Malvar and Dinei Florencio
This paper introduces a new watermarking modulation technique,
which we call improved spread spectrum (ISS). Unlike in traditional
spread spectrum (SS), in ISS the carrier signal does not act
as a noise source, leading significant performance gains. In typical
examples, the gain of ISS over SS is 20 dB or more in signalto-
noise ratio or 20 orders of magnitude or more in error probability.
The proposed method achieves roughly the same noise
robustness gain as quantization index modulation (QIM). Nevertheless,
while QIM is quite sensitive to amplitude variations, ISS
is as robust in practice as traditional SS.