摘要： 在对数字水印信道容量分析时，通常假设水印攻击信道的概率分布是完全已知的，但实际中对水印攻击信道的信息在某种意义上是不完整的，如信道估计误差、拉伸和几何攻击等。该文提出了一类带边信息的时变水印信道模型，它包含时变攻击的确定和随机两部分，在对水印信道的概率分布作很少假设条件下，获得了这类水印信道容量的上界和下界，同时也证实了在实际应用中加性高斯噪声信道模型不足以描述水印信道，最后用数值仿真验证了这个结论。

关键词: 数字水印, 信道容量, 信息论, 时变

Abstract: In the study of digital watermark channel capacity, the known probability distribution is supposed for watermark attack channel, but it is not always true, for example channel estimation errors, scaling and geometrical transformations etc. This paper proposes mathematical model for time-varying watermark channel with side information, composed of the deterministic and the random components of the time-varying attack. Minimal assumptions are made regarding the probability distributions of the watermark channel. Lower and upper bounds on the mutual information between the received signal and the cover signal allows to estimate capacity of watermark channel. Therefore, simple additive Gaussian noise channel model is not sufficient to describe the watermark channel. The theoretical results is valid by numerical simulate.

Key words: Digital watermark, Channel capacity, Information theory, Time-varying