Error Correction Code And Its Applied Research In The Digital Watermarking Technology

Digital Watermarking Technology is a new Technology of information hidden. Along with the fast development of internet and other information industry, it has been widely used and has arrested great attentions from the academia, industry and army because of its excellent performance in information hidden. Recently, with the development of the coding technology, digital watermarking system based on coding technology has become more and more important. Since robustness is one of the important requirements of digital watermarking system, it can be improved by coding technology. In order to improve robustness of watermark and protect the copyright of digital works, forward error correction codes and watermarking system are researched in this paper.The main contents and results are as follows.1. Based on the bipartite graph, the definition and constructions of LDPC codes were addressed. Especially, the construction methods of Quasi-cyclic LDPC codes were studied, and the decoding performance was also investigated by computer simulation. It was shown that QC-LDPC codes have power error correcting ability at moderate or short length. The Bit error rate is very close to that of the best LDPC codes on AWGN channel. So it can be expected that the QC-LDPC codes will have wide application in future.2. The principles of soft decoding and message passing were discussed. Based on the bipartite graph and the relating mathematic theory, the Sum-Product Algorithm and its reduced complexity algorithms were presented for decoding. At the end, an improved decoding algorithm, based on min-sum-product (MSP) and sequential-sum-product(S-SP), is presented. The simulation results have shown thatλ-min algorithms with reduced complexity works as well as the standard Sum-Product Algorithms only with a little performance loss. And the improved decoding algorithm is better thanλ-min algorithms. Therefore, It can be expected to be used in high data rate communication.3. The Digital Watermarking Technology was researched. In order to build a perfect digital watermarking system later, some classical algorithms of digital watermarking system were studied at first.4. After studying the theory of wavelet transform, a digital water marking system based on QC-LDPC code model is presented. By applying the QC-LDPC codes andλ-min algorithm in the model simulation, it shows that this scheme can greatly improve the robustness and transparency clarity of watermarking.Recently, digital watermarking system based on error correction code has attracted much attention particularly in the field of information safety field. With the maturity of technology, more and more digital watermarking systems like this will be widely used in the future.