Ldpc Codes And Its Applications, In The Compressed Image Transmission

Low-density parity-check (LDPC) codes are a class of linear block code which have a sparse check matrix, it could provide near Shannon-Limit performance. LDPC codes have a outstanding bit error rate performance, when they have a longer code length, the performance may even better than the Turbo codes. The irregular LDPC codes still have a good performance even when there has a low signal to noise ratio (SNR), and their error floor can be very low when they have been designed. The LDPC codes have become one of the most attractive issues in channel coding community, and it has been successfully applied in various of fields.With the continuous development of information technology, people are rapidly increasing demand for multimedia information, efficient and reliable transmission of multimedia information has become a hot research in the field of communication. In the development of this trend, The LDPC Codes and its application in image transmission are studied in this paper.In this paper, we review the basic knowledge of channel coding firstly. And then the development of LDPC codes and their basic feature are introduced. Besides, the representation method, construction method and encoding method for LDPC codes are expounded. After this, we introduce the decoding algorithm of LDPC codes, simulate their performance under different decoding algorithm, and analyse the performance when the decoding conditions are changed. At last, the application of LDPC codes for image transmission is researched. We focus on the following two aspects. In the first part, a channel coding algorithm based on regular LDPC codes is proposed. The JPEG2000 code stream can be protected by using the channel coding rate obtained by this algorithm. This improves the transmission reliability effectively, and the simulation result shows the superiority of the algorithm. In the second part, an image transmission scheme based on irregular LDPC codes is proposed. We optimize the degree distribution of irregular LDPC codes using the Gaussian approximation, and then the UEP-LDPC codes with UEP capabilities are designed. Based on the characteristics of JPEG2000 bit stream, the different significant bit stream are mapped to the bit nodes with different degrees, so that an unequal error protection is performed. Through the simulation results, we can validate the reliability and effectiveness of the image transmission system.