Research On Algorithms Of Outer Coding And Implementation Based On Digital Video Broadcasting-Terrestrial

Reed-Solomon RS(204,188) shortened code is applied to the digital vedio broadcasting-terrestrial as a kind of outer coder. The shortened Reed-Solomon code is implemented by adding 51 bytes, all set to zero, before the 188 information bytes at the input of an RS(255,239) encoder. Then, it generates an error protected packet, consist of 16 bytes. After encoding, we obtain RS(204,188) by removing the 51 bytes, all set to zero, before the 188 information bytes. when decoding,51 bytes, all set to zero, will be added before the 188 information bytes, then 239 bytes are sent to the input port of an RS(255,239) decoder. The output of the decoder is consisted of 255 bytes. we can get the correct information bytes by removing 51 bytes of them. Based on this theory, this paper studies the RS(255,239) encoders and decoders.The main work of this paper follows.Firstly, the design program about the encoder and decoder is provided. Secondly, The programs of encoding and decoding to make the simulation of process are designed. I focused on algorithms for solving key equation, at last, the inversionless BM algorithm is chosed as the way to solve key equation. Thirdly, a specific circuit structure of each module is given out for encoding and decoding programs and optimizations are maded for some circuit structures. Fourthly, each module is carried out in very high speed integrated circuit hardware description language. The modules includes multiplier in Galois field, s-matrix computing module, module for solving key equation, module for Chien searching, module for computing values, module for judging and correcting. In the end, it goes through cascade testing, achieving the function of error correction and the speed of the circuit. The maximum frequency of the circuit is close to 110MHz.The innovation of this paper follows:The ROM is used to achieve the inverse device instead of using multipliers. I get the contents of the ROM by using multipliers with MATLAB. It is easy to achieve the inverse device in program. The results are very accurate, but in circuit design, from the simulation, it takes more expensive hardware resources. There are errors in the results. It is very complex to realize an inverse device by using multipliers. I use more hardware resources to improve the speed of the circuit for saving more time. Searching for error locations and calculating error values are working in parallel rather than traditional approach, which looks for error locations firstly, then calculates the error values. This method will result in more time delayed. It is easy to ensure data synchronization, although from another point of view, this would increase the redundant computation, increasing the consumption of hardware resources.