Low Complexity Design Of Codec For LT Fountain Code

Digital fountain code is an ideal coding scheme for large scale data distribution and reliable broadcast, and has two advantages, such as non-bit-rate and less feedback, which is very suitable for channel coding in wireless communication. As the first implementation of digital fountain code, the LT code requires long code length to obtain low decoding redundancy, which will increase code generation matrix data and lead to too much occupation of the hardware resources for LT Codec design.System Verilog language is applied to design the LT Codec with low complexity and medium code length in this thesis. This paper summarizes the research status of LT code, introduces the design theory of LT code, including the degree distribution, the principle of encoding and decoding, performance indicators, and introduces the application of codebook technology in the design of LT Codec. Then introduces the background of this thesis, discusses the design parameters and the influence on the performance of the system. Design and complete the LT Codec circuit with that the bit rate is 4Mbits, the data transceiver operating frequency is 16MHz, the decoding redundancy is less than 0.5, code length is 1024. In order to reduce the design complexity, in LT encoder design, the code book technique is applied to compress the data of generate matrix, the truncation of the degree distribution function and the improved look-up table method are also applied. In the design of the decoder, the decompression process is removed, and the compressed data is used for decoding directly, the function of the location vector table and the function of searching for empty address are applied.After the RTL-level design of LT Codec, the function simulation with System Verilog platform and FPGA verification are implemented. And the results show that the design of LT codec has specifications of low complexity, the LT Codec occupies 2735 of combinational logic unit,1407 of register unit,667Kbit.s of memory unit.. The maximum working frequency of the data transceive is 50MHz.The bit error rate of the LT codec and the statistics of decoding redundancy also meet the design requirements.