In this paper, a low-complexity LDPC decoder structure was proposed by optimizing the confidence propagation algorithm based on the deep space standard LDPC codes developed by the Consultative Committee for Space Data Systems (CCSDS). With the improved decoding algorithm, the structure made full use of the quasi-cyclic structure to reduce the variables in the decoder and the storage unit use for the index position of the check nodes, which saves the hardware resources greatly. Furthermore, the updating of the check nodes takes advantages of the information iterative structure of the JPL-LDPC decoder, which can reduce the computational complexity. By improving the searching methods, the computational complexity and the difficulty in FPGA implementation were reduced. The decoding performance of the decoder is close to that of the floating-point BP algorithm, which can be widely used in deep space communication with low signal-to-noise ratio.performance close to a floating-point the BP algorithm performance, can be widely used in deep space communications suitable for low signal-to-noise ratio transmission.
In order to meet the requirements of low bit error-rate of the channel code in the space optical communication system, a construction method of low density parity check ( LDPC) codes with excellent performance is proposed based on protograph and quasi-cyclic expansion. It can be applied in high-speed encoding and decoding with efficient quasi-cyclic expansion. According to the proposed method, a LDPC ( 8832, 1472) suitable for the space optical communication system is constructed, in which the LDPC codes of the protograph perform very well. Simulation shows that the LDPC codes have superior error-correction performance and show no sign of error floor when the BER is in the order of 10-9, which are suitable for the long-distance space optical communication systems.
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