Low Rate QC LDPC Codes with Reconfigurable Structures for Space Information Networks

—This paper presents the construction of the efficient low rate Quasi-Cyclic (QC) Low-Density Parity-Check (LDPC) codes and their reconfigurable structures for space information networks. The code is firstly produced by a seed AccumulateRepeat-Accumulate (ARA) protograph and then extended to a QC generalized LDPC code, where a parity check node pair is replaced with a more powerful pre-coding Hamming node. The code matrix is optimized by both the Progressive Edge progressive (PEG) and the QC oriented modified approximate cycle extrinsic message degree (QC-MACE) algorithm. The QC form in the code saves much storage and reduces coding complexity greatly. The reconfigurable code structure is also given and it can be used in variable space channels. Simulation results show that the proposed code obtains 0.05 dB gain and has better error floor, when compared to the Turbo code in the Consultative Committee for Space Data Systems (CCSDS) with same parameters at a Bit-Error-Rate (BER) of 10. And the coding gain is also about 0.1 dB over that of the currently low rate and short QC LDPC codes at a BER of 10. Besides, it has good features of low decoding complexity and low latency and so on.