In this letter, we propose a new technique to design quasi-cyclic low-density parity-check (QC-LDPC) codes with girth 8 and variable node degrees 3 and 4. Small trapping sets are avoided in the designed codes by imposing simple constraints on the cycles of length 8 in the code's Tanner graph. We also derive lower bounds on the block length of the codes that can satisfy such constraints. Simulation results are provided to demonstrate the superiority of the designed codes in comparison with similar codes in the literature.

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Keywords error floor, girth, Low-density parity check (LDPC) codes, quasi cyclic (QC) LDPC codes, trapping sets
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Journal IEEE Communications Letters
Naseri, S. (Sima), & Banihashemi, A. (2019). Construction of Girth-8 QC-LDPC Codes Free of Small Trapping Sets. IEEE Communications Letters, 23(11), 1904–1908. doi:10.1109/LCOMM.2019.2933828