Reconstruct LDPC codes in an error-free environment

This paper presents two algorithms to recover LDPC codes in an error-free environment. Both algorithms reconstruct the sparse parity-check matrices of LDPC codes based on elementary row transformation, and are equivalent to recognize LDPC codes. The first one is appropriate to the LDPC codes whose parity-check matrices have the double-diagonal structure; the second one is a general algorithm that ensures the second-best solution for every type of LDPC codes. Simulation results show that, these algorithms work well with most of LDPC standards and protocols, including 802.16e, 802.11n, DVB-S2 GJB7296 and GB20600.