Study of bifurcation behavior of LDPC decoders

The use of low-density-parity-check (LDPC) codes in coding digital messages has aroused much research interest because of their excellent bit-error performance. The behavior of the iterative LDPC decoders of finite length, however, has not been fully evaluated under different signal-to-noise conditions. By considering the finite-length LDPC decoders as high-dimensional nonlinear dynamical systems, we attempt to investigate their dynamical behavior and bifurcation phenomena for a range of signal-to-noise ratios (SNRs). Extensive simulations have been performed on both regular and irregular LDPC codes. Moreover, we derive the Jacobian of the system and calculate the corresponding eigenvalues. Results show that bifurcations, including fold, flip and Neimark-Sacker bifurcations, are exhibited by the LDPC decoder. Results are useful for optimizing the choice of parameters that may enhance the effectiveness of the decoding algorithm and improve the convergence rates.