  The Alternating Direction Method of Multipliers (ADMM) decoding of Low
Density Parity Check (LDPC) codes has received many attentions due to its
excellent performance at the error floor region. In this paper, we develop a
parameter-free decoder based on Linear Program (LP) decoding by replacing the
binary constraint with the intersection of a box and an $\ell_p$ sphere. An
efficient $\ell_2$-box ADMM is designed to handle this model in a distributed
fashion. Numerical experiments demonstrate that our decoder attains better
adaptability to different Signal-to-Noise Ratio and channels.
