Controlling the Error Floor in LDPC Decoding

The error floor of LDPC is revisited as an effect of dynamic message behavior in the so-called absorbing sets of the code. It is shown that if the signal growth in the absorbing sets is properly balanced by the growth of set-external messages, the error floor can be lowered to essentially arbitrarily low levels. Importance sampling techniques are discussed and used to verify the analysis, as well as to discuss the impact of iterations and message quantization on the code performance in the ultra-low BER (error floor) regime.