Quantization Effects in Low-Density Parity-Check Decoders

A. class of combinatorial structures, called absorbing sets, strongly influences the performance of low-density parity- check (LDPC) decoders. In particular, the quantization scheme strongly affects which absorbing sets dominate in the error-floor region. Absorbing sets may be characterized as weak or strong. They are a characteristic of the parity check matrix of a code. Conventional quantization schemes applied to a (2209,1978) array-based LDPC code can induce low-weight weak absorbing sets and, as a result, elevate the error floor. Adaptive quantization schemes alleviate the effects of weak absorbing sets, and, as a result, only the strong ones dominate the error floor of an optimized decoder implementation. Another benefit of an adaptive quantization scheme is that it performs well even in very few iterations.