  The error correction performance of low-density parity-check (LDPC) codes
under iterative message-passing decoding is degraded by the presence of certain
harmful objects existing in their Tanner graph representation. Depending on the
context, such harmful objects are known as stopping sets, trapping sets,
absorbing sets, or pseudocodewords. In this paper, we propose a general
procedure based on edge spreading that enables the design of quasi-cyclic (QC)
spatially coupled low-density parity-check codes (SC-LDPCCs) that are derived
from QC-LDPC block codes and possess a significantly reduced multiplicity of
harmful objects with respect to the original QC-LDPC block code. This procedure
relies on a novel algorithm that greedily spans the search space of potential
candidates to reduce the multiplicity of the target harmful object(s) in the
Tanner graph. The effectiveness of the method we propose is validated via
examples and numerical computer simulations.
