  It is shown that dominant trapping sets of regular LDPC codes, so called
absorption sets, undergo a two-phased dynamic behavior in the iterative
message-passing decoding algorithm. Using a linear dynamic model for the
iteration behavior of these sets, it is shown that they undergo an initial
geometric growth phase which stabilizes in a final bit-flipping behavior where
the algorithm reaches a fixed point. This analysis is shown to lead to very
accurate numerical calculations of the error floor bit error rates down to
error rates that are inaccessible by simulation. The topology of the dominant
absorption sets of an example code, the IEEE 802.3an (2048,1723) regular LDPC
code, are identified and tabulated using topological relationships in
combination with search algorithms.
