  We propose a new family of spatially coupled product codes, called sub-block
rearranged staircase (SR-staircase) codes. Each code block of SR-staircase
codes is obtained by encoding rearranged preceding code blocks and new
information block, where the rearrangement involves sub-blocks decomposition
and transposition. The proposed codes can be constructed to have each code
block size of $1/q$ to that of the conventional staircase codes while having
the same rate and component codes, for any positive integer $q$. In this
regard, we can use strong algebraic component codes to construct SR-staircase
codes with a similar or the same code block size and rate as staircase codes
with weak component codes. We characterize the decoding threshold of the
proposed codes under iterative bounded distance decoding (iBDD) by using
density evolution. We also derive the conditions under which they achieve a
better decoding threshold than that of staircase codes. Further, we investigate
the error floor performance by analyzing the contributing error patterns and
their multiplicities. Both theoretical and simulation results show that the
designed SR-staircase codes outperform staircase codes in terms of waterfall
and error floor while the performance can be further improved by using a large
coupling width.
