  In this paper, we discuss a construction of CSS codes derived from pairs of
practical irregular LDPC codes. Our design of irregular LDPC codes is based the
design written in the standardization of IEEE802.16e. Our research has tried to
make a CSS code with a pair of LDPC codes of type IEEE802.16e. To our regret,
we proved that it was impossible to construct a CSS code if one of classical
codes was of type IEEE802.16e with rate 1/2 and 2/3B. We would like to report
the discussion on its impossibility in this paper. This is the first paper to
analyze the possibility of a CSS code construction by using two irregular LDPC
codes which are practically useful.
