The error-correcting performance of low-density parity check (LDPC) codes, when
decoded using practical iterative decoding algorithms, is known to be close to
Shannon limits. In this paper we study the LDPC codes performance when varying
code rate, constellation level and the maximum number of iteration, this paper shows
better coding gain can be obtained at the cost of higher complexity or higher bit rate.
For some cases, due to their inability to reach very low bit error rates (e.g., 10− 12) at
low signal-to-noise ratios (SNRs), a consequence the error rate floor phenomenon
associated with iterative LDPC decoders is produced. This paper demonstrates that
the concatenation system used LDPC as an inner code and the Bose, Chaudhuri, and
Hocquenghem codes (BCH) as an outer code can successfully lower the floor.
Connecting BCH codes lower the LDPC BER floor by a factor( from 32 to 22) at
about SNR (from -1dB to 1.8 dB) with the same overall cod rate(i.e without any
reduction in the bandwith efficiency) and restricted few number of iteration ( only 5