LDPC Error Floor Improvement

Abstract

The error-correcting performance of low-density parity check (LDPC) codes, whendecoded using practical iterative decoding algorithms, is known to be close toShannon limits. In this paper we study the LDPC codes performance when varyingcode rate, constellation level and the maximum number of iteration, this paper showsbetter 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) atlow signal-to-noise ratios (SNRs), a consequence the error rate floor phenomenonassociated with iterative LDPC decoders is produced. This paper demonstrates thatthe concatenation system used LDPC as an inner code and the Bose, Chaudhuri, andHocquenghem 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) atabout SNR (from -1dB to 1.8 dB) with the same overall cod rate(i.e without anyreduction in the bandwith efficiency) and restricted few number of iteration ( only 5iterations).

Keywords

LDPC, BCH, Error Floor.