Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : LDPC


LDPC Error Floor Improvement

Aseel Hameed Majeed

Engineering and Technology Journal, 2012, Volume 30, Issue 3, Pages 474-488

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
iterations).

Evaluation of Low Density Parity Check Codes Over Various Channel Types

Mahmood Farhan Mosleh

Engineering and Technology Journal, 2011, Volume 29, Issue 5, Pages 961-971

Low density parity check (LDPC) codes are one of the best error correcting
codes in today’s coding world and are known to approach the Shannon limit. As
with all other channel coding schemes, LDPC codes add redundancy to the
uncoded input data to make it more immune to channel impairments. In this paper,
the impact of low-Density Parity-Check code (LDPC) on the performance of
system under Binary Phase Shift keying (BPSK) over an Additive White Gaussian
Noise (AWGN) and other fading (Raleigh and Rician) channels is investigated.
Obtained results show that LDPC can improve transceiver system for various
channel types. At Bit Error Rate (BER) of 10-4 such code with code rate of ½
reduces the Signal to Noise Ratio (SNR) by range of 6.5 to 9 dB for fading
channels in contrast to uncoded system. By studying modern research it has been
found that turbo code can achieved same manner but LDPC decoder faster than
turbo decoder and can be implemented in parallel.