الفهرس 
الغلافOnly 14 pages are availabe for public view
 |  | from | 147 |  |  |
| | | from | 147 | | |
Abstract
Abstract
Scientists have competed to design a coding scheme approaching the theoretical limit
introduced by Shannon as the design has been focused primarily on finding codes that
can be decoded with optimal and feasible decoding algorithms. Generalized LDPC
(Low Density Parity Check) codes were found to compare well with many capacity-
approach codes as they expose very good• performance. Most of the work, on iterative
decoding algorithms and their performance, has been so far dedicated to LDPC codes.
LDPC codes are well treated with both types of decoding; the Hard-Decision Decoding
(HDD) and the Soft-Decision Decoding (SDD). On the other hand the iterative decoding
of GLDPC codes, on both AWGN and BSC channels, was not sufficiently investigated.
This dissertation investigates iterative decoding of GLDPC codes on BSC and AWGN
channels. The research aims to achieve two targets. First, it proceeds to improve the
error performance of HD decoders of GLDPC codes. Second, it seeks to lower the
complexity of the SD decoders which are indeed peculiar in its error performance. For
HD decoding of GLDPC codes, two new Bit-Flipping (BF) algorithms were proposed.
The first one, named Two-Side State-Aided Bit-Flipping Decoding of GLDPC, proceeds
over BSC and the simulation results show that it improves the error performance over the
existing algorithms. The local decoding failure is also analyzed to provide a reasonable
treatment for the most of its causes. The second algorithm, named Classification-Based
. Algorithm for Bit-flipping Decoding of GLDPC Codes over AWGN Channels, exploits
the advantage of the fast BF decoding with only initial help from the channel soft infor-
mation and in the same time it improves its error performance. The decoding errors of
the constituent decoders are also analyzed to present the best possible handling with the
generated trapping sets by reducing their effect at a cost of little increase in the decoder
overhead. It is proved to outperform previous iterative BF algorithms in terms of error
performance in less number of iterations. For SD decoding of GLDPC codes, a new
Chase-based Message Passing (MP) Soft Decoding algorithm over AWGN Channels
was proposed. It presents a lowered complexity version of a reliability-based iterative
decoding algorithm for GLDPC codes with BCH constituent codes using Soft-Input
Soft-Output (5150) Chase-If algorithm. It reduces the complexity of the conventional
xiii