Fast convergence algorithm for LDPC codes.pdf

Fast convergence algorithm for LDPC Codes
Frank Kienle, T. Lehnigk-Emden, Norbert Wehn
Microelectronic System Design Research Group, University of Kaiserslautern
Erwin-Schroedinger-Strasse, 67663 Kaiserslautern, Germany
Email: {kienlejlehnigk wehn} ***@-
Abstract- Low-Density Parity-Check (LDPC) codes are one Pmax p3 p2
of the most powerful codes known today. They are decoded I- I
iteratively by a message passing algorithm. There exist many IN - -I
different update schemes of the exchanged messages. The major 1-9-
difference of all update schemes is the convergence speed, . the P -A- - -(\
munications performance for a limited number of Permutation (1-1)
iterations. CN * , grouping a _,P ,
This paper presents a new decoding algorithm which
utilizes the encoder property of linear encodable LDPC codes.
The basic idea is to interpret the LDPC encoder as an encoder
with puncturing unit which opens as well the door for hybrid
ARQ schemes. The presented new decoding algorithm shows a PN
faster convergence behavior than state of art decoding schemes
and it results in a lower error floor.
Fig. 1. Tanner-graphs of an irregular LDPC code with IN (Information
Node), CN (Check Node), PN (Parity Node) and pi (fraction of nodes with
I. INTRODUCTION degree i )
Low-Density Parity-Check (LDPC) codes were introduced
by Gallager 1963 [1]