ABSTRACT
Low Density Parity Check Codes are a class of linear block error-correcting codes that can be defined by the very sparse parity-check matrix. Their error performance approach Shannon limits. Message-passing schedule is an important factor which affects the performance of decoding. An signifi question is whether different schedules could improve decoding performance.
This paper mainly contains the following aspects:
(1) First, simply introduce the development of error-correcting codes; introduce the background of LDPC Codes.
(2) Introduce the graph theory of LDPC Codes; analyze the impact of cycle; and
research how to construct the parity check matrix.
(3) Combined with probability statistic knowledge, introduce the basic theory of Message Passing Algorithm; analyze the classical decoding algorithm of LDPC Codes, including Sum Product Algorithm which based on probability and LLR.
(4) Finally, MATLAB simulation results showed that LDPC codes bring encoding gain for communication systems and the error performance is better than the uncode system.
Key words: LDPC Codes, Graphical models, Circle, Message Passing Algorithm