Research On Construction Of LDPC Codes With Low Error Floor

Low density parity check (LDPC) codes have been shown to achieve remarkable performance which is very close to the Shannon limit, and have attracted a lot of attentation in the channel coding field. Due to the advantage of LDPC codes, such as good distance features, low decoding complexity, they have received great interests in research field and IT field. With the intensive research, LDPC codes have potential applications in the field such as wireless communication, optical network and digital storage.Based on the existing knowledge of LDPC codes, this paper mainly focus on minimum distance, stopping set and error floor of LDPC codes. Some results are obtained and summarized as follow:1. The basic principle of LDPC codes is illuminated. The principles of coding and decoding for LDPC codes are briefly summarized.2. Some bounds of LDPC codes'minimum distance are summarized. Increasing minimum distance of LDPC coeds can improve finding error and correcting error performance of the codes.Based on error impulse method, an algorithm for computing minimum distance of LDPC codes is analyzed intensively. The algorithm can get approximate minimum distance of LDPC codes, and thus estimate the FERs of LDPC codes efficiently, which is approved by simulation.3. A novel algorithm to eliminate small stopping sets in irregular LDPC codes is researched in detail. By adding several new check nodes and edges which connect the new check nodes with bit nodes form stopping sets, the number of small stopping sets is decreasing efficiently, and thus the error floor is reduced significantly, which is also approved by simulation.