Construction Of LDPC Code And Its Application In Coded SC-FDE System

With the development of wireless communications, the demands of effective and reliable wirelesstransmittion become much higher and higher. However, there are still multi-path effects,interferences and noises, which influence the communication quality severely. But it is helpful toutilize channel coding to eliminate channel interferences and improve the performance ofcommunication transmition. Low-Density Parity-Check (LDPC) code, as an excellenterror-correcting code, has the ability of approaching Shannon limit and efficient coding/decoding.LDPC code is promising to be the coding scheme of the international wireless communicationsstandards, i.e. the 4th generation mobile communication. Meanwhile, Single Carrier FrequencyDomain Equalization (SC-FDE) not only has low peak average ratio and less sensitivity withfrequency and phase offset, but also has good feature of anti-multi-path fading effectively. It hasbeen accepted by IEEE802.16a wireless communications physical layer standard, thus it has beenthe hot-spot in researches. Based on these backgrounds, LDPC coding construction and itsapplication in coded SC-FDE systems is researched relative deeply, and associated optimizedcoding modulation system is constructed. The content of this paper is listed as follows:Firstly, the principle of LDPC coding/decoding and density revolution analysis are described.According to some classical LDPC codes construction algorithms, an improved algorithm with girthconditioning for irregular short LDPC codes is proposed. The analysis and simulation results showthat the LDPC codes constructed by this algorithm have better performance. Secondly, by studyingquasi-cyclic LDPC codes construction, a quasi-cyclic LDPC code construction method based onpseudo-cyclic Maximum Distance Separable (MDS) code is proposed according to current standardcodes. The parity-check matrix of a quasi-cyclic LDPC code can be constructed by calculating thegenerator polynomials of pseudo-cyclic MDS codes. Therefore, it has characteristic of simplerealization and flexible parameters choices, and has merits of quasi-cyclic LDPC theory researchand practical implementation. Thirdly, the principle of the SC-FDE systems is analyzed, and the keytechnologies in applications of communication systems are studied. The simulations under differentparameters with SC-FDE systems have been done to manifest the performance of the systems.Finally, the extension/puncturing rate-compatible LDPC code has been modified to improveperformance. Furthermore, the LDPC coded SC-FDE systems are studied and simulatedassociatedly to verify the better performance of the whole system.The creativities of the paper are listed as follows. With deeply studying the LDPC constructionby the characteristic of randomness, the minimum girth, connectivity and minimum distance, two LDPC construction methods according to relevant knowledge of graph theory and modern algebraare proposed. These two methods not only provide the theory guidance for further LDPC codesstudying, but also extend the LDPC codes construction method and the research scope as well.Furthermore, with the modified RC-LDPC codes and quasi-cyclic LDPC codes based onpseudo-cyclic MDS codes in SC-FDE systems, they can further improve the performance of thewhole systems, which has relative strong theoretical construction guiding and engineering practicalvalues for designing communication systems better to combat multi-path fading.