| Designing codes with approaching Shannon's capacity performance and low coding and decoding complexity is a challenging and meaningful issue in channel coding field. Low-Density Parity-Check codes are a class of capacity approaching error-correcting codes. For long code lengths, LDPC codes can even outperform Turbo codes. Due to the advantages of LDPC codes, such as lower complexity of decoding and lower error floor, their applications in reliable communications have received great interests and have become one of most attractive field in channel coding community.In this dissertation, based on the analysis of LDPC codes coding and decoding algorithm, PEG algorithm to construct a large girth for LDPC codes is interpreted in detail. An improved PEG algorithm is proposed in this thesis. An analysis and comparison results show that the improved algorithm has a good performance. Based on the LDPC codes, Extending and puncturing methods with rate-compatible are investigated. Additionally, Combining Extending with puncturing algorithm, we construct RC-LDPC codes that have a wide range of code rates.For HARQ with different retransmission and combining, we proposed LDPC-HARQ system. The incremental redundancy HARQ (IR-HARQ) system is discussed significantly and the throughput is analyzed. The theoretical analysis and simulation results show the advantage of HARQ system with RC-LDPC codes.According to the accomplished project, m sequence is used before frame, local m sequence correlates with receiving information sequence and data must be detected synchronously. Given the SNR and the threshold, we calculate the probability of false synchronization and missed synchronization. The simulation is also given. |
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